Takashi Iwai | 5f8206c | 2009-02-09 08:50:43 +0100 | [diff] [blame] | 1 | <?xml version="1.0" encoding="UTF-8"?> |
| 2 | <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" |
| 3 | "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4 | |
| 5 | <!-- ****************************************************** --> |
| 6 | <!-- Header --> |
| 7 | <!-- ****************************************************** --> |
Takashi Iwai | 5f8206c | 2009-02-09 08:50:43 +0100 | [diff] [blame] | 8 | <book id="Writing-an-ALSA-Driver"> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 9 | <bookinfo> |
| 10 | <title>Writing an ALSA Driver</title> |
| 11 | <author> |
| 12 | <firstname>Takashi</firstname> |
| 13 | <surname>Iwai</surname> |
| 14 | <affiliation> |
| 15 | <address> |
| 16 | <email>tiwai@suse.de</email> |
| 17 | </address> |
| 18 | </affiliation> |
| 19 | </author> |
| 20 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 21 | <date>Oct 15, 2007</date> |
Clemens Ladisch | d1761d1 | 2007-09-10 08:05:19 +0200 | [diff] [blame] | 22 | <edition>0.3.7</edition> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 23 | |
| 24 | <abstract> |
| 25 | <para> |
| 26 | This document describes how to write an ALSA (Advanced Linux |
| 27 | Sound Architecture) driver. |
| 28 | </para> |
| 29 | </abstract> |
| 30 | |
| 31 | <legalnotice> |
| 32 | <para> |
Takashi Iwai | 7c22f1a | 2005-10-10 11:46:31 +0200 | [diff] [blame] | 33 | Copyright (c) 2002-2005 Takashi Iwai <email>tiwai@suse.de</email> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 34 | </para> |
| 35 | |
| 36 | <para> |
| 37 | This document is free; you can redistribute it and/or modify it |
| 38 | under the terms of the GNU General Public License as published by |
| 39 | the Free Software Foundation; either version 2 of the License, or |
| 40 | (at your option) any later version. |
| 41 | </para> |
| 42 | |
| 43 | <para> |
| 44 | This document is distributed in the hope that it will be useful, |
| 45 | but <emphasis>WITHOUT ANY WARRANTY</emphasis>; without even the |
| 46 | implied warranty of <emphasis>MERCHANTABILITY or FITNESS FOR A |
| 47 | PARTICULAR PURPOSE</emphasis>. See the GNU General Public License |
| 48 | for more details. |
| 49 | </para> |
| 50 | |
| 51 | <para> |
| 52 | You should have received a copy of the GNU General Public |
| 53 | License along with this program; if not, write to the Free |
| 54 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, |
| 55 | MA 02111-1307 USA |
| 56 | </para> |
| 57 | </legalnotice> |
| 58 | |
| 59 | </bookinfo> |
| 60 | |
| 61 | <!-- ****************************************************** --> |
| 62 | <!-- Preface --> |
| 63 | <!-- ****************************************************** --> |
| 64 | <preface id="preface"> |
| 65 | <title>Preface</title> |
| 66 | <para> |
| 67 | This document describes how to write an |
| 68 | <ulink url="http://www.alsa-project.org/"><citetitle> |
| 69 | ALSA (Advanced Linux Sound Architecture)</citetitle></ulink> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 70 | driver. The document focuses mainly on PCI soundcards. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 71 | In the case of other device types, the API might |
| 72 | be different, too. However, at least the ALSA kernel API is |
| 73 | consistent, and therefore it would be still a bit help for |
| 74 | writing them. |
| 75 | </para> |
| 76 | |
| 77 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 78 | This document targets people who already have enough |
| 79 | C language skills and have basic linux kernel programming |
| 80 | knowledge. This document doesn't explain the general |
| 81 | topic of linux kernel coding and doesn't cover low-level |
| 82 | driver implementation details. It only describes |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 83 | the standard way to write a PCI sound driver on ALSA. |
| 84 | </para> |
| 85 | |
| 86 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 87 | If you are already familiar with the older ALSA ver.0.5.x API, you |
| 88 | can check the drivers such as <filename>sound/pci/es1938.c</filename> or |
| 89 | <filename>sound/pci/maestro3.c</filename> which have also almost the same |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 90 | code-base in the ALSA 0.5.x tree, so you can compare the differences. |
| 91 | </para> |
| 92 | |
| 93 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 94 | This document is still a draft version. Any feedback and |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 95 | corrections, please!! |
| 96 | </para> |
| 97 | </preface> |
| 98 | |
| 99 | |
| 100 | <!-- ****************************************************** --> |
| 101 | <!-- File Tree Structure --> |
| 102 | <!-- ****************************************************** --> |
| 103 | <chapter id="file-tree"> |
| 104 | <title>File Tree Structure</title> |
| 105 | |
| 106 | <section id="file-tree-general"> |
| 107 | <title>General</title> |
| 108 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 109 | The ALSA drivers are provided in two ways. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 110 | </para> |
| 111 | |
| 112 | <para> |
| 113 | One is the trees provided as a tarball or via cvs from the |
| 114 | ALSA's ftp site, and another is the 2.6 (or later) Linux kernel |
| 115 | tree. To synchronize both, the ALSA driver tree is split into |
| 116 | two different trees: alsa-kernel and alsa-driver. The former |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 117 | contains purely the source code for the Linux 2.6 (or later) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 118 | tree. This tree is designed only for compilation on 2.6 or |
| 119 | later environment. The latter, alsa-driver, contains many subtle |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 120 | files for compiling ALSA drivers outside of the Linux kernel tree, |
| 121 | wrapper functions for older 2.2 and 2.4 kernels, to adapt the latest kernel API, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 122 | and additional drivers which are still in development or in |
| 123 | tests. The drivers in alsa-driver tree will be moved to |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 124 | alsa-kernel (and eventually to the 2.6 kernel tree) when they are |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 125 | finished and confirmed to work fine. |
| 126 | </para> |
| 127 | |
| 128 | <para> |
| 129 | The file tree structure of ALSA driver is depicted below. Both |
| 130 | alsa-kernel and alsa-driver have almost the same file |
| 131 | structure, except for <quote>core</quote> directory. It's |
| 132 | named as <quote>acore</quote> in alsa-driver tree. |
| 133 | |
| 134 | <example> |
| 135 | <title>ALSA File Tree Structure</title> |
| 136 | <literallayout> |
| 137 | sound |
| 138 | /core |
| 139 | /oss |
| 140 | /seq |
| 141 | /oss |
| 142 | /instr |
| 143 | /ioctl32 |
| 144 | /include |
| 145 | /drivers |
| 146 | /mpu401 |
| 147 | /opl3 |
| 148 | /i2c |
| 149 | /l3 |
| 150 | /synth |
| 151 | /emux |
| 152 | /pci |
| 153 | /(cards) |
| 154 | /isa |
| 155 | /(cards) |
| 156 | /arm |
| 157 | /ppc |
| 158 | /sparc |
| 159 | /usb |
| 160 | /pcmcia /(cards) |
| 161 | /oss |
| 162 | </literallayout> |
| 163 | </example> |
| 164 | </para> |
| 165 | </section> |
| 166 | |
| 167 | <section id="file-tree-core-directory"> |
| 168 | <title>core directory</title> |
| 169 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 170 | This directory contains the middle layer which is the heart |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 171 | of ALSA drivers. In this directory, the native ALSA modules are |
| 172 | stored. The sub-directories contain different modules and are |
| 173 | dependent upon the kernel config. |
| 174 | </para> |
| 175 | |
| 176 | <section id="file-tree-core-directory-oss"> |
| 177 | <title>core/oss</title> |
| 178 | |
| 179 | <para> |
| 180 | The codes for PCM and mixer OSS emulation modules are stored |
| 181 | in this directory. The rawmidi OSS emulation is included in |
| 182 | the ALSA rawmidi code since it's quite small. The sequencer |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 183 | code is stored in <filename>core/seq/oss</filename> directory (see |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 184 | <link linkend="file-tree-core-directory-seq-oss"><citetitle> |
| 185 | below</citetitle></link>). |
| 186 | </para> |
| 187 | </section> |
| 188 | |
| 189 | <section id="file-tree-core-directory-ioctl32"> |
| 190 | <title>core/ioctl32</title> |
| 191 | |
| 192 | <para> |
| 193 | This directory contains the 32bit-ioctl wrappers for 64bit |
| 194 | architectures such like x86-64, ppc64 and sparc64. For 32bit |
| 195 | and alpha architectures, these are not compiled. |
| 196 | </para> |
| 197 | </section> |
| 198 | |
| 199 | <section id="file-tree-core-directory-seq"> |
| 200 | <title>core/seq</title> |
| 201 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 202 | This directory and its sub-directories are for the ALSA |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 203 | sequencer. This directory contains the sequencer core and |
| 204 | primary sequencer modules such like snd-seq-midi, |
| 205 | snd-seq-virmidi, etc. They are compiled only when |
| 206 | <constant>CONFIG_SND_SEQUENCER</constant> is set in the kernel |
| 207 | config. |
| 208 | </para> |
| 209 | </section> |
| 210 | |
| 211 | <section id="file-tree-core-directory-seq-oss"> |
| 212 | <title>core/seq/oss</title> |
| 213 | <para> |
| 214 | This contains the OSS sequencer emulation codes. |
| 215 | </para> |
| 216 | </section> |
| 217 | |
| 218 | <section id="file-tree-core-directory-deq-instr"> |
| 219 | <title>core/seq/instr</title> |
| 220 | <para> |
| 221 | This directory contains the modules for the sequencer |
| 222 | instrument layer. |
| 223 | </para> |
| 224 | </section> |
| 225 | </section> |
| 226 | |
| 227 | <section id="file-tree-include-directory"> |
| 228 | <title>include directory</title> |
| 229 | <para> |
| 230 | This is the place for the public header files of ALSA drivers, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 231 | which are to be exported to user-space, or included by |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 232 | several files at different directories. Basically, the private |
| 233 | header files should not be placed in this directory, but you may |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 234 | still find files there, due to historical reasons :) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 235 | </para> |
| 236 | </section> |
| 237 | |
| 238 | <section id="file-tree-drivers-directory"> |
| 239 | <title>drivers directory</title> |
| 240 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 241 | This directory contains code shared among different drivers |
| 242 | on different architectures. They are hence supposed not to be |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 243 | architecture-specific. |
| 244 | For example, the dummy pcm driver and the serial MIDI |
| 245 | driver are found in this directory. In the sub-directories, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 246 | there is code for components which are independent from |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 247 | bus and cpu architectures. |
| 248 | </para> |
| 249 | |
| 250 | <section id="file-tree-drivers-directory-mpu401"> |
| 251 | <title>drivers/mpu401</title> |
| 252 | <para> |
| 253 | The MPU401 and MPU401-UART modules are stored here. |
| 254 | </para> |
| 255 | </section> |
| 256 | |
| 257 | <section id="file-tree-drivers-directory-opl3"> |
| 258 | <title>drivers/opl3 and opl4</title> |
| 259 | <para> |
| 260 | The OPL3 and OPL4 FM-synth stuff is found here. |
| 261 | </para> |
| 262 | </section> |
| 263 | </section> |
| 264 | |
| 265 | <section id="file-tree-i2c-directory"> |
| 266 | <title>i2c directory</title> |
| 267 | <para> |
| 268 | This contains the ALSA i2c components. |
| 269 | </para> |
| 270 | |
| 271 | <para> |
| 272 | Although there is a standard i2c layer on Linux, ALSA has its |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 273 | own i2c code for some cards, because the soundcard needs only a |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 274 | simple operation and the standard i2c API is too complicated for |
| 275 | such a purpose. |
| 276 | </para> |
| 277 | |
| 278 | <section id="file-tree-i2c-directory-l3"> |
| 279 | <title>i2c/l3</title> |
| 280 | <para> |
| 281 | This is a sub-directory for ARM L3 i2c. |
| 282 | </para> |
| 283 | </section> |
| 284 | </section> |
| 285 | |
| 286 | <section id="file-tree-synth-directory"> |
| 287 | <title>synth directory</title> |
| 288 | <para> |
| 289 | This contains the synth middle-level modules. |
| 290 | </para> |
| 291 | |
| 292 | <para> |
| 293 | So far, there is only Emu8000/Emu10k1 synth driver under |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 294 | the <filename>synth/emux</filename> sub-directory. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 295 | </para> |
| 296 | </section> |
| 297 | |
| 298 | <section id="file-tree-pci-directory"> |
| 299 | <title>pci directory</title> |
| 300 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 301 | This directory and its sub-directories hold the top-level card modules |
| 302 | for PCI soundcards and the code specific to the PCI BUS. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 303 | </para> |
| 304 | |
| 305 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 306 | The drivers compiled from a single file are stored directly |
| 307 | in the pci directory, while the drivers with several source files are |
| 308 | stored on their own sub-directory (e.g. emu10k1, ice1712). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 309 | </para> |
| 310 | </section> |
| 311 | |
| 312 | <section id="file-tree-isa-directory"> |
| 313 | <title>isa directory</title> |
| 314 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 315 | This directory and its sub-directories hold the top-level card modules |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 316 | for ISA soundcards. |
| 317 | </para> |
| 318 | </section> |
| 319 | |
| 320 | <section id="file-tree-arm-ppc-sparc-directories"> |
| 321 | <title>arm, ppc, and sparc directories</title> |
| 322 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 323 | They are used for top-level card modules which are |
| 324 | specific to one of these architectures. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 325 | </para> |
| 326 | </section> |
| 327 | |
| 328 | <section id="file-tree-usb-directory"> |
| 329 | <title>usb directory</title> |
| 330 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 331 | This directory contains the USB-audio driver. In the latest version, the |
| 332 | USB MIDI driver is integrated in the usb-audio driver. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 333 | </para> |
| 334 | </section> |
| 335 | |
| 336 | <section id="file-tree-pcmcia-directory"> |
| 337 | <title>pcmcia directory</title> |
| 338 | <para> |
| 339 | The PCMCIA, especially PCCard drivers will go here. CardBus |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 340 | drivers will be in the pci directory, because their API is identical |
| 341 | to that of standard PCI cards. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 342 | </para> |
| 343 | </section> |
| 344 | |
| 345 | <section id="file-tree-oss-directory"> |
| 346 | <title>oss directory</title> |
| 347 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 348 | The OSS/Lite source files are stored here in Linux 2.6 (or |
| 349 | later) tree. In the ALSA driver tarball, this directory is empty, |
| 350 | of course :) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 351 | </para> |
| 352 | </section> |
| 353 | </chapter> |
| 354 | |
| 355 | |
| 356 | <!-- ****************************************************** --> |
| 357 | <!-- Basic Flow for PCI Drivers --> |
| 358 | <!-- ****************************************************** --> |
| 359 | <chapter id="basic-flow"> |
| 360 | <title>Basic Flow for PCI Drivers</title> |
| 361 | |
| 362 | <section id="basic-flow-outline"> |
| 363 | <title>Outline</title> |
| 364 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 365 | The minimum flow for PCI soundcards is as follows: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 366 | |
| 367 | <itemizedlist> |
| 368 | <listitem><para>define the PCI ID table (see the section |
| 369 | <link linkend="pci-resource-entries"><citetitle>PCI Entries |
| 370 | </citetitle></link>).</para></listitem> |
| 371 | <listitem><para>create <function>probe()</function> callback.</para></listitem> |
| 372 | <listitem><para>create <function>remove()</function> callback.</para></listitem> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 373 | <listitem><para>create a <structname>pci_driver</structname> structure |
| 374 | containing the three pointers above.</para></listitem> |
| 375 | <listitem><para>create an <function>init()</function> function just calling |
| 376 | the <function>pci_register_driver()</function> to register the pci_driver table |
| 377 | defined above.</para></listitem> |
| 378 | <listitem><para>create an <function>exit()</function> function to call |
| 379 | the <function>pci_unregister_driver()</function> function.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 380 | </itemizedlist> |
| 381 | </para> |
| 382 | </section> |
| 383 | |
| 384 | <section id="basic-flow-example"> |
| 385 | <title>Full Code Example</title> |
| 386 | <para> |
| 387 | The code example is shown below. Some parts are kept |
| 388 | unimplemented at this moment but will be filled in the |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 389 | next sections. The numbers in the comment lines of the |
| 390 | <function>snd_mychip_probe()</function> function |
| 391 | refer to details explained in the following section. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 392 | |
| 393 | <example> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 394 | <title>Basic Flow for PCI Drivers - Example</title> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 395 | <programlisting> |
| 396 | <![CDATA[ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 397 | #include <linux/init.h> |
| 398 | #include <linux/pci.h> |
| 399 | #include <linux/slab.h> |
| 400 | #include <sound/core.h> |
| 401 | #include <sound/initval.h> |
| 402 | |
| 403 | /* module parameters (see "Module Parameters") */ |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 404 | /* SNDRV_CARDS: maximum number of cards supported by this module */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 405 | static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX; |
| 406 | static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR; |
| 407 | static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP; |
| 408 | |
| 409 | /* definition of the chip-specific record */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 410 | struct mychip { |
| 411 | struct snd_card *card; |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 412 | /* the rest of the implementation will be in section |
| 413 | * "PCI Resource Management" |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 414 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 415 | }; |
| 416 | |
| 417 | /* chip-specific destructor |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 418 | * (see "PCI Resource Management") |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 419 | */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 420 | static int snd_mychip_free(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 421 | { |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 422 | .... /* will be implemented later... */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 423 | } |
| 424 | |
| 425 | /* component-destructor |
| 426 | * (see "Management of Cards and Components") |
| 427 | */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 428 | static int snd_mychip_dev_free(struct snd_device *device) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 429 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 430 | return snd_mychip_free(device->device_data); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 431 | } |
| 432 | |
| 433 | /* chip-specific constructor |
| 434 | * (see "Management of Cards and Components") |
| 435 | */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 436 | static int __devinit snd_mychip_create(struct snd_card *card, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 437 | struct pci_dev *pci, |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 438 | struct mychip **rchip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 439 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 440 | struct mychip *chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 441 | int err; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 442 | static struct snd_device_ops ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 443 | .dev_free = snd_mychip_dev_free, |
| 444 | }; |
| 445 | |
| 446 | *rchip = NULL; |
| 447 | |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 448 | /* check PCI availability here |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 449 | * (see "PCI Resource Management") |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 450 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 451 | .... |
| 452 | |
| 453 | /* allocate a chip-specific data with zero filled */ |
Takashi Iwai | 561b220 | 2005-09-09 14:22:34 +0200 | [diff] [blame] | 454 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 455 | if (chip == NULL) |
| 456 | return -ENOMEM; |
| 457 | |
| 458 | chip->card = card; |
| 459 | |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 460 | /* rest of initialization here; will be implemented |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 461 | * later, see "PCI Resource Management" |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 462 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 463 | .... |
| 464 | |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 465 | err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops); |
| 466 | if (err < 0) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 467 | snd_mychip_free(chip); |
| 468 | return err; |
| 469 | } |
| 470 | |
| 471 | snd_card_set_dev(card, &pci->dev); |
| 472 | |
| 473 | *rchip = chip; |
| 474 | return 0; |
| 475 | } |
| 476 | |
| 477 | /* constructor -- see "Constructor" sub-section */ |
| 478 | static int __devinit snd_mychip_probe(struct pci_dev *pci, |
| 479 | const struct pci_device_id *pci_id) |
| 480 | { |
| 481 | static int dev; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 482 | struct snd_card *card; |
| 483 | struct mychip *chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 484 | int err; |
| 485 | |
| 486 | /* (1) */ |
| 487 | if (dev >= SNDRV_CARDS) |
| 488 | return -ENODEV; |
| 489 | if (!enable[dev]) { |
| 490 | dev++; |
| 491 | return -ENOENT; |
| 492 | } |
| 493 | |
| 494 | /* (2) */ |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 495 | err = snd_card_create(index[dev], id[dev], THIS_MODULE, 0, &card); |
| 496 | if (err < 0) |
| 497 | return err; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 498 | |
| 499 | /* (3) */ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 500 | err = snd_mychip_create(card, pci, &chip); |
| 501 | if (err < 0) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 502 | snd_card_free(card); |
| 503 | return err; |
| 504 | } |
| 505 | |
| 506 | /* (4) */ |
| 507 | strcpy(card->driver, "My Chip"); |
| 508 | strcpy(card->shortname, "My Own Chip 123"); |
| 509 | sprintf(card->longname, "%s at 0x%lx irq %i", |
| 510 | card->shortname, chip->ioport, chip->irq); |
| 511 | |
| 512 | /* (5) */ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 513 | .... /* implemented later */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 514 | |
| 515 | /* (6) */ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 516 | err = snd_card_register(card); |
| 517 | if (err < 0) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 518 | snd_card_free(card); |
| 519 | return err; |
| 520 | } |
| 521 | |
| 522 | /* (7) */ |
| 523 | pci_set_drvdata(pci, card); |
| 524 | dev++; |
| 525 | return 0; |
| 526 | } |
| 527 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 528 | /* destructor -- see the "Destructor" sub-section */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 529 | static void __devexit snd_mychip_remove(struct pci_dev *pci) |
| 530 | { |
| 531 | snd_card_free(pci_get_drvdata(pci)); |
| 532 | pci_set_drvdata(pci, NULL); |
| 533 | } |
| 534 | ]]> |
| 535 | </programlisting> |
| 536 | </example> |
| 537 | </para> |
| 538 | </section> |
| 539 | |
| 540 | <section id="basic-flow-constructor"> |
| 541 | <title>Constructor</title> |
| 542 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 543 | The real constructor of PCI drivers is the <function>probe</function> callback. |
| 544 | The <function>probe</function> callback and other component-constructors which are called |
| 545 | from the <function>probe</function> callback should be defined with |
| 546 | the <parameter>__devinit</parameter> prefix. You |
| 547 | cannot use the <parameter>__init</parameter> prefix for them, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 548 | because any PCI device could be a hotplug device. |
| 549 | </para> |
| 550 | |
| 551 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 552 | In the <function>probe</function> callback, the following scheme is often used. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 553 | </para> |
| 554 | |
| 555 | <section id="basic-flow-constructor-device-index"> |
| 556 | <title>1) Check and increment the device index.</title> |
| 557 | <para> |
| 558 | <informalexample> |
| 559 | <programlisting> |
| 560 | <![CDATA[ |
| 561 | static int dev; |
| 562 | .... |
| 563 | if (dev >= SNDRV_CARDS) |
| 564 | return -ENODEV; |
| 565 | if (!enable[dev]) { |
| 566 | dev++; |
| 567 | return -ENOENT; |
| 568 | } |
| 569 | ]]> |
| 570 | </programlisting> |
| 571 | </informalexample> |
| 572 | |
| 573 | where enable[dev] is the module option. |
| 574 | </para> |
| 575 | |
| 576 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 577 | Each time the <function>probe</function> callback is called, check the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 578 | availability of the device. If not available, simply increment |
| 579 | the device index and returns. dev will be incremented also |
| 580 | later (<link |
| 581 | linkend="basic-flow-constructor-set-pci"><citetitle>step |
| 582 | 7</citetitle></link>). |
| 583 | </para> |
| 584 | </section> |
| 585 | |
| 586 | <section id="basic-flow-constructor-create-card"> |
| 587 | <title>2) Create a card instance</title> |
| 588 | <para> |
| 589 | <informalexample> |
| 590 | <programlisting> |
| 591 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 592 | struct snd_card *card; |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 593 | int err; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 594 | .... |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 595 | err = snd_card_create(index[dev], id[dev], THIS_MODULE, 0, &card); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 596 | ]]> |
| 597 | </programlisting> |
| 598 | </informalexample> |
| 599 | </para> |
| 600 | |
| 601 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 602 | The details will be explained in the section |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 603 | <link linkend="card-management-card-instance"><citetitle> |
| 604 | Management of Cards and Components</citetitle></link>. |
| 605 | </para> |
| 606 | </section> |
| 607 | |
| 608 | <section id="basic-flow-constructor-create-main"> |
| 609 | <title>3) Create a main component</title> |
| 610 | <para> |
| 611 | In this part, the PCI resources are allocated. |
| 612 | |
| 613 | <informalexample> |
| 614 | <programlisting> |
| 615 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 616 | struct mychip *chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 617 | .... |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 618 | err = snd_mychip_create(card, pci, &chip); |
| 619 | if (err < 0) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 620 | snd_card_free(card); |
| 621 | return err; |
| 622 | } |
| 623 | ]]> |
| 624 | </programlisting> |
| 625 | </informalexample> |
| 626 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 627 | The details will be explained in the section <link |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 628 | linkend="pci-resource"><citetitle>PCI Resource |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 629 | Management</citetitle></link>. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 630 | </para> |
| 631 | </section> |
| 632 | |
| 633 | <section id="basic-flow-constructor-main-component"> |
| 634 | <title>4) Set the driver ID and name strings.</title> |
| 635 | <para> |
| 636 | <informalexample> |
| 637 | <programlisting> |
| 638 | <![CDATA[ |
| 639 | strcpy(card->driver, "My Chip"); |
| 640 | strcpy(card->shortname, "My Own Chip 123"); |
| 641 | sprintf(card->longname, "%s at 0x%lx irq %i", |
| 642 | card->shortname, chip->ioport, chip->irq); |
| 643 | ]]> |
| 644 | </programlisting> |
| 645 | </informalexample> |
| 646 | |
| 647 | The driver field holds the minimal ID string of the |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 648 | chip. This is used by alsa-lib's configurator, so keep it |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 649 | simple but unique. |
| 650 | Even the same driver can have different driver IDs to |
| 651 | distinguish the functionality of each chip type. |
| 652 | </para> |
| 653 | |
| 654 | <para> |
| 655 | The shortname field is a string shown as more verbose |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 656 | name. The longname field contains the information |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 657 | shown in <filename>/proc/asound/cards</filename>. |
| 658 | </para> |
| 659 | </section> |
| 660 | |
| 661 | <section id="basic-flow-constructor-create-other"> |
| 662 | <title>5) Create other components, such as mixer, MIDI, etc.</title> |
| 663 | <para> |
| 664 | Here you define the basic components such as |
| 665 | <link linkend="pcm-interface"><citetitle>PCM</citetitle></link>, |
| 666 | mixer (e.g. <link linkend="api-ac97"><citetitle>AC97</citetitle></link>), |
| 667 | MIDI (e.g. <link linkend="midi-interface"><citetitle>MPU-401</citetitle></link>), |
| 668 | and other interfaces. |
| 669 | Also, if you want a <link linkend="proc-interface"><citetitle>proc |
| 670 | file</citetitle></link>, define it here, too. |
| 671 | </para> |
| 672 | </section> |
| 673 | |
| 674 | <section id="basic-flow-constructor-register-card"> |
| 675 | <title>6) Register the card instance.</title> |
| 676 | <para> |
| 677 | <informalexample> |
| 678 | <programlisting> |
| 679 | <![CDATA[ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 680 | err = snd_card_register(card); |
| 681 | if (err < 0) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 682 | snd_card_free(card); |
| 683 | return err; |
| 684 | } |
| 685 | ]]> |
| 686 | </programlisting> |
| 687 | </informalexample> |
| 688 | </para> |
| 689 | |
| 690 | <para> |
| 691 | Will be explained in the section <link |
| 692 | linkend="card-management-registration"><citetitle>Management |
| 693 | of Cards and Components</citetitle></link>, too. |
| 694 | </para> |
| 695 | </section> |
| 696 | |
| 697 | <section id="basic-flow-constructor-set-pci"> |
| 698 | <title>7) Set the PCI driver data and return zero.</title> |
| 699 | <para> |
| 700 | <informalexample> |
| 701 | <programlisting> |
| 702 | <![CDATA[ |
| 703 | pci_set_drvdata(pci, card); |
| 704 | dev++; |
| 705 | return 0; |
| 706 | ]]> |
| 707 | </programlisting> |
| 708 | </informalexample> |
| 709 | |
| 710 | In the above, the card record is stored. This pointer is |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 711 | used in the remove callback and power-management |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 712 | callbacks, too. |
| 713 | </para> |
| 714 | </section> |
| 715 | </section> |
| 716 | |
| 717 | <section id="basic-flow-destructor"> |
| 718 | <title>Destructor</title> |
| 719 | <para> |
| 720 | The destructor, remove callback, simply releases the card |
| 721 | instance. Then the ALSA middle layer will release all the |
| 722 | attached components automatically. |
| 723 | </para> |
| 724 | |
| 725 | <para> |
| 726 | It would be typically like the following: |
| 727 | |
| 728 | <informalexample> |
| 729 | <programlisting> |
| 730 | <![CDATA[ |
| 731 | static void __devexit snd_mychip_remove(struct pci_dev *pci) |
| 732 | { |
| 733 | snd_card_free(pci_get_drvdata(pci)); |
| 734 | pci_set_drvdata(pci, NULL); |
| 735 | } |
| 736 | ]]> |
| 737 | </programlisting> |
| 738 | </informalexample> |
| 739 | |
| 740 | The above code assumes that the card pointer is set to the PCI |
| 741 | driver data. |
| 742 | </para> |
| 743 | </section> |
| 744 | |
| 745 | <section id="basic-flow-header-files"> |
| 746 | <title>Header Files</title> |
| 747 | <para> |
| 748 | For the above example, at least the following include files |
| 749 | are necessary. |
| 750 | |
| 751 | <informalexample> |
| 752 | <programlisting> |
| 753 | <![CDATA[ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 754 | #include <linux/init.h> |
| 755 | #include <linux/pci.h> |
| 756 | #include <linux/slab.h> |
| 757 | #include <sound/core.h> |
| 758 | #include <sound/initval.h> |
| 759 | ]]> |
| 760 | </programlisting> |
| 761 | </informalexample> |
| 762 | |
| 763 | where the last one is necessary only when module options are |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 764 | defined in the source file. If the code is split into several |
| 765 | files, the files without module options don't need them. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 766 | </para> |
| 767 | |
| 768 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 769 | In addition to these headers, you'll need |
| 770 | <filename><linux/interrupt.h></filename> for interrupt |
| 771 | handling, and <filename><asm/io.h></filename> for I/O |
| 772 | access. If you use the <function>mdelay()</function> or |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 773 | <function>udelay()</function> functions, you'll need to include |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 774 | <filename><linux/delay.h></filename> too. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 775 | </para> |
| 776 | |
| 777 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 778 | The ALSA interfaces like the PCM and control APIs are defined in other |
| 779 | <filename><sound/xxx.h></filename> header files. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 780 | They have to be included after |
| 781 | <filename><sound/core.h></filename>. |
| 782 | </para> |
| 783 | |
| 784 | </section> |
| 785 | </chapter> |
| 786 | |
| 787 | |
| 788 | <!-- ****************************************************** --> |
| 789 | <!-- Management of Cards and Components --> |
| 790 | <!-- ****************************************************** --> |
| 791 | <chapter id="card-management"> |
| 792 | <title>Management of Cards and Components</title> |
| 793 | |
| 794 | <section id="card-management-card-instance"> |
| 795 | <title>Card Instance</title> |
| 796 | <para> |
| 797 | For each soundcard, a <quote>card</quote> record must be allocated. |
| 798 | </para> |
| 799 | |
| 800 | <para> |
| 801 | A card record is the headquarters of the soundcard. It manages |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 802 | the whole list of devices (components) on the soundcard, such as |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 803 | PCM, mixers, MIDI, synthesizer, and so on. Also, the card |
| 804 | record holds the ID and the name strings of the card, manages |
| 805 | the root of proc files, and controls the power-management states |
| 806 | and hotplug disconnections. The component list on the card |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 807 | record is used to manage the correct release of resources at |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 808 | destruction. |
| 809 | </para> |
| 810 | |
| 811 | <para> |
