Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook V4.1//EN"> |
| 2 | |
| 3 | <book> |
| 4 | <?dbhtml filename="index.html"> |
| 5 | |
| 6 | <!-- ****************************************************** --> |
| 7 | <!-- Header --> |
| 8 | <!-- ****************************************************** --> |
| 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 | |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 21 | <date>November 17, 2005</date> |
| 22 | <edition>0.3.6</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> |
| 70 | driver. The document focuses mainly on the PCI soundcard. |
| 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> |
| 78 | The target of this document is ones who already have enough |
| 79 | skill of C language and have the basic knowledge of linux |
| 80 | kernel programming. This document doesn't explain the general |
| 81 | topics of linux kernel codes and doesn't cover the detail of |
| 82 | implementation of each low-level driver. It describes only how is |
| 83 | the standard way to write a PCI sound driver on ALSA. |
| 84 | </para> |
| 85 | |
| 86 | <para> |
| 87 | If you are already familiar with the older ALSA ver.0.5.x, you |
| 88 | can check the drivers such as <filename>es1938.c</filename> or |
| 89 | <filename>maestro3.c</filename> which have also almost the same |
| 90 | code-base in the ALSA 0.5.x tree, so you can compare the differences. |
| 91 | </para> |
| 92 | |
| 93 | <para> |
| 94 | This document is still a draft version. Any feedbacks and |
| 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> |
| 109 | The ALSA drivers are provided in the two ways. |
| 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 |
| 117 | contains purely the source codes for the Linux 2.6 (or later) |
| 118 | tree. This tree is designed only for compilation on 2.6 or |
| 119 | later environment. The latter, alsa-driver, contains many subtle |
| 120 | files for compiling the ALSA driver on the outside of Linux |
| 121 | kernel like configure script, the wrapper functions for older, |
| 122 | 2.2 and 2.4 kernels, to adapt the latest kernel API, |
| 123 | and additional drivers which are still in development or in |
| 124 | tests. The drivers in alsa-driver tree will be moved to |
| 125 | alsa-kernel (eventually 2.6 kernel tree) once when they are |
| 126 | finished and confirmed to work fine. |
| 127 | </para> |
| 128 | |
| 129 | <para> |
| 130 | The file tree structure of ALSA driver is depicted below. Both |
| 131 | alsa-kernel and alsa-driver have almost the same file |
| 132 | structure, except for <quote>core</quote> directory. It's |
| 133 | named as <quote>acore</quote> in alsa-driver tree. |
| 134 | |
| 135 | <example> |
| 136 | <title>ALSA File Tree Structure</title> |
| 137 | <literallayout> |
| 138 | sound |
| 139 | /core |
| 140 | /oss |
| 141 | /seq |
| 142 | /oss |
| 143 | /instr |
| 144 | /ioctl32 |
| 145 | /include |
| 146 | /drivers |
| 147 | /mpu401 |
| 148 | /opl3 |
| 149 | /i2c |
| 150 | /l3 |
| 151 | /synth |
| 152 | /emux |
| 153 | /pci |
| 154 | /(cards) |
| 155 | /isa |
| 156 | /(cards) |
| 157 | /arm |
| 158 | /ppc |
| 159 | /sparc |
| 160 | /usb |
| 161 | /pcmcia /(cards) |
| 162 | /oss |
| 163 | </literallayout> |
| 164 | </example> |
| 165 | </para> |
| 166 | </section> |
| 167 | |
| 168 | <section id="file-tree-core-directory"> |
| 169 | <title>core directory</title> |
| 170 | <para> |
| 171 | This directory contains the middle layer, that is, the heart |
| 172 | of ALSA drivers. In this directory, the native ALSA modules are |
| 173 | stored. The sub-directories contain different modules and are |
| 174 | dependent upon the kernel config. |
| 175 | </para> |
| 176 | |
| 177 | <section id="file-tree-core-directory-oss"> |
| 178 | <title>core/oss</title> |
| 179 | |
| 180 | <para> |
| 181 | The codes for PCM and mixer OSS emulation modules are stored |
| 182 | in this directory. The rawmidi OSS emulation is included in |
| 183 | the ALSA rawmidi code since it's quite small. The sequencer |
| 184 | code is stored in core/seq/oss directory (see |
| 185 | <link linkend="file-tree-core-directory-seq-oss"><citetitle> |
| 186 | below</citetitle></link>). |
| 187 | </para> |
| 188 | </section> |
| 189 | |
| 190 | <section id="file-tree-core-directory-ioctl32"> |
| 191 | <title>core/ioctl32</title> |
| 192 | |
| 193 | <para> |
| 194 | This directory contains the 32bit-ioctl wrappers for 64bit |
| 195 | architectures such like x86-64, ppc64 and sparc64. For 32bit |
| 196 | and alpha architectures, these are not compiled. |
| 197 | </para> |
| 198 | </section> |
| 199 | |
| 200 | <section id="file-tree-core-directory-seq"> |
| 201 | <title>core/seq</title> |
| 202 | <para> |
| 203 | This and its sub-directories are for the ALSA |
| 204 | sequencer. This directory contains the sequencer core and |
| 205 | primary sequencer modules such like snd-seq-midi, |
| 206 | snd-seq-virmidi, etc. They are compiled only when |
| 207 | <constant>CONFIG_SND_SEQUENCER</constant> is set in the kernel |
| 208 | config. |
| 209 | </para> |
| 210 | </section> |
| 211 | |
| 212 | <section id="file-tree-core-directory-seq-oss"> |
| 213 | <title>core/seq/oss</title> |
| 214 | <para> |
| 215 | This contains the OSS sequencer emulation codes. |
| 216 | </para> |
| 217 | </section> |
| 218 | |
| 219 | <section id="file-tree-core-directory-deq-instr"> |
| 220 | <title>core/seq/instr</title> |
| 221 | <para> |
| 222 | This directory contains the modules for the sequencer |
| 223 | instrument layer. |
| 224 | </para> |
| 225 | </section> |
| 226 | </section> |
| 227 | |
| 228 | <section id="file-tree-include-directory"> |
| 229 | <title>include directory</title> |
| 230 | <para> |
| 231 | This is the place for the public header files of ALSA drivers, |
| 232 | which are to be exported to the user-space, or included by |
| 233 | several files at different directories. Basically, the private |
| 234 | header files should not be placed in this directory, but you may |
| 235 | still find files there, due to historical reason :) |
| 236 | </para> |
| 237 | </section> |
| 238 | |