| 812 | As mentioned above, to create a card instance, call |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 813 | <function>snd_card_create()</function>. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 814 | |
| 815 | <informalexample> |
| 816 | <programlisting> |
| 817 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 818 | struct snd_card *card; |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 819 | int err; |
| 820 | err = snd_card_create(index, id, module, extra_size, &card); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 821 | ]]> |
| 822 | </programlisting> |
| 823 | </informalexample> |
| 824 | </para> |
| 825 | |
| 826 | <para> |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 827 | The function takes five arguments, the card-index number, the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 828 | id string, the module pointer (usually |
| 829 | <constant>THIS_MODULE</constant>), |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 830 | the size of extra-data space, and the pointer to return the |
| 831 | card instance. The extra_size argument is used to |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 832 | allocate card->private_data for the |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 833 | chip-specific data. Note that these data |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 834 | are allocated by <function>snd_card_create()</function>. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 835 | </para> |
| 836 | </section> |
| 837 | |
| 838 | <section id="card-management-component"> |
| 839 | <title>Components</title> |
| 840 | <para> |
| 841 | After the card is created, you can attach the components |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 842 | (devices) to the card instance. In an ALSA driver, a component is |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 843 | represented as a struct <structname>snd_device</structname> object. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 844 | A component can be a PCM instance, a control interface, a raw |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 845 | MIDI interface, etc. Each such instance has one component |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 846 | entry. |
| 847 | </para> |
| 848 | |
| 849 | <para> |
| 850 | A component can be created via |
| 851 | <function>snd_device_new()</function> function. |
| 852 | |
| 853 | <informalexample> |
| 854 | <programlisting> |
| 855 | <![CDATA[ |
| 856 | snd_device_new(card, SNDRV_DEV_XXX, chip, &ops); |
| 857 | ]]> |
| 858 | </programlisting> |
| 859 | </informalexample> |
| 860 | </para> |
| 861 | |
| 862 | <para> |
| 863 | This takes the card pointer, the device-level |
| 864 | (<constant>SNDRV_DEV_XXX</constant>), the data pointer, and the |
| 865 | callback pointers (<parameter>&ops</parameter>). The |
| 866 | device-level defines the type of components and the order of |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 867 | registration and de-registration. For most components, the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 868 | device-level is already defined. For a user-defined component, |
| 869 | you can use <constant>SNDRV_DEV_LOWLEVEL</constant>. |
| 870 | </para> |
| 871 | |
| 872 | <para> |
| 873 | This function itself doesn't allocate the data space. The data |
| 874 | must be allocated manually beforehand, and its pointer is passed |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 875 | as the argument. This pointer is used as the |
| 876 | (<parameter>chip</parameter> identifier in the above example) |
| 877 | for the instance. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 878 | </para> |
| 879 | |
| 880 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 881 | Each pre-defined ALSA component such as ac97 and pcm calls |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 882 | <function>snd_device_new()</function> inside its |
| 883 | constructor. The destructor for each component is defined in the |
| 884 | callback pointers. Hence, you don't need to take care of |
| 885 | calling a destructor for such a component. |
| 886 | </para> |
| 887 | |
| 888 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 889 | If you wish to create your own component, you need to |
| 890 | set the destructor function to the dev_free callback in |
| 891 | the <parameter>ops</parameter>, so that it can be released |
| 892 | automatically via <function>snd_card_free()</function>. |
| 893 | The next example will show an implementation of chip-specific |
| 894 | data. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 895 | </para> |
| 896 | </section> |
| 897 | |
| 898 | <section id="card-management-chip-specific"> |
| 899 | <title>Chip-Specific Data</title> |
| 900 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 901 | Chip-specific information, e.g. the I/O port address, its |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 902 | resource pointer, or the irq number, is stored in the |
| 903 | chip-specific record. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 904 | |
| 905 | <informalexample> |
| 906 | <programlisting> |
| 907 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 908 | struct mychip { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 909 | .... |
| 910 | }; |
| 911 | ]]> |
| 912 | </programlisting> |
| 913 | </informalexample> |
| 914 | </para> |
| 915 | |
| 916 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 917 | In general, there are two ways of allocating the chip record. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 918 | </para> |
| 919 | |
| 920 | <section id="card-management-chip-specific-snd-card-new"> |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 921 | <title>1. Allocating via <function>snd_card_create()</function>.</title> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 922 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 923 | As mentioned above, you can pass the extra-data-length |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 924 | to the 4th argument of <function>snd_card_create()</function>, i.e. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 925 | |
| 926 | <informalexample> |
| 927 | <programlisting> |
| 928 | <![CDATA[ |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 929 | err = snd_card_create(index[dev], id[dev], THIS_MODULE, |
| 930 | sizeof(struct mychip), &card); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 931 | ]]> |
| 932 | </programlisting> |
| 933 | </informalexample> |
| 934 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 935 | struct <structname>mychip</structname> is the type of the chip record. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 936 | </para> |
| 937 | |
| 938 | <para> |
| 939 | In return, the allocated record can be accessed as |
| 940 | |
| 941 | <informalexample> |
| 942 | <programlisting> |
| 943 | <![CDATA[ |
Takashi Iwai | 437a5a4 | 2006-11-21 12:14:23 +0100 | [diff] [blame] | 944 | struct mychip *chip = card->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 945 | ]]> |
| 946 | </programlisting> |
| 947 | </informalexample> |
| 948 | |
| 949 | With this method, you don't have to allocate twice. |
| 950 | The record is released together with the card instance. |
| 951 | </para> |
| 952 | </section> |
| 953 | |
| 954 | <section id="card-management-chip-specific-allocate-extra"> |
| 955 | <title>2. Allocating an extra device.</title> |
| 956 | |
| 957 | <para> |
| 958 | After allocating a card instance via |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 959 | <function>snd_card_create()</function> (with |
| 960 | <constant>0</constant> on the 4th arg), call |
Takashi Iwai | 561b220 | 2005-09-09 14:22:34 +0200 | [diff] [blame] | 961 | <function>kzalloc()</function>. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 962 | |
| 963 | <informalexample> |
| 964 | <programlisting> |
| 965 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 966 | struct snd_card *card; |
| 967 | struct mychip *chip; |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 968 | err = snd_card_create(index[dev], id[dev], THIS_MODULE, 0, &card); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 969 | ..... |
Takashi Iwai | 561b220 | 2005-09-09 14:22:34 +0200 | [diff] [blame] | 970 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 971 | ]]> |
| 972 | </programlisting> |
| 973 | </informalexample> |
| 974 | </para> |
| 975 | |
| 976 | <para> |
| 977 | The chip record should have the field to hold the card |
| 978 | pointer at least, |
| 979 | |
| 980 | <informalexample> |
| 981 | <programlisting> |
| 982 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 983 | struct mychip { |
| 984 | struct snd_card *card; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 985 | .... |
| 986 | }; |
| 987 | ]]> |
| 988 | </programlisting> |
| 989 | </informalexample> |
| 990 | </para> |
| 991 | |
| 992 | <para> |
| 993 | Then, set the card pointer in the returned chip instance. |
| 994 | |
| 995 | <informalexample> |
| 996 | <programlisting> |
| 997 | <![CDATA[ |
| 998 | chip->card = card; |
| 999 | ]]> |
| 1000 | </programlisting> |
| 1001 | </informalexample> |
| 1002 | </para> |
| 1003 | |
| 1004 | <para> |
| 1005 | Next, initialize the fields, and register this chip |
| 1006 | record as a low-level device with a specified |
| 1007 | <parameter>ops</parameter>, |
| 1008 | |
| 1009 | <informalexample> |
| 1010 | <programlisting> |
| 1011 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1012 | static struct snd_device_ops ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1013 | .dev_free = snd_mychip_dev_free, |
| 1014 | }; |
| 1015 | .... |
| 1016 | snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops); |
| 1017 | ]]> |
| 1018 | </programlisting> |
| 1019 | </informalexample> |
| 1020 | |
| 1021 | <function>snd_mychip_dev_free()</function> is the |
| 1022 | device-destructor function, which will call the real |
| 1023 | destructor. |
| 1024 | </para> |
| 1025 | |
| 1026 | <para> |
| 1027 | <informalexample> |
| 1028 | <programlisting> |
| 1029 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1030 | static int snd_mychip_dev_free(struct snd_device *device) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1031 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1032 | return snd_mychip_free(device->device_data); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1033 | } |
| 1034 | ]]> |
| 1035 | </programlisting> |
| 1036 | </informalexample> |
| 1037 | |
| 1038 | where <function>snd_mychip_free()</function> is the real destructor. |
| 1039 | </para> |
| 1040 | </section> |
| 1041 | </section> |
| 1042 | |
| 1043 | <section id="card-management-registration"> |
| 1044 | <title>Registration and Release</title> |
| 1045 | <para> |
| 1046 | After all components are assigned, register the card instance |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1047 | by calling <function>snd_card_register()</function>. Access |
| 1048 | to the device files is enabled at this point. That is, before |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1049 | <function>snd_card_register()</function> is called, the |
| 1050 | components are safely inaccessible from external side. If this |
| 1051 | call fails, exit the probe function after releasing the card via |
| 1052 | <function>snd_card_free()</function>. |
| 1053 | </para> |
| 1054 | |
| 1055 | <para> |
| 1056 | For releasing the card instance, you can call simply |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1057 | <function>snd_card_free()</function>. As mentioned earlier, all |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1058 | components are released automatically by this call. |
| 1059 | </para> |
| 1060 | |
| 1061 | <para> |
| 1062 | As further notes, the destructors (both |
| 1063 | <function>snd_mychip_dev_free</function> and |
| 1064 | <function>snd_mychip_free</function>) cannot be defined with |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1065 | the <parameter>__devexit</parameter> prefix, because they may be |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1066 | called from the constructor, too, at the false path. |
| 1067 | </para> |
| 1068 | |
| 1069 | <para> |
| 1070 | For a device which allows hotplugging, you can use |
Takashi Iwai | 2b29b13 | 2006-06-23 14:38:26 +0200 | [diff] [blame] | 1071 | <function>snd_card_free_when_closed</function>. This one will |
| 1072 | postpone the destruction until all devices are closed. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1073 | </para> |
| 1074 | |
| 1075 | </section> |
| 1076 | |
| 1077 | </chapter> |
| 1078 | |
| 1079 | |
| 1080 | <!-- ****************************************************** --> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1081 | <!-- PCI Resource Management --> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1082 | <!-- ****************************************************** --> |
| 1083 | <chapter id="pci-resource"> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1084 | <title>PCI Resource Management</title> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1085 | |
| 1086 | <section id="pci-resource-example"> |
| 1087 | <title>Full Code Example</title> |
| 1088 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1089 | In this section, we'll complete the chip-specific constructor, |
| 1090 | destructor and PCI entries. Example code is shown first, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1091 | below. |
| 1092 | |
| 1093 | <example> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1094 | <title>PCI Resource Management Example</title> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1095 | <programlisting> |
| 1096 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1097 | struct mychip { |
| 1098 | struct snd_card *card; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1099 | struct pci_dev *pci; |
| 1100 | |
| 1101 | unsigned long port; |
| 1102 | int irq; |
| 1103 | }; |
| 1104 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1105 | static int snd_mychip_free(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1106 | { |
| 1107 | /* disable hardware here if any */ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1108 | .... /* (not implemented in this document) */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1109 | |
| 1110 | /* release the irq */ |
| 1111 | if (chip->irq >= 0) |
Takashi Iwai | 437a5a4 | 2006-11-21 12:14:23 +0100 | [diff] [blame] | 1112 | free_irq(chip->irq, chip); |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1113 | /* release the I/O ports & memory */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1114 | pci_release_regions(chip->pci); |
| 1115 | /* disable the PCI entry */ |
| 1116 | pci_disable_device(chip->pci); |
| 1117 | /* release the data */ |
| 1118 | kfree(chip); |
| 1119 | return 0; |
| 1120 | } |
| 1121 | |
| 1122 | /* chip-specific constructor */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1123 | static int __devinit snd_mychip_create(struct snd_card *card, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1124 | struct pci_dev *pci, |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1125 | struct mychip **rchip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1126 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1127 | struct mychip *chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1128 | int err; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1129 | static struct snd_device_ops ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1130 | .dev_free = snd_mychip_dev_free, |
| 1131 | }; |
| 1132 | |
| 1133 | *rchip = NULL; |
| 1134 | |
| 1135 | /* initialize the PCI entry */ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1136 | err = pci_enable_device(pci); |
| 1137 | if (err < 0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1138 | return err; |
| 1139 | /* check PCI availability (28bit DMA) */ |
Yang Hongyang | 2c5510d | 2009-04-06 19:01:19 -0700 | [diff] [blame] | 1140 | if (pci_set_dma_mask(pci, DMA_BIT_MASK(28)) < 0 || |
| 1141 | pci_set_consistent_dma_mask(pci, DMA_BIT_MASK(28)) < 0) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1142 | printk(KERN_ERR "error to set 28bit mask DMA\n"); |
| 1143 | pci_disable_device(pci); |
| 1144 | return -ENXIO; |
| 1145 | } |
| 1146 | |
Takashi Iwai | 561b220 | 2005-09-09 14:22:34 +0200 | [diff] [blame] | 1147 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1148 | if (chip == NULL) { |
| 1149 | pci_disable_device(pci); |
| 1150 | return -ENOMEM; |
| 1151 | } |
| 1152 | |
| 1153 | /* initialize the stuff */ |
| 1154 | chip->card = card; |
| 1155 | chip->pci = pci; |
| 1156 | chip->irq = -1; |
| 1157 | |
| 1158 | /* (1) PCI resource allocation */ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1159 | err = pci_request_regions(pci, "My Chip"); |
| 1160 | if (err < 0) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1161 | kfree(chip); |
| 1162 | pci_disable_device(pci); |
| 1163 | return err; |
| 1164 | } |
| 1165 | chip->port = pci_resource_start(pci, 0); |
| 1166 | if (request_irq(pci->irq, snd_mychip_interrupt, |
Takashi Iwai | ce1fd36 | 2011-06-14 08:54:14 +0200 | [diff] [blame] | 1167 | IRQF_SHARED, KBUILD_MODNAME, chip)) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1168 | printk(KERN_ERR "cannot grab irq %d\n", pci->irq); |
| 1169 | snd_mychip_free(chip); |
| 1170 | return -EBUSY; |
| 1171 | } |
| 1172 | chip->irq = pci->irq; |
| 1173 | |
| 1174 | /* (2) initialization of the chip hardware */ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1175 | .... /* (not implemented in this document) */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1176 | |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1177 | err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops); |
| 1178 | if (err < 0) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1179 | snd_mychip_free(chip); |
| 1180 | return err; |
| 1181 | } |
| 1182 | |
| 1183 | snd_card_set_dev(card, &pci->dev); |
| 1184 | |
| 1185 | *rchip = chip; |
| 1186 | return 0; |
| 1187 | } |
| 1188 | |
| 1189 | /* PCI IDs */ |
Takashi Iwai | f40b689 | 2006-07-05 16:51:05 +0200 | [diff] [blame] | 1190 | static struct pci_device_id snd_mychip_ids[] = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1191 | { PCI_VENDOR_ID_FOO, PCI_DEVICE_ID_BAR, |
| 1192 | PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, }, |
| 1193 | .... |
| 1194 | { 0, } |
| 1195 | }; |
| 1196 | MODULE_DEVICE_TABLE(pci, snd_mychip_ids); |
| 1197 | |
| 1198 | /* pci_driver definition */ |
| 1199 | static struct pci_driver driver = { |
Takashi Iwai | ce1fd36 | 2011-06-14 08:54:14 +0200 | [diff] [blame] | 1200 | .name = KBUILD_MODNAME, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1201 | .id_table = snd_mychip_ids, |
| 1202 | .probe = snd_mychip_probe, |
| 1203 | .remove = __devexit_p(snd_mychip_remove), |
| 1204 | }; |
| 1205 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1206 | /* module initialization */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1207 | static int __init alsa_card_mychip_init(void) |
| 1208 | { |
Takashi Iwai | 01d25d4 | 2005-04-11 16:58:24 +0200 | [diff] [blame] | 1209 | return pci_register_driver(&driver); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1210 | } |
| 1211 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1212 | /* module clean up */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1213 | static void __exit alsa_card_mychip_exit(void) |
| 1214 | { |
| 1215 | pci_unregister_driver(&driver); |
| 1216 | } |
| 1217 | |
| 1218 | module_init(alsa_card_mychip_init) |
| 1219 | module_exit(alsa_card_mychip_exit) |
| 1220 | |
| 1221 | EXPORT_NO_SYMBOLS; /* for old kernels only */ |
| 1222 | ]]> |
| 1223 | </programlisting> |
| 1224 | </example> |
| 1225 | </para> |
| 1226 | </section> |
| 1227 | |
| 1228 | <section id="pci-resource-some-haftas"> |
| 1229 | <title>Some Hafta's</title> |
| 1230 | <para> |
| 1231 | The allocation of PCI resources is done in the |
| 1232 | <function>probe()</function> function, and usually an extra |
| 1233 | <function>xxx_create()</function> function is written for this |
Tobias Klauser | 56b146d | 2006-04-10 22:54:21 -0700 | [diff] [blame] | 1234 | purpose. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1235 | </para> |
| 1236 | |
| 1237 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1238 | In the case of PCI devices, you first have to call |
| 1239 | the <function>pci_enable_device()</function> function before |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1240 | allocating resources. Also, you need to set the proper PCI DMA |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1241 | mask to limit the accessed I/O range. In some cases, you might |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1242 | need to call <function>pci_set_master()</function> function, |
Tobias Klauser | 56b146d | 2006-04-10 22:54:21 -0700 | [diff] [blame] | 1243 | too. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1244 | </para> |
| 1245 | |
| 1246 | <para> |
| 1247 | Suppose the 28bit mask, and the code to be added would be like: |
| 1248 | |
| 1249 | <informalexample> |
| 1250 | <programlisting> |
| 1251 | <![CDATA[ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1252 | err = pci_enable_device(pci); |
| 1253 | if (err < 0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1254 | return err; |
Yang Hongyang | 2c5510d | 2009-04-06 19:01:19 -0700 | [diff] [blame] | 1255 | if (pci_set_dma_mask(pci, DMA_BIT_MASK(28)) < 0 || |
| 1256 | pci_set_consistent_dma_mask(pci, DMA_BIT_MASK(28)) < 0) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1257 | printk(KERN_ERR "error to set 28bit mask DMA\n"); |
| 1258 | pci_disable_device(pci); |
| 1259 | return -ENXIO; |
| 1260 | } |
| 1261 | |
| 1262 | ]]> |
| 1263 | </programlisting> |
| 1264 | </informalexample> |
| 1265 | </para> |
| 1266 | </section> |
| 1267 | |
| 1268 | <section id="pci-resource-resource-allocation"> |
| 1269 | <title>Resource Allocation</title> |
| 1270 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1271 | The allocation of I/O ports and irqs is done via standard kernel |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1272 | functions. Unlike ALSA ver.0.5.x., there are no helpers for |
| 1273 | that. And these resources must be released in the destructor |
| 1274 | function (see below). Also, on ALSA 0.9.x, you don't need to |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1275 | allocate (pseudo-)DMA for PCI like in ALSA 0.5.x. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1276 | </para> |
| 1277 | |
| 1278 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1279 | Now assume that the PCI device has an I/O port with 8 bytes |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1280 | and an interrupt. Then struct <structname>mychip</structname> will have the |
Tobias Klauser | 56b146d | 2006-04-10 22:54:21 -0700 | [diff] [blame] | 1281 | following fields: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1282 | |
| 1283 | <informalexample> |
| 1284 | <programlisting> |
| 1285 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1286 | struct mychip { |
| 1287 | struct snd_card *card; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1288 | |
| 1289 | unsigned long port; |
| 1290 | int irq; |
| 1291 | }; |
| 1292 | ]]> |
| 1293 | </programlisting> |
| 1294 | </informalexample> |
| 1295 | </para> |
| 1296 | |
| 1297 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1298 | For an I/O port (and also a memory region), you need to have |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1299 | the resource pointer for the standard resource management. For |
| 1300 | an irq, you have to keep only the irq number (integer). But you |
| 1301 | need to initialize this number as -1 before actual allocation, |
| 1302 | since irq 0 is valid. The port address and its resource pointer |
| 1303 | can be initialized as null by |
Takashi Iwai | 561b220 | 2005-09-09 14:22:34 +0200 | [diff] [blame] | 1304 | <function>kzalloc()</function> automatically, so you |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1305 | don't have to take care of resetting them. |
| 1306 | </para> |
| 1307 | |
| 1308 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1309 | The allocation of an I/O port is done like this: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1310 | |
| 1311 | <informalexample> |
| 1312 | <programlisting> |
| 1313 | <![CDATA[ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1314 | err = pci_request_regions(pci, "My Chip"); |
| 1315 | if (err < 0) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1316 | kfree(chip); |
| 1317 | pci_disable_device(pci); |
| 1318 | return err; |
| 1319 | } |
| 1320 | chip->port = pci_resource_start(pci, 0); |
| 1321 | ]]> |
| 1322 | </programlisting> |
| 1323 | </informalexample> |
| 1324 | </para> |
| 1325 | |
| 1326 | <para> |
| 1327 | <!-- obsolete --> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1328 | It will reserve the I/O port region of 8 bytes of the given |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1329 | PCI device. The returned value, chip->res_port, is allocated |
| 1330 | via <function>kmalloc()</function> by |
| 1331 | <function>request_region()</function>. The pointer must be |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1332 | released via <function>kfree()</function>, but there is a |
| 1333 | problem with this. This issue will be explained later. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1334 | </para> |
| 1335 | |
| 1336 | <para> |
| 1337 | The allocation of an interrupt source is done like this: |
| 1338 | |
| 1339 | <informalexample> |
| 1340 | <programlisting> |
| 1341 | <![CDATA[ |
| 1342 | if (request_irq(pci->irq, snd_mychip_interrupt, |
Takashi Iwai | ce1fd36 | 2011-06-14 08:54:14 +0200 | [diff] [blame] | 1343 | IRQF_SHARED, KBUILD_MODNAME, chip)) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1344 | printk(KERN_ERR "cannot grab irq %d\n", pci->irq); |
| 1345 | snd_mychip_free(chip); |
| 1346 | return -EBUSY; |
| 1347 | } |
| 1348 | chip->irq = pci->irq; |
| 1349 | ]]> |
| 1350 | </programlisting> |
| 1351 | </informalexample> |
| 1352 | |
| 1353 | where <function>snd_mychip_interrupt()</function> is the |
| 1354 | interrupt handler defined <link |
| 1355 | linkend="pcm-interface-interrupt-handler"><citetitle>later</citetitle></link>. |
| 1356 | Note that chip->irq should be defined |
| 1357 | only when <function>request_irq()</function> succeeded. |
| 1358 | </para> |
| 1359 | |
| 1360 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1361 | On the PCI bus, interrupts can be shared. Thus, |
| 1362 | <constant>IRQF_SHARED</constant> is used as the interrupt flag of |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1363 | <function>request_irq()</function>. |
| 1364 | </para> |
| 1365 | |
| 1366 | <para> |
| 1367 | The last argument of <function>request_irq()</function> is the |
| 1368 | data pointer passed to the interrupt handler. Usually, the |
| 1369 | chip-specific record is used for that, but you can use what you |
| 1370 | like, too. |
| 1371 | </para> |
| 1372 | |
| 1373 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1374 | I won't give details about the interrupt handler at this |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1375 | point, but at least its appearance can be explained now. The |
| 1376 | interrupt handler looks usually like the following: |
| 1377 | |
| 1378 | <informalexample> |
| 1379 | <programlisting> |
| 1380 | <![CDATA[ |
Takashi Iwai | ad4d1de | 2007-01-16 17:46:35 +0100 | [diff] [blame] | 1381 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1382 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1383 | struct mychip *chip = dev_id; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1384 | .... |
| 1385 | return IRQ_HANDLED; |
| 1386 | } |
| 1387 | ]]> |
| 1388 | </programlisting> |
| 1389 | </informalexample> |
| 1390 | </para> |
| 1391 | |
| 1392 | <para> |
| 1393 | Now let's write the corresponding destructor for the resources |
| 1394 | above. The role of destructor is simple: disable the hardware |
| 1395 | (if already activated) and release the resources. So far, we |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1396 | have no hardware part, so the disabling code is not written here. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1397 | </para> |
| 1398 | |
| 1399 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1400 | To release the resources, the <quote>check-and-release</quote> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1401 | method is a safer way. For the interrupt, do like this: |
| 1402 | |
| 1403 | <informalexample> |
| 1404 | <programlisting> |
| 1405 | <![CDATA[ |
| 1406 | if (chip->irq >= 0) |
Takashi Iwai | 437a5a4 | 2006-11-21 12:14:23 +0100 | [diff] [blame] | 1407 | free_irq(chip->irq, chip); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1408 | ]]> |
| 1409 | </programlisting> |
| 1410 | </informalexample> |
| 1411 | |
| 1412 | Since the irq number can start from 0, you should initialize |
| 1413 | chip->irq with a negative value (e.g. -1), so that you can |
| 1414 | check the validity of the irq number as above. |
| 1415 | </para> |
| 1416 | |
| 1417 | <para> |
| 1418 | When you requested I/O ports or memory regions via |
| 1419 | <function>pci_request_region()</function> or |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1420 | <function>pci_request_regions()</function> like in this example, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1421 | release the resource(s) using the corresponding function, |
| 1422 | <function>pci_release_region()</function> or |
| 1423 | <function>pci_release_regions()</function>. |
| 1424 | |
| 1425 | <informalexample> |
| 1426 | <programlisting> |
| 1427 | <![CDATA[ |
| 1428 | pci_release_regions(chip->pci); |
| 1429 | ]]> |
| 1430 | </programlisting> |
| 1431 | </informalexample> |
| 1432 | </para> |
| 1433 | |
| 1434 | <para> |
| 1435 | When you requested manually via <function>request_region()</function> |
| 1436 | or <function>request_mem_region</function>, you can release it via |
| 1437 | <function>release_resource()</function>. Suppose that you keep |
| 1438 | the resource pointer returned from <function>request_region()</function> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1439 | in chip->res_port, the release procedure looks like: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1440 | |
| 1441 | <informalexample> |
| 1442 | <programlisting> |
| 1443 | <![CDATA[ |
Takashi Iwai | b1d5776 | 2005-10-10 11:56:31 +0200 | [diff] [blame] | 1444 | release_and_free_resource(chip->res_port); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1445 | ]]> |
| 1446 | </programlisting> |
| 1447 | </informalexample> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1448 | </para> |
| 1449 | |
| 1450 | <para> |
| 1451 | Don't forget to call <function>pci_disable_device()</function> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1452 | before the end. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1453 | </para> |
| 1454 | |
| 1455 | <para> |
| 1456 | And finally, release the chip-specific record. |
| 1457 | |
| 1458 | <informalexample> |
| 1459 | <programlisting> |
| 1460 | <![CDATA[ |
| 1461 | kfree(chip); |
| 1462 | ]]> |
| 1463 | </programlisting> |
| 1464 | </informalexample> |
| 1465 | </para> |
| 1466 | |
| 1467 | <para> |
| 1468 | Again, remember that you cannot |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1469 | use the <parameter>__devexit</parameter> prefix for this destructor. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1470 | </para> |
| 1471 | |
| 1472 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1473 | We didn't implement the hardware disabling part in the above. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1474 | If you need to do this, please note that the destructor may be |
| 1475 | called even before the initialization of the chip is completed. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1476 | It would be better to have a flag to skip hardware disabling |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1477 | if the hardware was not initialized yet. |
| 1478 | </para> |
| 1479 | |
| 1480 | <para> |
| 1481 | When the chip-data is assigned to the card using |
| 1482 | <function>snd_device_new()</function> with |
| 1483 | <constant>SNDRV_DEV_LOWLELVEL</constant> , its destructor is |
| 1484 | called at the last. That is, it is assured that all other |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1485 | components like PCMs and controls have already been released. |
| 1486 | You don't have to stop PCMs, etc. explicitly, but just |
| 1487 | call low-level hardware stopping. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1488 | </para> |
| 1489 | |
| 1490 | <para> |
| 1491 | The management of a memory-mapped region is almost as same as |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1492 | the management of an I/O port. You'll need three fields like |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1493 | the following: |
| 1494 | |
| 1495 | <informalexample> |
| 1496 | <programlisting> |
| 1497 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1498 | struct mychip { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1499 | .... |
| 1500 | unsigned long iobase_phys; |
| 1501 | void __iomem *iobase_virt; |
| 1502 | }; |
| 1503 | ]]> |
| 1504 | </programlisting> |
| 1505 | </informalexample> |
| 1506 | |
| 1507 | and the allocation would be like below: |
| 1508 | |
| 1509 | <informalexample> |
| 1510 | <programlisting> |
| 1511 | <![CDATA[ |
| 1512 | if ((err = pci_request_regions(pci, "My Chip")) < 0) { |
| 1513 | kfree(chip); |
| 1514 | return err; |
| 1515 | } |
| 1516 | chip->iobase_phys = pci_resource_start(pci, 0); |
| 1517 | chip->iobase_virt = ioremap_nocache(chip->iobase_phys, |
| 1518 | pci_resource_len(pci, 0)); |
| 1519 | ]]> |
| 1520 | </programlisting> |
| 1521 | </informalexample> |
| 1522 | |
| 1523 | and the corresponding destructor would be: |
| 1524 | |
| 1525 | <informalexample> |
| 1526 | <programlisting> |
| 1527 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1528 | static int snd_mychip_free(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1529 | { |
| 1530 | .... |
| 1531 | if (chip->iobase_virt) |
| 1532 | iounmap(chip->iobase_virt); |
| 1533 | .... |
| 1534 | pci_release_regions(chip->pci); |
| 1535 | .... |
| 1536 | } |
| 1537 | ]]> |
| 1538 | </programlisting> |
| 1539 | </informalexample> |
| 1540 | </para> |
| 1541 | |
| 1542 | </section> |
| 1543 | |
| 1544 | <section id="pci-resource-device-struct"> |
| 1545 | <title>Registration of Device Struct</title> |
| 1546 | <para> |
| 1547 | At some point, typically after calling <function>snd_device_new()</function>, |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1548 | you need to register the struct <structname>device</structname> of the chip |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1549 | you're handling for udev and co. ALSA provides a macro for compatibility with |
| 1550 | older kernels. Simply call like the following: |
| 1551 | <informalexample> |
| 1552 | <programlisting> |
| 1553 | <![CDATA[ |
| 1554 | snd_card_set_dev(card, &pci->dev); |
| 1555 | ]]> |
| 1556 | </programlisting> |
| 1557 | </informalexample> |
| 1558 | so that it stores the PCI's device pointer to the card. This will be |
| 1559 | referred by ALSA core functions later when the devices are registered. |
| 1560 | </para> |
| 1561 | <para> |
| 1562 | In the case of non-PCI, pass the proper device struct pointer of the BUS |
| 1563 | instead. (In the case of legacy ISA without PnP, you don't have to do |
| 1564 | anything.) |
| 1565 | </para> |
| 1566 | </section> |
| 1567 | |
| 1568 | <section id="pci-resource-entries"> |
| 1569 | <title>PCI Entries</title> |
| 1570 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1571 | So far, so good. Let's finish the missing PCI |
| 1572 | stuff. At first, we need a |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1573 | <structname>pci_device_id</structname> table for this |
| 1574 | chipset. It's a table of PCI vendor/device ID number, and some |
| 1575 | masks. |
| 1576 | </para> |
| 1577 | |
| 1578 | <para> |
| 1579 | For example, |
| 1580 | |
| 1581 | <informalexample> |
| 1582 | <programlisting> |
| 1583 | <![CDATA[ |
Takashi Iwai | f40b689 | 2006-07-05 16:51:05 +0200 | [diff] [blame] | 1584 | static struct pci_device_id snd_mychip_ids[] = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1585 | { PCI_VENDOR_ID_FOO, PCI_DEVICE_ID_BAR, |
| 1586 | PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, }, |
| 1587 | .... |
| 1588 | { 0, } |
| 1589 | }; |
| 1590 | MODULE_DEVICE_TABLE(pci, snd_mychip_ids); |
| 1591 | ]]> |
| 1592 | </programlisting> |
| 1593 | </informalexample> |
| 1594 | </para> |
| 1595 | |
| 1596 | <para> |
| 1597 | The first and second fields of |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1598 | the <structname>pci_device_id</structname> structure are the vendor and |
| 1599 | device IDs. If you have no reason to filter the matching |
| 1600 | devices, you can leave the remaining fields as above. The last |
| 1601 | field of the <structname>pci_device_id</structname> struct contains |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1602 | private data for this entry. You can specify any value here, for |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1603 | example, to define specific operations for supported device IDs. |
| 1604 | Such an example is found in the intel8x0 driver. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1605 | </para> |
| 1606 | |
| 1607 | <para> |
| 1608 | The last entry of this list is the terminator. You must |
| 1609 | specify this all-zero entry. |
| 1610 | </para> |
| 1611 | |
| 1612 | <para> |
| 1613 | Then, prepare the <structname>pci_driver</structname> record: |
| 1614 | |
| 1615 | <informalexample> |
| 1616 | <programlisting> |
| 1617 | <![CDATA[ |
| 1618 | static struct pci_driver driver = { |
Takashi Iwai | ce1fd36 | 2011-06-14 08:54:14 +0200 | [diff] [blame] | 1619 | .name = KBUILD_MODNAME, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1620 | .id_table = snd_mychip_ids, |
| 1621 | .probe = snd_mychip_probe, |
| 1622 | .remove = __devexit_p(snd_mychip_remove), |
| 1623 | }; |
| 1624 | ]]> |
| 1625 | </programlisting> |
| 1626 | </informalexample> |
| 1627 | </para> |
| 1628 | |
| 1629 | <para> |
| 1630 | The <structfield>probe</structfield> and |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1631 | <structfield>remove</structfield> functions have already |
| 1632 | been defined in the previous sections. |
| 1633 | The <structfield>remove</structfield> function should |
| 1634 | be defined with the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1635 | <function>__devexit_p()</function> macro, so that it's not |
| 1636 | defined for built-in (and non-hot-pluggable) case. The |
| 1637 | <structfield>name</structfield> |
| 1638 | field is the name string of this device. Note that you must not |
| 1639 | use a slash <quote>/</quote> in this string. |
| 1640 | </para> |
| 1641 | |
| 1642 | <para> |
| 1643 | And at last, the module entries: |
| 1644 | |
| 1645 | <informalexample> |
| 1646 | <programlisting> |
| 1647 | <![CDATA[ |
| 1648 | static int __init alsa_card_mychip_init(void) |
| 1649 | { |
Takashi Iwai | 01d25d4 | 2005-04-11 16:58:24 +0200 | [diff] [blame] | 1650 | return pci_register_driver(&driver); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1651 | } |
| 1652 | |
| 1653 | static void __exit alsa_card_mychip_exit(void) |
| 1654 | { |
| 1655 | pci_unregister_driver(&driver); |
| 1656 | } |
| 1657 | |
| 1658 | module_init(alsa_card_mychip_init) |
| 1659 | module_exit(alsa_card_mychip_exit) |
| 1660 | ]]> |
| 1661 | </programlisting> |
| 1662 | </informalexample> |
| 1663 | </para> |
| 1664 | |
| 1665 | <para> |
| 1666 | Note that these module entries are tagged with |
| 1667 | <parameter>__init</parameter> and |
| 1668 | <parameter>__exit</parameter> prefixes, not |
| 1669 | <parameter>__devinit</parameter> nor |
| 1670 | <parameter>__devexit</parameter>. |
| 1671 | </para> |
| 1672 | |
| 1673 | <para> |
| 1674 | Oh, one thing was forgotten. If you have no exported symbols, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1675 | you need to declare it in 2.2 or 2.4 kernels (it's not necessary in 2.6 kernels). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1676 | |
| 1677 | <informalexample> |
| 1678 | <programlisting> |
| 1679 | <![CDATA[ |
| 1680 | EXPORT_NO_SYMBOLS; |
| 1681 | ]]> |
| 1682 | </programlisting> |
| 1683 | </informalexample> |
| 1684 | |
| 1685 | That's all! |
| 1686 | </para> |
| 1687 | </section> |
| 1688 | </chapter> |
| 1689 | |
| 1690 | |
| 1691 | <!-- ****************************************************** --> |
| 1692 | <!-- PCM Interface --> |
| 1693 | <!-- ****************************************************** --> |
| 1694 | <chapter id="pcm-interface"> |
| 1695 | <title>PCM Interface</title> |
| 1696 | |
| 1697 | <section id="pcm-interface-general"> |
| 1698 | <title>General</title> |
| 1699 | <para> |
| 1700 | The PCM middle layer of ALSA is quite powerful and it is only |
| 1701 | necessary for each driver to implement the low-level functions |
| 1702 | to access its hardware. |
| 1703 | </para> |
| 1704 | |
| 1705 | <para> |
| 1706 | For accessing to the PCM layer, you need to include |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1707 | <filename><sound/pcm.h></filename> first. In addition, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1708 | <filename><sound/pcm_params.h></filename> might be needed |
| 1709 | if you access to some functions related with hw_param. |
| 1710 | </para> |
| 1711 | |
| 1712 | <para> |
| 1713 | Each card device can have up to four pcm instances. A pcm |
| 1714 | instance corresponds to a pcm device file. The limitation of |
| 1715 | number of instances comes only from the available bit size of |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1716 | the Linux's device numbers. Once when 64bit device number is |
| 1717 | used, we'll have more pcm instances available. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1718 | </para> |
| 1719 | |
| 1720 | <para> |
| 1721 | A pcm instance consists of pcm playback and capture streams, |
| 1722 | and each pcm stream consists of one or more pcm substreams. Some |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1723 | soundcards support multiple playback functions. For example, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1724 | emu10k1 has a PCM playback of 32 stereo substreams. In this case, at |
| 1725 | each open, a free substream is (usually) automatically chosen |
| 1726 | and opened. Meanwhile, when only one substream exists and it was |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1727 | already opened, the successful open will either block |
| 1728 | or error with <constant>EAGAIN</constant> according to the |
| 1729 | file open mode. But you don't have to care about such details in your |
| 1730 | driver. The PCM middle layer will take care of such work. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1731 | </para> |
| 1732 | </section> |
| 1733 | |
| 1734 | <section id="pcm-interface-example"> |
| 1735 | <title>Full Code Example</title> |
| 1736 | <para> |
| 1737 | The example code below does not include any hardware access |
| 1738 | routines but shows only the skeleton, how to build up the PCM |
| 1739 | interfaces. |
| 1740 | |
| 1741 | <example> |
| 1742 | <title>PCM Example Code</title> |
| 1743 | <programlisting> |
| 1744 | <![CDATA[ |
| 1745 | #include <sound/pcm.h> |
| 1746 | .... |
| 1747 | |
| 1748 | /* hardware definition */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1749 | static struct snd_pcm_hardware snd_mychip_playback_hw = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1750 | .info = (SNDRV_PCM_INFO_MMAP | |
| 1751 | SNDRV_PCM_INFO_INTERLEAVED | |
| 1752 | SNDRV_PCM_INFO_BLOCK_TRANSFER | |
| 1753 | SNDRV_PCM_INFO_MMAP_VALID), |
| 1754 | .formats = SNDRV_PCM_FMTBIT_S16_LE, |
| 1755 | .rates = SNDRV_PCM_RATE_8000_48000, |
| 1756 | .rate_min = 8000, |
| 1757 | .rate_max = 48000, |
| 1758 | .channels_min = 2, |
| 1759 | .channels_max = 2, |
| 1760 | .buffer_bytes_max = 32768, |
| 1761 | .period_bytes_min = 4096, |
| 1762 | .period_bytes_max = 32768, |
| 1763 | .periods_min = 1, |
| 1764 | .periods_max = 1024, |
| 1765 | }; |
| 1766 | |
| 1767 | /* hardware definition */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1768 | static struct snd_pcm_hardware snd_mychip_capture_hw = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1769 | .info = (SNDRV_PCM_INFO_MMAP | |
| 1770 | SNDRV_PCM_INFO_INTERLEAVED | |
| 1771 | SNDRV_PCM_INFO_BLOCK_TRANSFER | |
| 1772 | SNDRV_PCM_INFO_MMAP_VALID), |
| 1773 | .formats = SNDRV_PCM_FMTBIT_S16_LE, |
| 1774 | .rates = SNDRV_PCM_RATE_8000_48000, |
| 1775 | .rate_min = 8000, |
| 1776 | .rate_max = 48000, |
| 1777 | .channels_min = 2, |
| 1778 | .channels_max = 2, |
| 1779 | .buffer_bytes_max = 32768, |
| 1780 | .period_bytes_min = 4096, |
| 1781 | .period_bytes_max = 32768, |
| 1782 | .periods_min = 1, |
| 1783 | .periods_max = 1024, |
| 1784 | }; |
| 1785 | |
| 1786 | /* open callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1787 | static int snd_mychip_playback_open(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1788 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1789 | struct mychip *chip = snd_pcm_substream_chip(substream); |
| 1790 | struct snd_pcm_runtime *runtime = substream->runtime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1791 | |
| 1792 | runtime->hw = snd_mychip_playback_hw; |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1793 | /* more hardware-initialization will be done here */ |
| 1794 | .... |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1795 | return 0; |
| 1796 | } |
| 1797 | |
| 1798 | /* close callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1799 | static int snd_mychip_playback_close(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1800 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1801 | struct mychip *chip = snd_pcm_substream_chip(substream); |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1802 | /* the hardware-specific codes will be here */ |
| 1803 | .... |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1804 | return 0; |
| 1805 | |
| 1806 | } |
| 1807 | |
| 1808 | /* open callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1809 | static int snd_mychip_capture_open(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1810 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1811 | struct mychip *chip = snd_pcm_substream_chip(substream); |
| 1812 | struct snd_pcm_runtime *runtime = substream->runtime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1813 | |
| 1814 | runtime->hw = snd_mychip_capture_hw; |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1815 | /* more hardware-initialization will be done here */ |
| 1816 | .... |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1817 | return 0; |
| 1818 | } |
| 1819 | |
| 1820 | /* close callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1821 | static int snd_mychip_capture_close(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1822 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1823 | struct mychip *chip = snd_pcm_substream_chip(substream); |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1824 | /* the hardware-specific codes will be here */ |
| 1825 | .... |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1826 | return 0; |
| 1827 | |
| 1828 | } |
| 1829 | |
| 1830 | /* hw_params callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1831 | static int snd_mychip_pcm_hw_params(struct snd_pcm_substream *substream, |
| 1832 | struct snd_pcm_hw_params *hw_params) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1833 | { |
| 1834 | return snd_pcm_lib_malloc_pages(substream, |
| 1835 | params_buffer_bytes(hw_params)); |
| 1836 | } |
| 1837 | |
| 1838 | /* hw_free callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1839 | static int snd_mychip_pcm_hw_free(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1840 | { |
| 1841 | return snd_pcm_lib_free_pages(substream); |
| 1842 | } |
| 1843 | |
| 1844 | /* prepare callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1845 | static int snd_mychip_pcm_prepare(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1846 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1847 | struct mychip *chip = snd_pcm_substream_chip(substream); |
| 1848 | struct snd_pcm_runtime *runtime = substream->runtime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1849 | |
| 1850 | /* set up the hardware with the current configuration |
| 1851 | * for example... |
| 1852 | */ |
| 1853 | mychip_set_sample_format(chip, runtime->format); |
| 1854 | mychip_set_sample_rate(chip, runtime->rate); |
| 1855 | mychip_set_channels(chip, runtime->channels); |
Takashi Iwai | 0b7bed4 | 2006-03-02 15:35:55 +0100 | [diff] [blame] | 1856 | mychip_set_dma_setup(chip, runtime->dma_addr, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1857 | chip->buffer_size, |
| 1858 | chip->period_size); |
| 1859 | return 0; |
| 1860 | } |
| 1861 | |
| 1862 | /* trigger callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1863 | static int snd_mychip_pcm_trigger(struct snd_pcm_substream *substream, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1864 | int cmd) |
| 1865 | { |
| 1866 | switch (cmd) { |
| 1867 | case SNDRV_PCM_TRIGGER_START: |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1868 | /* do something to start the PCM engine */ |
| 1869 | .... |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1870 | break; |
| 1871 | case SNDRV_PCM_TRIGGER_STOP: |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1872 | /* do something to stop the PCM engine */ |
| 1873 | .... |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1874 | break; |
| 1875 | default: |
| 1876 | return -EINVAL; |
| 1877 | } |
| 1878 | } |
| 1879 | |
| 1880 | /* pointer callback */ |
| 1881 | static snd_pcm_uframes_t |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1882 | snd_mychip_pcm_pointer(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1883 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1884 | struct mychip *chip = snd_pcm_substream_chip(substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1885 | unsigned int current_ptr; |
| 1886 | |
| 1887 | /* get the current hardware pointer */ |
| 1888 | current_ptr = mychip_get_hw_pointer(chip); |
| 1889 | return current_ptr; |
| 1890 | } |
| 1891 | |
| 1892 | /* operators */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1893 | static struct snd_pcm_ops snd_mychip_playback_ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1894 | .open = snd_mychip_playback_open, |
| 1895 | .close = snd_mychip_playback_close, |
| 1896 | .ioctl = snd_pcm_lib_ioctl, |
| 1897 | .hw_params = snd_mychip_pcm_hw_params, |
| 1898 | .hw_free = snd_mychip_pcm_hw_free, |
| 1899 | .prepare = snd_mychip_pcm_prepare, |
| 1900 | .trigger = snd_mychip_pcm_trigger, |
| 1901 | .pointer = snd_mychip_pcm_pointer, |
| 1902 | }; |
| 1903 | |
| 1904 | /* operators */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1905 | static struct snd_pcm_ops snd_mychip_capture_ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1906 | .open = snd_mychip_capture_open, |
| 1907 | .close = snd_mychip_capture_close, |
| 1908 | .ioctl = snd_pcm_lib_ioctl, |
| 1909 | .hw_params = snd_mychip_pcm_hw_params, |
| 1910 | .hw_free = snd_mychip_pcm_hw_free, |
| 1911 | .prepare = snd_mychip_pcm_prepare, |
| 1912 | .trigger = snd_mychip_pcm_trigger, |
| 1913 | .pointer = snd_mychip_pcm_pointer, |
| 1914 | }; |
| 1915 | |
| 1916 | /* |
| 1917 | * definitions of capture are omitted here... |
| 1918 | */ |
| 1919 | |
| 1920 | /* create a pcm device */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1921 | static int __devinit snd_mychip_new_pcm(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1922 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1923 | struct snd_pcm *pcm; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1924 | int err; |
| 1925 | |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1926 | err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1, &pcm); |
| 1927 | if (err < 0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1928 | return err; |
| 1929 | pcm->private_data = chip; |
| 1930 | strcpy(pcm->name, "My Chip"); |
| 1931 | chip->pcm = pcm; |
| 1932 | /* set operators */ |
| 1933 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, |
| 1934 | &snd_mychip_playback_ops); |
| 1935 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, |
| 1936 | &snd_mychip_capture_ops); |
| 1937 | /* pre-allocation of buffers */ |
| 1938 | /* NOTE: this may fail */ |
| 1939 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, |
| 1940 | snd_dma_pci_data(chip->pci), |
| 1941 | 64*1024, 64*1024); |
| 1942 | return 0; |
| 1943 | } |
| 1944 | ]]> |
| 1945 | </programlisting> |
| 1946 | </example> |
| 1947 | </para> |
| 1948 | </section> |
| 1949 | |
| 1950 | <section id="pcm-interface-constructor"> |
| 1951 | <title>Constructor</title> |
| 1952 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1953 | A pcm instance is allocated by the <function>snd_pcm_new()</function> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1954 | function. It would be better to create a constructor for pcm, |
| 1955 | namely, |
| 1956 | |
| 1957 | <informalexample> |
| 1958 | <programlisting> |
| 1959 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1960 | static int __devinit snd_mychip_new_pcm(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1961 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1962 | struct snd_pcm *pcm; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1963 | int err; |
| 1964 | |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 1965 | err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1, &pcm); |
| 1966 | if (err < 0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1967 | return err; |
| 1968 | pcm->private_data = chip; |
| 1969 | strcpy(pcm->name, "My Chip"); |
| 1970 | chip->pcm = pcm; |
| 1971 | .... |
| 1972 | return 0; |
| 1973 | } |
| 1974 | ]]> |
| 1975 | </programlisting> |
| 1976 | </informalexample> |
| 1977 | </para> |
| 1978 | |
| 1979 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1980 | The <function>snd_pcm_new()</function> function takes four |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1981 | arguments. The first argument is the card pointer to which this |
| 1982 | pcm is assigned, and the second is the ID string. |
| 1983 | </para> |
| 1984 | |
| 1985 | <para> |
| 1986 | The third argument (<parameter>index</parameter>, 0 in the |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1987 | above) is the index of this new pcm. It begins from zero. If |
| 1988 | you create more than one pcm instances, specify the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1989 | different numbers in this argument. For example, |
| 1990 | <parameter>index</parameter> = 1 for the second PCM device. |
| 1991 | </para> |
| 1992 | |
| 1993 | <para> |
| 1994 | The fourth and fifth arguments are the number of substreams |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 1995 | for playback and capture, respectively. Here 1 is used for |
| 1996 | both arguments. When no playback or capture substreams are available, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1997 | pass 0 to the corresponding argument. |
| 1998 | </para> |
| 1999 | |
| 2000 | <para> |
| 2001 | If a chip supports multiple playbacks or captures, you can |
| 2002 | specify more numbers, but they must be handled properly in |
| 2003 | open/close, etc. callbacks. When you need to know which |
| 2004 | substream you are referring to, then it can be obtained from |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2005 | struct <structname>snd_pcm_substream</structname> data passed to each callback |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2006 | as follows: |
| 2007 | |
| 2008 | <informalexample> |
| 2009 | <programlisting> |
| 2010 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2011 | struct snd_pcm_substream *substream; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2012 | int index = substream->number; |
| 2013 | ]]> |
| 2014 | </programlisting> |
| 2015 | </informalexample> |
| 2016 | </para> |
| 2017 | |
| 2018 | <para> |
| 2019 | After the pcm is created, you need to set operators for each |
| 2020 | pcm stream. |
| 2021 | |
| 2022 | <informalexample> |
| 2023 | <programlisting> |
| 2024 | <![CDATA[ |
| 2025 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, |
| 2026 | &snd_mychip_playback_ops); |
| 2027 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, |
| 2028 | &snd_mychip_capture_ops); |
| 2029 | ]]> |
| 2030 | </programlisting> |
| 2031 | </informalexample> |
| 2032 | </para> |
| 2033 | |
| 2034 | <para> |
| 2035 | The operators are defined typically like this: |
| 2036 | |
| 2037 | <informalexample> |
| 2038 | <programlisting> |
| 2039 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2040 | static struct snd_pcm_ops snd_mychip_playback_ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2041 | .open = snd_mychip_pcm_open, |
| 2042 | .close = snd_mychip_pcm_close, |
| 2043 | .ioctl = snd_pcm_lib_ioctl, |
| 2044 | .hw_params = snd_mychip_pcm_hw_params, |
| 2045 | .hw_free = snd_mychip_pcm_hw_free, |
| 2046 | .prepare = snd_mychip_pcm_prepare, |
| 2047 | .trigger = snd_mychip_pcm_trigger, |
| 2048 | .pointer = snd_mychip_pcm_pointer, |
| 2049 | }; |
| 2050 | ]]> |
| 2051 | </programlisting> |
| 2052 | </informalexample> |
| 2053 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2054 | All the callbacks are described in the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2055 | <link linkend="pcm-interface-operators"><citetitle> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2056 | Operators</citetitle></link> subsection. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2057 | </para> |
| 2058 | |
| 2059 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2060 | After setting the operators, you probably will want to |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2061 | pre-allocate the buffer. For the pre-allocation, simply call |
| 2062 | the following: |
| 2063 | |
| 2064 | <informalexample> |
| 2065 | <programlisting> |
| 2066 | <![CDATA[ |
| 2067 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, |
| 2068 | snd_dma_pci_data(chip->pci), |
| 2069 | 64*1024, 64*1024); |
| 2070 | ]]> |
| 2071 | </programlisting> |
| 2072 | </informalexample> |
| 2073 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2074 | It will allocate a buffer up to 64kB as default. |
| 2075 | Buffer management details will be described in the later section <link |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2076 | linkend="buffer-and-memory"><citetitle>Buffer and Memory |
| 2077 | Management</citetitle></link>. |
| 2078 | </para> |
| 2079 | |
| 2080 | <para> |
| 2081 | Additionally, you can set some extra information for this pcm |
| 2082 | in pcm->info_flags. |
| 2083 | The available values are defined as |
| 2084 | <constant>SNDRV_PCM_INFO_XXX</constant> in |
| 2085 | <filename><sound/asound.h></filename>, which is used for |
| 2086 | the hardware definition (described later). When your soundchip |
| 2087 | supports only half-duplex, specify like this: |
| 2088 | |
| 2089 | <informalexample> |
| 2090 | <programlisting> |
| 2091 | <![CDATA[ |
| 2092 | pcm->info_flags = SNDRV_PCM_INFO_HALF_DUPLEX; |
| 2093 | ]]> |
| 2094 | </programlisting> |
| 2095 | </informalexample> |
| 2096 | </para> |
| 2097 | </section> |
| 2098 | |
| 2099 | <section id="pcm-interface-destructor"> |
| 2100 | <title>... And the Destructor?</title> |
| 2101 | <para> |
| 2102 | The destructor for a pcm instance is not always |
| 2103 | necessary. Since the pcm device will be released by the middle |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2104 | layer code automatically, you don't have to call the destructor |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2105 | explicitly. |
| 2106 | </para> |
| 2107 | |
| 2108 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2109 | The destructor would be necessary if you created |
| 2110 | special records internally and needed to release them. In such a |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2111 | case, set the destructor function to |
| 2112 | pcm->private_free: |
| 2113 | |
| 2114 | <example> |
| 2115 | <title>PCM Instance with a Destructor</title> |
| 2116 | <programlisting> |
| 2117 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2118 | static void mychip_pcm_free(struct snd_pcm *pcm) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2119 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2120 | struct mychip *chip = snd_pcm_chip(pcm); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2121 | /* free your own data */ |
| 2122 | kfree(chip->my_private_pcm_data); |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 2123 | /* do what you like else */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2124 | .... |
| 2125 | } |
| 2126 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2127 | static int __devinit snd_mychip_new_pcm(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2128 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2129 | struct snd_pcm *pcm; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2130 | .... |
| 2131 | /* allocate your own data */ |
| 2132 | chip->my_private_pcm_data = kmalloc(...); |
| 2133 | /* set the destructor */ |
| 2134 | pcm->private_data = chip; |
| 2135 | pcm->private_free = mychip_pcm_free; |
| 2136 | .... |
| 2137 | } |
| 2138 | ]]> |
| 2139 | </programlisting> |
| 2140 | </example> |
| 2141 | </para> |
| 2142 | </section> |
| 2143 | |
| 2144 | <section id="pcm-interface-runtime"> |
| 2145 | <title>Runtime Pointer - The Chest of PCM Information</title> |
| 2146 | <para> |
| 2147 | When the PCM substream is opened, a PCM runtime instance is |
| 2148 | allocated and assigned to the substream. This pointer is |
| 2149 | accessible via <constant>substream->runtime</constant>. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2150 | This runtime pointer holds most information you need |
| 2151 | to control the PCM: the copy of hw_params and sw_params configurations, the buffer |
| 2152 | pointers, mmap records, spinlocks, etc. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2153 | </para> |
| 2154 | |
| 2155 | <para> |
| 2156 | The definition of runtime instance is found in |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2157 | <filename><sound/pcm.h></filename>. Here are |
| 2158 | the contents of this file: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2159 | <informalexample> |
| 2160 | <programlisting> |
| 2161 | <![CDATA[ |
| 2162 | struct _snd_pcm_runtime { |
| 2163 | /* -- Status -- */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2164 | struct snd_pcm_substream *trigger_master; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2165 | snd_timestamp_t trigger_tstamp; /* trigger timestamp */ |
| 2166 | int overrange; |
| 2167 | snd_pcm_uframes_t avail_max; |
| 2168 | snd_pcm_uframes_t hw_ptr_base; /* Position at buffer restart */ |
| 2169 | snd_pcm_uframes_t hw_ptr_interrupt; /* Position at interrupt time*/ |
| 2170 | |
| 2171 | /* -- HW params -- */ |
| 2172 | snd_pcm_access_t access; /* access mode */ |
| 2173 | snd_pcm_format_t format; /* SNDRV_PCM_FORMAT_* */ |
| 2174 | snd_pcm_subformat_t subformat; /* subformat */ |
| 2175 | unsigned int rate; /* rate in Hz */ |
| 2176 | unsigned int channels; /* channels */ |
| 2177 | snd_pcm_uframes_t period_size; /* period size */ |
| 2178 | unsigned int periods; /* periods */ |
| 2179 | snd_pcm_uframes_t buffer_size; /* buffer size */ |
| 2180 | unsigned int tick_time; /* tick time */ |
| 2181 | snd_pcm_uframes_t min_align; /* Min alignment for the format */ |
| 2182 | size_t byte_align; |
| 2183 | unsigned int frame_bits; |
| 2184 | unsigned int sample_bits; |
| 2185 | unsigned int info; |
| 2186 | unsigned int rate_num; |
| 2187 | unsigned int rate_den; |
| 2188 | |
| 2189 | /* -- SW params -- */ |
Takashi Iwai | 07799e7 | 2005-10-10 11:49:49 +0200 | [diff] [blame] | 2190 | struct timespec tstamp_mode; /* mmap timestamp is updated */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2191 | unsigned int period_step; |
| 2192 | unsigned int sleep_min; /* min ticks to sleep */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2193 | snd_pcm_uframes_t start_threshold; |
| 2194 | snd_pcm_uframes_t stop_threshold; |
| 2195 | snd_pcm_uframes_t silence_threshold; /* Silence filling happens when |
| 2196 | noise is nearest than this */ |
| 2197 | snd_pcm_uframes_t silence_size; /* Silence filling size */ |
| 2198 | snd_pcm_uframes_t boundary; /* pointers wrap point */ |
| 2199 | |
| 2200 | snd_pcm_uframes_t silenced_start; |
| 2201 | snd_pcm_uframes_t silenced_size; |
| 2202 | |
| 2203 | snd_pcm_sync_id_t sync; /* hardware synchronization ID */ |
| 2204 | |
| 2205 | /* -- mmap -- */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2206 | volatile struct snd_pcm_mmap_status *status; |
| 2207 | volatile struct snd_pcm_mmap_control *control; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2208 | atomic_t mmap_count; |
| 2209 | |
| 2210 | /* -- locking / scheduling -- */ |
| 2211 | spinlock_t lock; |
| 2212 | wait_queue_head_t sleep; |
| 2213 | struct timer_list tick_timer; |
| 2214 | struct fasync_struct *fasync; |
| 2215 | |
| 2216 | /* -- private section -- */ |
| 2217 | void *private_data; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2218 | void (*private_free)(struct snd_pcm_runtime *runtime); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2219 | |
| 2220 | /* -- hardware description -- */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2221 | struct snd_pcm_hardware hw; |
| 2222 | struct snd_pcm_hw_constraints hw_constraints; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2223 | |
| 2224 | /* -- interrupt callbacks -- */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2225 | void (*transfer_ack_begin)(struct snd_pcm_substream *substream); |
| 2226 | void (*transfer_ack_end)(struct snd_pcm_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2227 | |
| 2228 | /* -- timer -- */ |
| 2229 | unsigned int timer_resolution; /* timer resolution */ |
| 2230 | |
| 2231 | /* -- DMA -- */ |
| 2232 | unsigned char *dma_area; /* DMA area */ |
| 2233 | dma_addr_t dma_addr; /* physical bus address (not accessible from main CPU) */ |
| 2234 | size_t dma_bytes; /* size of DMA area */ |
| 2235 | |
| 2236 | struct snd_dma_buffer *dma_buffer_p; /* allocated buffer */ |
| 2237 | |
| 2238 | #if defined(CONFIG_SND_PCM_OSS) || defined(CONFIG_SND_PCM_OSS_MODULE) |
| 2239 | /* -- OSS things -- */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2240 | struct snd_pcm_oss_runtime oss; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2241 | #endif |
| 2242 | }; |
| 2243 | ]]> |
| 2244 | </programlisting> |
| 2245 | </informalexample> |
| 2246 | </para> |
| 2247 | |
| 2248 | <para> |
| 2249 | For the operators (callbacks) of each sound driver, most of |
| 2250 | these records are supposed to be read-only. Only the PCM |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2251 | middle-layer changes / updates them. The exceptions are |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2252 | the hardware description (hw), interrupt callbacks |
| 2253 | (transfer_ack_xxx), DMA buffer information, and the private |
| 2254 | data. Besides, if you use the standard buffer allocation |
| 2255 | method via <function>snd_pcm_lib_malloc_pages()</function>, |
| 2256 | you don't need to set the DMA buffer information by yourself. |
| 2257 | </para> |
| 2258 | |
| 2259 | <para> |
| 2260 | In the sections below, important records are explained. |
| 2261 | </para> |
| 2262 | |
| 2263 | <section id="pcm-interface-runtime-hw"> |
| 2264 | <title>Hardware Description</title> |
| 2265 | <para> |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2266 | The hardware descriptor (struct <structname>snd_pcm_hardware</structname>) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2267 | contains the definitions of the fundamental hardware |
| 2268 | configuration. Above all, you'll need to define this in |
| 2269 | <link linkend="pcm-interface-operators-open-callback"><citetitle> |
| 2270 | the open callback</citetitle></link>. |
| 2271 | Note that the runtime instance holds the copy of the |
| 2272 | descriptor, not the pointer to the existing descriptor. That |
| 2273 | is, in the open callback, you can modify the copied descriptor |
| 2274 | (<constant>runtime->hw</constant>) as you need. For example, if the maximum |
| 2275 | number of channels is 1 only on some chip models, you can |
| 2276 | still use the same hardware descriptor and change the |
| 2277 | channels_max later: |
| 2278 | <informalexample> |
| 2279 | <programlisting> |
| 2280 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2281 | struct snd_pcm_runtime *runtime = substream->runtime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2282 | ... |
| 2283 | runtime->hw = snd_mychip_playback_hw; /* common definition */ |
| 2284 | if (chip->model == VERY_OLD_ONE) |
| 2285 | runtime->hw.channels_max = 1; |
| 2286 | ]]> |
| 2287 | </programlisting> |
| 2288 | </informalexample> |
| 2289 | </para> |
| 2290 | |
| 2291 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2292 | Typically, you'll have a hardware descriptor as below: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2293 | <informalexample> |
| 2294 | <programlisting> |
| 2295 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2296 | static struct snd_pcm_hardware snd_mychip_playback_hw = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2297 | .info = (SNDRV_PCM_INFO_MMAP | |
| 2298 | SNDRV_PCM_INFO_INTERLEAVED | |
| 2299 | SNDRV_PCM_INFO_BLOCK_TRANSFER | |
| 2300 | SNDRV_PCM_INFO_MMAP_VALID), |
| 2301 | .formats = SNDRV_PCM_FMTBIT_S16_LE, |
| 2302 | .rates = SNDRV_PCM_RATE_8000_48000, |
| 2303 | .rate_min = 8000, |
| 2304 | .rate_max = 48000, |
| 2305 | .channels_min = 2, |
| 2306 | .channels_max = 2, |
| 2307 | .buffer_bytes_max = 32768, |
| 2308 | .period_bytes_min = 4096, |
| 2309 | .period_bytes_max = 32768, |
| 2310 | .periods_min = 1, |
| 2311 | .periods_max = 1024, |
| 2312 | }; |
| 2313 | ]]> |
| 2314 | </programlisting> |
| 2315 | </informalexample> |
| 2316 | </para> |
| 2317 | |
| 2318 | <para> |
| 2319 | <itemizedlist> |
| 2320 | <listitem><para> |
| 2321 | The <structfield>info</structfield> field contains the type and |
| 2322 | capabilities of this pcm. The bit flags are defined in |
| 2323 | <filename><sound/asound.h></filename> as |
| 2324 | <constant>SNDRV_PCM_INFO_XXX</constant>. Here, at least, you |
| 2325 | have to specify whether the mmap is supported and which |
| 2326 | interleaved format is supported. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2327 | When the is supported, add the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2328 | <constant>SNDRV_PCM_INFO_MMAP</constant> flag here. When the |
| 2329 | hardware supports the interleaved or the non-interleaved |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2330 | formats, <constant>SNDRV_PCM_INFO_INTERLEAVED</constant> or |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2331 | <constant>SNDRV_PCM_INFO_NONINTERLEAVED</constant> flag must |
| 2332 | be set, respectively. If both are supported, you can set both, |
| 2333 | too. |
| 2334 | </para> |
| 2335 | |
| 2336 | <para> |
| 2337 | In the above example, <constant>MMAP_VALID</constant> and |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2338 | <constant>BLOCK_TRANSFER</constant> are specified for the OSS mmap |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2339 | mode. Usually both are set. Of course, |
| 2340 | <constant>MMAP_VALID</constant> is set only if the mmap is |
| 2341 | really supported. |
| 2342 | </para> |
| 2343 | |
| 2344 | <para> |
| 2345 | The other possible flags are |
| 2346 | <constant>SNDRV_PCM_INFO_PAUSE</constant> and |
| 2347 | <constant>SNDRV_PCM_INFO_RESUME</constant>. The |
| 2348 | <constant>PAUSE</constant> bit means that the pcm supports the |
| 2349 | <quote>pause</quote> operation, while the |
| 2350 | <constant>RESUME</constant> bit means that the pcm supports |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 2351 | the full <quote>suspend/resume</quote> operation. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2352 | If the <constant>PAUSE</constant> flag is set, |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 2353 | the <structfield>trigger</structfield> callback below |
| 2354 | must handle the corresponding (pause push/release) commands. |