| 239 | <section id="file-tree-drivers-directory"> |
| 240 | <title>drivers directory</title> |
| 241 | <para> |
| 242 | This directory contains the codes shared among different drivers |
| 243 | on the different architectures. They are hence supposed not to be |
| 244 | architecture-specific. |
| 245 | For example, the dummy pcm driver and the serial MIDI |
| 246 | driver are found in this directory. In the sub-directories, |
| 247 | there are the codes for components which are independent from |
| 248 | bus and cpu architectures. |
| 249 | </para> |
| 250 | |
| 251 | <section id="file-tree-drivers-directory-mpu401"> |
| 252 | <title>drivers/mpu401</title> |
| 253 | <para> |
| 254 | The MPU401 and MPU401-UART modules are stored here. |
| 255 | </para> |
| 256 | </section> |
| 257 | |
| 258 | <section id="file-tree-drivers-directory-opl3"> |
| 259 | <title>drivers/opl3 and opl4</title> |
| 260 | <para> |
| 261 | The OPL3 and OPL4 FM-synth stuff is found here. |
| 262 | </para> |
| 263 | </section> |
| 264 | </section> |
| 265 | |
| 266 | <section id="file-tree-i2c-directory"> |
| 267 | <title>i2c directory</title> |
| 268 | <para> |
| 269 | This contains the ALSA i2c components. |
| 270 | </para> |
| 271 | |
| 272 | <para> |
| 273 | Although there is a standard i2c layer on Linux, ALSA has its |
| 274 | own i2c codes for some cards, because the soundcard needs only a |
| 275 | simple operation and the standard i2c API is too complicated for |
| 276 | such a purpose. |
| 277 | </para> |
| 278 | |
| 279 | <section id="file-tree-i2c-directory-l3"> |
| 280 | <title>i2c/l3</title> |
| 281 | <para> |
| 282 | This is a sub-directory for ARM L3 i2c. |
| 283 | </para> |
| 284 | </section> |
| 285 | </section> |
| 286 | |
| 287 | <section id="file-tree-synth-directory"> |
| 288 | <title>synth directory</title> |
| 289 | <para> |
| 290 | This contains the synth middle-level modules. |
| 291 | </para> |
| 292 | |
| 293 | <para> |
| 294 | So far, there is only Emu8000/Emu10k1 synth driver under |
| 295 | synth/emux sub-directory. |
| 296 | </para> |
| 297 | </section> |
| 298 | |
| 299 | <section id="file-tree-pci-directory"> |
| 300 | <title>pci directory</title> |
| 301 | <para> |
| 302 | This and its sub-directories hold the top-level card modules |
| 303 | for PCI soundcards and the codes specific to the PCI BUS. |
| 304 | </para> |
| 305 | |
| 306 | <para> |
| 307 | The drivers compiled from a single file is stored directly on |
| 308 | pci directory, while the drivers with several source files are |
| 309 | stored on its own sub-directory (e.g. emu10k1, ice1712). |
| 310 | </para> |
| 311 | </section> |
| 312 | |
| 313 | <section id="file-tree-isa-directory"> |
| 314 | <title>isa directory</title> |
| 315 | <para> |
| 316 | This and its sub-directories hold the top-level card modules |
| 317 | for ISA soundcards. |
| 318 | </para> |
| 319 | </section> |
| 320 | |
| 321 | <section id="file-tree-arm-ppc-sparc-directories"> |
| 322 | <title>arm, ppc, and sparc directories</title> |
| 323 | <para> |
| 324 | These are for the top-level card modules which are |
| 325 | specific to each given architecture. |
| 326 | </para> |
| 327 | </section> |
| 328 | |
| 329 | <section id="file-tree-usb-directory"> |
| 330 | <title>usb directory</title> |
| 331 | <para> |
| 332 | This contains the USB-audio driver. On the latest version, the |
| 333 | USB MIDI driver is integrated together with usb-audio driver. |
| 334 | </para> |
| 335 | </section> |
| 336 | |
| 337 | <section id="file-tree-pcmcia-directory"> |
| 338 | <title>pcmcia directory</title> |
| 339 | <para> |
| 340 | The PCMCIA, especially PCCard drivers will go here. CardBus |
| 341 | drivers will be on pci directory, because its API is identical |
| 342 | with the standard PCI cards. |
| 343 | </para> |
| 344 | </section> |
| 345 | |
| 346 | <section id="file-tree-oss-directory"> |
| 347 | <title>oss directory</title> |
| 348 | <para> |
| 349 | The OSS/Lite source files are stored here on Linux 2.6 (or |
| 350 | later) tree. (In the ALSA driver tarball, it's empty, of course :) |
| 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> |
| 365 | The minimum flow of PCI soundcard is like the following: |
| 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> |
| 373 | <listitem><para>create pci_driver table which contains the three pointers above.</para></listitem> |
Takashi Iwai | 01d25d4 | 2005-04-11 16:58:24 +0200 | [diff] [blame] | 374 | <listitem><para>create <function>init()</function> function just calling <function>pci_register_driver()</function> to register the pci_driver table defined above.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 375 | <listitem><para>create <function>exit()</function> function to call <function>pci_unregister_driver()</function> function.</para></listitem> |
| 376 | </itemizedlist> |
| 377 | </para> |
| 378 | </section> |
| 379 | |
| 380 | <section id="basic-flow-example"> |
| 381 | <title>Full Code Example</title> |
| 382 | <para> |
| 383 | The code example is shown below. Some parts are kept |
| 384 | unimplemented at this moment but will be filled in the |
| 385 | succeeding sections. The numbers in comment lines of |
| 386 | <function>snd_mychip_probe()</function> function are the |
| 387 | markers. |
| 388 | |
| 389 | <example> |
| 390 | <title>Basic Flow for PCI Drivers Example</title> |
| 391 | <programlisting> |
| 392 | <![CDATA[ |
| 393 | #include <sound/driver.h> |
| 394 | #include <linux/init.h> |
| 395 | #include <linux/pci.h> |
| 396 | #include <linux/slab.h> |
| 397 | #include <sound/core.h> |
| 398 | #include <sound/initval.h> |
| 399 | |
| 400 | /* module parameters (see "Module Parameters") */ |
| 401 | static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX; |
| 402 | static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR; |
| 403 | static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP; |
| 404 | |
| 405 | /* definition of the chip-specific record */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 406 | struct mychip { |
| 407 | struct snd_card *card; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 408 | // rest of implementation will be in the section |