| 2355 | The suspend/resume trigger commands can be defined even without |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2356 | the <constant>RESUME</constant> flag. See <link |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 2357 | linkend="power-management"><citetitle> |
| 2358 | Power Management</citetitle></link> section for details. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2359 | </para> |
| 2360 | |
| 2361 | <para> |
| 2362 | When the PCM substreams can be synchronized (typically, |
Nicolas Kaiser | 5bda9fa | 2007-01-22 14:54:33 +0100 | [diff] [blame] | 2363 | synchronized start/stop of a playback and a capture streams), |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2364 | you can give <constant>SNDRV_PCM_INFO_SYNC_START</constant>, |
| 2365 | too. In this case, you'll need to check the linked-list of |
| 2366 | PCM substreams in the trigger callback. This will be |
| 2367 | described in the later section. |
| 2368 | </para> |
| 2369 | </listitem> |
| 2370 | |
| 2371 | <listitem> |
| 2372 | <para> |
| 2373 | <structfield>formats</structfield> field contains the bit-flags |
| 2374 | of supported formats (<constant>SNDRV_PCM_FMTBIT_XXX</constant>). |
| 2375 | If the hardware supports more than one format, give all or'ed |
| 2376 | bits. In the example above, the signed 16bit little-endian |
| 2377 | format is specified. |
| 2378 | </para> |
| 2379 | </listitem> |
| 2380 | |
| 2381 | <listitem> |
| 2382 | <para> |
| 2383 | <structfield>rates</structfield> field contains the bit-flags of |
| 2384 | supported rates (<constant>SNDRV_PCM_RATE_XXX</constant>). |
| 2385 | When the chip supports continuous rates, pass |
| 2386 | <constant>CONTINUOUS</constant> bit additionally. |
| 2387 | The pre-defined rate bits are provided only for typical |
| 2388 | rates. If your chip supports unconventional rates, you need to add |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2389 | the <constant>KNOT</constant> bit and set up the hardware |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2390 | constraint manually (explained later). |
| 2391 | </para> |
| 2392 | </listitem> |
| 2393 | |
| 2394 | <listitem> |
| 2395 | <para> |
| 2396 | <structfield>rate_min</structfield> and |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2397 | <structfield>rate_max</structfield> define the minimum and |
| 2398 | maximum sample rate. This should correspond somehow to |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2399 | <structfield>rates</structfield> bits. |
| 2400 | </para> |
| 2401 | </listitem> |
| 2402 | |
| 2403 | <listitem> |
| 2404 | <para> |
| 2405 | <structfield>channel_min</structfield> and |
| 2406 | <structfield>channel_max</structfield> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2407 | define, as you might already expected, the minimum and maximum |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2408 | number of channels. |
| 2409 | </para> |
| 2410 | </listitem> |
| 2411 | |
| 2412 | <listitem> |
| 2413 | <para> |
| 2414 | <structfield>buffer_bytes_max</structfield> defines the |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2415 | maximum buffer size in bytes. There is no |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2416 | <structfield>buffer_bytes_min</structfield> field, since |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2417 | it can be calculated from the minimum period size and the |
| 2418 | minimum number of periods. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2419 | Meanwhile, <structfield>period_bytes_min</structfield> and |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2420 | define the minimum and maximum size of the period in bytes. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2421 | <structfield>periods_max</structfield> and |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2422 | <structfield>periods_min</structfield> define the maximum and |
| 2423 | minimum number of periods in the buffer. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2424 | </para> |
| 2425 | |
| 2426 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2427 | The <quote>period</quote> is a term that corresponds to |
| 2428 | a fragment in the OSS world. The period defines the size at |
| 2429 | which a PCM interrupt is generated. This size strongly |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2430 | depends on the hardware. |
| 2431 | Generally, the smaller period size will give you more |
| 2432 | interrupts, that is, more controls. |
| 2433 | In the case of capture, this size defines the input latency. |
| 2434 | On the other hand, the whole buffer size defines the |
| 2435 | output latency for the playback direction. |
| 2436 | </para> |
| 2437 | </listitem> |
| 2438 | |
| 2439 | <listitem> |
| 2440 | <para> |
| 2441 | There is also a field <structfield>fifo_size</structfield>. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2442 | This specifies the size of the hardware FIFO, but currently it |
| 2443 | is neither used in the driver nor in the alsa-lib. So, you |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2444 | can ignore this field. |
| 2445 | </para> |
| 2446 | </listitem> |
| 2447 | </itemizedlist> |
| 2448 | </para> |
| 2449 | </section> |
| 2450 | |
| 2451 | <section id="pcm-interface-runtime-config"> |
| 2452 | <title>PCM Configurations</title> |
| 2453 | <para> |
| 2454 | Ok, let's go back again to the PCM runtime records. |
| 2455 | The most frequently referred records in the runtime instance are |
| 2456 | the PCM configurations. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2457 | The PCM configurations are stored in the runtime instance |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2458 | after the application sends <type>hw_params</type> data via |
| 2459 | alsa-lib. There are many fields copied from hw_params and |
| 2460 | sw_params structs. For example, |
| 2461 | <structfield>format</structfield> holds the format type |
| 2462 | chosen by the application. This field contains the enum value |
| 2463 | <constant>SNDRV_PCM_FORMAT_XXX</constant>. |
| 2464 | </para> |
| 2465 | |
| 2466 | <para> |
| 2467 | One thing to be noted is that the configured buffer and period |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2468 | sizes are stored in <quote>frames</quote> in the runtime. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2469 | In the ALSA world, 1 frame = channels * samples-size. |
| 2470 | For conversion between frames and bytes, you can use the |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2471 | <function>frames_to_bytes()</function> and |
| 2472 | <function>bytes_to_frames()</function> helper functions. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2473 | <informalexample> |
| 2474 | <programlisting> |
| 2475 | <![CDATA[ |
| 2476 | period_bytes = frames_to_bytes(runtime, runtime->period_size); |
| 2477 | ]]> |
| 2478 | </programlisting> |
| 2479 | </informalexample> |
| 2480 | </para> |
| 2481 | |
| 2482 | <para> |
| 2483 | Also, many software parameters (sw_params) are |
| 2484 | stored in frames, too. Please check the type of the field. |
| 2485 | <type>snd_pcm_uframes_t</type> is for the frames as unsigned |
| 2486 | integer while <type>snd_pcm_sframes_t</type> is for the frames |
| 2487 | as signed integer. |
| 2488 | </para> |
| 2489 | </section> |
| 2490 | |
| 2491 | <section id="pcm-interface-runtime-dma"> |
| 2492 | <title>DMA Buffer Information</title> |
| 2493 | <para> |
| 2494 | The DMA buffer is defined by the following four fields, |
| 2495 | <structfield>dma_area</structfield>, |
| 2496 | <structfield>dma_addr</structfield>, |
| 2497 | <structfield>dma_bytes</structfield> and |
| 2498 | <structfield>dma_private</structfield>. |
| 2499 | The <structfield>dma_area</structfield> holds the buffer |
| 2500 | pointer (the logical address). You can call |
| 2501 | <function>memcpy</function> from/to |
| 2502 | this pointer. Meanwhile, <structfield>dma_addr</structfield> |
| 2503 | holds the physical address of the buffer. This field is |
| 2504 | specified only when the buffer is a linear buffer. |
| 2505 | <structfield>dma_bytes</structfield> holds the size of buffer |
| 2506 | in bytes. <structfield>dma_private</structfield> is used for |
| 2507 | the ALSA DMA allocator. |
| 2508 | </para> |
| 2509 | |
| 2510 | <para> |
| 2511 | If you use a standard ALSA function, |
| 2512 | <function>snd_pcm_lib_malloc_pages()</function>, for |
| 2513 | allocating the buffer, these fields are set by the ALSA middle |
| 2514 | layer, and you should <emphasis>not</emphasis> change them by |
| 2515 | yourself. You can read them but not write them. |
| 2516 | On the other hand, if you want to allocate the buffer by |
| 2517 | yourself, you'll need to manage it in hw_params callback. |
| 2518 | At least, <structfield>dma_bytes</structfield> is mandatory. |
| 2519 | <structfield>dma_area</structfield> is necessary when the |
| 2520 | buffer is mmapped. If your driver doesn't support mmap, this |
| 2521 | field is not necessary. <structfield>dma_addr</structfield> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2522 | is also optional. You can use |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2523 | <structfield>dma_private</structfield> as you like, too. |
| 2524 | </para> |
| 2525 | </section> |
| 2526 | |
| 2527 | <section id="pcm-interface-runtime-status"> |
| 2528 | <title>Running Status</title> |
| 2529 | <para> |
| 2530 | The running status can be referred via <constant>runtime->status</constant>. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2531 | This is the pointer to the struct <structname>snd_pcm_mmap_status</structname> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2532 | record. For example, you can get the current DMA hardware |
| 2533 | pointer via <constant>runtime->status->hw_ptr</constant>. |
| 2534 | </para> |
| 2535 | |
| 2536 | <para> |
| 2537 | The DMA application pointer can be referred via |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2538 | <constant>runtime->control</constant>, which points to the |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2539 | struct <structname>snd_pcm_mmap_control</structname> record. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2540 | However, accessing directly to this value is not recommended. |
| 2541 | </para> |
| 2542 | </section> |
| 2543 | |
| 2544 | <section id="pcm-interface-runtime-private"> |
| 2545 | <title>Private Data</title> |
| 2546 | <para> |
| 2547 | You can allocate a record for the substream and store it in |
| 2548 | <constant>runtime->private_data</constant>. Usually, this |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2549 | is done in |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2550 | <link linkend="pcm-interface-operators-open-callback"><citetitle> |
| 2551 | the open callback</citetitle></link>. |
| 2552 | Don't mix this with <constant>pcm->private_data</constant>. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2553 | The <constant>pcm->private_data</constant> usually points to the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2554 | chip instance assigned statically at the creation of PCM, while the |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2555 | <constant>runtime->private_data</constant> points to a dynamic |
| 2556 | data structure created at the PCM open callback. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2557 | |
| 2558 | <informalexample> |
| 2559 | <programlisting> |
| 2560 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2561 | static int snd_xxx_open(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2562 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2563 | struct my_pcm_data *data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2564 | .... |
| 2565 | data = kmalloc(sizeof(*data), GFP_KERNEL); |
| 2566 | substream->runtime->private_data = data; |
| 2567 | .... |
| 2568 | } |
| 2569 | ]]> |
| 2570 | </programlisting> |
| 2571 | </informalexample> |
| 2572 | </para> |
| 2573 | |
| 2574 | <para> |
| 2575 | The allocated object must be released in |
| 2576 | <link linkend="pcm-interface-operators-open-callback"><citetitle> |
| 2577 | the close callback</citetitle></link>. |
| 2578 | </para> |
| 2579 | </section> |
| 2580 | |
| 2581 | <section id="pcm-interface-runtime-intr"> |
| 2582 | <title>Interrupt Callbacks</title> |
| 2583 | <para> |
| 2584 | The field <structfield>transfer_ack_begin</structfield> and |
| 2585 | <structfield>transfer_ack_end</structfield> are called at |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2586 | the beginning and at the end of |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2587 | <function>snd_pcm_period_elapsed()</function>, respectively. |
| 2588 | </para> |
| 2589 | </section> |
| 2590 | |
| 2591 | </section> |
| 2592 | |
| 2593 | <section id="pcm-interface-operators"> |
| 2594 | <title>Operators</title> |
| 2595 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2596 | OK, now let me give details about each pcm callback |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2597 | (<parameter>ops</parameter>). In general, every callback must |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2598 | return 0 if successful, or a negative error number |
| 2599 | such as <constant>-EINVAL</constant>. To choose an appropriate |
| 2600 | error number, it is advised to check what value other parts of |
| 2601 | the kernel return when the same kind of request fails. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2602 | </para> |
| 2603 | |
| 2604 | <para> |
| 2605 | The callback function takes at least the argument with |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2606 | <structname>snd_pcm_substream</structname> pointer. To retrieve |
| 2607 | the chip record from the given substream instance, you can use the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2608 | following macro. |
| 2609 | |
| 2610 | <informalexample> |
| 2611 | <programlisting> |
| 2612 | <![CDATA[ |
| 2613 | int xxx() { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2614 | struct mychip *chip = snd_pcm_substream_chip(substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2615 | .... |
| 2616 | } |
| 2617 | ]]> |
| 2618 | </programlisting> |
| 2619 | </informalexample> |
| 2620 | |
| 2621 | The macro reads <constant>substream->private_data</constant>, |
| 2622 | which is a copy of <constant>pcm->private_data</constant>. |
| 2623 | You can override the former if you need to assign different data |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2624 | records per PCM substream. For example, the cmi8330 driver assigns |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2625 | different private_data for playback and capture directions, |
| 2626 | because it uses two different codecs (SB- and AD-compatible) for |
| 2627 | different directions. |
| 2628 | </para> |
| 2629 | |
| 2630 | <section id="pcm-interface-operators-open-callback"> |
| 2631 | <title>open callback</title> |
| 2632 | <para> |
| 2633 | <informalexample> |
| 2634 | <programlisting> |
| 2635 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2636 | static int snd_xxx_open(struct snd_pcm_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2637 | ]]> |
| 2638 | </programlisting> |
| 2639 | </informalexample> |
| 2640 | |
| 2641 | This is called when a pcm substream is opened. |
| 2642 | </para> |
| 2643 | |
| 2644 | <para> |
| 2645 | At least, here you have to initialize the runtime->hw |
| 2646 | record. Typically, this is done by like this: |
| 2647 | |
| 2648 | <informalexample> |
| 2649 | <programlisting> |
| 2650 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2651 | static int snd_xxx_open(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2652 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2653 | struct mychip *chip = snd_pcm_substream_chip(substream); |
| 2654 | struct snd_pcm_runtime *runtime = substream->runtime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2655 | |
| 2656 | runtime->hw = snd_mychip_playback_hw; |
| 2657 | return 0; |
| 2658 | } |
| 2659 | ]]> |
| 2660 | </programlisting> |
| 2661 | </informalexample> |
| 2662 | |
| 2663 | where <parameter>snd_mychip_playback_hw</parameter> is the |
| 2664 | pre-defined hardware description. |
| 2665 | </para> |
| 2666 | |
| 2667 | <para> |
| 2668 | You can allocate a private data in this callback, as described |
| 2669 | in <link linkend="pcm-interface-runtime-private"><citetitle> |
| 2670 | Private Data</citetitle></link> section. |
| 2671 | </para> |
| 2672 | |
| 2673 | <para> |
| 2674 | If the hardware configuration needs more constraints, set the |
| 2675 | hardware constraints here, too. |
| 2676 | See <link linkend="pcm-interface-constraints"><citetitle> |
| 2677 | Constraints</citetitle></link> for more details. |
| 2678 | </para> |
| 2679 | </section> |
| 2680 | |
| 2681 | <section id="pcm-interface-operators-close-callback"> |
| 2682 | <title>close callback</title> |
| 2683 | <para> |
| 2684 | <informalexample> |
| 2685 | <programlisting> |
| 2686 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2687 | static int snd_xxx_close(struct snd_pcm_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2688 | ]]> |
| 2689 | </programlisting> |
| 2690 | </informalexample> |
| 2691 | |
| 2692 | Obviously, this is called when a pcm substream is closed. |
| 2693 | </para> |
| 2694 | |
| 2695 | <para> |
| 2696 | Any private instance for a pcm substream allocated in the |
| 2697 | open callback will be released here. |
| 2698 | |
| 2699 | <informalexample> |
| 2700 | <programlisting> |
| 2701 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2702 | static int snd_xxx_close(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2703 | { |
| 2704 | .... |
| 2705 | kfree(substream->runtime->private_data); |
| 2706 | .... |
| 2707 | } |
| 2708 | ]]> |
| 2709 | </programlisting> |
| 2710 | </informalexample> |
| 2711 | </para> |
| 2712 | </section> |
| 2713 | |
| 2714 | <section id="pcm-interface-operators-ioctl-callback"> |
| 2715 | <title>ioctl callback</title> |
| 2716 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2717 | This is used for any special call to pcm ioctls. But |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2718 | usually you can pass a generic ioctl callback, |
| 2719 | <function>snd_pcm_lib_ioctl</function>. |
| 2720 | </para> |
| 2721 | </section> |
| 2722 | |
| 2723 | <section id="pcm-interface-operators-hw-params-callback"> |
| 2724 | <title>hw_params callback</title> |
| 2725 | <para> |
| 2726 | <informalexample> |
| 2727 | <programlisting> |
| 2728 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2729 | static int snd_xxx_hw_params(struct snd_pcm_substream *substream, |
| 2730 | struct snd_pcm_hw_params *hw_params); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2731 | ]]> |
| 2732 | </programlisting> |
| 2733 | </informalexample> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2734 | </para> |
| 2735 | |
| 2736 | <para> |
| 2737 | This is called when the hardware parameter |
| 2738 | (<structfield>hw_params</structfield>) is set |
| 2739 | up by the application, |
| 2740 | that is, once when the buffer size, the period size, the |
| 2741 | format, etc. are defined for the pcm substream. |
| 2742 | </para> |
| 2743 | |
| 2744 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2745 | Many hardware setups should be done in this callback, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2746 | including the allocation of buffers. |
| 2747 | </para> |
| 2748 | |
| 2749 | <para> |
| 2750 | Parameters to be initialized are retrieved by |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2751 | <function>params_xxx()</function> macros. To allocate |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2752 | buffer, you can call a helper function, |
| 2753 | |
| 2754 | <informalexample> |
| 2755 | <programlisting> |
| 2756 | <![CDATA[ |
| 2757 | snd_pcm_lib_malloc_pages(substream, params_buffer_bytes(hw_params)); |
| 2758 | ]]> |
| 2759 | </programlisting> |
| 2760 | </informalexample> |
| 2761 | |
| 2762 | <function>snd_pcm_lib_malloc_pages()</function> is available |
| 2763 | only when the DMA buffers have been pre-allocated. |
| 2764 | See the section <link |
| 2765 | linkend="buffer-and-memory-buffer-types"><citetitle> |
| 2766 | Buffer Types</citetitle></link> for more details. |
| 2767 | </para> |
| 2768 | |
| 2769 | <para> |
| 2770 | Note that this and <structfield>prepare</structfield> callbacks |
| 2771 | may be called multiple times per initialization. |
| 2772 | For example, the OSS emulation may |
| 2773 | call these callbacks at each change via its ioctl. |
| 2774 | </para> |
| 2775 | |
| 2776 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2777 | Thus, you need to be careful not to allocate the same buffers |
| 2778 | many times, which will lead to memory leaks! Calling the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2779 | helper function above many times is OK. It will release the |
| 2780 | previous buffer automatically when it was already allocated. |
| 2781 | </para> |
| 2782 | |
| 2783 | <para> |
| 2784 | Another note is that this callback is non-atomic |
| 2785 | (schedulable). This is important, because the |
| 2786 | <structfield>trigger</structfield> callback |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2787 | is atomic (non-schedulable). That is, mutexes or any |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2788 | schedule-related functions are not available in |
| 2789 | <structfield>trigger</structfield> callback. |
| 2790 | Please see the subsection |
| 2791 | <link linkend="pcm-interface-atomicity"><citetitle> |
| 2792 | Atomicity</citetitle></link> for details. |
| 2793 | </para> |
| 2794 | </section> |
| 2795 | |
| 2796 | <section id="pcm-interface-operators-hw-free-callback"> |
| 2797 | <title>hw_free callback</title> |
| 2798 | <para> |
| 2799 | <informalexample> |
| 2800 | <programlisting> |
| 2801 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2802 | static int snd_xxx_hw_free(struct snd_pcm_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2803 | ]]> |
| 2804 | </programlisting> |
| 2805 | </informalexample> |
| 2806 | </para> |
| 2807 | |
| 2808 | <para> |
| 2809 | This is called to release the resources allocated via |
| 2810 | <structfield>hw_params</structfield>. For example, releasing the |
| 2811 | buffer via |
| 2812 | <function>snd_pcm_lib_malloc_pages()</function> is done by |
| 2813 | calling the following: |
| 2814 | |
| 2815 | <informalexample> |
| 2816 | <programlisting> |
| 2817 | <![CDATA[ |
| 2818 | snd_pcm_lib_free_pages(substream); |
| 2819 | ]]> |
| 2820 | </programlisting> |
| 2821 | </informalexample> |
| 2822 | </para> |
| 2823 | |
| 2824 | <para> |
| 2825 | This function is always called before the close callback is called. |
| 2826 | Also, the callback may be called multiple times, too. |
| 2827 | Keep track whether the resource was already released. |
| 2828 | </para> |
| 2829 | </section> |
| 2830 | |
| 2831 | <section id="pcm-interface-operators-prepare-callback"> |
| 2832 | <title>prepare callback</title> |
| 2833 | <para> |
| 2834 | <informalexample> |
| 2835 | <programlisting> |
| 2836 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2837 | static int snd_xxx_prepare(struct snd_pcm_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2838 | ]]> |
| 2839 | </programlisting> |
| 2840 | </informalexample> |
| 2841 | </para> |
| 2842 | |
| 2843 | <para> |
| 2844 | This callback is called when the pcm is |
| 2845 | <quote>prepared</quote>. You can set the format type, sample |
| 2846 | rate, etc. here. The difference from |
| 2847 | <structfield>hw_params</structfield> is that the |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2848 | <structfield>prepare</structfield> callback will be called each |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2849 | time |
| 2850 | <function>snd_pcm_prepare()</function> is called, i.e. when |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2851 | recovering after underruns, etc. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2852 | </para> |
| 2853 | |
| 2854 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2855 | Note that this callback is now non-atomic. |
| 2856 | You can use schedule-related functions safely in this callback. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2857 | </para> |
| 2858 | |
| 2859 | <para> |
| 2860 | In this and the following callbacks, you can refer to the |
| 2861 | values via the runtime record, |
| 2862 | substream->runtime. |
| 2863 | For example, to get the current |
| 2864 | rate, format or channels, access to |
| 2865 | runtime->rate, |
| 2866 | runtime->format or |
| 2867 | runtime->channels, respectively. |
| 2868 | The physical address of the allocated buffer is set to |
| 2869 | runtime->dma_area. The buffer and period sizes are |
| 2870 | in runtime->buffer_size and runtime->period_size, |
| 2871 | respectively. |
| 2872 | </para> |
| 2873 | |
| 2874 | <para> |
| 2875 | Be careful that this callback will be called many times at |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2876 | each setup, too. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2877 | </para> |
| 2878 | </section> |
| 2879 | |
| 2880 | <section id="pcm-interface-operators-trigger-callback"> |
| 2881 | <title>trigger callback</title> |
| 2882 | <para> |
| 2883 | <informalexample> |
| 2884 | <programlisting> |
| 2885 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2886 | static int snd_xxx_trigger(struct snd_pcm_substream *substream, int cmd); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2887 | ]]> |
| 2888 | </programlisting> |
| 2889 | </informalexample> |
| 2890 | |
| 2891 | This is called when the pcm is started, stopped or paused. |
| 2892 | </para> |
| 2893 | |
| 2894 | <para> |
| 2895 | Which action is specified in the second argument, |
| 2896 | <constant>SNDRV_PCM_TRIGGER_XXX</constant> in |
| 2897 | <filename><sound/pcm.h></filename>. At least, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2898 | the <constant>START</constant> and <constant>STOP</constant> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2899 | commands must be defined in this callback. |
| 2900 | |
| 2901 | <informalexample> |
| 2902 | <programlisting> |
| 2903 | <![CDATA[ |
| 2904 | switch (cmd) { |
| 2905 | case SNDRV_PCM_TRIGGER_START: |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 2906 | /* do something to start the PCM engine */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2907 | break; |
| 2908 | case SNDRV_PCM_TRIGGER_STOP: |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 2909 | /* do something to stop the PCM engine */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2910 | break; |
| 2911 | default: |
| 2912 | return -EINVAL; |
| 2913 | } |
| 2914 | ]]> |
| 2915 | </programlisting> |
| 2916 | </informalexample> |
| 2917 | </para> |
| 2918 | |
| 2919 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2920 | When the pcm supports the pause operation (given in the info |
| 2921 | field of the hardware table), the <constant>PAUSE_PUSE</constant> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2922 | and <constant>PAUSE_RELEASE</constant> commands must be |
| 2923 | handled here, too. The former is the command to pause the pcm, |
| 2924 | and the latter to restart the pcm again. |
| 2925 | </para> |
| 2926 | |
| 2927 | <para> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 2928 | When the pcm supports the suspend/resume operation, |
| 2929 | regardless of full or partial suspend/resume support, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2930 | the <constant>SUSPEND</constant> and <constant>RESUME</constant> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2931 | commands must be handled, too. |
| 2932 | These commands are issued when the power-management status is |
| 2933 | changed. Obviously, the <constant>SUSPEND</constant> and |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2934 | <constant>RESUME</constant> commands |
| 2935 | suspend and resume the pcm substream, and usually, they |
| 2936 | are identical to the <constant>STOP</constant> and |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2937 | <constant>START</constant> commands, respectively. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2938 | See the <link linkend="power-management"><citetitle> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 2939 | Power Management</citetitle></link> section for details. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2940 | </para> |
| 2941 | |
| 2942 | <para> |
| 2943 | As mentioned, this callback is atomic. You cannot call |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2944 | functions which may sleep. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2945 | The trigger callback should be as minimal as possible, |
| 2946 | just really triggering the DMA. The other stuff should be |
| 2947 | initialized hw_params and prepare callbacks properly |
| 2948 | beforehand. |
| 2949 | </para> |
| 2950 | </section> |
| 2951 | |
| 2952 | <section id="pcm-interface-operators-pointer-callback"> |
| 2953 | <title>pointer callback</title> |
| 2954 | <para> |
| 2955 | <informalexample> |
| 2956 | <programlisting> |
| 2957 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2958 | static snd_pcm_uframes_t snd_xxx_pointer(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2959 | ]]> |
| 2960 | </programlisting> |
| 2961 | </informalexample> |
| 2962 | |
| 2963 | This callback is called when the PCM middle layer inquires |
| 2964 | the current hardware position on the buffer. The position must |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2965 | be returned in frames, |
| 2966 | ranging from 0 to buffer_size - 1. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2967 | </para> |
| 2968 | |
| 2969 | <para> |
| 2970 | This is called usually from the buffer-update routine in the |
| 2971 | pcm middle layer, which is invoked when |
| 2972 | <function>snd_pcm_period_elapsed()</function> is called in the |
| 2973 | interrupt routine. Then the pcm middle layer updates the |
| 2974 | position and calculates the available space, and wakes up the |
| 2975 | sleeping poll threads, etc. |
| 2976 | </para> |
| 2977 | |
| 2978 | <para> |
| 2979 | This callback is also atomic. |
| 2980 | </para> |
| 2981 | </section> |
| 2982 | |
| 2983 | <section id="pcm-interface-operators-copy-silence"> |
| 2984 | <title>copy and silence callbacks</title> |
| 2985 | <para> |
| 2986 | These callbacks are not mandatory, and can be omitted in |
| 2987 | most cases. These callbacks are used when the hardware buffer |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 2988 | cannot be in the normal memory space. Some chips have their |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2989 | own buffer on the hardware which is not mappable. In such a |
| 2990 | case, you have to transfer the data manually from the memory |
| 2991 | buffer to the hardware buffer. Or, if the buffer is |
| 2992 | non-contiguous on both physical and virtual memory spaces, |
| 2993 | these callbacks must be defined, too. |
| 2994 | </para> |
| 2995 | |
| 2996 | <para> |
| 2997 | If these two callbacks are defined, copy and set-silence |
| 2998 | operations are done by them. The detailed will be described in |
| 2999 | the later section <link |
| 3000 | linkend="buffer-and-memory"><citetitle>Buffer and Memory |
| 3001 | Management</citetitle></link>. |
| 3002 | </para> |
| 3003 | </section> |
| 3004 | |
| 3005 | <section id="pcm-interface-operators-ack"> |
| 3006 | <title>ack callback</title> |
| 3007 | <para> |
| 3008 | This callback is also not mandatory. This callback is called |
| 3009 | when the appl_ptr is updated in read or write operations. |
| 3010 | Some drivers like emu10k1-fx and cs46xx need to track the |
| 3011 | current appl_ptr for the internal buffer, and this callback |
| 3012 | is useful only for such a purpose. |
| 3013 | </para> |
| 3014 | <para> |
| 3015 | This callback is atomic. |
| 3016 | </para> |
| 3017 | </section> |
| 3018 | |
| 3019 | <section id="pcm-interface-operators-page-callback"> |
| 3020 | <title>page callback</title> |
| 3021 | |
| 3022 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3023 | This callback is optional too. This callback is used |
| 3024 | mainly for non-contiguous buffers. The mmap calls this |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3025 | callback to get the page address. Some examples will be |
| 3026 | explained in the later section <link |
| 3027 | linkend="buffer-and-memory"><citetitle>Buffer and Memory |
| 3028 | Management</citetitle></link>, too. |
| 3029 | </para> |
| 3030 | </section> |
| 3031 | </section> |
| 3032 | |
| 3033 | <section id="pcm-interface-interrupt-handler"> |
| 3034 | <title>Interrupt Handler</title> |
| 3035 | <para> |
| 3036 | The rest of pcm stuff is the PCM interrupt handler. The |
| 3037 | role of PCM interrupt handler in the sound driver is to update |
| 3038 | the buffer position and to tell the PCM middle layer when the |
| 3039 | buffer position goes across the prescribed period size. To |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3040 | inform this, call the <function>snd_pcm_period_elapsed()</function> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3041 | function. |
| 3042 | </para> |
| 3043 | |
| 3044 | <para> |
| 3045 | There are several types of sound chips to generate the interrupts. |
| 3046 | </para> |
| 3047 | |
| 3048 | <section id="pcm-interface-interrupt-handler-boundary"> |
| 3049 | <title>Interrupts at the period (fragment) boundary</title> |
| 3050 | <para> |
| 3051 | This is the most frequently found type: the hardware |
| 3052 | generates an interrupt at each period boundary. |
| 3053 | In this case, you can call |
| 3054 | <function>snd_pcm_period_elapsed()</function> at each |
| 3055 | interrupt. |
| 3056 | </para> |
| 3057 | |
| 3058 | <para> |
| 3059 | <function>snd_pcm_period_elapsed()</function> takes the |
| 3060 | substream pointer as its argument. Thus, you need to keep the |
| 3061 | substream pointer accessible from the chip instance. For |
| 3062 | example, define substream field in the chip record to hold the |
| 3063 | current running substream pointer, and set the pointer value |
| 3064 | at open callback (and reset at close callback). |
| 3065 | </para> |
| 3066 | |
| 3067 | <para> |
Adrian Bunk | 0418726 | 2006-06-30 18:23:04 +0200 | [diff] [blame] | 3068 | If you acquire a spinlock in the interrupt handler, and the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3069 | lock is used in other pcm callbacks, too, then you have to |
| 3070 | release the lock before calling |
| 3071 | <function>snd_pcm_period_elapsed()</function>, because |
| 3072 | <function>snd_pcm_period_elapsed()</function> calls other pcm |
| 3073 | callbacks inside. |
| 3074 | </para> |
| 3075 | |
| 3076 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3077 | Typical code would be like: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3078 | |
| 3079 | <example> |
| 3080 | <title>Interrupt Handler Case #1</title> |
| 3081 | <programlisting> |
| 3082 | <![CDATA[ |
Takashi Iwai | ad4d1de | 2007-01-16 17:46:35 +0100 | [diff] [blame] | 3083 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3084 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3085 | struct mychip *chip = dev_id; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3086 | spin_lock(&chip->lock); |
| 3087 | .... |
| 3088 | if (pcm_irq_invoked(chip)) { |
| 3089 | /* call updater, unlock before it */ |
| 3090 | spin_unlock(&chip->lock); |
| 3091 | snd_pcm_period_elapsed(chip->substream); |
| 3092 | spin_lock(&chip->lock); |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 3093 | /* acknowledge the interrupt if necessary */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3094 | } |
| 3095 | .... |
| 3096 | spin_unlock(&chip->lock); |
| 3097 | return IRQ_HANDLED; |
| 3098 | } |
| 3099 | ]]> |
| 3100 | </programlisting> |
| 3101 | </example> |
| 3102 | </para> |
| 3103 | </section> |
| 3104 | |
| 3105 | <section id="pcm-interface-interrupt-handler-timer"> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3106 | <title>High frequency timer interrupts</title> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3107 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3108 | This happense when the hardware doesn't generate interrupts |
| 3109 | at the period boundary but issues timer interrupts at a fixed |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3110 | timer rate (e.g. es1968 or ymfpci drivers). |
| 3111 | In this case, you need to check the current hardware |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3112 | position and accumulate the processed sample length at each |
| 3113 | interrupt. When the accumulated size exceeds the period |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3114 | size, call |
| 3115 | <function>snd_pcm_period_elapsed()</function> and reset the |
| 3116 | accumulator. |
| 3117 | </para> |
| 3118 | |
| 3119 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3120 | Typical code would be like the following. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3121 | |
| 3122 | <example> |
| 3123 | <title>Interrupt Handler Case #2</title> |
| 3124 | <programlisting> |
| 3125 | <![CDATA[ |
Takashi Iwai | ad4d1de | 2007-01-16 17:46:35 +0100 | [diff] [blame] | 3126 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3127 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3128 | struct mychip *chip = dev_id; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3129 | spin_lock(&chip->lock); |
| 3130 | .... |
| 3131 | if (pcm_irq_invoked(chip)) { |
| 3132 | unsigned int last_ptr, size; |
| 3133 | /* get the current hardware pointer (in frames) */ |
| 3134 | last_ptr = get_hw_ptr(chip); |
| 3135 | /* calculate the processed frames since the |
| 3136 | * last update |
| 3137 | */ |
| 3138 | if (last_ptr < chip->last_ptr) |
| 3139 | size = runtime->buffer_size + last_ptr |
| 3140 | - chip->last_ptr; |
| 3141 | else |
| 3142 | size = last_ptr - chip->last_ptr; |
| 3143 | /* remember the last updated point */ |
| 3144 | chip->last_ptr = last_ptr; |
| 3145 | /* accumulate the size */ |
| 3146 | chip->size += size; |
| 3147 | /* over the period boundary? */ |
| 3148 | if (chip->size >= runtime->period_size) { |
| 3149 | /* reset the accumulator */ |
| 3150 | chip->size %= runtime->period_size; |
| 3151 | /* call updater */ |
| 3152 | spin_unlock(&chip->lock); |
| 3153 | snd_pcm_period_elapsed(substream); |
| 3154 | spin_lock(&chip->lock); |
| 3155 | } |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 3156 | /* acknowledge the interrupt if necessary */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3157 | } |
| 3158 | .... |
| 3159 | spin_unlock(&chip->lock); |
| 3160 | return IRQ_HANDLED; |
| 3161 | } |
| 3162 | ]]> |
| 3163 | </programlisting> |
| 3164 | </example> |
| 3165 | </para> |
| 3166 | </section> |
| 3167 | |
| 3168 | <section id="pcm-interface-interrupt-handler-both"> |
| 3169 | <title>On calling <function>snd_pcm_period_elapsed()</function></title> |
| 3170 | <para> |
| 3171 | In both cases, even if more than one period are elapsed, you |
| 3172 | don't have to call |
| 3173 | <function>snd_pcm_period_elapsed()</function> many times. Call |
| 3174 | only once. And the pcm layer will check the current hardware |
| 3175 | pointer and update to the latest status. |
| 3176 | </para> |
| 3177 | </section> |
| 3178 | </section> |
| 3179 | |
| 3180 | <section id="pcm-interface-atomicity"> |
| 3181 | <title>Atomicity</title> |
| 3182 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3183 | One of the most important (and thus difficult to debug) problems |
| 3184 | in kernel programming are race conditions. |
| 3185 | In the Linux kernel, they are usually avoided via spin-locks, mutexes |
| 3186 | or semaphores. In general, if a race condition can happen |
| 3187 | in an interrupt handler, it has to be managed atomically, and you |
| 3188 | have to use a spinlock to protect the critical session. If the |
| 3189 | critical section is not in interrupt handler code and |
| 3190 | if taking a relatively long time to execute is acceptable, you |
| 3191 | should use mutexes or semaphores instead. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3192 | </para> |
| 3193 | |
| 3194 | <para> |
| 3195 | As already seen, some pcm callbacks are atomic and some are |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3196 | not. For example, the <parameter>hw_params</parameter> callback is |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3197 | non-atomic, while <parameter>trigger</parameter> callback is |
| 3198 | atomic. This means, the latter is called already in a spinlock |
| 3199 | held by the PCM middle layer. Please take this atomicity into |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3200 | account when you choose a locking scheme in the callbacks. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3201 | </para> |
| 3202 | |
| 3203 | <para> |
| 3204 | In the atomic callbacks, you cannot use functions which may call |
| 3205 | <function>schedule</function> or go to |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3206 | <function>sleep</function>. Semaphores and mutexes can sleep, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3207 | and hence they cannot be used inside the atomic callbacks |
| 3208 | (e.g. <parameter>trigger</parameter> callback). |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3209 | To implement some delay in such a callback, please use |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3210 | <function>udelay()</function> or <function>mdelay()</function>. |
| 3211 | </para> |
| 3212 | |
| 3213 | <para> |
| 3214 | All three atomic callbacks (trigger, pointer, and ack) are |
| 3215 | called with local interrupts disabled. |
| 3216 | </para> |
| 3217 | |
| 3218 | </section> |
| 3219 | <section id="pcm-interface-constraints"> |
| 3220 | <title>Constraints</title> |
| 3221 | <para> |
| 3222 | If your chip supports unconventional sample rates, or only the |
| 3223 | limited samples, you need to set a constraint for the |
| 3224 | condition. |
| 3225 | </para> |
| 3226 | |
| 3227 | <para> |
| 3228 | For example, in order to restrict the sample rates in the some |
| 3229 | supported values, use |
| 3230 | <function>snd_pcm_hw_constraint_list()</function>. |
| 3231 | You need to call this function in the open callback. |
| 3232 | |
| 3233 | <example> |
| 3234 | <title>Example of Hardware Constraints</title> |
| 3235 | <programlisting> |
| 3236 | <![CDATA[ |
| 3237 | static unsigned int rates[] = |
| 3238 | {4000, 10000, 22050, 44100}; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3239 | static struct snd_pcm_hw_constraint_list constraints_rates = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3240 | .count = ARRAY_SIZE(rates), |
| 3241 | .list = rates, |
| 3242 | .mask = 0, |
| 3243 | }; |
| 3244 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3245 | static int snd_mychip_pcm_open(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3246 | { |
| 3247 | int err; |
| 3248 | .... |
| 3249 | err = snd_pcm_hw_constraint_list(substream->runtime, 0, |
| 3250 | SNDRV_PCM_HW_PARAM_RATE, |
| 3251 | &constraints_rates); |
| 3252 | if (err < 0) |
| 3253 | return err; |
| 3254 | .... |
| 3255 | } |
| 3256 | ]]> |
| 3257 | </programlisting> |
| 3258 | </example> |
| 3259 | </para> |
| 3260 | |
| 3261 | <para> |
| 3262 | There are many different constraints. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3263 | Look at <filename>sound/pcm.h</filename> for a complete list. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3264 | You can even define your own constraint rules. |
| 3265 | For example, let's suppose my_chip can manage a substream of 1 channel |
| 3266 | if and only if the format is S16_LE, otherwise it supports any format |
Nicolas Kaiser | 5bda9fa | 2007-01-22 14:54:33 +0100 | [diff] [blame] | 3267 | specified in the <structname>snd_pcm_hardware</structname> structure (or in any |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3268 | other constraint_list). You can build a rule like this: |
| 3269 | |
| 3270 | <example> |
| 3271 | <title>Example of Hardware Constraints for Channels</title> |
| 3272 | <programlisting> |
| 3273 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3274 | static int hw_rule_format_by_channels(struct snd_pcm_hw_params *params, |
| 3275 | struct snd_pcm_hw_rule *rule) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3276 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3277 | struct snd_interval *c = hw_param_interval(params, |
| 3278 | SNDRV_PCM_HW_PARAM_CHANNELS); |
| 3279 | struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT); |
| 3280 | struct snd_mask fmt; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3281 | |
| 3282 | snd_mask_any(&fmt); /* Init the struct */ |
| 3283 | if (c->min < 2) { |
| 3284 | fmt.bits[0] &= SNDRV_PCM_FMTBIT_S16_LE; |
| 3285 | return snd_mask_refine(f, &fmt); |
| 3286 | } |
| 3287 | return 0; |
| 3288 | } |
| 3289 | ]]> |
| 3290 | </programlisting> |
| 3291 | </example> |
| 3292 | </para> |
| 3293 | |
| 3294 | <para> |
| 3295 | Then you need to call this function to add your rule: |
| 3296 | |
| 3297 | <informalexample> |
| 3298 | <programlisting> |
| 3299 | <![CDATA[ |
| 3300 | snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS, |
| 3301 | hw_rule_channels_by_format, 0, SNDRV_PCM_HW_PARAM_FORMAT, |
| 3302 | -1); |
| 3303 | ]]> |
| 3304 | </programlisting> |
| 3305 | </informalexample> |
| 3306 | </para> |
| 3307 | |
| 3308 | <para> |
| 3309 | The rule function is called when an application sets the number of |
| 3310 | channels. But an application can set the format before the number of |
| 3311 | channels. Thus you also need to define the inverse rule: |
| 3312 | |
| 3313 | <example> |
| 3314 | <title>Example of Hardware Constraints for Channels</title> |
| 3315 | <programlisting> |
| 3316 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3317 | static int hw_rule_channels_by_format(struct snd_pcm_hw_params *params, |
| 3318 | struct snd_pcm_hw_rule *rule) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3319 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3320 | struct snd_interval *c = hw_param_interval(params, |
| 3321 | SNDRV_PCM_HW_PARAM_CHANNELS); |
| 3322 | struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT); |
| 3323 | struct snd_interval ch; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3324 | |
| 3325 | snd_interval_any(&ch); |
| 3326 | if (f->bits[0] == SNDRV_PCM_FMTBIT_S16_LE) { |
| 3327 | ch.min = ch.max = 1; |
| 3328 | ch.integer = 1; |
| 3329 | return snd_interval_refine(c, &ch); |
| 3330 | } |
| 3331 | return 0; |
| 3332 | } |
| 3333 | ]]> |
| 3334 | </programlisting> |
| 3335 | </example> |
| 3336 | </para> |
| 3337 | |
| 3338 | <para> |
| 3339 | ...and in the open callback: |
| 3340 | <informalexample> |
| 3341 | <programlisting> |
| 3342 | <![CDATA[ |
| 3343 | snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_FORMAT, |
| 3344 | hw_rule_format_by_channels, 0, SNDRV_PCM_HW_PARAM_CHANNELS, |
| 3345 | -1); |
| 3346 | ]]> |
| 3347 | </programlisting> |
| 3348 | </informalexample> |
| 3349 | </para> |
| 3350 | |
| 3351 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3352 | I won't give more details here, rather I |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3353 | would like to say, <quote>Luke, use the source.</quote> |
| 3354 | </para> |
| 3355 | </section> |
| 3356 | |
| 3357 | </chapter> |
| 3358 | |
| 3359 | |
| 3360 | <!-- ****************************************************** --> |
| 3361 | <!-- Control Interface --> |
| 3362 | <!-- ****************************************************** --> |
| 3363 | <chapter id="control-interface"> |
| 3364 | <title>Control Interface</title> |
| 3365 | |
| 3366 | <section id="control-interface-general"> |
| 3367 | <title>General</title> |
| 3368 | <para> |
| 3369 | The control interface is used widely for many switches, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3370 | sliders, etc. which are accessed from user-space. Its most |
| 3371 | important use is the mixer interface. In other words, since ALSA |
| 3372 | 0.9.x, all the mixer stuff is implemented on the control kernel API. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3373 | </para> |
| 3374 | |
| 3375 | <para> |
| 3376 | ALSA has a well-defined AC97 control module. If your chip |
| 3377 | supports only the AC97 and nothing else, you can skip this |
| 3378 | section. |
| 3379 | </para> |
| 3380 | |
| 3381 | <para> |
| 3382 | The control API is defined in |
| 3383 | <filename><sound/control.h></filename>. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3384 | Include this file if you want to add your own controls. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3385 | </para> |
| 3386 | </section> |
| 3387 | |
| 3388 | <section id="control-interface-definition"> |
| 3389 | <title>Definition of Controls</title> |
| 3390 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3391 | To create a new control, you need to define the |
| 3392 | following three |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3393 | callbacks: <structfield>info</structfield>, |
| 3394 | <structfield>get</structfield> and |
| 3395 | <structfield>put</structfield>. Then, define a |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3396 | struct <structname>snd_kcontrol_new</structname> record, such as: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3397 | |
| 3398 | <example> |
| 3399 | <title>Definition of a Control</title> |
| 3400 | <programlisting> |
| 3401 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3402 | static struct snd_kcontrol_new my_control __devinitdata = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3403 | .iface = SNDRV_CTL_ELEM_IFACE_MIXER, |
| 3404 | .name = "PCM Playback Switch", |
| 3405 | .index = 0, |
| 3406 | .access = SNDRV_CTL_ELEM_ACCESS_READWRITE, |
Takashi Iwai | 0b7bed4 | 2006-03-02 15:35:55 +0100 | [diff] [blame] | 3407 | .private_value = 0xffff, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3408 | .info = my_control_info, |
| 3409 | .get = my_control_get, |
| 3410 | .put = my_control_put |
| 3411 | }; |
| 3412 | ]]> |
| 3413 | </programlisting> |
| 3414 | </example> |
| 3415 | </para> |
| 3416 | |
| 3417 | <para> |
| 3418 | Most likely the control is created via |
| 3419 | <function>snd_ctl_new1()</function>, and in such a case, you can |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3420 | add the <parameter>__devinitdata</parameter> prefix to the |
| 3421 | definition as above. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3422 | </para> |
| 3423 | |
| 3424 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3425 | The <structfield>iface</structfield> field specifies the control |
| 3426 | type, <constant>SNDRV_CTL_ELEM_IFACE_XXX</constant>, which |
Clemens Ladisch | 67ed416 | 2005-07-29 15:32:58 +0200 | [diff] [blame] | 3427 | is usually <constant>MIXER</constant>. |
| 3428 | Use <constant>CARD</constant> for global controls that are not |
| 3429 | logically part of the mixer. |
| 3430 | If the control is closely associated with some specific device on |
| 3431 | the sound card, use <constant>HWDEP</constant>, |
| 3432 | <constant>PCM</constant>, <constant>RAWMIDI</constant>, |
| 3433 | <constant>TIMER</constant>, or <constant>SEQUENCER</constant>, and |
| 3434 | specify the device number with the |
| 3435 | <structfield>device</structfield> and |
| 3436 | <structfield>subdevice</structfield> fields. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3437 | </para> |
| 3438 | |
| 3439 | <para> |
| 3440 | The <structfield>name</structfield> is the name identifier |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3441 | string. Since ALSA 0.9.x, the control name is very important, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3442 | because its role is classified from its name. There are |
| 3443 | pre-defined standard control names. The details are described in |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3444 | the <link linkend="control-interface-control-names"><citetitle> |
| 3445 | Control Names</citetitle></link> subsection. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3446 | </para> |
| 3447 | |
| 3448 | <para> |
| 3449 | The <structfield>index</structfield> field holds the index number |
| 3450 | of this control. If there are several different controls with |
| 3451 | the same name, they can be distinguished by the index |
| 3452 | number. This is the case when |
| 3453 | several codecs exist on the card. If the index is zero, you can |
| 3454 | omit the definition above. |
| 3455 | </para> |
| 3456 | |
| 3457 | <para> |
| 3458 | The <structfield>access</structfield> field contains the access |
| 3459 | type of this control. Give the combination of bit masks, |
| 3460 | <constant>SNDRV_CTL_ELEM_ACCESS_XXX</constant>, there. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3461 | The details will be explained in |
| 3462 | the <link linkend="control-interface-access-flags"><citetitle> |
| 3463 | Access Flags</citetitle></link> subsection. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3464 | </para> |
| 3465 | |
| 3466 | <para> |
Takashi Iwai | 0b7bed4 | 2006-03-02 15:35:55 +0100 | [diff] [blame] | 3467 | The <structfield>private_value</structfield> field contains |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3468 | an arbitrary long integer value for this record. When using |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3469 | the generic <structfield>info</structfield>, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3470 | <structfield>get</structfield> and |
| 3471 | <structfield>put</structfield> callbacks, you can pass a value |
| 3472 | through this field. If several small numbers are necessary, you can |
| 3473 | combine them in bitwise. Or, it's possible to give a pointer |
| 3474 | (casted to unsigned long) of some record to this field, too. |
| 3475 | </para> |
| 3476 | |
| 3477 | <para> |
Clemens Ladisch | d1761d1 | 2007-09-10 08:05:19 +0200 | [diff] [blame] | 3478 | The <structfield>tlv</structfield> field can be used to provide |
| 3479 | metadata about the control; see the |
| 3480 | <link linkend="control-interface-tlv"> |
| 3481 | <citetitle>Metadata</citetitle></link> subsection. |
| 3482 | </para> |
| 3483 | |
| 3484 | <para> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3485 | The other three are |
| 3486 | <link linkend="control-interface-callbacks"><citetitle> |
| 3487 | callback functions</citetitle></link>. |
| 3488 | </para> |
| 3489 | </section> |
| 3490 | |
| 3491 | <section id="control-interface-control-names"> |
| 3492 | <title>Control Names</title> |
| 3493 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3494 | There are some standards to define the control names. A |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3495 | control is usually defined from the three parts as |
| 3496 | <quote>SOURCE DIRECTION FUNCTION</quote>. |
| 3497 | </para> |
| 3498 | |
| 3499 | <para> |
| 3500 | The first, <constant>SOURCE</constant>, specifies the source |
| 3501 | of the control, and is a string such as <quote>Master</quote>, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3502 | <quote>PCM</quote>, <quote>CD</quote> and |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3503 | <quote>Line</quote>. There are many pre-defined sources. |
| 3504 | </para> |
| 3505 | |
| 3506 | <para> |
| 3507 | The second, <constant>DIRECTION</constant>, is one of the |
| 3508 | following strings according to the direction of the control: |
| 3509 | <quote>Playback</quote>, <quote>Capture</quote>, <quote>Bypass |
| 3510 | Playback</quote> and <quote>Bypass Capture</quote>. Or, it can |
| 3511 | be omitted, meaning both playback and capture directions. |
| 3512 | </para> |
| 3513 | |
| 3514 | <para> |
| 3515 | The third, <constant>FUNCTION</constant>, is one of the |
| 3516 | following strings according to the function of the control: |
| 3517 | <quote>Switch</quote>, <quote>Volume</quote> and |
| 3518 | <quote>Route</quote>. |
| 3519 | </para> |
| 3520 | |
| 3521 | <para> |
| 3522 | The example of control names are, thus, <quote>Master Capture |
| 3523 | Switch</quote> or <quote>PCM Playback Volume</quote>. |
| 3524 | </para> |
| 3525 | |
| 3526 | <para> |
| 3527 | There are some exceptions: |
| 3528 | </para> |
| 3529 | |
| 3530 | <section id="control-interface-control-names-global"> |
| 3531 | <title>Global capture and playback</title> |
| 3532 | <para> |
| 3533 | <quote>Capture Source</quote>, <quote>Capture Switch</quote> |
| 3534 | and <quote>Capture Volume</quote> are used for the global |
| 3535 | capture (input) source, switch and volume. Similarly, |
| 3536 | <quote>Playback Switch</quote> and <quote>Playback |
| 3537 | Volume</quote> are used for the global output gain switch and |
| 3538 | volume. |
| 3539 | </para> |
| 3540 | </section> |
| 3541 | |
| 3542 | <section id="control-interface-control-names-tone"> |
| 3543 | <title>Tone-controls</title> |
| 3544 | <para> |
| 3545 | tone-control switch and volumes are specified like |
| 3546 | <quote>Tone Control - XXX</quote>, e.g. <quote>Tone Control - |
| 3547 | Switch</quote>, <quote>Tone Control - Bass</quote>, |
| 3548 | <quote>Tone Control - Center</quote>. |
| 3549 | </para> |
| 3550 | </section> |
| 3551 | |
| 3552 | <section id="control-interface-control-names-3d"> |
| 3553 | <title>3D controls</title> |
| 3554 | <para> |
| 3555 | 3D-control switches and volumes are specified like <quote>3D |
| 3556 | Control - XXX</quote>, e.g. <quote>3D Control - |
| 3557 | Switch</quote>, <quote>3D Control - Center</quote>, <quote>3D |
| 3558 | Control - Space</quote>. |
| 3559 | </para> |
| 3560 | </section> |
| 3561 | |
| 3562 | <section id="control-interface-control-names-mic"> |
| 3563 | <title>Mic boost</title> |
| 3564 | <para> |
| 3565 | Mic-boost switch is set as <quote>Mic Boost</quote> or |
| 3566 | <quote>Mic Boost (6dB)</quote>. |
| 3567 | </para> |
| 3568 | |
| 3569 | <para> |
| 3570 | More precise information can be found in |
| 3571 | <filename>Documentation/sound/alsa/ControlNames.txt</filename>. |
| 3572 | </para> |
| 3573 | </section> |
| 3574 | </section> |
| 3575 | |
| 3576 | <section id="control-interface-access-flags"> |
| 3577 | <title>Access Flags</title> |
| 3578 | |
| 3579 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3580 | The access flag is the bitmask which specifies the access type |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3581 | of the given control. The default access type is |
| 3582 | <constant>SNDRV_CTL_ELEM_ACCESS_READWRITE</constant>, |
| 3583 | which means both read and write are allowed to this control. |
| 3584 | When the access flag is omitted (i.e. = 0), it is |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3585 | considered as <constant>READWRITE</constant> access as default. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3586 | </para> |
| 3587 | |
| 3588 | <para> |
| 3589 | When the control is read-only, pass |
| 3590 | <constant>SNDRV_CTL_ELEM_ACCESS_READ</constant> instead. |
| 3591 | In this case, you don't have to define |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3592 | the <structfield>put</structfield> callback. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3593 | Similarly, when the control is write-only (although it's a rare |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3594 | case), you can use the <constant>WRITE</constant> flag instead, and |
| 3595 | you don't need the <structfield>get</structfield> callback. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3596 | </para> |
| 3597 | |
| 3598 | <para> |
| 3599 | If the control value changes frequently (e.g. the VU meter), |
| 3600 | <constant>VOLATILE</constant> flag should be given. This means |
| 3601 | that the control may be changed without |
| 3602 | <link linkend="control-interface-change-notification"><citetitle> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3603 | notification</citetitle></link>. Applications should poll such |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3604 | a control constantly. |
| 3605 | </para> |
| 3606 | |
| 3607 | <para> |
| 3608 | When the control is inactive, set |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3609 | the <constant>INACTIVE</constant> flag, too. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3610 | There are <constant>LOCK</constant> and |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3611 | <constant>OWNER</constant> flags to change the write |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3612 | permissions. |
| 3613 | </para> |
| 3614 | |
| 3615 | </section> |
| 3616 | |
| 3617 | <section id="control-interface-callbacks"> |
| 3618 | <title>Callbacks</title> |
| 3619 | |
| 3620 | <section id="control-interface-callbacks-info"> |
| 3621 | <title>info callback</title> |
| 3622 | <para> |
| 3623 | The <structfield>info</structfield> callback is used to get |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3624 | detailed information on this control. This must store the |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3625 | values of the given struct <structname>snd_ctl_elem_info</structname> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3626 | object. For example, for a boolean control with a single |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3627 | element: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3628 | |
| 3629 | <example> |
| 3630 | <title>Example of info callback</title> |
| 3631 | <programlisting> |
| 3632 | <![CDATA[ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 3633 | static int snd_myctl_mono_info(struct snd_kcontrol *kcontrol, |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3634 | struct snd_ctl_elem_info *uinfo) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3635 | { |
| 3636 | uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN; |
| 3637 | uinfo->count = 1; |
| 3638 | uinfo->value.integer.min = 0; |
| 3639 | uinfo->value.integer.max = 1; |
| 3640 | return 0; |
| 3641 | } |
| 3642 | ]]> |
| 3643 | </programlisting> |
| 3644 | </example> |
| 3645 | </para> |
| 3646 | |
| 3647 | <para> |
| 3648 | The <structfield>type</structfield> field specifies the type |
| 3649 | of the control. There are <constant>BOOLEAN</constant>, |
| 3650 | <constant>INTEGER</constant>, <constant>ENUMERATED</constant>, |
| 3651 | <constant>BYTES</constant>, <constant>IEC958</constant> and |
| 3652 | <constant>INTEGER64</constant>. The |
| 3653 | <structfield>count</structfield> field specifies the |
| 3654 | number of elements in this control. For example, a stereo |
| 3655 | volume would have count = 2. The |
| 3656 | <structfield>value</structfield> field is a union, and |
| 3657 | the values stored are depending on the type. The boolean and |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3658 | integer types are identical. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3659 | </para> |
| 3660 | |
| 3661 | <para> |
| 3662 | The enumerated type is a bit different from others. You'll |
| 3663 | need to set the string for the currently given item index. |
| 3664 | |
| 3665 | <informalexample> |
| 3666 | <programlisting> |
| 3667 | <![CDATA[ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 3668 | static int snd_myctl_enum_info(struct snd_kcontrol *kcontrol, |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3669 | struct snd_ctl_elem_info *uinfo) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3670 | { |
| 3671 | static char *texts[4] = { |
| 3672 | "First", "Second", "Third", "Fourth" |
| 3673 | }; |
| 3674 | uinfo->type = SNDRV_CTL_ELEM_TYPE_ENUMERATED; |
| 3675 | uinfo->count = 1; |
| 3676 | uinfo->value.enumerated.items = 4; |
| 3677 | if (uinfo->value.enumerated.item > 3) |
| 3678 | uinfo->value.enumerated.item = 3; |
| 3679 | strcpy(uinfo->value.enumerated.name, |
| 3680 | texts[uinfo->value.enumerated.item]); |
| 3681 | return 0; |
| 3682 | } |
| 3683 | ]]> |
| 3684 | </programlisting> |
| 3685 | </informalexample> |
| 3686 | </para> |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 3687 | |
| 3688 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3689 | Some common info callbacks are available for your convenience: |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 3690 | <function>snd_ctl_boolean_mono_info()</function> and |
| 3691 | <function>snd_ctl_boolean_stereo_info()</function>. |
| 3692 | Obviously, the former is an info callback for a mono channel |
| 3693 | boolean item, just like <function>snd_myctl_mono_info</function> |
| 3694 | above, and the latter is for a stereo channel boolean item. |
| 3695 | </para> |
| 3696 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3697 | </section> |
| 3698 | |
| 3699 | <section id="control-interface-callbacks-get"> |
| 3700 | <title>get callback</title> |
| 3701 | |
| 3702 | <para> |
| 3703 | This callback is used to read the current value of the |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3704 | control and to return to user-space. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3705 | </para> |
| 3706 | |
| 3707 | <para> |
| 3708 | For example, |
| 3709 | |
| 3710 | <example> |
| 3711 | <title>Example of get callback</title> |
| 3712 | <programlisting> |
| 3713 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3714 | static int snd_myctl_get(struct snd_kcontrol *kcontrol, |
| 3715 | struct snd_ctl_elem_value *ucontrol) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3716 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3717 | struct mychip *chip = snd_kcontrol_chip(kcontrol); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3718 | ucontrol->value.integer.value[0] = get_some_value(chip); |
| 3719 | return 0; |
| 3720 | } |
| 3721 | ]]> |
| 3722 | </programlisting> |
| 3723 | </example> |
| 3724 | </para> |
| 3725 | |
| 3726 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3727 | The <structfield>value</structfield> field depends on |
| 3728 | the type of control as well as on the info callback. For example, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3729 | the sb driver uses this field to store the register offset, |
| 3730 | the bit-shift and the bit-mask. The |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3731 | <structfield>private_value</structfield> field is set as follows: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3732 | <informalexample> |
| 3733 | <programlisting> |
| 3734 | <![CDATA[ |
| 3735 | .private_value = reg | (shift << 16) | (mask << 24) |
| 3736 | ]]> |
| 3737 | </programlisting> |
| 3738 | </informalexample> |
| 3739 | and is retrieved in callbacks like |
| 3740 | <informalexample> |
| 3741 | <programlisting> |
| 3742 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3743 | static int snd_sbmixer_get_single(struct snd_kcontrol *kcontrol, |
| 3744 | struct snd_ctl_elem_value *ucontrol) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3745 | { |
| 3746 | int reg = kcontrol->private_value & 0xff; |
| 3747 | int shift = (kcontrol->private_value >> 16) & 0xff; |
| 3748 | int mask = (kcontrol->private_value >> 24) & 0xff; |
| 3749 | .... |
| 3750 | } |
| 3751 | ]]> |
| 3752 | </programlisting> |
| 3753 | </informalexample> |
| 3754 | </para> |
| 3755 | |
| 3756 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3757 | In the <structfield>get</structfield> callback, |
| 3758 | you have to fill all the elements if the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3759 | control has more than one elements, |
| 3760 | i.e. <structfield>count</structfield> > 1. |
| 3761 | In the example above, we filled only one element |
| 3762 | (<structfield>value.integer.value[0]</structfield>) since it's |
| 3763 | assumed as <structfield>count</structfield> = 1. |
| 3764 | </para> |
| 3765 | </section> |
| 3766 | |
| 3767 | <section id="control-interface-callbacks-put"> |
| 3768 | <title>put callback</title> |
| 3769 | |
| 3770 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3771 | This callback is used to write a value from user-space. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3772 | </para> |
| 3773 | |
| 3774 | <para> |
| 3775 | For example, |
| 3776 | |
| 3777 | <example> |
| 3778 | <title>Example of put callback</title> |
| 3779 | <programlisting> |
| 3780 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3781 | static int snd_myctl_put(struct snd_kcontrol *kcontrol, |
| 3782 | struct snd_ctl_elem_value *ucontrol) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3783 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3784 | struct mychip *chip = snd_kcontrol_chip(kcontrol); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3785 | int changed = 0; |
| 3786 | if (chip->current_value != |
| 3787 | ucontrol->value.integer.value[0]) { |
| 3788 | change_current_value(chip, |
| 3789 | ucontrol->value.integer.value[0]); |
| 3790 | changed = 1; |
| 3791 | } |
| 3792 | return changed; |
| 3793 | } |
| 3794 | ]]> |
| 3795 | </programlisting> |
| 3796 | </example> |
| 3797 | |
| 3798 | As seen above, you have to return 1 if the value is |
| 3799 | changed. If the value is not changed, return 0 instead. |
| 3800 | If any fatal error happens, return a negative error code as |
| 3801 | usual. |
| 3802 | </para> |
| 3803 | |
| 3804 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3805 | As in the <structfield>get</structfield> callback, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3806 | when the control has more than one elements, |
Nicolas Kaiser | 5bda9fa | 2007-01-22 14:54:33 +0100 | [diff] [blame] | 3807 | all elements must be evaluated in this callback, too. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3808 | </para> |
| 3809 | </section> |
| 3810 | |
| 3811 | <section id="control-interface-callbacks-all"> |
| 3812 | <title>Callbacks are not atomic</title> |
| 3813 | <para> |
| 3814 | All these three callbacks are basically not atomic. |
| 3815 | </para> |
| 3816 | </section> |
| 3817 | </section> |
| 3818 | |
| 3819 | <section id="control-interface-constructor"> |
| 3820 | <title>Constructor</title> |
| 3821 | <para> |
| 3822 | When everything is ready, finally we can create a new |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3823 | control. To create a control, there are two functions to be |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3824 | called, <function>snd_ctl_new1()</function> and |
| 3825 | <function>snd_ctl_add()</function>. |
| 3826 | </para> |
| 3827 | |
| 3828 | <para> |
| 3829 | In the simplest way, you can do like this: |
| 3830 | |
| 3831 | <informalexample> |
| 3832 | <programlisting> |
| 3833 | <![CDATA[ |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 3834 | err = snd_ctl_add(card, snd_ctl_new1(&my_control, chip)); |
| 3835 | if (err < 0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3836 | return err; |
| 3837 | ]]> |
| 3838 | </programlisting> |
| 3839 | </informalexample> |
| 3840 | |
| 3841 | where <parameter>my_control</parameter> is the |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3842 | struct <structname>snd_kcontrol_new</structname> object defined above, and chip |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3843 | is the object pointer to be passed to |
| 3844 | kcontrol->private_data |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3845 | which can be referred to in callbacks. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3846 | </para> |
| 3847 | |
| 3848 | <para> |
| 3849 | <function>snd_ctl_new1()</function> allocates a new |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3850 | <structname>snd_kcontrol</structname> instance (that's why the definition |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3851 | of <parameter>my_control</parameter> can be with |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3852 | the <parameter>__devinitdata</parameter> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3853 | prefix), and <function>snd_ctl_add</function> assigns the given |
| 3854 | control component to the card. |
| 3855 | </para> |
| 3856 | </section> |
| 3857 | |
| 3858 | <section id="control-interface-change-notification"> |
| 3859 | <title>Change Notification</title> |
| 3860 | <para> |
| 3861 | If you need to change and update a control in the interrupt |
| 3862 | routine, you can call <function>snd_ctl_notify()</function>. For |
| 3863 | example, |
| 3864 | |
| 3865 | <informalexample> |
| 3866 | <programlisting> |
| 3867 | <![CDATA[ |
| 3868 | snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, id_pointer); |
| 3869 | ]]> |
| 3870 | </programlisting> |
| 3871 | </informalexample> |
| 3872 | |
| 3873 | This function takes the card pointer, the event-mask, and the |
| 3874 | control id pointer for the notification. The event-mask |
| 3875 | specifies the types of notification, for example, in the above |