| 409 | // "PCI Resource Managements" |
| 410 | }; |
| 411 | |
| 412 | /* chip-specific destructor |
| 413 | * (see "PCI Resource Managements") |
| 414 | */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 415 | static int snd_mychip_free(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 416 | { |
| 417 | .... // will be implemented later... |
| 418 | } |
| 419 | |
| 420 | /* component-destructor |
| 421 | * (see "Management of Cards and Components") |
| 422 | */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 423 | static int snd_mychip_dev_free(struct snd_device *device) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 424 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 425 | return snd_mychip_free(device->device_data); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 426 | } |
| 427 | |
| 428 | /* chip-specific constructor |
| 429 | * (see "Management of Cards and Components") |
| 430 | */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 431 | static int __devinit snd_mychip_create(struct snd_card *card, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 432 | struct pci_dev *pci, |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 433 | struct mychip **rchip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 434 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 435 | struct mychip *chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 436 | int err; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 437 | static struct snd_device_ops ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 438 | .dev_free = snd_mychip_dev_free, |
| 439 | }; |
| 440 | |
| 441 | *rchip = NULL; |
| 442 | |
| 443 | // check PCI availability here |
| 444 | // (see "PCI Resource Managements") |
| 445 | .... |
| 446 | |
| 447 | /* allocate a chip-specific data with zero filled */ |
Takashi Iwai | 561b220 | 2005-09-09 14:22:34 +0200 | [diff] [blame] | 448 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 449 | if (chip == NULL) |
| 450 | return -ENOMEM; |
| 451 | |
| 452 | chip->card = card; |
| 453 | |
| 454 | // rest of initialization here; will be implemented |
| 455 | // later, see "PCI Resource Managements" |
| 456 | .... |
| 457 | |
| 458 | if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, |
| 459 | chip, &ops)) < 0) { |
| 460 | snd_mychip_free(chip); |
| 461 | return err; |
| 462 | } |
| 463 | |
| 464 | snd_card_set_dev(card, &pci->dev); |
| 465 | |
| 466 | *rchip = chip; |
| 467 | return 0; |
| 468 | } |
| 469 | |
| 470 | /* constructor -- see "Constructor" sub-section */ |
| 471 | static int __devinit snd_mychip_probe(struct pci_dev *pci, |
| 472 | const struct pci_device_id *pci_id) |
| 473 | { |
| 474 | static int dev; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 475 | struct snd_card *card; |
| 476 | struct mychip *chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 477 | int err; |
| 478 | |
| 479 | /* (1) */ |
| 480 | if (dev >= SNDRV_CARDS) |
| 481 | return -ENODEV; |
| 482 | if (!enable[dev]) { |
| 483 | dev++; |
| 484 | return -ENOENT; |
| 485 | } |
| 486 | |
| 487 | /* (2) */ |
| 488 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, 0); |
| 489 | if (card == NULL) |
| 490 | return -ENOMEM; |
| 491 | |
| 492 | /* (3) */ |
| 493 | if ((err = snd_mychip_create(card, pci, &chip)) < 0) { |
| 494 | snd_card_free(card); |
| 495 | return err; |
| 496 | } |
| 497 | |
| 498 | /* (4) */ |
| 499 | strcpy(card->driver, "My Chip"); |
| 500 | strcpy(card->shortname, "My Own Chip 123"); |
| 501 | sprintf(card->longname, "%s at 0x%lx irq %i", |
| 502 | card->shortname, chip->ioport, chip->irq); |
| 503 | |
| 504 | /* (5) */ |
| 505 | .... // implemented later |
| 506 | |
| 507 | /* (6) */ |
| 508 | if ((err = snd_card_register(card)) < 0) { |
| 509 | snd_card_free(card); |
| 510 | return err; |
| 511 | } |
| 512 | |
| 513 | /* (7) */ |
| 514 | pci_set_drvdata(pci, card); |
| 515 | dev++; |
| 516 | return 0; |
| 517 | } |
| 518 | |
| 519 | /* destructor -- see "Destructor" sub-section */ |
| 520 | static void __devexit snd_mychip_remove(struct pci_dev *pci) |
| 521 | { |
| 522 | snd_card_free(pci_get_drvdata(pci)); |
| 523 | pci_set_drvdata(pci, NULL); |
| 524 | } |
| 525 | ]]> |
| 526 | </programlisting> |
| 527 | </example> |
| 528 | </para> |
| 529 | </section> |
| 530 | |
| 531 | <section id="basic-flow-constructor"> |
| 532 | <title>Constructor</title> |
| 533 | <para> |
| 534 | The real constructor of PCI drivers is probe callback. The |
| 535 | probe callback and other component-constructors which are called |
| 536 | from probe callback should be defined with |
| 537 | <parameter>__devinit</parameter> prefix. You |
| 538 | cannot use <parameter>__init</parameter> prefix for them, |
| 539 | because any PCI device could be a hotplug device. |
| 540 | </para> |
| 541 | |
| 542 | <para> |
| 543 | In the probe callback, the following scheme is often used. |
| 544 | </para> |
| 545 | |
| 546 | <section id="basic-flow-constructor-device-index"> |
| 547 | <title>1) Check and increment the device index.</title> |
| 548 | <para> |
| 549 | <informalexample> |
| 550 | <programlisting> |
| 551 | <![CDATA[ |
| 552 | static int dev; |
| 553 | .... |
| 554 | if (dev >= SNDRV_CARDS) |
| 555 | return -ENODEV; |
| 556 | if (!enable[dev]) { |
| 557 | dev++; |
| 558 | return -ENOENT; |
| 559 | } |
| 560 | ]]> |
| 561 | </programlisting> |
| 562 | </informalexample> |
| 563 | |
| 564 | where enable[dev] is the module option. |
| 565 | </para> |
| 566 | |
| 567 | <para> |
| 568 | At each time probe callback is called, check the |
| 569 | availability of the device. If not available, simply increment |
| 570 | the device index and returns. dev will be incremented also |
| 571 | later (<link |
| 572 | linkend="basic-flow-constructor-set-pci"><citetitle>step |
| 573 | 7</citetitle></link>). |
| 574 | </para> |
| 575 | </section> |
| 576 | |
| 577 | <section id="basic-flow-constructor-create-card"> |
| 578 | <title>2) Create a card instance</title> |
| 579 | <para> |
| 580 | <informalexample> |
| 581 | <programlisting> |