| 3876 | example, the change of control values is notified. |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3877 | The id pointer is the pointer of struct <structname>snd_ctl_elem_id</structname> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3878 | to be notified. |
| 3879 | You can find some examples in <filename>es1938.c</filename> or |
| 3880 | <filename>es1968.c</filename> for hardware volume interrupts. |
| 3881 | </para> |
| 3882 | </section> |
| 3883 | |
Clemens Ladisch | d1761d1 | 2007-09-10 08:05:19 +0200 | [diff] [blame] | 3884 | <section id="control-interface-tlv"> |
| 3885 | <title>Metadata</title> |
| 3886 | <para> |
| 3887 | To provide information about the dB values of a mixer control, use |
| 3888 | on of the <constant>DECLARE_TLV_xxx</constant> macros from |
| 3889 | <filename><sound/tlv.h></filename> to define a variable |
| 3890 | containing this information, set the<structfield>tlv.p |
| 3891 | </structfield> field to point to this variable, and include the |
| 3892 | <constant>SNDRV_CTL_ELEM_ACCESS_TLV_READ</constant> flag in the |
| 3893 | <structfield>access</structfield> field; like this: |
| 3894 | <informalexample> |
| 3895 | <programlisting> |
| 3896 | <![CDATA[ |
| 3897 | static DECLARE_TLV_DB_SCALE(db_scale_my_control, -4050, 150, 0); |
| 3898 | |
| 3899 | static struct snd_kcontrol_new my_control __devinitdata = { |
| 3900 | ... |
| 3901 | .access = SNDRV_CTL_ELEM_ACCESS_READWRITE | |
| 3902 | SNDRV_CTL_ELEM_ACCESS_TLV_READ, |
| 3903 | ... |
| 3904 | .tlv.p = db_scale_my_control, |
| 3905 | }; |
| 3906 | ]]> |
| 3907 | </programlisting> |
| 3908 | </informalexample> |
| 3909 | </para> |
| 3910 | |
| 3911 | <para> |
| 3912 | The <function>DECLARE_TLV_DB_SCALE</function> macro defines |
| 3913 | information about a mixer control where each step in the control's |
| 3914 | value changes the dB value by a constant dB amount. |
| 3915 | The first parameter is the name of the variable to be defined. |
| 3916 | The second parameter is the minimum value, in units of 0.01 dB. |
| 3917 | The third parameter is the step size, in units of 0.01 dB. |
| 3918 | Set the fourth parameter to 1 if the minimum value actually mutes |
| 3919 | the control. |
| 3920 | </para> |
| 3921 | |
| 3922 | <para> |
| 3923 | The <function>DECLARE_TLV_DB_LINEAR</function> macro defines |
| 3924 | information about a mixer control where the control's value affects |
| 3925 | the output linearly. |
| 3926 | The first parameter is the name of the variable to be defined. |
| 3927 | The second parameter is the minimum value, in units of 0.01 dB. |
| 3928 | The third parameter is the maximum value, in units of 0.01 dB. |
| 3929 | If the minimum value mutes the control, set the second parameter to |
| 3930 | <constant>TLV_DB_GAIN_MUTE</constant>. |
| 3931 | </para> |
| 3932 | </section> |
| 3933 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3934 | </chapter> |
| 3935 | |
| 3936 | |
| 3937 | <!-- ****************************************************** --> |
| 3938 | <!-- API for AC97 Codec --> |
| 3939 | <!-- ****************************************************** --> |
| 3940 | <chapter id="api-ac97"> |
| 3941 | <title>API for AC97 Codec</title> |
| 3942 | |
| 3943 | <section> |
| 3944 | <title>General</title> |
| 3945 | <para> |
| 3946 | The ALSA AC97 codec layer is a well-defined one, and you don't |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 3947 | have to write much code to control it. Only low-level control |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3948 | routines are necessary. The AC97 codec API is defined in |
| 3949 | <filename><sound/ac97_codec.h></filename>. |
| 3950 | </para> |
| 3951 | </section> |
| 3952 | |
| 3953 | <section id="api-ac97-example"> |
| 3954 | <title>Full Code Example</title> |
| 3955 | <para> |
| 3956 | <example> |
| 3957 | <title>Example of AC97 Interface</title> |
| 3958 | <programlisting> |
| 3959 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3960 | struct mychip { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3961 | .... |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3962 | struct snd_ac97 *ac97; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3963 | .... |
| 3964 | }; |
| 3965 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3966 | static unsigned short snd_mychip_ac97_read(struct snd_ac97 *ac97, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3967 | unsigned short reg) |
| 3968 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3969 | struct mychip *chip = ac97->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3970 | .... |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 3971 | /* read a register value here from the codec */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3972 | return the_register_value; |
| 3973 | } |
| 3974 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3975 | static void snd_mychip_ac97_write(struct snd_ac97 *ac97, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3976 | unsigned short reg, unsigned short val) |
| 3977 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3978 | struct mychip *chip = ac97->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3979 | .... |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 3980 | /* write the given register value to the codec */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3981 | } |
| 3982 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3983 | static int snd_mychip_ac97(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3984 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3985 | struct snd_ac97_bus *bus; |
| 3986 | struct snd_ac97_template ac97; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3987 | int err; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3988 | static struct snd_ac97_bus_ops ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3989 | .write = snd_mychip_ac97_write, |
| 3990 | .read = snd_mychip_ac97_read, |
| 3991 | }; |
| 3992 | |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 3993 | err = snd_ac97_bus(chip->card, 0, &ops, NULL, &bus); |
| 3994 | if (err < 0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3995 | return err; |
| 3996 | memset(&ac97, 0, sizeof(ac97)); |
| 3997 | ac97.private_data = chip; |
| 3998 | return snd_ac97_mixer(bus, &ac97, &chip->ac97); |
| 3999 | } |
| 4000 | |
| 4001 | ]]> |
| 4002 | </programlisting> |
| 4003 | </example> |
| 4004 | </para> |
| 4005 | </section> |
| 4006 | |
| 4007 | <section id="api-ac97-constructor"> |
| 4008 | <title>Constructor</title> |
| 4009 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4010 | To create an ac97 instance, first call <function>snd_ac97_bus</function> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4011 | with an <type>ac97_bus_ops_t</type> record with callback functions. |
| 4012 | |
| 4013 | <informalexample> |
| 4014 | <programlisting> |
| 4015 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4016 | struct snd_ac97_bus *bus; |
| 4017 | static struct snd_ac97_bus_ops ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4018 | .write = snd_mychip_ac97_write, |
| 4019 | .read = snd_mychip_ac97_read, |
| 4020 | }; |
| 4021 | |
| 4022 | snd_ac97_bus(card, 0, &ops, NULL, &pbus); |
| 4023 | ]]> |
| 4024 | </programlisting> |
| 4025 | </informalexample> |
| 4026 | |
| 4027 | The bus record is shared among all belonging ac97 instances. |
| 4028 | </para> |
| 4029 | |
| 4030 | <para> |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4031 | And then call <function>snd_ac97_mixer()</function> with an |
| 4032 | struct <structname>snd_ac97_template</structname> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4033 | record together with the bus pointer created above. |
| 4034 | |
| 4035 | <informalexample> |
| 4036 | <programlisting> |
| 4037 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4038 | struct snd_ac97_template ac97; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4039 | int err; |
| 4040 | |
| 4041 | memset(&ac97, 0, sizeof(ac97)); |
| 4042 | ac97.private_data = chip; |
| 4043 | snd_ac97_mixer(bus, &ac97, &chip->ac97); |
| 4044 | ]]> |
| 4045 | </programlisting> |
| 4046 | </informalexample> |
| 4047 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4048 | where chip->ac97 is a pointer to a newly created |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4049 | <type>ac97_t</type> instance. |
| 4050 | In this case, the chip pointer is set as the private data, so that |
| 4051 | the read/write callback functions can refer to this chip instance. |
| 4052 | This instance is not necessarily stored in the chip |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4053 | record. If you need to change the register values from the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4054 | driver, or need the suspend/resume of ac97 codecs, keep this |
| 4055 | pointer to pass to the corresponding functions. |
| 4056 | </para> |
| 4057 | </section> |
| 4058 | |
| 4059 | <section id="api-ac97-callbacks"> |
| 4060 | <title>Callbacks</title> |
| 4061 | <para> |
| 4062 | The standard callbacks are <structfield>read</structfield> and |
| 4063 | <structfield>write</structfield>. Obviously they |
| 4064 | correspond to the functions for read and write accesses to the |
| 4065 | hardware low-level codes. |
| 4066 | </para> |
| 4067 | |
| 4068 | <para> |
| 4069 | The <structfield>read</structfield> callback returns the |
| 4070 | register value specified in the argument. |
| 4071 | |
| 4072 | <informalexample> |
| 4073 | <programlisting> |
| 4074 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4075 | static unsigned short snd_mychip_ac97_read(struct snd_ac97 *ac97, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4076 | unsigned short reg) |
| 4077 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4078 | struct mychip *chip = ac97->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4079 | .... |
| 4080 | return the_register_value; |
| 4081 | } |
| 4082 | ]]> |
| 4083 | </programlisting> |
| 4084 | </informalexample> |
| 4085 | |
| 4086 | Here, the chip can be cast from ac97->private_data. |
| 4087 | </para> |
| 4088 | |
| 4089 | <para> |
| 4090 | Meanwhile, the <structfield>write</structfield> callback is |
| 4091 | used to set the register value. |
| 4092 | |
| 4093 | <informalexample> |
| 4094 | <programlisting> |
| 4095 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4096 | static void snd_mychip_ac97_write(struct snd_ac97 *ac97, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4097 | unsigned short reg, unsigned short val) |
| 4098 | ]]> |
| 4099 | </programlisting> |
| 4100 | </informalexample> |
| 4101 | </para> |
| 4102 | |
| 4103 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4104 | These callbacks are non-atomic like the control API callbacks. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4105 | </para> |
| 4106 | |
| 4107 | <para> |
| 4108 | There are also other callbacks: |
| 4109 | <structfield>reset</structfield>, |
| 4110 | <structfield>wait</structfield> and |
| 4111 | <structfield>init</structfield>. |
| 4112 | </para> |
| 4113 | |
| 4114 | <para> |
| 4115 | The <structfield>reset</structfield> callback is used to reset |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4116 | the codec. If the chip requires a special kind of reset, you can |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4117 | define this callback. |
| 4118 | </para> |
| 4119 | |
| 4120 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4121 | The <structfield>wait</structfield> callback is used to |
| 4122 | add some waiting time in the standard initialization of the codec. If the |
| 4123 | chip requires the extra waiting time, define this callback. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4124 | </para> |
| 4125 | |
| 4126 | <para> |
| 4127 | The <structfield>init</structfield> callback is used for |
| 4128 | additional initialization of the codec. |
| 4129 | </para> |
| 4130 | </section> |
| 4131 | |
| 4132 | <section id="api-ac97-updating-registers"> |
| 4133 | <title>Updating Registers in The Driver</title> |
| 4134 | <para> |
| 4135 | If you need to access to the codec from the driver, you can |
| 4136 | call the following functions: |
| 4137 | <function>snd_ac97_write()</function>, |
| 4138 | <function>snd_ac97_read()</function>, |
| 4139 | <function>snd_ac97_update()</function> and |
| 4140 | <function>snd_ac97_update_bits()</function>. |
| 4141 | </para> |
| 4142 | |
| 4143 | <para> |
| 4144 | Both <function>snd_ac97_write()</function> and |
| 4145 | <function>snd_ac97_update()</function> functions are used to |
| 4146 | set a value to the given register |
| 4147 | (<constant>AC97_XXX</constant>). The difference between them is |
| 4148 | that <function>snd_ac97_update()</function> doesn't write a |
| 4149 | value if the given value has been already set, while |
| 4150 | <function>snd_ac97_write()</function> always rewrites the |
| 4151 | value. |
| 4152 | |
| 4153 | <informalexample> |
| 4154 | <programlisting> |
| 4155 | <![CDATA[ |
| 4156 | snd_ac97_write(ac97, AC97_MASTER, 0x8080); |
| 4157 | snd_ac97_update(ac97, AC97_MASTER, 0x8080); |
| 4158 | ]]> |
| 4159 | </programlisting> |
| 4160 | </informalexample> |
| 4161 | </para> |
| 4162 | |
| 4163 | <para> |
| 4164 | <function>snd_ac97_read()</function> is used to read the value |
| 4165 | of the given register. For example, |
| 4166 | |
| 4167 | <informalexample> |
| 4168 | <programlisting> |
| 4169 | <![CDATA[ |
| 4170 | value = snd_ac97_read(ac97, AC97_MASTER); |
| 4171 | ]]> |
| 4172 | </programlisting> |
| 4173 | </informalexample> |
| 4174 | </para> |
| 4175 | |
| 4176 | <para> |
| 4177 | <function>snd_ac97_update_bits()</function> is used to update |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4178 | some bits in the given register. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4179 | |
| 4180 | <informalexample> |
| 4181 | <programlisting> |
| 4182 | <![CDATA[ |
| 4183 | snd_ac97_update_bits(ac97, reg, mask, value); |
| 4184 | ]]> |
| 4185 | </programlisting> |
| 4186 | </informalexample> |
| 4187 | </para> |
| 4188 | |
| 4189 | <para> |
| 4190 | Also, there is a function to change the sample rate (of a |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4191 | given register such as |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4192 | <constant>AC97_PCM_FRONT_DAC_RATE</constant>) when VRA or |
| 4193 | DRA is supported by the codec: |
| 4194 | <function>snd_ac97_set_rate()</function>. |
| 4195 | |
| 4196 | <informalexample> |
| 4197 | <programlisting> |
| 4198 | <![CDATA[ |
| 4199 | snd_ac97_set_rate(ac97, AC97_PCM_FRONT_DAC_RATE, 44100); |
| 4200 | ]]> |
| 4201 | </programlisting> |
| 4202 | </informalexample> |
| 4203 | </para> |
| 4204 | |
| 4205 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4206 | The following registers are available to set the rate: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4207 | <constant>AC97_PCM_MIC_ADC_RATE</constant>, |
| 4208 | <constant>AC97_PCM_FRONT_DAC_RATE</constant>, |
| 4209 | <constant>AC97_PCM_LR_ADC_RATE</constant>, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4210 | <constant>AC97_SPDIF</constant>. When |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4211 | <constant>AC97_SPDIF</constant> is specified, the register is |
| 4212 | not really changed but the corresponding IEC958 status bits will |
| 4213 | be updated. |
| 4214 | </para> |
| 4215 | </section> |
| 4216 | |
| 4217 | <section id="api-ac97-clock-adjustment"> |
| 4218 | <title>Clock Adjustment</title> |
| 4219 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4220 | In some chips, the clock of the codec isn't 48000 but using a |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4221 | PCI clock (to save a quartz!). In this case, change the field |
| 4222 | bus->clock to the corresponding |
| 4223 | value. For example, intel8x0 |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4224 | and es1968 drivers have their own function to read from the clock. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4225 | </para> |
| 4226 | </section> |
| 4227 | |
| 4228 | <section id="api-ac97-proc-files"> |
| 4229 | <title>Proc Files</title> |
| 4230 | <para> |
| 4231 | The ALSA AC97 interface will create a proc file such as |
| 4232 | <filename>/proc/asound/card0/codec97#0/ac97#0-0</filename> and |
| 4233 | <filename>ac97#0-0+regs</filename>. You can refer to these files to |
| 4234 | see the current status and registers of the codec. |
| 4235 | </para> |
| 4236 | </section> |
| 4237 | |
| 4238 | <section id="api-ac97-multiple-codecs"> |
| 4239 | <title>Multiple Codecs</title> |
| 4240 | <para> |
| 4241 | When there are several codecs on the same card, you need to |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4242 | call <function>snd_ac97_mixer()</function> multiple times with |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4243 | ac97.num=1 or greater. The <structfield>num</structfield> field |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4244 | specifies the codec number. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4245 | </para> |
| 4246 | |
| 4247 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4248 | If you set up multiple codecs, you either need to write |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4249 | different callbacks for each codec or check |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4250 | ac97->num in the callback routines. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4251 | </para> |
| 4252 | </section> |
| 4253 | |
| 4254 | </chapter> |
| 4255 | |
| 4256 | |
| 4257 | <!-- ****************************************************** --> |
| 4258 | <!-- MIDI (MPU401-UART) Interface --> |
| 4259 | <!-- ****************************************************** --> |
| 4260 | <chapter id="midi-interface"> |
| 4261 | <title>MIDI (MPU401-UART) Interface</title> |
| 4262 | |
| 4263 | <section id="midi-interface-general"> |
| 4264 | <title>General</title> |
| 4265 | <para> |
| 4266 | Many soundcards have built-in MIDI (MPU401-UART) |
| 4267 | interfaces. When the soundcard supports the standard MPU401-UART |
| 4268 | interface, most likely you can use the ALSA MPU401-UART API. The |
| 4269 | MPU401-UART API is defined in |
| 4270 | <filename><sound/mpu401.h></filename>. |
| 4271 | </para> |
| 4272 | |
| 4273 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4274 | Some soundchips have a similar but slightly different |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4275 | implementation of mpu401 stuff. For example, emu10k1 has its own |
| 4276 | mpu401 routines. |
| 4277 | </para> |
| 4278 | </section> |
| 4279 | |
| 4280 | <section id="midi-interface-constructor"> |
| 4281 | <title>Constructor</title> |
| 4282 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4283 | To create a rawmidi object, call |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4284 | <function>snd_mpu401_uart_new()</function>. |
| 4285 | |
| 4286 | <informalexample> |
| 4287 | <programlisting> |
| 4288 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4289 | struct snd_rawmidi *rmidi; |
Takashi Iwai | 302e4c2 | 2006-05-23 13:24:30 +0200 | [diff] [blame] | 4290 | snd_mpu401_uart_new(card, 0, MPU401_HW_MPU401, port, info_flags, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4291 | irq, irq_flags, &rmidi); |
| 4292 | ]]> |
| 4293 | </programlisting> |
| 4294 | </informalexample> |
| 4295 | </para> |
| 4296 | |
| 4297 | <para> |
| 4298 | The first argument is the card pointer, and the second is the |
| 4299 | index of this component. You can create up to 8 rawmidi |
| 4300 | devices. |
| 4301 | </para> |
| 4302 | |
| 4303 | <para> |
| 4304 | The third argument is the type of the hardware, |
| 4305 | <constant>MPU401_HW_XXX</constant>. If it's not a special one, |
| 4306 | you can use <constant>MPU401_HW_MPU401</constant>. |
| 4307 | </para> |
| 4308 | |
| 4309 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4310 | The 4th argument is the I/O port address. Many |
| 4311 | backward-compatible MPU401 have an I/O port such as 0x330. Or, it |
| 4312 | might be a part of its own PCI I/O region. It depends on the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4313 | chip design. |
| 4314 | </para> |
| 4315 | |
| 4316 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4317 | The 5th argument is a bitflag for additional information. |
| 4318 | When the I/O port address above is part of the PCI I/O |
| 4319 | region, the MPU401 I/O port might have been already allocated |
Takashi Iwai | 302e4c2 | 2006-05-23 13:24:30 +0200 | [diff] [blame] | 4320 | (reserved) by the driver itself. In such a case, pass a bit flag |
| 4321 | <constant>MPU401_INFO_INTEGRATED</constant>, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4322 | and the mpu401-uart layer will allocate the I/O ports by itself. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4323 | </para> |
| 4324 | |
Takashi Iwai | 302e4c2 | 2006-05-23 13:24:30 +0200 | [diff] [blame] | 4325 | <para> |
| 4326 | When the controller supports only the input or output MIDI stream, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4327 | pass the <constant>MPU401_INFO_INPUT</constant> or |
Takashi Iwai | 302e4c2 | 2006-05-23 13:24:30 +0200 | [diff] [blame] | 4328 | <constant>MPU401_INFO_OUTPUT</constant> bitflag, respectively. |
| 4329 | Then the rawmidi instance is created as a single stream. |
| 4330 | </para> |
| 4331 | |
| 4332 | <para> |
| 4333 | <constant>MPU401_INFO_MMIO</constant> bitflag is used to change |
| 4334 | the access method to MMIO (via readb and writeb) instead of |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4335 | iob and outb. In this case, you have to pass the iomapped address |
Takashi Iwai | 302e4c2 | 2006-05-23 13:24:30 +0200 | [diff] [blame] | 4336 | to <function>snd_mpu401_uart_new()</function>. |
| 4337 | </para> |
| 4338 | |
| 4339 | <para> |
| 4340 | When <constant>MPU401_INFO_TX_IRQ</constant> is set, the output |
| 4341 | stream isn't checked in the default interrupt handler. The driver |
| 4342 | needs to call <function>snd_mpu401_uart_interrupt_tx()</function> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4343 | by itself to start processing the output stream in the irq handler. |
Takashi Iwai | 302e4c2 | 2006-05-23 13:24:30 +0200 | [diff] [blame] | 4344 | </para> |
| 4345 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4346 | <para> |
| 4347 | Usually, the port address corresponds to the command port and |
| 4348 | port + 1 corresponds to the data port. If not, you may change |
| 4349 | the <structfield>cport</structfield> field of |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4350 | struct <structname>snd_mpu401</structname> manually |
| 4351 | afterward. However, <structname>snd_mpu401</structname> pointer is not |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4352 | returned explicitly by |
| 4353 | <function>snd_mpu401_uart_new()</function>. You need to cast |
| 4354 | rmidi->private_data to |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4355 | <structname>snd_mpu401</structname> explicitly, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4356 | |
| 4357 | <informalexample> |
| 4358 | <programlisting> |
| 4359 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4360 | struct snd_mpu401 *mpu; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4361 | mpu = rmidi->private_data; |
| 4362 | ]]> |
| 4363 | </programlisting> |
| 4364 | </informalexample> |
| 4365 | |
| 4366 | and reset the cport as you like: |
| 4367 | |
| 4368 | <informalexample> |
| 4369 | <programlisting> |
| 4370 | <![CDATA[ |
| 4371 | mpu->cport = my_own_control_port; |
| 4372 | ]]> |
| 4373 | </programlisting> |
| 4374 | </informalexample> |
| 4375 | </para> |
| 4376 | |
| 4377 | <para> |
| 4378 | The 6th argument specifies the irq number for UART. If the irq |
| 4379 | is already allocated, pass 0 to the 7th argument |
| 4380 | (<parameter>irq_flags</parameter>). Otherwise, pass the flags |
| 4381 | for irq allocation |
| 4382 | (<constant>SA_XXX</constant> bits) to it, and the irq will be |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4383 | reserved by the mpu401-uart layer. If the card doesn't generate |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4384 | UART interrupts, pass -1 as the irq number. Then a timer |
| 4385 | interrupt will be invoked for polling. |
| 4386 | </para> |
| 4387 | </section> |
| 4388 | |
| 4389 | <section id="midi-interface-interrupt-handler"> |
| 4390 | <title>Interrupt Handler</title> |
| 4391 | <para> |
| 4392 | When the interrupt is allocated in |
| 4393 | <function>snd_mpu401_uart_new()</function>, the private |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4394 | interrupt handler is used, hence you don't have anything else to do |
| 4395 | than creating the mpu401 stuff. Otherwise, you have to call |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4396 | <function>snd_mpu401_uart_interrupt()</function> explicitly when |
| 4397 | a UART interrupt is invoked and checked in your own interrupt |
| 4398 | handler. |
| 4399 | </para> |
| 4400 | |
| 4401 | <para> |
| 4402 | In this case, you need to pass the private_data of the |
| 4403 | returned rawmidi object from |
| 4404 | <function>snd_mpu401_uart_new()</function> as the second |
| 4405 | argument of <function>snd_mpu401_uart_interrupt()</function>. |
| 4406 | |
| 4407 | <informalexample> |
| 4408 | <programlisting> |
| 4409 | <![CDATA[ |
| 4410 | snd_mpu401_uart_interrupt(irq, rmidi->private_data, regs); |
| 4411 | ]]> |
| 4412 | </programlisting> |
| 4413 | </informalexample> |
| 4414 | </para> |
| 4415 | </section> |
| 4416 | |
| 4417 | </chapter> |
| 4418 | |
| 4419 | |
| 4420 | <!-- ****************************************************** --> |
| 4421 | <!-- RawMIDI Interface --> |
| 4422 | <!-- ****************************************************** --> |
| 4423 | <chapter id="rawmidi-interface"> |
| 4424 | <title>RawMIDI Interface</title> |
| 4425 | |
| 4426 | <section id="rawmidi-interface-overview"> |
| 4427 | <title>Overview</title> |
| 4428 | |
| 4429 | <para> |
| 4430 | The raw MIDI interface is used for hardware MIDI ports that can |
| 4431 | be accessed as a byte stream. It is not used for synthesizer |
| 4432 | chips that do not directly understand MIDI. |
| 4433 | </para> |
| 4434 | |
| 4435 | <para> |
| 4436 | ALSA handles file and buffer management. All you have to do is |
| 4437 | to write some code to move data between the buffer and the |
| 4438 | hardware. |
| 4439 | </para> |
| 4440 | |
| 4441 | <para> |
| 4442 | The rawmidi API is defined in |
| 4443 | <filename><sound/rawmidi.h></filename>. |
| 4444 | </para> |
| 4445 | </section> |
| 4446 | |
| 4447 | <section id="rawmidi-interface-constructor"> |
| 4448 | <title>Constructor</title> |
| 4449 | |
| 4450 | <para> |
| 4451 | To create a rawmidi device, call the |
| 4452 | <function>snd_rawmidi_new</function> function: |
| 4453 | <informalexample> |
| 4454 | <programlisting> |
| 4455 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4456 | struct snd_rawmidi *rmidi; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4457 | err = snd_rawmidi_new(chip->card, "MyMIDI", 0, outs, ins, &rmidi); |
| 4458 | if (err < 0) |
| 4459 | return err; |
| 4460 | rmidi->private_data = chip; |
| 4461 | strcpy(rmidi->name, "My MIDI"); |
| 4462 | rmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT | |
| 4463 | SNDRV_RAWMIDI_INFO_INPUT | |
| 4464 | SNDRV_RAWMIDI_INFO_DUPLEX; |
| 4465 | ]]> |
| 4466 | </programlisting> |
| 4467 | </informalexample> |
| 4468 | </para> |
| 4469 | |
| 4470 | <para> |
| 4471 | The first argument is the card pointer, the second argument is |
| 4472 | the ID string. |
| 4473 | </para> |
| 4474 | |
| 4475 | <para> |
| 4476 | The third argument is the index of this component. You can |
| 4477 | create up to 8 rawmidi devices. |
| 4478 | </para> |
| 4479 | |
| 4480 | <para> |
| 4481 | The fourth and fifth arguments are the number of output and |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4482 | input substreams, respectively, of this device (a substream is |
| 4483 | the equivalent of a MIDI port). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4484 | </para> |
| 4485 | |
| 4486 | <para> |
| 4487 | Set the <structfield>info_flags</structfield> field to specify |
| 4488 | the capabilities of the device. |
| 4489 | Set <constant>SNDRV_RAWMIDI_INFO_OUTPUT</constant> if there is |
| 4490 | at least one output port, |
| 4491 | <constant>SNDRV_RAWMIDI_INFO_INPUT</constant> if there is at |
| 4492 | least one input port, |
| 4493 | and <constant>SNDRV_RAWMIDI_INFO_DUPLEX</constant> if the device |
| 4494 | can handle output and input at the same time. |
| 4495 | </para> |
| 4496 | |
| 4497 | <para> |
| 4498 | After the rawmidi device is created, you need to set the |
| 4499 | operators (callbacks) for each substream. There are helper |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4500 | functions to set the operators for all the substreams of a device: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4501 | <informalexample> |
| 4502 | <programlisting> |
| 4503 | <![CDATA[ |
| 4504 | snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, &snd_mymidi_output_ops); |
| 4505 | snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT, &snd_mymidi_input_ops); |
| 4506 | ]]> |
| 4507 | </programlisting> |
| 4508 | </informalexample> |
| 4509 | </para> |
| 4510 | |
| 4511 | <para> |
| 4512 | The operators are usually defined like this: |
| 4513 | <informalexample> |
| 4514 | <programlisting> |
| 4515 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4516 | static struct snd_rawmidi_ops snd_mymidi_output_ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4517 | .open = snd_mymidi_output_open, |
| 4518 | .close = snd_mymidi_output_close, |
| 4519 | .trigger = snd_mymidi_output_trigger, |
| 4520 | }; |
| 4521 | ]]> |
| 4522 | </programlisting> |
| 4523 | </informalexample> |
| 4524 | These callbacks are explained in the <link |
| 4525 | linkend="rawmidi-interface-callbacks"><citetitle>Callbacks</citetitle></link> |
| 4526 | section. |
| 4527 | </para> |
| 4528 | |
| 4529 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4530 | If there are more than one substream, you should give a |
| 4531 | unique name to each of them: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4532 | <informalexample> |
| 4533 | <programlisting> |
| 4534 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4535 | struct snd_rawmidi_substream *substream; |
Takashi Iwai | 95a5b08 | 2007-07-26 16:50:09 +0200 | [diff] [blame] | 4536 | list_for_each_entry(substream, |
| 4537 | &rmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT].substreams, |
| 4538 | list { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4539 | sprintf(substream->name, "My MIDI Port %d", substream->number + 1); |
| 4540 | } |
| 4541 | /* same for SNDRV_RAWMIDI_STREAM_INPUT */ |
| 4542 | ]]> |
| 4543 | </programlisting> |
| 4544 | </informalexample> |
| 4545 | </para> |
| 4546 | </section> |
| 4547 | |
| 4548 | <section id="rawmidi-interface-callbacks"> |
| 4549 | <title>Callbacks</title> |
| 4550 | |
| 4551 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4552 | In all the callbacks, the private data that you've set for the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4553 | rawmidi device can be accessed as |
| 4554 | substream->rmidi->private_data. |
| 4555 | <!-- <code> isn't available before DocBook 4.3 --> |
| 4556 | </para> |
| 4557 | |
| 4558 | <para> |
| 4559 | If there is more than one port, your callbacks can determine the |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4560 | port index from the struct snd_rawmidi_substream data passed to each |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4561 | callback: |
| 4562 | <informalexample> |
| 4563 | <programlisting> |
| 4564 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4565 | struct snd_rawmidi_substream *substream; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4566 | int index = substream->number; |
| 4567 | ]]> |
| 4568 | </programlisting> |
| 4569 | </informalexample> |
| 4570 | </para> |
| 4571 | |
| 4572 | <section id="rawmidi-interface-op-open"> |
| 4573 | <title><function>open</function> callback</title> |
| 4574 | |
| 4575 | <informalexample> |
| 4576 | <programlisting> |
| 4577 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4578 | static int snd_xxx_open(struct snd_rawmidi_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4579 | ]]> |
| 4580 | </programlisting> |
| 4581 | </informalexample> |
| 4582 | |
| 4583 | <para> |
| 4584 | This is called when a substream is opened. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4585 | You can initialize the hardware here, but you shouldn't |
| 4586 | start transmitting/receiving data yet. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4587 | </para> |
| 4588 | </section> |
| 4589 | |
| 4590 | <section id="rawmidi-interface-op-close"> |
| 4591 | <title><function>close</function> callback</title> |
| 4592 | |
| 4593 | <informalexample> |
| 4594 | <programlisting> |
| 4595 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4596 | static int snd_xxx_close(struct snd_rawmidi_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4597 | ]]> |
| 4598 | </programlisting> |
| 4599 | </informalexample> |
| 4600 | |
| 4601 | <para> |
| 4602 | Guess what. |
| 4603 | </para> |
| 4604 | |
| 4605 | <para> |
| 4606 | The <function>open</function> and <function>close</function> |
| 4607 | callbacks of a rawmidi device are serialized with a mutex, |
| 4608 | and can sleep. |
| 4609 | </para> |
| 4610 | </section> |
| 4611 | |
| 4612 | <section id="rawmidi-interface-op-trigger-out"> |
| 4613 | <title><function>trigger</function> callback for output |
| 4614 | substreams</title> |
| 4615 | |
| 4616 | <informalexample> |
| 4617 | <programlisting> |
| 4618 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4619 | static void snd_xxx_output_trigger(struct snd_rawmidi_substream *substream, int up); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4620 | ]]> |
| 4621 | </programlisting> |
| 4622 | </informalexample> |
| 4623 | |
| 4624 | <para> |
| 4625 | This is called with a nonzero <parameter>up</parameter> |
| 4626 | parameter when there is some data in the substream buffer that |
| 4627 | must be transmitted. |
| 4628 | </para> |
| 4629 | |
| 4630 | <para> |
| 4631 | To read data from the buffer, call |
| 4632 | <function>snd_rawmidi_transmit_peek</function>. It will |
| 4633 | return the number of bytes that have been read; this will be |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4634 | less than the number of bytes requested when there are no more |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4635 | data in the buffer. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4636 | After the data have been transmitted successfully, call |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4637 | <function>snd_rawmidi_transmit_ack</function> to remove the |
| 4638 | data from the substream buffer: |
| 4639 | <informalexample> |
| 4640 | <programlisting> |
| 4641 | <![CDATA[ |
| 4642 | unsigned char data; |
| 4643 | while (snd_rawmidi_transmit_peek(substream, &data, 1) == 1) { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4644 | if (snd_mychip_try_to_transmit(data)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4645 | snd_rawmidi_transmit_ack(substream, 1); |
| 4646 | else |
| 4647 | break; /* hardware FIFO full */ |
| 4648 | } |
| 4649 | ]]> |
| 4650 | </programlisting> |
| 4651 | </informalexample> |
| 4652 | </para> |
| 4653 | |
| 4654 | <para> |
| 4655 | If you know beforehand that the hardware will accept data, you |
| 4656 | can use the <function>snd_rawmidi_transmit</function> function |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4657 | which reads some data and removes them from the buffer at once: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4658 | <informalexample> |
| 4659 | <programlisting> |
| 4660 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4661 | while (snd_mychip_transmit_possible()) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4662 | unsigned char data; |
| 4663 | if (snd_rawmidi_transmit(substream, &data, 1) != 1) |
| 4664 | break; /* no more data */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4665 | snd_mychip_transmit(data); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4666 | } |
| 4667 | ]]> |
| 4668 | </programlisting> |