| 582 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 583 | struct snd_card *card; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 584 | .... |
| 585 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, 0); |
| 586 | ]]> |
| 587 | </programlisting> |
| 588 | </informalexample> |
| 589 | </para> |
| 590 | |
| 591 | <para> |
| 592 | The detail will be explained in the section |
| 593 | <link linkend="card-management-card-instance"><citetitle> |
| 594 | Management of Cards and Components</citetitle></link>. |
| 595 | </para> |
| 596 | </section> |
| 597 | |
| 598 | <section id="basic-flow-constructor-create-main"> |
| 599 | <title>3) Create a main component</title> |
| 600 | <para> |
| 601 | In this part, the PCI resources are allocated. |
| 602 | |
| 603 | <informalexample> |
| 604 | <programlisting> |
| 605 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 606 | struct mychip *chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 607 | .... |
| 608 | if ((err = snd_mychip_create(card, pci, &chip)) < 0) { |
| 609 | snd_card_free(card); |
| 610 | return err; |
| 611 | } |
| 612 | ]]> |
| 613 | </programlisting> |
| 614 | </informalexample> |
| 615 | |
| 616 | The detail will be explained in the section <link |
| 617 | linkend="pci-resource"><citetitle>PCI Resource |
| 618 | Managements</citetitle></link>. |
| 619 | </para> |
| 620 | </section> |
| 621 | |
| 622 | <section id="basic-flow-constructor-main-component"> |
| 623 | <title>4) Set the driver ID and name strings.</title> |
| 624 | <para> |
| 625 | <informalexample> |
| 626 | <programlisting> |
| 627 | <![CDATA[ |
| 628 | strcpy(card->driver, "My Chip"); |
| 629 | strcpy(card->shortname, "My Own Chip 123"); |
| 630 | sprintf(card->longname, "%s at 0x%lx irq %i", |
| 631 | card->shortname, chip->ioport, chip->irq); |
| 632 | ]]> |
| 633 | </programlisting> |
| 634 | </informalexample> |
| 635 | |
| 636 | The driver field holds the minimal ID string of the |
| 637 | chip. This is referred by alsa-lib's configurator, so keep it |
| 638 | simple but unique. |
| 639 | Even the same driver can have different driver IDs to |
| 640 | distinguish the functionality of each chip type. |
| 641 | </para> |
| 642 | |
| 643 | <para> |
| 644 | The shortname field is a string shown as more verbose |
| 645 | name. The longname field contains the information which is |
| 646 | shown in <filename>/proc/asound/cards</filename>. |
| 647 | </para> |
| 648 | </section> |
| 649 | |
| 650 | <section id="basic-flow-constructor-create-other"> |
| 651 | <title>5) Create other components, such as mixer, MIDI, etc.</title> |
| 652 | <para> |
| 653 | Here you define the basic components such as |
| 654 | <link linkend="pcm-interface"><citetitle>PCM</citetitle></link>, |
| 655 | mixer (e.g. <link linkend="api-ac97"><citetitle>AC97</citetitle></link>), |
| 656 | MIDI (e.g. <link linkend="midi-interface"><citetitle>MPU-401</citetitle></link>), |
| 657 | and other interfaces. |
| 658 | Also, if you want a <link linkend="proc-interface"><citetitle>proc |
| 659 | file</citetitle></link>, define it here, too. |
| 660 | </para> |
| 661 | </section> |
| 662 | |
| 663 | <section id="basic-flow-constructor-register-card"> |
| 664 | <title>6) Register the card instance.</title> |
| 665 | <para> |
| 666 | <informalexample> |
| 667 | <programlisting> |
| 668 | <![CDATA[ |
| 669 | if ((err = snd_card_register(card)) < 0) { |
| 670 | snd_card_free(card); |
| 671 | return err; |
| 672 | } |
| 673 | ]]> |
| 674 | </programlisting> |
| 675 | </informalexample> |
| 676 | </para> |
| 677 | |
| 678 | <para> |
| 679 | Will be explained in the section <link |
| 680 | linkend="card-management-registration"><citetitle>Management |
| 681 | of Cards and Components</citetitle></link>, too. |
| 682 | </para> |
| 683 | </section> |
| 684 | |
| 685 | <section id="basic-flow-constructor-set-pci"> |
| 686 | <title>7) Set the PCI driver data and return zero.</title> |
| 687 | <para> |
| 688 | <informalexample> |
| 689 | <programlisting> |
| 690 | <![CDATA[ |
| 691 | pci_set_drvdata(pci, card); |
| 692 | dev++; |
| 693 | return 0; |
| 694 | ]]> |
| 695 | </programlisting> |
| 696 | </informalexample> |
| 697 | |
| 698 | In the above, the card record is stored. This pointer is |
| 699 | referred in the remove callback and power-management |
| 700 | callbacks, too. |
| 701 | </para> |
| 702 | </section> |
| 703 | </section> |
| 704 | |
| 705 | <section id="basic-flow-destructor"> |
| 706 | <title>Destructor</title> |
| 707 | <para> |
| 708 | The destructor, remove callback, simply releases the card |
| 709 | instance. Then the ALSA middle layer will release all the |
| 710 | attached components automatically. |
| 711 | </para> |
| 712 | |
| 713 | <para> |
| 714 | It would be typically like the following: |
| 715 | |
| 716 | <informalexample> |
| 717 | <programlisting> |
| 718 | <![CDATA[ |
| 719 | static void __devexit snd_mychip_remove(struct pci_dev *pci) |
| 720 | { |
| 721 | snd_card_free(pci_get_drvdata(pci)); |
| 722 | pci_set_drvdata(pci, NULL); |
| 723 | } |
| 724 | ]]> |
| 725 | </programlisting> |
| 726 | </informalexample> |
| 727 | |
| 728 | The above code assumes that the card pointer is set to the PCI |
| 729 | driver data. |
| 730 | </para> |
| 731 | </section> |
| 732 | |
| 733 | <section id="basic-flow-header-files"> |
| 734 | <title>Header Files</title> |
| 735 | <para> |
| 736 | For the above example, at least the following include files |
| 737 | are necessary. |
| 738 | |
| 739 | <informalexample> |
| 740 | <programlisting> |
| 741 | <![CDATA[ |
| 742 | #include <sound/driver.h> |
| 743 | #include <linux/init.h> |
| 744 | #include <linux/pci.h> |
| 745 | #include <linux/slab.h> |
| 746 | #include <sound/core.h> |
| 747 | #include <sound/initval.h> |
| 748 | ]]> |
| 749 | </programlisting> |
| 750 | </informalexample> |
| 751 | |
| 752 | where the last one is necessary only when module options are |
| 753 | defined in the source file. If the codes are split to several |
| 754 | files, the file without module options don't need them. |
| 755 | </para> |
| 756 | |
| 757 | <para> |
| 758 | In addition to them, you'll need |
| 759 | <filename><linux/interrupt.h></filename> for the interrupt |
| 760 | handling, and <filename><asm/io.h></filename> for the i/o |
| 761 | access. If you use <function>mdelay()</function> or |
| 762 | <function>udelay()</function> functions, you'll need to include |
| 763 | <filename><linux/delay.h></filename>, too. |
| 764 | </para> |
| 765 | |
| 766 | <para> |
| 767 | The ALSA interfaces like PCM or control API are defined in other |
| 768 | header files as <filename><sound/xxx.h></filename>. |
| 769 | They have to be included after |
| 770 | <filename><sound/core.h></filename>. |
| 771 | </para> |
| 772 | |
| 773 | </section> |
| 774 | </chapter> |
| 775 | |
| 776 | |
| 777 | <!-- ****************************************************** --> |
| 778 | <!-- Management of Cards and Components --> |
| 779 | <!-- ****************************************************** --> |
| 780 | <chapter id="card-management"> |
| 781 | <title>Management of Cards and Components</title> |
| 782 | |
| 783 | <section id="card-management-card-instance"> |
| 784 | <title>Card Instance</title> |
| 785 | <para> |
| 786 | For each soundcard, a <quote>card</quote> record must be allocated. |
| 787 | </para> |
| 788 | |
| 789 | <para> |
| 790 | A card record is the headquarters of the soundcard. It manages |
| 791 | the list of whole devices (components) on the soundcard, such as |
| 792 | PCM, mixers, MIDI, synthesizer, and so on. Also, the card |
| 793 | record holds the ID and the name strings of the card, manages |
| 794 | the root of proc files, and controls the power-management states |
| 795 | and hotplug disconnections. The component list on the card |
| 796 | record is used to manage the proper releases of resources at |
| 797 | destruction. |
| 798 | </para> |
| 799 | |
| 800 | <para> |
| 801 | As mentioned above, to create a card instance, call |
| 802 | <function>snd_card_new()</function>. |
| 803 | |
| 804 | <informalexample> |
| 805 | <programlisting> |
| 806 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 807 | struct snd_card *card; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 808 | card = snd_card_new(index, id, module, extra_size); |
| 809 | ]]> |
| 810 | </programlisting> |
| 811 | </informalexample> |
| 812 | </para> |
| 813 | |
| 814 | <para> |
| 815 | The function takes four arguments, the card-index number, the |
| 816 | id string, the module pointer (usually |
| 817 | <constant>THIS_MODULE</constant>), |
| 818 | and the size of extra-data space. The last argument is used to |
| 819 | allocate card->private_data for the |
| 820 | chip-specific data. Note that this data |
| 821 | <emphasis>is</emphasis> allocated by |
| 822 | <function>snd_card_new()</function>. |
| 823 | </para> |
| 824 | </section> |
| 825 | |
| 826 | <section id="card-management-component"> |
| 827 | <title>Components</title> |
| 828 | <para> |
| 829 | After the card is created, you can attach the components |
| 830 | (devices) to the card instance. On ALSA driver, a component is |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 831 | represented as a struct <structname>snd_device</structname> object. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 832 | A component can be a PCM instance, a control interface, a raw |
| 833 | MIDI interface, etc. Each of such instances has one component |
| 834 | entry. |
| 835 | </para> |
| 836 | |
| 837 | <para> |
| 838 | A component can be created via |
| 839 | <function>snd_device_new()</function> function. |
| 840 | |
| 841 | <informalexample> |
| 842 | <programlisting> |
| 843 | <![CDATA[ |
| 844 | snd_device_new(card, SNDRV_DEV_XXX, chip, &ops); |
| 845 | ]]> |
| 846 | </programlisting> |
| 847 | </informalexample> |
| 848 | </para> |
| 849 | |
| 850 | <para> |
| 851 | This takes the card pointer, the device-level |
| 852 | (<constant>SNDRV_DEV_XXX</constant>), the data pointer, and the |
| 853 | callback pointers (<parameter>&ops</parameter>). The |
| 854 | device-level defines the type of components and the order of |
| 855 | registration and de-registration. For most of components, the |
| 856 | device-level is already defined. For a user-defined component, |
| 857 | you can use <constant>SNDRV_DEV_LOWLEVEL</constant>. |
| 858 | </para> |
| 859 | |
| 860 | <para> |
| 861 | This function itself doesn't allocate the data space. The data |
| 862 | must be allocated manually beforehand, and its pointer is passed |
| 863 | as the argument. This pointer is used as the identifier |
| 864 | (<parameter>chip</parameter> in the above example) for the |
| 865 | instance. |
| 866 | </para> |
| 867 | |
| 868 | <para> |
| 869 | Each ALSA pre-defined component such as ac97 or pcm calls |
| 870 | <function>snd_device_new()</function> inside its |
| 871 | constructor. The destructor for each component is defined in the |
| 872 | callback pointers. Hence, you don't need to take care of |
| 873 | calling a destructor for such a component. |
| 874 | </para> |
| 875 | |
| 876 | <para> |
| 877 | If you would like to create your own component, you need to |
| 878 | set the destructor function to dev_free callback in |
| 879 | <parameter>ops</parameter>, so that it can be released |
| 880 | automatically via <function>snd_card_free()</function>. The |
| 881 | example will be shown later as an implementation of a |
| 882 | chip-specific data. |
| 883 | </para> |
| 884 | </section> |
| 885 | |
| 886 | <section id="card-management-chip-specific"> |
| 887 | <title>Chip-Specific Data</title> |
| 888 | <para> |
| 889 | The chip-specific information, e.g. the i/o port address, its |
| 890 | resource pointer, or the irq number, is stored in the |
| 891 | chip-specific record. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 892 | |
| 893 | <informalexample> |
| 894 | <programlisting> |
| 895 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 896 | struct mychip { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 897 | .... |
| 898 | }; |
| 899 | ]]> |
| 900 | </programlisting> |
| 901 | </informalexample> |
| 902 | </para> |
| 903 | |
| 904 | <para> |
| 905 | In general, there are two ways to allocate the chip record. |