| 4669 | </informalexample> |
| 4670 | </para> |
| 4671 | |
| 4672 | <para> |
| 4673 | If you know beforehand how many bytes you can accept, you can |
| 4674 | use a buffer size greater than one with the |
| 4675 | <function>snd_rawmidi_transmit*</function> functions. |
| 4676 | </para> |
| 4677 | |
| 4678 | <para> |
| 4679 | The <function>trigger</function> callback must not sleep. If |
| 4680 | the hardware FIFO is full before the substream buffer has been |
| 4681 | emptied, you have to continue transmitting data later, either |
| 4682 | in an interrupt handler, or with a timer if the hardware |
| 4683 | doesn't have a MIDI transmit interrupt. |
| 4684 | </para> |
| 4685 | |
| 4686 | <para> |
| 4687 | The <function>trigger</function> callback is called with a |
| 4688 | zero <parameter>up</parameter> parameter when the transmission |
| 4689 | of data should be aborted. |
| 4690 | </para> |
| 4691 | </section> |
| 4692 | |
| 4693 | <section id="rawmidi-interface-op-trigger-in"> |
| 4694 | <title><function>trigger</function> callback for input |
| 4695 | substreams</title> |
| 4696 | |
| 4697 | <informalexample> |
| 4698 | <programlisting> |
| 4699 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4700 | static void snd_xxx_input_trigger(struct snd_rawmidi_substream *substream, int up); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4701 | ]]> |
| 4702 | </programlisting> |
| 4703 | </informalexample> |
| 4704 | |
| 4705 | <para> |
| 4706 | This is called with a nonzero <parameter>up</parameter> |
| 4707 | parameter to enable receiving data, or with a zero |
| 4708 | <parameter>up</parameter> parameter do disable receiving data. |
| 4709 | </para> |
| 4710 | |
| 4711 | <para> |
| 4712 | The <function>trigger</function> callback must not sleep; the |
| 4713 | actual reading of data from the device is usually done in an |
| 4714 | interrupt handler. |
| 4715 | </para> |
| 4716 | |
| 4717 | <para> |
| 4718 | When data reception is enabled, your interrupt handler should |
| 4719 | call <function>snd_rawmidi_receive</function> for all received |
| 4720 | data: |
| 4721 | <informalexample> |
| 4722 | <programlisting> |
| 4723 | <![CDATA[ |
| 4724 | void snd_mychip_midi_interrupt(...) |
| 4725 | { |
| 4726 | while (mychip_midi_available()) { |
| 4727 | unsigned char data; |
| 4728 | data = mychip_midi_read(); |
| 4729 | snd_rawmidi_receive(substream, &data, 1); |
| 4730 | } |
| 4731 | } |
| 4732 | ]]> |
| 4733 | </programlisting> |
| 4734 | </informalexample> |
| 4735 | </para> |
| 4736 | </section> |
| 4737 | |
| 4738 | <section id="rawmidi-interface-op-drain"> |
| 4739 | <title><function>drain</function> callback</title> |
| 4740 | |
| 4741 | <informalexample> |
| 4742 | <programlisting> |
| 4743 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4744 | static void snd_xxx_drain(struct snd_rawmidi_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4745 | ]]> |
| 4746 | </programlisting> |
| 4747 | </informalexample> |
| 4748 | |
| 4749 | <para> |
| 4750 | This is only used with output substreams. This function should wait |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4751 | until all data read from the substream buffer have been transmitted. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4752 | This ensures that the device can be closed and the driver unloaded |
| 4753 | without losing data. |
| 4754 | </para> |
| 4755 | |
| 4756 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4757 | This callback is optional. If you do not set |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4758 | <structfield>drain</structfield> in the struct snd_rawmidi_ops |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4759 | structure, ALSA will simply wait for 50 milliseconds |
| 4760 | instead. |
| 4761 | </para> |
| 4762 | </section> |
| 4763 | </section> |
| 4764 | |
| 4765 | </chapter> |
| 4766 | |
| 4767 | |
| 4768 | <!-- ****************************************************** --> |
| 4769 | <!-- Miscellaneous Devices --> |
| 4770 | <!-- ****************************************************** --> |
| 4771 | <chapter id="misc-devices"> |
| 4772 | <title>Miscellaneous Devices</title> |
| 4773 | |
| 4774 | <section id="misc-devices-opl3"> |
| 4775 | <title>FM OPL3</title> |
| 4776 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4777 | The FM OPL3 is still used in many chips (mainly for backward |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4778 | compatibility). ALSA has a nice OPL3 FM control layer, too. The |
| 4779 | OPL3 API is defined in |
| 4780 | <filename><sound/opl3.h></filename>. |
| 4781 | </para> |
| 4782 | |
| 4783 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4784 | FM registers can be directly accessed through the direct-FM API, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4785 | defined in <filename><sound/asound_fm.h></filename>. In |
| 4786 | ALSA native mode, FM registers are accessed through |
Lucas De Marchi | 25985ed | 2011-03-30 22:57:33 -0300 | [diff] [blame] | 4787 | the Hardware-Dependent Device direct-FM extension API, whereas in |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4788 | OSS compatible mode, FM registers can be accessed with the OSS |
| 4789 | direct-FM compatible API in <filename>/dev/dmfmX</filename> device. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4790 | </para> |
| 4791 | |
| 4792 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4793 | To create the OPL3 component, you have two functions to |
| 4794 | call. The first one is a constructor for the <type>opl3_t</type> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4795 | instance. |
| 4796 | |
| 4797 | <informalexample> |
| 4798 | <programlisting> |
| 4799 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4800 | struct snd_opl3 *opl3; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4801 | snd_opl3_create(card, lport, rport, OPL3_HW_OPL3_XXX, |
| 4802 | integrated, &opl3); |
| 4803 | ]]> |
| 4804 | </programlisting> |
| 4805 | </informalexample> |
| 4806 | </para> |
| 4807 | |
| 4808 | <para> |
| 4809 | The first argument is the card pointer, the second one is the |
| 4810 | left port address, and the third is the right port address. In |
| 4811 | most cases, the right port is placed at the left port + 2. |
| 4812 | </para> |
| 4813 | |
| 4814 | <para> |
| 4815 | The fourth argument is the hardware type. |
| 4816 | </para> |
| 4817 | |
| 4818 | <para> |
| 4819 | When the left and right ports have been already allocated by |
| 4820 | the card driver, pass non-zero to the fifth argument |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4821 | (<parameter>integrated</parameter>). Otherwise, the opl3 module will |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4822 | allocate the specified ports by itself. |
| 4823 | </para> |
| 4824 | |
| 4825 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4826 | When the accessing the hardware requires special method |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4827 | instead of the standard I/O access, you can create opl3 instance |
| 4828 | separately with <function>snd_opl3_new()</function>. |
| 4829 | |
| 4830 | <informalexample> |
| 4831 | <programlisting> |
| 4832 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4833 | struct snd_opl3 *opl3; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4834 | snd_opl3_new(card, OPL3_HW_OPL3_XXX, &opl3); |
| 4835 | ]]> |
| 4836 | </programlisting> |
| 4837 | </informalexample> |
| 4838 | </para> |
| 4839 | |
| 4840 | <para> |
| 4841 | Then set <structfield>command</structfield>, |
| 4842 | <structfield>private_data</structfield> and |
| 4843 | <structfield>private_free</structfield> for the private |
| 4844 | access function, the private data and the destructor. |
| 4845 | The l_port and r_port are not necessarily set. Only the |
| 4846 | command must be set properly. You can retrieve the data |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4847 | from the opl3->private_data field. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4848 | </para> |
| 4849 | |
| 4850 | <para> |
| 4851 | After creating the opl3 instance via <function>snd_opl3_new()</function>, |
| 4852 | call <function>snd_opl3_init()</function> to initialize the chip to the |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4853 | proper state. Note that <function>snd_opl3_create()</function> always |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4854 | calls it internally. |
| 4855 | </para> |
| 4856 | |
| 4857 | <para> |
| 4858 | If the opl3 instance is created successfully, then create a |
| 4859 | hwdep device for this opl3. |
| 4860 | |
| 4861 | <informalexample> |
| 4862 | <programlisting> |
| 4863 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4864 | struct snd_hwdep *opl3hwdep; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4865 | snd_opl3_hwdep_new(opl3, 0, 1, &opl3hwdep); |
| 4866 | ]]> |
| 4867 | </programlisting> |
| 4868 | </informalexample> |
| 4869 | </para> |
| 4870 | |
| 4871 | <para> |
| 4872 | The first argument is the <type>opl3_t</type> instance you |
| 4873 | created, and the second is the index number, usually 0. |
| 4874 | </para> |
| 4875 | |
| 4876 | <para> |
| 4877 | The third argument is the index-offset for the sequencer |
| 4878 | client assigned to the OPL3 port. When there is an MPU401-UART, |
| 4879 | give 1 for here (UART always takes 0). |
| 4880 | </para> |
| 4881 | </section> |
| 4882 | |
| 4883 | <section id="misc-devices-hardware-dependent"> |
| 4884 | <title>Hardware-Dependent Devices</title> |
| 4885 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4886 | Some chips need user-space access for special |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4887 | controls or for loading the micro code. In such a case, you can |
| 4888 | create a hwdep (hardware-dependent) device. The hwdep API is |
| 4889 | defined in <filename><sound/hwdep.h></filename>. You can |
| 4890 | find examples in opl3 driver or |
| 4891 | <filename>isa/sb/sb16_csp.c</filename>. |
| 4892 | </para> |
| 4893 | |
| 4894 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4895 | The creation of the <type>hwdep</type> instance is done via |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4896 | <function>snd_hwdep_new()</function>. |
| 4897 | |
| 4898 | <informalexample> |
| 4899 | <programlisting> |
| 4900 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4901 | struct snd_hwdep *hw; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4902 | snd_hwdep_new(card, "My HWDEP", 0, &hw); |
| 4903 | ]]> |
| 4904 | </programlisting> |
| 4905 | </informalexample> |
| 4906 | |
| 4907 | where the third argument is the index number. |
| 4908 | </para> |
| 4909 | |
| 4910 | <para> |
| 4911 | You can then pass any pointer value to the |
| 4912 | <parameter>private_data</parameter>. |
| 4913 | If you assign a private data, you should define the |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4914 | destructor, too. The destructor function is set in |
| 4915 | the <structfield>private_free</structfield> field. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4916 | |
| 4917 | <informalexample> |
| 4918 | <programlisting> |
| 4919 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4920 | struct mydata *p = kmalloc(sizeof(*p), GFP_KERNEL); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4921 | hw->private_data = p; |
| 4922 | hw->private_free = mydata_free; |
| 4923 | ]]> |
| 4924 | </programlisting> |
| 4925 | </informalexample> |
| 4926 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4927 | and the implementation of the destructor would be: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4928 | |
| 4929 | <informalexample> |
| 4930 | <programlisting> |
| 4931 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4932 | static void mydata_free(struct snd_hwdep *hw) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4933 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4934 | struct mydata *p = hw->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4935 | kfree(p); |
| 4936 | } |
| 4937 | ]]> |
| 4938 | </programlisting> |
| 4939 | </informalexample> |
| 4940 | </para> |
| 4941 | |
| 4942 | <para> |
| 4943 | The arbitrary file operations can be defined for this |
| 4944 | instance. The file operators are defined in |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4945 | the <parameter>ops</parameter> table. For example, assume that |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4946 | this chip needs an ioctl. |
| 4947 | |
| 4948 | <informalexample> |
| 4949 | <programlisting> |
| 4950 | <![CDATA[ |
| 4951 | hw->ops.open = mydata_open; |
| 4952 | hw->ops.ioctl = mydata_ioctl; |
| 4953 | hw->ops.release = mydata_release; |
| 4954 | ]]> |
| 4955 | </programlisting> |
| 4956 | </informalexample> |
| 4957 | |
| 4958 | And implement the callback functions as you like. |
| 4959 | </para> |
| 4960 | </section> |
| 4961 | |
| 4962 | <section id="misc-devices-IEC958"> |
| 4963 | <title>IEC958 (S/PDIF)</title> |
| 4964 | <para> |
| 4965 | Usually the controls for IEC958 devices are implemented via |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4966 | the control interface. There is a macro to compose a name string for |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4967 | IEC958 controls, <function>SNDRV_CTL_NAME_IEC958()</function> |
| 4968 | defined in <filename><include/asound.h></filename>. |
| 4969 | </para> |
| 4970 | |
| 4971 | <para> |
| 4972 | There are some standard controls for IEC958 status bits. These |
| 4973 | controls use the type <type>SNDRV_CTL_ELEM_TYPE_IEC958</type>, |
| 4974 | and the size of element is fixed as 4 bytes array |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 4975 | (value.iec958.status[x]). For the <structfield>info</structfield> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4976 | callback, you don't specify |
| 4977 | the value field for this type (the count field must be set, |
| 4978 | though). |
| 4979 | </para> |
| 4980 | |
| 4981 | <para> |
| 4982 | <quote>IEC958 Playback Con Mask</quote> is used to return the |
| 4983 | bit-mask for the IEC958 status bits of consumer mode. Similarly, |
| 4984 | <quote>IEC958 Playback Pro Mask</quote> returns the bitmask for |
| 4985 | professional mode. They are read-only controls, and are defined |
| 4986 | as MIXER controls (iface = |
| 4987 | <constant>SNDRV_CTL_ELEM_IFACE_MIXER</constant>). |
| 4988 | </para> |
| 4989 | |
| 4990 | <para> |
| 4991 | Meanwhile, <quote>IEC958 Playback Default</quote> control is |
| 4992 | defined for getting and setting the current default IEC958 |
| 4993 | bits. Note that this one is usually defined as a PCM control |
| 4994 | (iface = <constant>SNDRV_CTL_ELEM_IFACE_PCM</constant>), |
| 4995 | although in some places it's defined as a MIXER control. |
| 4996 | </para> |
| 4997 | |
| 4998 | <para> |
| 4999 | In addition, you can define the control switches to |
| 5000 | enable/disable or to set the raw bit mode. The implementation |
| 5001 | will depend on the chip, but the control should be named as |
| 5002 | <quote>IEC958 xxx</quote>, preferably using |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5003 | the <function>SNDRV_CTL_NAME_IEC958()</function> macro. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5004 | </para> |
| 5005 | |
| 5006 | <para> |
| 5007 | You can find several cases, for example, |
| 5008 | <filename>pci/emu10k1</filename>, |
| 5009 | <filename>pci/ice1712</filename>, or |
| 5010 | <filename>pci/cmipci.c</filename>. |
| 5011 | </para> |
| 5012 | </section> |
| 5013 | |
| 5014 | </chapter> |
| 5015 | |
| 5016 | |
| 5017 | <!-- ****************************************************** --> |
| 5018 | <!-- Buffer and Memory Management --> |
| 5019 | <!-- ****************************************************** --> |
| 5020 | <chapter id="buffer-and-memory"> |
| 5021 | <title>Buffer and Memory Management</title> |
| 5022 | |
| 5023 | <section id="buffer-and-memory-buffer-types"> |
| 5024 | <title>Buffer Types</title> |
| 5025 | <para> |
| 5026 | ALSA provides several different buffer allocation functions |
| 5027 | depending on the bus and the architecture. All these have a |
| 5028 | consistent API. The allocation of physically-contiguous pages is |
| 5029 | done via |
| 5030 | <function>snd_malloc_xxx_pages()</function> function, where xxx |
| 5031 | is the bus type. |
| 5032 | </para> |
| 5033 | |
| 5034 | <para> |
| 5035 | The allocation of pages with fallback is |
| 5036 | <function>snd_malloc_xxx_pages_fallback()</function>. This |
| 5037 | function tries to allocate the specified pages but if the pages |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5038 | are not available, it tries to reduce the page sizes until |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5039 | enough space is found. |
| 5040 | </para> |
| 5041 | |
| 5042 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5043 | The release the pages, call |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5044 | <function>snd_free_xxx_pages()</function> function. |
| 5045 | </para> |
| 5046 | |
| 5047 | <para> |
| 5048 | Usually, ALSA drivers try to allocate and reserve |
| 5049 | a large contiguous physical space |
| 5050 | at the time the module is loaded for the later use. |
| 5051 | This is called <quote>pre-allocation</quote>. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5052 | As already written, you can call the following function at |
| 5053 | pcm instance construction time (in the case of PCI bus). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5054 | |
| 5055 | <informalexample> |
| 5056 | <programlisting> |
| 5057 | <![CDATA[ |
| 5058 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, |
| 5059 | snd_dma_pci_data(pci), size, max); |
| 5060 | ]]> |
| 5061 | </programlisting> |
| 5062 | </informalexample> |
| 5063 | |
| 5064 | where <parameter>size</parameter> is the byte size to be |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5065 | pre-allocated and the <parameter>max</parameter> is the maximum |
| 5066 | size to be changed via the <filename>prealloc</filename> proc file. |
| 5067 | The allocator will try to get an area as large as possible |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5068 | within the given size. |
| 5069 | </para> |
| 5070 | |
| 5071 | <para> |
| 5072 | The second argument (type) and the third argument (device pointer) |
| 5073 | are dependent on the bus. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5074 | In the case of the ISA bus, pass <function>snd_dma_isa_data()</function> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5075 | as the third argument with <constant>SNDRV_DMA_TYPE_DEV</constant> type. |
| 5076 | For the continuous buffer unrelated to the bus can be pre-allocated |
| 5077 | with <constant>SNDRV_DMA_TYPE_CONTINUOUS</constant> type and the |
| 5078 | <function>snd_dma_continuous_data(GFP_KERNEL)</function> device pointer, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5079 | where <constant>GFP_KERNEL</constant> is the kernel allocation flag to |
David S. Miller | 759ee81 | 2008-08-27 00:33:26 -0700 | [diff] [blame] | 5080 | use. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5081 | For the PCI scatter-gather buffers, use |
| 5082 | <constant>SNDRV_DMA_TYPE_DEV_SG</constant> with |
| 5083 | <function>snd_dma_pci_data(pci)</function> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5084 | (see the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5085 | <link linkend="buffer-and-memory-non-contiguous"><citetitle>Non-Contiguous Buffers |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5086 | </citetitle></link> section). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5087 | </para> |
| 5088 | |
| 5089 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5090 | Once the buffer is pre-allocated, you can use the |
| 5091 | allocator in the <structfield>hw_params</structfield> callback: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5092 | |
| 5093 | <informalexample> |
| 5094 | <programlisting> |
| 5095 | <![CDATA[ |
| 5096 | snd_pcm_lib_malloc_pages(substream, size); |
| 5097 | ]]> |
| 5098 | </programlisting> |
| 5099 | </informalexample> |
| 5100 | |
| 5101 | Note that you have to pre-allocate to use this function. |
| 5102 | </para> |
| 5103 | </section> |
| 5104 | |
| 5105 | <section id="buffer-and-memory-external-hardware"> |
| 5106 | <title>External Hardware Buffers</title> |
| 5107 | <para> |
| 5108 | Some chips have their own hardware buffers and the DMA |
| 5109 | transfer from the host memory is not available. In such a case, |
| 5110 | you need to either 1) copy/set the audio data directly to the |
| 5111 | external hardware buffer, or 2) make an intermediate buffer and |
| 5112 | copy/set the data from it to the external hardware buffer in |
| 5113 | interrupts (or in tasklets, preferably). |
| 5114 | </para> |
| 5115 | |
| 5116 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5117 | The first case works fine if the external hardware buffer is large |
| 5118 | enough. This method doesn't need any extra buffers and thus is |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5119 | more effective. You need to define the |
| 5120 | <structfield>copy</structfield> and |
| 5121 | <structfield>silence</structfield> callbacks for |
| 5122 | the data transfer. However, there is a drawback: it cannot |
| 5123 | be mmapped. The examples are GUS's GF1 PCM or emu8000's |
| 5124 | wavetable PCM. |
| 5125 | </para> |
| 5126 | |
| 5127 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5128 | The second case allows for mmap on the buffer, although you have |
| 5129 | to handle an interrupt or a tasklet to transfer the data |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5130 | from the intermediate buffer to the hardware buffer. You can find an |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5131 | example in the vxpocket driver. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5132 | </para> |
| 5133 | |
| 5134 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5135 | Another case is when the chip uses a PCI memory-map |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5136 | region for the buffer instead of the host memory. In this case, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5137 | mmap is available only on certain architectures like the Intel one. |
| 5138 | In non-mmap mode, the data cannot be transferred as in the normal |
| 5139 | way. Thus you need to define the <structfield>copy</structfield> and |
| 5140 | <structfield>silence</structfield> callbacks as well, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5141 | as in the cases above. The examples are found in |
| 5142 | <filename>rme32.c</filename> and <filename>rme96.c</filename>. |
| 5143 | </para> |
| 5144 | |
| 5145 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5146 | The implementation of the <structfield>copy</structfield> and |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5147 | <structfield>silence</structfield> callbacks depends upon |
| 5148 | whether the hardware supports interleaved or non-interleaved |
| 5149 | samples. The <structfield>copy</structfield> callback is |
| 5150 | defined like below, a bit |
| 5151 | differently depending whether the direction is playback or |
| 5152 | capture: |
| 5153 | |
| 5154 | <informalexample> |
| 5155 | <programlisting> |
| 5156 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5157 | static int playback_copy(struct snd_pcm_substream *substream, int channel, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5158 | snd_pcm_uframes_t pos, void *src, snd_pcm_uframes_t count); |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5159 | static int capture_copy(struct snd_pcm_substream *substream, int channel, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5160 | snd_pcm_uframes_t pos, void *dst, snd_pcm_uframes_t count); |
| 5161 | ]]> |
| 5162 | </programlisting> |
| 5163 | </informalexample> |
| 5164 | </para> |
| 5165 | |
| 5166 | <para> |
| 5167 | In the case of interleaved samples, the second argument |
| 5168 | (<parameter>channel</parameter>) is not used. The third argument |
| 5169 | (<parameter>pos</parameter>) points the |
| 5170 | current position offset in frames. |
| 5171 | </para> |
| 5172 | |
| 5173 | <para> |
| 5174 | The meaning of the fourth argument is different between |
| 5175 | playback and capture. For playback, it holds the source data |
| 5176 | pointer, and for capture, it's the destination data pointer. |
| 5177 | </para> |
| 5178 | |
| 5179 | <para> |
| 5180 | The last argument is the number of frames to be copied. |
| 5181 | </para> |
| 5182 | |
| 5183 | <para> |
| 5184 | What you have to do in this callback is again different |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5185 | between playback and capture directions. In the |
| 5186 | playback case, you copy the given amount of data |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5187 | (<parameter>count</parameter>) at the specified pointer |
| 5188 | (<parameter>src</parameter>) to the specified offset |
| 5189 | (<parameter>pos</parameter>) on the hardware buffer. When |
| 5190 | coded like memcpy-like way, the copy would be like: |
| 5191 | |
| 5192 | <informalexample> |
| 5193 | <programlisting> |
| 5194 | <![CDATA[ |
| 5195 | my_memcpy(my_buffer + frames_to_bytes(runtime, pos), src, |
| 5196 | frames_to_bytes(runtime, count)); |
| 5197 | ]]> |
| 5198 | </programlisting> |
| 5199 | </informalexample> |
| 5200 | </para> |
| 5201 | |
| 5202 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5203 | For the capture direction, you copy the given amount of |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5204 | data (<parameter>count</parameter>) at the specified offset |
| 5205 | (<parameter>pos</parameter>) on the hardware buffer to the |
| 5206 | specified pointer (<parameter>dst</parameter>). |
| 5207 | |
| 5208 | <informalexample> |
| 5209 | <programlisting> |
| 5210 | <![CDATA[ |
| 5211 | my_memcpy(dst, my_buffer + frames_to_bytes(runtime, pos), |
| 5212 | frames_to_bytes(runtime, count)); |
| 5213 | ]]> |
| 5214 | </programlisting> |
| 5215 | </informalexample> |
| 5216 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5217 | Note that both the position and the amount of data are given |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5218 | in frames. |
| 5219 | </para> |
| 5220 | |
| 5221 | <para> |
| 5222 | In the case of non-interleaved samples, the implementation |
| 5223 | will be a bit more complicated. |
| 5224 | </para> |
| 5225 | |
| 5226 | <para> |
| 5227 | You need to check the channel argument, and if it's -1, copy |
| 5228 | the whole channels. Otherwise, you have to copy only the |
| 5229 | specified channel. Please check |
| 5230 | <filename>isa/gus/gus_pcm.c</filename> as an example. |
| 5231 | </para> |
| 5232 | |
| 5233 | <para> |
| 5234 | The <structfield>silence</structfield> callback is also |
| 5235 | implemented in a similar way. |
| 5236 | |
| 5237 | <informalexample> |
| 5238 | <programlisting> |
| 5239 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5240 | static int silence(struct snd_pcm_substream *substream, int channel, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5241 | snd_pcm_uframes_t pos, snd_pcm_uframes_t count); |
| 5242 | ]]> |
| 5243 | </programlisting> |
| 5244 | </informalexample> |
| 5245 | </para> |
| 5246 | |
| 5247 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5248 | The meanings of arguments are the same as in the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5249 | <structfield>copy</structfield> |
| 5250 | callback, although there is no <parameter>src/dst</parameter> |
| 5251 | argument. In the case of interleaved samples, the channel |
| 5252 | argument has no meaning, as well as on |
| 5253 | <structfield>copy</structfield> callback. |
| 5254 | </para> |
| 5255 | |
| 5256 | <para> |
| 5257 | The role of <structfield>silence</structfield> callback is to |
| 5258 | set the given amount |
| 5259 | (<parameter>count</parameter>) of silence data at the |
| 5260 | specified offset (<parameter>pos</parameter>) on the hardware |
| 5261 | buffer. Suppose that the data format is signed (that is, the |
| 5262 | silent-data is 0), and the implementation using a memset-like |
| 5263 | function would be like: |
| 5264 | |
| 5265 | <informalexample> |
| 5266 | <programlisting> |
| 5267 | <![CDATA[ |
| 5268 | my_memcpy(my_buffer + frames_to_bytes(runtime, pos), 0, |
| 5269 | frames_to_bytes(runtime, count)); |
| 5270 | ]]> |
| 5271 | </programlisting> |
| 5272 | </informalexample> |
| 5273 | </para> |
| 5274 | |
| 5275 | <para> |
| 5276 | In the case of non-interleaved samples, again, the |
| 5277 | implementation becomes a bit more complicated. See, for example, |
| 5278 | <filename>isa/gus/gus_pcm.c</filename>. |
| 5279 | </para> |
| 5280 | </section> |
| 5281 | |
| 5282 | <section id="buffer-and-memory-non-contiguous"> |
| 5283 | <title>Non-Contiguous Buffers</title> |
| 5284 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5285 | If your hardware supports the page table as in emu10k1 or the |
| 5286 | buffer descriptors as in via82xx, you can use the scatter-gather |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5287 | (SG) DMA. ALSA provides an interface for handling SG-buffers. |
| 5288 | The API is provided in <filename><sound/pcm.h></filename>. |
| 5289 | </para> |
| 5290 | |
| 5291 | <para> |
| 5292 | For creating the SG-buffer handler, call |
| 5293 | <function>snd_pcm_lib_preallocate_pages()</function> or |
| 5294 | <function>snd_pcm_lib_preallocate_pages_for_all()</function> |
| 5295 | with <constant>SNDRV_DMA_TYPE_DEV_SG</constant> |
| 5296 | in the PCM constructor like other PCI pre-allocator. |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5297 | You need to pass <function>snd_dma_pci_data(pci)</function>, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5298 | where pci is the struct <structname>pci_dev</structname> pointer |
| 5299 | of the chip as well. |
Giuliano Pochini | 44275f1 | 2006-01-27 12:02:05 +0100 | [diff] [blame] | 5300 | The <type>struct snd_sg_buf</type> instance is created as |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5301 | substream->dma_private. You can cast |
| 5302 | the pointer like: |
| 5303 | |
| 5304 | <informalexample> |
| 5305 | <programlisting> |
| 5306 | <![CDATA[ |
Giuliano Pochini | 44275f1 | 2006-01-27 12:02:05 +0100 | [diff] [blame] | 5307 | struct snd_sg_buf *sgbuf = (struct snd_sg_buf *)substream->dma_private; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5308 | ]]> |
| 5309 | </programlisting> |
| 5310 | </informalexample> |
| 5311 | </para> |
| 5312 | |
| 5313 | <para> |
| 5314 | Then call <function>snd_pcm_lib_malloc_pages()</function> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5315 | in the <structfield>hw_params</structfield> callback |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5316 | as well as in the case of normal PCI buffer. |
| 5317 | The SG-buffer handler will allocate the non-contiguous kernel |
| 5318 | pages of the given size and map them onto the virtually contiguous |
| 5319 | memory. The virtual pointer is addressed in runtime->dma_area. |
| 5320 | The physical address (runtime->dma_addr) is set to zero, |
André Goddard Rosa | af901ca | 2009-11-14 13:09:05 -0200 | [diff] [blame] | 5321 | because the buffer is physically non-contiguous. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5322 | The physical address table is set up in sgbuf->table. |
| 5323 | You can get the physical address at a certain offset via |
| 5324 | <function>snd_pcm_sgbuf_get_addr()</function>. |
| 5325 | </para> |
| 5326 | |
| 5327 | <para> |
| 5328 | When a SG-handler is used, you need to set |
| 5329 | <function>snd_pcm_sgbuf_ops_page</function> as |
| 5330 | the <structfield>page</structfield> callback. |
| 5331 | (See <link linkend="pcm-interface-operators-page-callback"> |
| 5332 | <citetitle>page callback section</citetitle></link>.) |
| 5333 | </para> |
| 5334 | |
| 5335 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5336 | To release the data, call |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5337 | <function>snd_pcm_lib_free_pages()</function> in the |
| 5338 | <structfield>hw_free</structfield> callback as usual. |
| 5339 | </para> |
| 5340 | </section> |
| 5341 | |
| 5342 | <section id="buffer-and-memory-vmalloced"> |
| 5343 | <title>Vmalloc'ed Buffers</title> |
| 5344 | <para> |
| 5345 | It's possible to use a buffer allocated via |
| 5346 | <function>vmalloc</function>, for example, for an intermediate |
| 5347 | buffer. Since the allocated pages are not contiguous, you need |
| 5348 | to set the <structfield>page</structfield> callback to obtain |
| 5349 | the physical address at every offset. |
| 5350 | </para> |
| 5351 | |
| 5352 | <para> |
| 5353 | The implementation of <structfield>page</structfield> callback |
| 5354 | would be like this: |
| 5355 | |
| 5356 | <informalexample> |
| 5357 | <programlisting> |
| 5358 | <![CDATA[ |
| 5359 | #include <linux/vmalloc.h> |
| 5360 | |
| 5361 | /* get the physical page pointer on the given offset */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5362 | static struct page *mychip_page(struct snd_pcm_substream *substream, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5363 | unsigned long offset) |
| 5364 | { |
| 5365 | void *pageptr = substream->runtime->dma_area + offset; |
| 5366 | return vmalloc_to_page(pageptr); |
| 5367 | } |
| 5368 | ]]> |
| 5369 | </programlisting> |
| 5370 | </informalexample> |
| 5371 | </para> |
| 5372 | </section> |
| 5373 | |
| 5374 | </chapter> |
| 5375 | |
| 5376 | |
| 5377 | <!-- ****************************************************** --> |
| 5378 | <!-- Proc Interface --> |
| 5379 | <!-- ****************************************************** --> |
| 5380 | <chapter id="proc-interface"> |
| 5381 | <title>Proc Interface</title> |
| 5382 | <para> |
| 5383 | ALSA provides an easy interface for procfs. The proc files are |
| 5384 | very useful for debugging. I recommend you set up proc files if |
| 5385 | you write a driver and want to get a running status or register |
| 5386 | dumps. The API is found in |
| 5387 | <filename><sound/info.h></filename>. |
| 5388 | </para> |
| 5389 | |
| 5390 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5391 | To create a proc file, call |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5392 | <function>snd_card_proc_new()</function>. |
| 5393 | |
| 5394 | <informalexample> |
| 5395 | <programlisting> |
| 5396 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5397 | struct snd_info_entry *entry; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5398 | int err = snd_card_proc_new(card, "my-file", &entry); |
| 5399 | ]]> |
| 5400 | </programlisting> |
| 5401 | </informalexample> |
| 5402 | |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5403 | where the second argument specifies the name of the proc file to be |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5404 | created. The above example will create a file |
| 5405 | <filename>my-file</filename> under the card directory, |
| 5406 | e.g. <filename>/proc/asound/card0/my-file</filename>. |
| 5407 | </para> |
| 5408 | |
| 5409 | <para> |
| 5410 | Like other components, the proc entry created via |
| 5411 | <function>snd_card_proc_new()</function> will be registered and |
| 5412 | released automatically in the card registration and release |
| 5413 | functions. |
| 5414 | </para> |
| 5415 | |
| 5416 | <para> |
| 5417 | When the creation is successful, the function stores a new |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5418 | instance in the pointer given in the third argument. |
| 5419 | It is initialized as a text proc file for read only. To use |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5420 | this proc file as a read-only text file as it is, set the read |
| 5421 | callback with a private data via |
| 5422 | <function>snd_info_set_text_ops()</function>. |
| 5423 | |
| 5424 | <informalexample> |
| 5425 | <programlisting> |
| 5426 | <![CDATA[ |
Takashi Iwai | bf85020 | 2006-04-28 15:13:41 +0200 | [diff] [blame] | 5427 | snd_info_set_text_ops(entry, chip, my_proc_read); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5428 | ]]> |
| 5429 | </programlisting> |
| 5430 | </informalexample> |
| 5431 | |
| 5432 | where the second argument (<parameter>chip</parameter>) is the |
| 5433 | private data to be used in the callbacks. The third parameter |