| 906 | </para> |
| 907 | |
| 908 | <section id="card-management-chip-specific-snd-card-new"> |
| 909 | <title>1. Allocating via <function>snd_card_new()</function>.</title> |
| 910 | <para> |
| 911 | As mentioned above, you can pass the extra-data-length to the 4th argument of <function>snd_card_new()</function>, i.e. |
| 912 | |
| 913 | <informalexample> |
| 914 | <programlisting> |
| 915 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 916 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, sizeof(struct mychip)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 917 | ]]> |
| 918 | </programlisting> |
| 919 | </informalexample> |
| 920 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 921 | whether struct <structname>mychip</structname> is the type of the chip record. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 922 | </para> |
| 923 | |
| 924 | <para> |
| 925 | In return, the allocated record can be accessed as |
| 926 | |
| 927 | <informalexample> |
| 928 | <programlisting> |
| 929 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 930 | struct mychip *chip = (struct mychip *)card->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 931 | ]]> |
| 932 | </programlisting> |
| 933 | </informalexample> |
| 934 | |
| 935 | With this method, you don't have to allocate twice. |
| 936 | The record is released together with the card instance. |
| 937 | </para> |
| 938 | </section> |
| 939 | |
| 940 | <section id="card-management-chip-specific-allocate-extra"> |
| 941 | <title>2. Allocating an extra device.</title> |
| 942 | |
| 943 | <para> |
| 944 | After allocating a card instance via |
| 945 | <function>snd_card_new()</function> (with |
| 946 | <constant>NULL</constant> on the 4th arg), call |
Takashi Iwai | 561b220 | 2005-09-09 14:22:34 +0200 | [diff] [blame] | 947 | <function>kzalloc()</function>. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 948 | |
| 949 | <informalexample> |
| 950 | <programlisting> |
| 951 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 952 | struct snd_card *card; |
| 953 | struct mychip *chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 954 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, NULL); |
| 955 | ..... |
Takashi Iwai | 561b220 | 2005-09-09 14:22:34 +0200 | [diff] [blame] | 956 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 957 | ]]> |
| 958 | </programlisting> |
| 959 | </informalexample> |
| 960 | </para> |
| 961 | |
| 962 | <para> |
| 963 | The chip record should have the field to hold the card |
| 964 | pointer at least, |
| 965 | |
| 966 | <informalexample> |
| 967 | <programlisting> |
| 968 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 969 | struct mychip { |
| 970 | struct snd_card *card; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 971 | .... |
| 972 | }; |
| 973 | ]]> |
| 974 | </programlisting> |
| 975 | </informalexample> |
| 976 | </para> |
| 977 | |
| 978 | <para> |
| 979 | Then, set the card pointer in the returned chip instance. |
| 980 | |
| 981 | <informalexample> |
| 982 | <programlisting> |
| 983 | <![CDATA[ |
| 984 | chip->card = card; |
| 985 | ]]> |
| 986 | </programlisting> |
| 987 | </informalexample> |
| 988 | </para> |
| 989 | |
| 990 | <para> |
| 991 | Next, initialize the fields, and register this chip |
| 992 | record as a low-level device with a specified |
| 993 | <parameter>ops</parameter>, |
| 994 | |
| 995 | <informalexample> |
| 996 | <programlisting> |
| 997 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 998 | static struct snd_device_ops ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 999 | .dev_free = snd_mychip_dev_free, |
| 1000 | }; |
| 1001 | .... |
| 1002 | snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops); |
| 1003 | ]]> |
| 1004 | </programlisting> |
| 1005 | </informalexample> |
| 1006 | |
| 1007 | <function>snd_mychip_dev_free()</function> is the |
| 1008 | device-destructor function, which will call the real |
| 1009 | destructor. |
| 1010 | </para> |
| 1011 | |
| 1012 | <para> |
| 1013 | <informalexample> |
| 1014 | <programlisting> |
| 1015 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1016 | static int snd_mychip_dev_free(struct snd_device *device) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1017 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1018 | return snd_mychip_free(device->device_data); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1019 | } |
| 1020 | ]]> |
| 1021 | </programlisting> |
| 1022 | </informalexample> |
| 1023 | |
| 1024 | where <function>snd_mychip_free()</function> is the real destructor. |
| 1025 | </para> |
| 1026 | </section> |
| 1027 | </section> |
| 1028 | |
| 1029 | <section id="card-management-registration"> |
| 1030 | <title>Registration and Release</title> |
| 1031 | <para> |
| 1032 | After all components are assigned, register the card instance |
| 1033 | by calling <function>snd_card_register()</function>. The access |
| 1034 | to the device files are enabled at this point. That is, before |
| 1035 | <function>snd_card_register()</function> is called, the |
| 1036 | components are safely inaccessible from external side. If this |
| 1037 | call fails, exit the probe function after releasing the card via |
| 1038 | <function>snd_card_free()</function>. |
| 1039 | </para> |
| 1040 | |
| 1041 | <para> |
| 1042 | For releasing the card instance, you can call simply |
| 1043 | <function>snd_card_free()</function>. As already mentioned, all |
| 1044 | components are released automatically by this call. |
| 1045 | </para> |
| 1046 | |
| 1047 | <para> |
| 1048 | As further notes, the destructors (both |
| 1049 | <function>snd_mychip_dev_free</function> and |
| 1050 | <function>snd_mychip_free</function>) cannot be defined with |
| 1051 | <parameter>__devexit</parameter> prefix, because they may be |
| 1052 | called from the constructor, too, at the false path. |
| 1053 | </para> |
| 1054 | |
| 1055 | <para> |
| 1056 | For a device which allows hotplugging, you can use |
| 1057 | <function>snd_card_free_in_thread</function>. This one will |
| 1058 | postpone the destruction and wait in a kernel-thread until all |
| 1059 | devices are closed. |
| 1060 | </para> |
| 1061 | |
| 1062 | </section> |
| 1063 | |
| 1064 | </chapter> |
| 1065 | |
| 1066 | |
| 1067 | <!-- ****************************************************** --> |
| 1068 | <!-- PCI Resource Managements --> |
| 1069 | <!-- ****************************************************** --> |
| 1070 | <chapter id="pci-resource"> |
| 1071 | <title>PCI Resource Managements</title> |
| 1072 | |
| 1073 | <section id="pci-resource-example"> |
| 1074 | <title>Full Code Example</title> |
| 1075 | <para> |
| 1076 | In this section, we'll finish the chip-specific constructor, |
| 1077 | destructor and PCI entries. The example code is shown first, |
| 1078 | below. |
| 1079 | |
| 1080 | <example> |
| 1081 | <title>PCI Resource Managements Example</title> |
| 1082 | <programlisting> |
| 1083 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1084 | struct mychip { |
| 1085 | struct snd_card *card; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1086 | struct pci_dev *pci; |
| 1087 | |
| 1088 | unsigned long port; |
| 1089 | int irq; |
| 1090 | }; |
| 1091 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1092 | static int snd_mychip_free(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1093 | { |
| 1094 | /* disable hardware here if any */ |
| 1095 | .... // (not implemented in this document) |
| 1096 | |
| 1097 | /* release the irq */ |
| 1098 | if (chip->irq >= 0) |
| 1099 | free_irq(chip->irq, (void *)chip); |
| 1100 | /* release the i/o ports & memory */ |
| 1101 | pci_release_regions(chip->pci); |
| 1102 | /* disable the PCI entry */ |
| 1103 | pci_disable_device(chip->pci); |
| 1104 | /* release the data */ |
| 1105 | kfree(chip); |
| 1106 | return 0; |
| 1107 | } |
| 1108 | |
| 1109 | /* chip-specific constructor */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1110 | static int __devinit snd_mychip_create(struct snd_card *card, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1111 | struct pci_dev *pci, |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1112 | struct mychip **rchip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1113 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1114 | struct mychip *chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1115 | int err; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1116 | static struct snd_device_ops ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1117 | .dev_free = snd_mychip_dev_free, |
| 1118 | }; |
| 1119 | |
| 1120 | *rchip = NULL; |
| 1121 | |
| 1122 | /* initialize the PCI entry */ |
| 1123 | if ((err = pci_enable_device(pci)) < 0) |
| 1124 | return err; |
| 1125 | /* check PCI availability (28bit DMA) */ |
| 1126 | if (pci_set_dma_mask(pci, 0x0fffffff) < 0 || |
| 1127 | pci_set_consistent_dma_mask(pci, 0x0fffffff) < 0) { |
| 1128 | printk(KERN_ERR "error to set 28bit mask DMA\n"); |
| 1129 | pci_disable_device(pci); |
| 1130 | return -ENXIO; |
| 1131 | } |
| 1132 | |
Takashi Iwai | 561b220 | 2005-09-09 14:22:34 +0200 | [diff] [blame] | 1133 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1134 | if (chip == NULL) { |
| 1135 | pci_disable_device(pci); |
| 1136 | return -ENOMEM; |
| 1137 | } |
| 1138 | |
| 1139 | /* initialize the stuff */ |
| 1140 | chip->card = card; |
| 1141 | chip->pci = pci; |
| 1142 | chip->irq = -1; |
| 1143 | |
| 1144 | /* (1) PCI resource allocation */ |
| 1145 | if ((err = pci_request_regions(pci, "My Chip")) < 0) { |
| 1146 | kfree(chip); |
| 1147 | pci_disable_device(pci); |
| 1148 | return err; |
| 1149 | } |
| 1150 | chip->port = pci_resource_start(pci, 0); |
| 1151 | if (request_irq(pci->irq, snd_mychip_interrupt, |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1152 | SA_INTERRUPT|SA_SHIRQ, "My Chip", chip)) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1153 | printk(KERN_ERR "cannot grab irq %d\n", pci->irq); |
| 1154 | snd_mychip_free(chip); |
| 1155 | return -EBUSY; |
| 1156 | } |
| 1157 | chip->irq = pci->irq; |
| 1158 | |
| 1159 | /* (2) initialization of the chip hardware */ |
| 1160 | .... // (not implemented in this document) |
| 1161 | |
| 1162 | if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, |
| 1163 | chip, &ops)) < 0) { |
| 1164 | snd_mychip_free(chip); |
| 1165 | return err; |
| 1166 | } |
| 1167 | |
| 1168 | snd_card_set_dev(card, &pci->dev); |
| 1169 | |
| 1170 | *rchip = chip; |
| 1171 | return 0; |
| 1172 | } |
| 1173 | |
| 1174 | /* PCI IDs */ |
| 1175 | static struct pci_device_id snd_mychip_ids[] = { |
| 1176 | { PCI_VENDOR_ID_FOO, PCI_DEVICE_ID_BAR, |
| 1177 | PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, }, |
| 1178 | .... |
| 1179 | { 0, } |
| 1180 | }; |
| 1181 | MODULE_DEVICE_TABLE(pci, snd_mychip_ids); |
| 1182 | |
| 1183 | /* pci_driver definition */ |
| 1184 | static struct pci_driver driver = { |
| 1185 | .name = "My Own Chip", |
| 1186 | .id_table = snd_mychip_ids, |
| 1187 | .probe = snd_mychip_probe, |
| 1188 | .remove = __devexit_p(snd_mychip_remove), |
| 1189 | }; |
| 1190 | |
| 1191 | /* initialization of the module */ |
| 1192 | static int __init alsa_card_mychip_init(void) |
| 1193 | { |
Takashi Iwai | 01d25d4 | 2005-04-11 16:58:24 +0200 | [diff] [blame] | 1194 | return pci_register_driver(&driver); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1195 | } |
| 1196 | |
| 1197 | /* clean up the module */ |
| 1198 | static void __exit alsa_card_mychip_exit(void) |
| 1199 | { |
| 1200 | pci_unregister_driver(&driver); |
| 1201 | } |
| 1202 | |
| 1203 | module_init(alsa_card_mychip_init) |
| 1204 | module_exit(alsa_card_mychip_exit) |
| 1205 | |
| 1206 | EXPORT_NO_SYMBOLS; /* for old kernels only */ |
| 1207 | ]]> |
| 1208 | </programlisting> |
| 1209 | </example> |
| 1210 | </para> |
| 1211 | </section> |
| 1212 | |
| 1213 | <section id="pci-resource-some-haftas"> |
| 1214 | <title>Some Hafta's</title> |
| 1215 | <para> |
| 1216 | The allocation of PCI resources is done in the |
| 1217 | <function>probe()</function> function, and usually an extra |
| 1218 | <function>xxx_create()</function> function is written for this |