| 5434 | specifies the read buffer size and the fourth |
| 5435 | (<parameter>my_proc_read</parameter>) is the callback function, which |
| 5436 | is defined like |
| 5437 | |
| 5438 | <informalexample> |
| 5439 | <programlisting> |
| 5440 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5441 | static void my_proc_read(struct snd_info_entry *entry, |
| 5442 | struct snd_info_buffer *buffer); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5443 | ]]> |
| 5444 | </programlisting> |
| 5445 | </informalexample> |
| 5446 | |
| 5447 | </para> |
| 5448 | |
| 5449 | <para> |
| 5450 | In the read callback, use <function>snd_iprintf()</function> for |
| 5451 | output strings, which works just like normal |
| 5452 | <function>printf()</function>. For example, |
| 5453 | |
| 5454 | <informalexample> |
| 5455 | <programlisting> |
| 5456 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5457 | static void my_proc_read(struct snd_info_entry *entry, |
| 5458 | struct snd_info_buffer *buffer) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5459 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5460 | struct my_chip *chip = entry->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5461 | |
| 5462 | snd_iprintf(buffer, "This is my chip!\n"); |
| 5463 | snd_iprintf(buffer, "Port = %ld\n", chip->port); |
| 5464 | } |
| 5465 | ]]> |
| 5466 | </programlisting> |
| 5467 | </informalexample> |
| 5468 | </para> |
| 5469 | |
| 5470 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5471 | The file permissions can be changed afterwards. As default, it's |
| 5472 | set as read only for all users. If you want to add write |
| 5473 | permission for the user (root as default), do as follows: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5474 | |
| 5475 | <informalexample> |
| 5476 | <programlisting> |
| 5477 | <![CDATA[ |
| 5478 | entry->mode = S_IFREG | S_IRUGO | S_IWUSR; |
| 5479 | ]]> |
| 5480 | </programlisting> |
| 5481 | </informalexample> |
| 5482 | |
| 5483 | and set the write buffer size and the callback |
| 5484 | |
| 5485 | <informalexample> |
| 5486 | <programlisting> |
| 5487 | <![CDATA[ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5488 | entry->c.text.write = my_proc_write; |
| 5489 | ]]> |
| 5490 | </programlisting> |
| 5491 | </informalexample> |
| 5492 | </para> |
| 5493 | |
| 5494 | <para> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5495 | For the write callback, you can use |
| 5496 | <function>snd_info_get_line()</function> to get a text line, and |
| 5497 | <function>snd_info_get_str()</function> to retrieve a string from |
| 5498 | the line. Some examples are found in |
| 5499 | <filename>core/oss/mixer_oss.c</filename>, core/oss/and |
| 5500 | <filename>pcm_oss.c</filename>. |
| 5501 | </para> |
| 5502 | |
| 5503 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5504 | For a raw-data proc-file, set the attributes as follows: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5505 | |
| 5506 | <informalexample> |
| 5507 | <programlisting> |
| 5508 | <![CDATA[ |
| 5509 | static struct snd_info_entry_ops my_file_io_ops = { |
| 5510 | .read = my_file_io_read, |
| 5511 | }; |
| 5512 | |
| 5513 | entry->content = SNDRV_INFO_CONTENT_DATA; |
| 5514 | entry->private_data = chip; |
| 5515 | entry->c.ops = &my_file_io_ops; |
| 5516 | entry->size = 4096; |
| 5517 | entry->mode = S_IFREG | S_IRUGO; |
| 5518 | ]]> |
| 5519 | </programlisting> |
| 5520 | </informalexample> |
Takashi Iwai | c56a3b1 | 2010-04-13 12:55:09 +0200 | [diff] [blame] | 5521 | |
| 5522 | For the raw data, <structfield>size</structfield> field must be |
| 5523 | set properly. This specifies the maximum size of the proc file access. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5524 | </para> |
| 5525 | |
| 5526 | <para> |
Takashi Iwai | c56a3b1 | 2010-04-13 12:55:09 +0200 | [diff] [blame] | 5527 | The read/write callbacks of raw mode are more direct than the text mode. |
| 5528 | You need to use a low-level I/O functions such as |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5529 | <function>copy_from/to_user()</function> to transfer the |
| 5530 | data. |
| 5531 | |
| 5532 | <informalexample> |
| 5533 | <programlisting> |
| 5534 | <![CDATA[ |
Takashi Iwai | c56a3b1 | 2010-04-13 12:55:09 +0200 | [diff] [blame] | 5535 | static ssize_t my_file_io_read(struct snd_info_entry *entry, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5536 | void *file_private_data, |
| 5537 | struct file *file, |
| 5538 | char *buf, |
Takashi Iwai | c56a3b1 | 2010-04-13 12:55:09 +0200 | [diff] [blame] | 5539 | size_t count, |
| 5540 | loff_t pos) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5541 | { |
Takashi Iwai | c56a3b1 | 2010-04-13 12:55:09 +0200 | [diff] [blame] | 5542 | if (copy_to_user(buf, local_data + pos, count)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5543 | return -EFAULT; |
Takashi Iwai | c56a3b1 | 2010-04-13 12:55:09 +0200 | [diff] [blame] | 5544 | return count; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5545 | } |
| 5546 | ]]> |
| 5547 | </programlisting> |
| 5548 | </informalexample> |
Takashi Iwai | c56a3b1 | 2010-04-13 12:55:09 +0200 | [diff] [blame] | 5549 | |
| 5550 | If the size of the info entry has been set up properly, |
| 5551 | <structfield>count</structfield> and <structfield>pos</structfield> are |
| 5552 | guaranteed to fit within 0 and the given size. |
| 5553 | You don't have to check the range in the callbacks unless any |
| 5554 | other condition is required. |
| 5555 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5556 | </para> |
| 5557 | |
| 5558 | </chapter> |
| 5559 | |
| 5560 | |
| 5561 | <!-- ****************************************************** --> |
| 5562 | <!-- Power Management --> |
| 5563 | <!-- ****************************************************** --> |
| 5564 | <chapter id="power-management"> |
| 5565 | <title>Power Management</title> |
| 5566 | <para> |
Paolo Ornati | 670e9f3 | 2006-10-03 22:57:56 +0200 | [diff] [blame] | 5567 | If the chip is supposed to work with suspend/resume |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5568 | functions, you need to add power-management code to the |
| 5569 | driver. The additional code for power-management should be |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5570 | <function>ifdef</function>'ed with |
| 5571 | <constant>CONFIG_PM</constant>. |
| 5572 | </para> |
| 5573 | |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5574 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5575 | If the driver <emphasis>fully</emphasis> supports suspend/resume |
| 5576 | that is, the device can be |
| 5577 | properly resumed to its state when suspend was called, |
| 5578 | you can set the <constant>SNDRV_PCM_INFO_RESUME</constant> flag |
| 5579 | in the pcm info field. Usually, this is possible when the |
| 5580 | registers of the chip can be safely saved and restored to |
| 5581 | RAM. If this is set, the trigger callback is called with |
| 5582 | <constant>SNDRV_PCM_TRIGGER_RESUME</constant> after the resume |
| 5583 | callback completes. |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5584 | </para> |
| 5585 | |
| 5586 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5587 | Even if the driver doesn't support PM fully but |
| 5588 | partial suspend/resume is still possible, it's still worthy to |
| 5589 | implement suspend/resume callbacks. In such a case, applications |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5590 | would reset the status by calling |
| 5591 | <function>snd_pcm_prepare()</function> and restart the stream |
| 5592 | appropriately. Hence, you can define suspend/resume callbacks |
| 5593 | below but don't set <constant>SNDRV_PCM_INFO_RESUME</constant> |
| 5594 | info flag to the PCM. |
| 5595 | </para> |
| 5596 | |
| 5597 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5598 | Note that the trigger with SUSPEND can always be called when |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5599 | <function>snd_pcm_suspend_all</function> is called, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5600 | regardless of the <constant>SNDRV_PCM_INFO_RESUME</constant> flag. |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5601 | The <constant>RESUME</constant> flag affects only the behavior |
| 5602 | of <function>snd_pcm_resume()</function>. |
| 5603 | (Thus, in theory, |
| 5604 | <constant>SNDRV_PCM_TRIGGER_RESUME</constant> isn't needed |
| 5605 | to be handled in the trigger callback when no |
| 5606 | <constant>SNDRV_PCM_INFO_RESUME</constant> flag is set. But, |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5607 | it's better to keep it for compatibility reasons.) |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5608 | </para> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5609 | <para> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5610 | In the earlier version of ALSA drivers, a common |
| 5611 | power-management layer was provided, but it has been removed. |
| 5612 | The driver needs to define the suspend/resume hooks according to |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5613 | the bus the device is connected to. In the case of PCI drivers, the |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5614 | callbacks look like below: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5615 | |
| 5616 | <informalexample> |
| 5617 | <programlisting> |
| 5618 | <![CDATA[ |
| 5619 | #ifdef CONFIG_PM |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5620 | static int snd_my_suspend(struct pci_dev *pci, pm_message_t state) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5621 | { |
Nicolas Kaiser | 5bda9fa | 2007-01-22 14:54:33 +0100 | [diff] [blame] | 5622 | .... /* do things for suspend */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5623 | return 0; |
| 5624 | } |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5625 | static int snd_my_resume(struct pci_dev *pci) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5626 | { |
Nicolas Kaiser | 5bda9fa | 2007-01-22 14:54:33 +0100 | [diff] [blame] | 5627 | .... /* do things for suspend */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5628 | return 0; |
| 5629 | } |
| 5630 | #endif |
| 5631 | ]]> |
| 5632 | </programlisting> |
| 5633 | </informalexample> |
| 5634 | </para> |
| 5635 | |
| 5636 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5637 | The scheme of the real suspend job is as follows. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5638 | |
| 5639 | <orderedlist> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5640 | <listitem><para>Retrieve the card and the chip data.</para></listitem> |
| 5641 | <listitem><para>Call <function>snd_power_change_state()</function> with |
| 5642 | <constant>SNDRV_CTL_POWER_D3hot</constant> to change the |
| 5643 | power status.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5644 | <listitem><para>Call <function>snd_pcm_suspend_all()</function> to suspend the running PCM streams.</para></listitem> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5645 | <listitem><para>If AC97 codecs are used, call |
Takashi Iwai | a730633 | 2006-05-04 11:58:43 +0200 | [diff] [blame] | 5646 | <function>snd_ac97_suspend()</function> for each codec.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5647 | <listitem><para>Save the register values if necessary.</para></listitem> |
| 5648 | <listitem><para>Stop the hardware if necessary.</para></listitem> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5649 | <listitem><para>Disable the PCI device by calling |
| 5650 | <function>pci_disable_device()</function>. Then, call |
| 5651 | <function>pci_save_state()</function> at last.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5652 | </orderedlist> |
| 5653 | </para> |
| 5654 | |
| 5655 | <para> |
| 5656 | A typical code would be like: |
| 5657 | |
| 5658 | <informalexample> |
| 5659 | <programlisting> |
| 5660 | <![CDATA[ |
Alexey Dobriyan | 32357988 | 2006-01-15 02:12:54 +0100 | [diff] [blame] | 5661 | static int mychip_suspend(struct pci_dev *pci, pm_message_t state) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5662 | { |
| 5663 | /* (1) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5664 | struct snd_card *card = pci_get_drvdata(pci); |
| 5665 | struct mychip *chip = card->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5666 | /* (2) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5667 | snd_power_change_state(card, SNDRV_CTL_POWER_D3hot); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5668 | /* (3) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5669 | snd_pcm_suspend_all(chip->pcm); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5670 | /* (4) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5671 | snd_ac97_suspend(chip->ac97); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5672 | /* (5) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5673 | snd_mychip_save_registers(chip); |
| 5674 | /* (6) */ |
| 5675 | snd_mychip_stop_hardware(chip); |
| 5676 | /* (7) */ |
| 5677 | pci_disable_device(pci); |
| 5678 | pci_save_state(pci); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5679 | return 0; |
| 5680 | } |
| 5681 | ]]> |
| 5682 | </programlisting> |
| 5683 | </informalexample> |
| 5684 | </para> |
| 5685 | |
| 5686 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5687 | The scheme of the real resume job is as follows. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5688 | |
| 5689 | <orderedlist> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5690 | <listitem><para>Retrieve the card and the chip data.</para></listitem> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5691 | <listitem><para>Set up PCI. First, call <function>pci_restore_state()</function>. |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5692 | Then enable the pci device again by calling <function>pci_enable_device()</function>. |
| 5693 | Call <function>pci_set_master()</function> if necessary, too.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5694 | <listitem><para>Re-initialize the chip.</para></listitem> |
| 5695 | <listitem><para>Restore the saved registers if necessary.</para></listitem> |
| 5696 | <listitem><para>Resume the mixer, e.g. calling |
| 5697 | <function>snd_ac97_resume()</function>.</para></listitem> |
| 5698 | <listitem><para>Restart the hardware (if any).</para></listitem> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5699 | <listitem><para>Call <function>snd_power_change_state()</function> with |
| 5700 | <constant>SNDRV_CTL_POWER_D0</constant> to notify the processes.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5701 | </orderedlist> |
| 5702 | </para> |
| 5703 | |
| 5704 | <para> |
| 5705 | A typical code would be like: |
| 5706 | |
| 5707 | <informalexample> |
| 5708 | <programlisting> |
| 5709 | <![CDATA[ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5710 | static int mychip_resume(struct pci_dev *pci) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5711 | { |
| 5712 | /* (1) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5713 | struct snd_card *card = pci_get_drvdata(pci); |
| 5714 | struct mychip *chip = card->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5715 | /* (2) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5716 | pci_restore_state(pci); |
| 5717 | pci_enable_device(pci); |
| 5718 | pci_set_master(pci); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5719 | /* (3) */ |
| 5720 | snd_mychip_reinit_chip(chip); |
| 5721 | /* (4) */ |
| 5722 | snd_mychip_restore_registers(chip); |
| 5723 | /* (5) */ |
| 5724 | snd_ac97_resume(chip->ac97); |
| 5725 | /* (6) */ |
| 5726 | snd_mychip_restart_chip(chip); |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5727 | /* (7) */ |
| 5728 | snd_power_change_state(card, SNDRV_CTL_POWER_D0); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5729 | return 0; |
| 5730 | } |
| 5731 | ]]> |
| 5732 | </programlisting> |
| 5733 | </informalexample> |
| 5734 | </para> |
| 5735 | |
| 5736 | <para> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5737 | As shown in the above, it's better to save registers after |
| 5738 | suspending the PCM operations via |
| 5739 | <function>snd_pcm_suspend_all()</function> or |
| 5740 | <function>snd_pcm_suspend()</function>. It means that the PCM |
| 5741 | streams are already stoppped when the register snapshot is |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5742 | taken. But, remember that you don't have to restart the PCM |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5743 | stream in the resume callback. It'll be restarted via |
| 5744 | trigger call with <constant>SNDRV_PCM_TRIGGER_RESUME</constant> |
| 5745 | when necessary. |
| 5746 | </para> |
| 5747 | |
| 5748 | <para> |
| 5749 | OK, we have all callbacks now. Let's set them up. In the |
| 5750 | initialization of the card, make sure that you can get the chip |
| 5751 | data from the card instance, typically via |
| 5752 | <structfield>private_data</structfield> field, in case you |
| 5753 | created the chip data individually. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5754 | |
| 5755 | <informalexample> |
| 5756 | <programlisting> |
| 5757 | <![CDATA[ |
| 5758 | static int __devinit snd_mychip_probe(struct pci_dev *pci, |
| 5759 | const struct pci_device_id *pci_id) |
| 5760 | { |
| 5761 | .... |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5762 | struct snd_card *card; |
| 5763 | struct mychip *chip; |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 5764 | int err; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5765 | .... |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 5766 | err = snd_card_create(index[dev], id[dev], THIS_MODULE, 0, &card); |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5767 | .... |
| 5768 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
| 5769 | .... |
| 5770 | card->private_data = chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5771 | .... |
| 5772 | } |
| 5773 | ]]> |
| 5774 | </programlisting> |
| 5775 | </informalexample> |
| 5776 | |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5777 | When you created the chip data with |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 5778 | <function>snd_card_create()</function>, it's anyway accessible |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5779 | via <structfield>private_data</structfield> field. |
| 5780 | |
| 5781 | <informalexample> |
| 5782 | <programlisting> |
| 5783 | <![CDATA[ |
| 5784 | static int __devinit snd_mychip_probe(struct pci_dev *pci, |
| 5785 | const struct pci_device_id *pci_id) |
| 5786 | { |
| 5787 | .... |
| 5788 | struct snd_card *card; |
| 5789 | struct mychip *chip; |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 5790 | int err; |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5791 | .... |
Takashi Iwai | d453379 | 2008-12-28 16:45:34 +0100 | [diff] [blame] | 5792 | err = snd_card_create(index[dev], id[dev], THIS_MODULE, |
| 5793 | sizeof(struct mychip), &card); |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5794 | .... |
| 5795 | chip = card->private_data; |
| 5796 | .... |
| 5797 | } |
| 5798 | ]]> |
| 5799 | </programlisting> |
| 5800 | </informalexample> |
| 5801 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5802 | </para> |
| 5803 | |
| 5804 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5805 | If you need a space to save the registers, allocate the |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5806 | buffer for it here, too, since it would be fatal |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5807 | if you cannot allocate a memory in the suspend phase. |
| 5808 | The allocated buffer should be released in the corresponding |
| 5809 | destructor. |
| 5810 | </para> |
| 5811 | |
| 5812 | <para> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5813 | And next, set suspend/resume callbacks to the pci_driver. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5814 | |
| 5815 | <informalexample> |
| 5816 | <programlisting> |
| 5817 | <![CDATA[ |
| 5818 | static struct pci_driver driver = { |
Takashi Iwai | ce1fd36 | 2011-06-14 08:54:14 +0200 | [diff] [blame] | 5819 | .name = KBUILD_MODNAME, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5820 | .id_table = snd_my_ids, |
| 5821 | .probe = snd_my_probe, |
| 5822 | .remove = __devexit_p(snd_my_remove), |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5823 | #ifdef CONFIG_PM |
| 5824 | .suspend = snd_my_suspend, |
| 5825 | .resume = snd_my_resume, |
| 5826 | #endif |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5827 | }; |
| 5828 | ]]> |
| 5829 | </programlisting> |
| 5830 | </informalexample> |
| 5831 | </para> |
| 5832 | |
| 5833 | </chapter> |
| 5834 | |
| 5835 | |
| 5836 | <!-- ****************************************************** --> |
| 5837 | <!-- Module Parameters --> |
| 5838 | <!-- ****************************************************** --> |
| 5839 | <chapter id="module-parameters"> |
| 5840 | <title>Module Parameters</title> |
| 5841 | <para> |
| 5842 | There are standard module options for ALSA. At least, each |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5843 | module should have the <parameter>index</parameter>, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5844 | <parameter>id</parameter> and <parameter>enable</parameter> |
| 5845 | options. |
| 5846 | </para> |
| 5847 | |
| 5848 | <para> |
| 5849 | If the module supports multiple cards (usually up to |
| 5850 | 8 = <constant>SNDRV_CARDS</constant> cards), they should be |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5851 | arrays. The default initial values are defined already as |
| 5852 | constants for easier programming: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5853 | |
| 5854 | <informalexample> |
| 5855 | <programlisting> |
| 5856 | <![CDATA[ |
| 5857 | static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX; |
| 5858 | static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR; |
| 5859 | static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP; |
| 5860 | ]]> |
| 5861 | </programlisting> |
| 5862 | </informalexample> |
| 5863 | </para> |
| 5864 | |
| 5865 | <para> |
| 5866 | If the module supports only a single card, they could be single |
| 5867 | variables, instead. <parameter>enable</parameter> option is not |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5868 | always necessary in this case, but it would be better to have a |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5869 | dummy option for compatibility. |
| 5870 | </para> |
| 5871 | |
| 5872 | <para> |
| 5873 | The module parameters must be declared with the standard |
| 5874 | <function>module_param()()</function>, |
| 5875 | <function>module_param_array()()</function> and |
| 5876 | <function>MODULE_PARM_DESC()</function> macros. |
| 5877 | </para> |
| 5878 | |
| 5879 | <para> |
| 5880 | The typical coding would be like below: |
| 5881 | |
| 5882 | <informalexample> |
| 5883 | <programlisting> |
| 5884 | <![CDATA[ |
| 5885 | #define CARD_NAME "My Chip" |
| 5886 | |
| 5887 | module_param_array(index, int, NULL, 0444); |
| 5888 | MODULE_PARM_DESC(index, "Index value for " CARD_NAME " soundcard."); |
| 5889 | module_param_array(id, charp, NULL, 0444); |
| 5890 | MODULE_PARM_DESC(id, "ID string for " CARD_NAME " soundcard."); |
| 5891 | module_param_array(enable, bool, NULL, 0444); |
| 5892 | MODULE_PARM_DESC(enable, "Enable " CARD_NAME " soundcard."); |
| 5893 | ]]> |
| 5894 | </programlisting> |
| 5895 | </informalexample> |
| 5896 | </para> |
| 5897 | |
| 5898 | <para> |
| 5899 | Also, don't forget to define the module description, classes, |
| 5900 | license and devices. Especially, the recent modprobe requires to |
| 5901 | define the module license as GPL, etc., otherwise the system is |
| 5902 | shown as <quote>tainted</quote>. |
| 5903 | |
| 5904 | <informalexample> |
| 5905 | <programlisting> |
| 5906 | <![CDATA[ |
| 5907 | MODULE_DESCRIPTION("My Chip"); |
| 5908 | MODULE_LICENSE("GPL"); |
| 5909 | MODULE_SUPPORTED_DEVICE("{{Vendor,My Chip Name}}"); |
| 5910 | ]]> |
| 5911 | </programlisting> |
| 5912 | </informalexample> |
| 5913 | </para> |
| 5914 | |
| 5915 | </chapter> |
| 5916 | |
| 5917 | |
| 5918 | <!-- ****************************************************** --> |
| 5919 | <!-- How To Put Your Driver --> |
| 5920 | <!-- ****************************************************** --> |
| 5921 | <chapter id="how-to-put-your-driver"> |
| 5922 | <title>How To Put Your Driver Into ALSA Tree</title> |
| 5923 | <section> |
| 5924 | <title>General</title> |
| 5925 | <para> |
| 5926 | So far, you've learned how to write the driver codes. |
| 5927 | And you might have a question now: how to put my own |
| 5928 | driver into the ALSA driver tree? |
| 5929 | Here (finally :) the standard procedure is described briefly. |
| 5930 | </para> |
| 5931 | |
| 5932 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5933 | Suppose that you create a new PCI driver for the card |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5934 | <quote>xyz</quote>. The card module name would be |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5935 | snd-xyz. The new driver is usually put into the alsa-driver |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5936 | tree, <filename>alsa-driver/pci</filename> directory in |
| 5937 | the case of PCI cards. |
| 5938 | Then the driver is evaluated, audited and tested |
| 5939 | by developers and users. After a certain time, the driver |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5940 | will go to the alsa-kernel tree (to the corresponding directory, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5941 | such as <filename>alsa-kernel/pci</filename>) and eventually |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5942 | will be integrated into the Linux 2.6 tree (the directory would be |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5943 | <filename>linux/sound/pci</filename>). |
| 5944 | </para> |
| 5945 | |
| 5946 | <para> |
| 5947 | In the following sections, the driver code is supposed |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 5948 | to be put into alsa-driver tree. The two cases are covered: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5949 | a driver consisting of a single source file and one consisting |
| 5950 | of several source files. |
| 5951 | </para> |
| 5952 | </section> |
| 5953 | |
| 5954 | <section> |
| 5955 | <title>Driver with A Single Source File</title> |
| 5956 | <para> |
| 5957 | <orderedlist> |
| 5958 | <listitem> |
| 5959 | <para> |
| 5960 | Modify alsa-driver/pci/Makefile |
| 5961 | </para> |
| 5962 | |
| 5963 | <para> |
| 5964 | Suppose you have a file xyz.c. Add the following |
| 5965 | two lines |
| 5966 | <informalexample> |
| 5967 | <programlisting> |
| 5968 | <![CDATA[ |
| 5969 | snd-xyz-objs := xyz.o |
| 5970 | obj-$(CONFIG_SND_XYZ) += snd-xyz.o |
| 5971 | ]]> |
| 5972 | </programlisting> |
| 5973 | </informalexample> |
| 5974 | </para> |
| 5975 | </listitem> |
| 5976 | |
| 5977 | <listitem> |
| 5978 | <para> |
| 5979 | Create the Kconfig entry |
| 5980 | </para> |
| 5981 | |
| 5982 | <para> |
| 5983 | Add the new entry of Kconfig for your xyz driver. |
| 5984 | <informalexample> |
| 5985 | <programlisting> |
| 5986 | <![CDATA[ |
| 5987 | config SND_XYZ |
| 5988 | tristate "Foobar XYZ" |
| 5989 | depends on SND |
| 5990 | select SND_PCM |
| 5991 | help |
| 5992 | Say Y here to include support for Foobar XYZ soundcard. |
| 5993 | |
| 5994 | To compile this driver as a module, choose M here: the module |
| 5995 | will be called snd-xyz. |
| 5996 | ]]> |
| 5997 | </programlisting> |
| 5998 | </informalexample> |
| 5999 | |
| 6000 | the line, select SND_PCM, specifies that the driver xyz supports |
| 6001 | PCM. In addition to SND_PCM, the following components are |
| 6002 | supported for select command: |
| 6003 | SND_RAWMIDI, SND_TIMER, SND_HWDEP, SND_MPU401_UART, |
| 6004 | SND_OPL3_LIB, SND_OPL4_LIB, SND_VX_LIB, SND_AC97_CODEC. |
| 6005 | Add the select command for each supported component. |
| 6006 | </para> |
| 6007 | |
| 6008 | <para> |
| 6009 | Note that some selections imply the lowlevel selections. |
| 6010 | For example, PCM includes TIMER, MPU401_UART includes RAWMIDI, |
| 6011 | AC97_CODEC includes PCM, and OPL3_LIB includes HWDEP. |
| 6012 | You don't need to give the lowlevel selections again. |
| 6013 | </para> |
| 6014 | |
| 6015 | <para> |
| 6016 | For the details of Kconfig script, refer to the kbuild |
| 6017 | documentation. |
| 6018 | </para> |
| 6019 | |
| 6020 | </listitem> |
| 6021 | |
| 6022 | <listitem> |
| 6023 | <para> |
| 6024 | Run cvscompile script to re-generate the configure script and |
| 6025 | build the whole stuff again. |
| 6026 | </para> |
| 6027 | </listitem> |
| 6028 | </orderedlist> |
| 6029 | </para> |
| 6030 | </section> |
| 6031 | |
| 6032 | <section> |
| 6033 | <title>Drivers with Several Source Files</title> |
| 6034 | <para> |
| 6035 | Suppose that the driver snd-xyz have several source files. |
| 6036 | They are located in the new subdirectory, |
| 6037 | pci/xyz. |
| 6038 | |
| 6039 | <orderedlist> |
| 6040 | <listitem> |
| 6041 | <para> |
| 6042 | Add a new directory (<filename>xyz</filename>) in |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 6043 | <filename>alsa-driver/pci/Makefile</filename> as below |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6044 | |
| 6045 | <informalexample> |
| 6046 | <programlisting> |
| 6047 | <![CDATA[ |
| 6048 | obj-$(CONFIG_SND) += xyz/ |
| 6049 | ]]> |
| 6050 | </programlisting> |
| 6051 | </informalexample> |
| 6052 | </para> |
| 6053 | </listitem> |
| 6054 | |
| 6055 | <listitem> |
| 6056 | <para> |
| 6057 | Under the directory <filename>xyz</filename>, create a Makefile |
| 6058 | |
| 6059 | <example> |
| 6060 | <title>Sample Makefile for a driver xyz</title> |
| 6061 | <programlisting> |
| 6062 | <![CDATA[ |
| 6063 | ifndef SND_TOPDIR |
| 6064 | SND_TOPDIR=../.. |
| 6065 | endif |
| 6066 | |
| 6067 | include $(SND_TOPDIR)/toplevel.config |
| 6068 | include $(SND_TOPDIR)/Makefile.conf |
| 6069 | |
| 6070 | snd-xyz-objs := xyz.o abc.o def.o |
| 6071 | |
| 6072 | obj-$(CONFIG_SND_XYZ) += snd-xyz.o |
| 6073 | |
| 6074 | include $(SND_TOPDIR)/Rules.make |
| 6075 | ]]> |
| 6076 | </programlisting> |
| 6077 | </example> |
| 6078 | </para> |
| 6079 | </listitem> |
| 6080 | |
| 6081 | <listitem> |
| 6082 | <para> |
| 6083 | Create the Kconfig entry |
| 6084 | </para> |
| 6085 | |
| 6086 | <para> |
| 6087 | This procedure is as same as in the last section. |
| 6088 | </para> |
| 6089 | </listitem> |
| 6090 | |
| 6091 | <listitem> |
| 6092 | <para> |
| 6093 | Run cvscompile script to re-generate the configure script and |
| 6094 | build the whole stuff again. |
| 6095 | </para> |
| 6096 | </listitem> |
| 6097 | </orderedlist> |
| 6098 | </para> |
| 6099 | </section> |
| 6100 | |
| 6101 | </chapter> |
| 6102 | |
| 6103 | <!-- ****************************************************** --> |
| 6104 | <!-- Useful Functions --> |
| 6105 | <!-- ****************************************************** --> |
| 6106 | <chapter id="useful-functions"> |
| 6107 | <title>Useful Functions</title> |
| 6108 | |
| 6109 | <section id="useful-functions-snd-printk"> |
| 6110 | <title><function>snd_printk()</function> and friends</title> |
| 6111 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 6112 | ALSA provides a verbose version of the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6113 | <function>printk()</function> function. If a kernel config |
| 6114 | <constant>CONFIG_SND_VERBOSE_PRINTK</constant> is set, this |
| 6115 | function prints the given message together with the file name |
| 6116 | and the line of the caller. The <constant>KERN_XXX</constant> |
| 6117 | prefix is processed as |
| 6118 | well as the original <function>printk()</function> does, so it's |
| 6119 | recommended to add this prefix, e.g. |
| 6120 | |
| 6121 | <informalexample> |
| 6122 | <programlisting> |
| 6123 | <![CDATA[ |
| 6124 | snd_printk(KERN_ERR "Oh my, sorry, it's extremely bad!\n"); |
| 6125 | ]]> |
| 6126 | </programlisting> |
| 6127 | </informalexample> |
| 6128 | </para> |
| 6129 | |
| 6130 | <para> |
| 6131 | There are also <function>printk()</function>'s for |
| 6132 | debugging. <function>snd_printd()</function> can be used for |
| 6133 | general debugging purposes. If |
| 6134 | <constant>CONFIG_SND_DEBUG</constant> is set, this function is |
| 6135 | compiled, and works just like |
| 6136 | <function>snd_printk()</function>. If the ALSA is compiled |
| 6137 | without the debugging flag, it's ignored. |
| 6138 | </para> |
| 6139 | |
| 6140 | <para> |
| 6141 | <function>snd_printdd()</function> is compiled in only when |
Takashi Iwai | 62cf872 | 2008-05-20 12:15:15 +0200 | [diff] [blame] | 6142 | <constant>CONFIG_SND_DEBUG_VERBOSE</constant> is set. Please note |
| 6143 | that <constant>CONFIG_SND_DEBUG_VERBOSE</constant> is not set as default |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6144 | even if you configure the alsa-driver with |
| 6145 | <option>--with-debug=full</option> option. You need to give |
| 6146 | explicitly <option>--with-debug=detect</option> option instead. |
| 6147 | </para> |
| 6148 | </section> |
| 6149 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6150 | <section id="useful-functions-snd-bug"> |
| 6151 | <title><function>snd_BUG()</function></title> |
| 6152 | <para> |
Michael Opdenacker | 3f03f7c | 2007-10-24 10:59:44 +0200 | [diff] [blame] | 6153 | It shows the <computeroutput>BUG?</computeroutput> message and |
Takashi Iwai | 7cc6dff | 2008-08-08 17:14:55 +0200 | [diff] [blame] | 6154 | stack trace as well as <function>snd_BUG_ON</function> at the point. |
Takashi Iwai | 7c22f1a | 2005-10-10 11:46:31 +0200 | [diff] [blame] | 6155 | It's useful to show that a fatal error happens there. |
| 6156 | </para> |
| 6157 | <para> |
| 6158 | When no debug flag is set, this macro is ignored. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6159 | </para> |
| 6160 | </section> |
Takashi Iwai | 5ef0346 | 2008-08-08 17:06:01 +0200 | [diff] [blame] | 6161 | |
| 6162 | <section id="useful-functions-snd-bug-on"> |
| 6163 | <title><function>snd_BUG_ON()</function></title> |
| 6164 | <para> |
| 6165 | <function>snd_BUG_ON()</function> macro is similar with |
| 6166 | <function>WARN_ON()</function> macro. For example, |
| 6167 | |
| 6168 | <informalexample> |
| 6169 | <programlisting> |
| 6170 | <![CDATA[ |
| 6171 | snd_BUG_ON(!pointer); |
| 6172 | ]]> |
| 6173 | </programlisting> |
| 6174 | </informalexample> |
| 6175 | |
| 6176 | or it can be used as the condition, |
| 6177 | <informalexample> |
| 6178 | <programlisting> |
| 6179 | <![CDATA[ |
| 6180 | if (snd_BUG_ON(non_zero_is_bug)) |
| 6181 | return -EINVAL; |
| 6182 | ]]> |
| 6183 | </programlisting> |
| 6184 | </informalexample> |
| 6185 | |
| 6186 | </para> |
| 6187 | |
| 6188 | <para> |
| 6189 | The macro takes an conditional expression to evaluate. |
| 6190 | When <constant>CONFIG_SND_DEBUG</constant>, is set, the |
| 6191 | expression is actually evaluated. If it's non-zero, it shows |
| 6192 | the warning message such as |
| 6193 | <computeroutput>BUG? (xxx)</computeroutput> |
| 6194 | normally followed by stack trace. It returns the evaluated |
| 6195 | value. |
| 6196 | When no <constant>CONFIG_SND_DEBUG</constant> is set, this |
| 6197 | macro always returns zero. |
| 6198 | </para> |
| 6199 | |
| 6200 | </section> |
| 6201 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6202 | </chapter> |
| 6203 | |
| 6204 | |
| 6205 | <!-- ****************************************************** --> |
| 6206 | <!-- Acknowledgments --> |
| 6207 | <!-- ****************************************************** --> |
Nicolas Kaiser | 5bda9fa | 2007-01-22 14:54:33 +0100 | [diff] [blame] | 6208 | <chapter id="acknowledgments"> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6209 | <title>Acknowledgments</title> |
| 6210 | <para> |
| 6211 | I would like to thank Phil Kerr for his help for improvement and |
| 6212 | corrections of this document. |
| 6213 | </para> |
| 6214 | <para> |
| 6215 | Kevin Conder reformatted the original plain-text to the |
| 6216 | DocBook format. |
| 6217 | </para> |
| 6218 | <para> |
| 6219 | Giuliano Pochini corrected typos and contributed the example codes |
| 6220 | in the hardware constraints section. |
| 6221 | </para> |
| 6222 | </chapter> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6223 | </book> |