| 1219 | purpose. |
| 1220 | </para> |
| 1221 | |
| 1222 | <para> |
| 1223 | In the case of PCI devices, you have to call at first |
| 1224 | <function>pci_enable_device()</function> function before |
| 1225 | allocating resources. Also, you need to set the proper PCI DMA |
| 1226 | mask to limit the accessed i/o range. In some cases, you might |
| 1227 | need to call <function>pci_set_master()</function> function, |
| 1228 | too. |
| 1229 | </para> |
| 1230 | |
| 1231 | <para> |
| 1232 | Suppose the 28bit mask, and the code to be added would be like: |
| 1233 | |
| 1234 | <informalexample> |
| 1235 | <programlisting> |
| 1236 | <![CDATA[ |
| 1237 | if ((err = pci_enable_device(pci)) < 0) |
| 1238 | return err; |
| 1239 | if (pci_set_dma_mask(pci, 0x0fffffff) < 0 || |
| 1240 | pci_set_consistent_dma_mask(pci, 0x0fffffff) < 0) { |
| 1241 | printk(KERN_ERR "error to set 28bit mask DMA\n"); |
| 1242 | pci_disable_device(pci); |
| 1243 | return -ENXIO; |
| 1244 | } |
| 1245 | |
| 1246 | ]]> |
| 1247 | </programlisting> |
| 1248 | </informalexample> |
| 1249 | </para> |
| 1250 | </section> |
| 1251 | |
| 1252 | <section id="pci-resource-resource-allocation"> |
| 1253 | <title>Resource Allocation</title> |
| 1254 | <para> |
| 1255 | The allocation of I/O ports and irqs are done via standard kernel |
| 1256 | functions. Unlike ALSA ver.0.5.x., there are no helpers for |
| 1257 | that. And these resources must be released in the destructor |
| 1258 | function (see below). Also, on ALSA 0.9.x, you don't need to |
| 1259 | allocate (pseudo-)DMA for PCI like ALSA 0.5.x. |
| 1260 | </para> |
| 1261 | |
| 1262 | <para> |
| 1263 | Now assume that this PCI device has an I/O port with 8 bytes |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1264 | and an interrupt. Then struct <structname>mychip</structname> will have the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1265 | following fields: |
| 1266 | |
| 1267 | <informalexample> |
| 1268 | <programlisting> |
| 1269 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1270 | struct mychip { |
| 1271 | struct snd_card *card; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1272 | |
| 1273 | unsigned long port; |
| 1274 | int irq; |
| 1275 | }; |
| 1276 | ]]> |
| 1277 | </programlisting> |
| 1278 | </informalexample> |
| 1279 | </para> |
| 1280 | |
| 1281 | <para> |
| 1282 | For an i/o port (and also a memory region), you need to have |
| 1283 | the resource pointer for the standard resource management. For |
| 1284 | an irq, you have to keep only the irq number (integer). But you |
| 1285 | need to initialize this number as -1 before actual allocation, |
| 1286 | since irq 0 is valid. The port address and its resource pointer |
| 1287 | can be initialized as null by |
Takashi Iwai | 561b220 | 2005-09-09 14:22:34 +0200 | [diff] [blame] | 1288 | <function>kzalloc()</function> automatically, so you |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1289 | don't have to take care of resetting them. |
| 1290 | </para> |
| 1291 | |
| 1292 | <para> |
| 1293 | The allocation of an i/o port is done like this: |
| 1294 | |
| 1295 | <informalexample> |
| 1296 | <programlisting> |
| 1297 | <![CDATA[ |
| 1298 | if ((err = pci_request_regions(pci, "My Chip")) < 0) { |
| 1299 | kfree(chip); |
| 1300 | pci_disable_device(pci); |
| 1301 | return err; |
| 1302 | } |
| 1303 | chip->port = pci_resource_start(pci, 0); |
| 1304 | ]]> |
| 1305 | </programlisting> |
| 1306 | </informalexample> |
| 1307 | </para> |
| 1308 | |
| 1309 | <para> |
| 1310 | <!-- obsolete --> |
| 1311 | It will reserve the i/o port region of 8 bytes of the given |
| 1312 | PCI device. The returned value, chip->res_port, is allocated |
| 1313 | via <function>kmalloc()</function> by |
| 1314 | <function>request_region()</function>. The pointer must be |
| 1315 | released via <function>kfree()</function>, but there is some |
| 1316 | problem regarding this. This issue will be explained more below. |
| 1317 | </para> |
| 1318 | |
| 1319 | <para> |
| 1320 | The allocation of an interrupt source is done like this: |
| 1321 | |
| 1322 | <informalexample> |
| 1323 | <programlisting> |
| 1324 | <![CDATA[ |
| 1325 | if (request_irq(pci->irq, snd_mychip_interrupt, |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1326 | SA_INTERRUPT|SA_SHIRQ, "My Chip", chip)) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1327 | printk(KERN_ERR "cannot grab irq %d\n", pci->irq); |
| 1328 | snd_mychip_free(chip); |
| 1329 | return -EBUSY; |
| 1330 | } |
| 1331 | chip->irq = pci->irq; |
| 1332 | ]]> |
| 1333 | </programlisting> |
| 1334 | </informalexample> |
| 1335 | |
| 1336 | where <function>snd_mychip_interrupt()</function> is the |
| 1337 | interrupt handler defined <link |
| 1338 | linkend="pcm-interface-interrupt-handler"><citetitle>later</citetitle></link>. |
| 1339 | Note that chip->irq should be defined |
| 1340 | only when <function>request_irq()</function> succeeded. |
| 1341 | </para> |
| 1342 | |
| 1343 | <para> |
| 1344 | On the PCI bus, the interrupts can be shared. Thus, |
| 1345 | <constant>SA_SHIRQ</constant> is given as the interrupt flag of |
| 1346 | <function>request_irq()</function>. |
| 1347 | </para> |
| 1348 | |
| 1349 | <para> |
| 1350 | The last argument of <function>request_irq()</function> is the |
| 1351 | data pointer passed to the interrupt handler. Usually, the |
| 1352 | chip-specific record is used for that, but you can use what you |
| 1353 | like, too. |
| 1354 | </para> |
| 1355 | |
| 1356 | <para> |
| 1357 | I won't define the detail of the interrupt handler at this |
| 1358 | point, but at least its appearance can be explained now. The |
| 1359 | interrupt handler looks usually like the following: |
| 1360 | |
| 1361 | <informalexample> |
| 1362 | <programlisting> |
| 1363 | <![CDATA[ |
| 1364 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id, |
| 1365 | struct pt_regs *regs) |
| 1366 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1367 | struct mychip *chip = dev_id; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1368 | .... |
| 1369 | return IRQ_HANDLED; |
| 1370 | } |
| 1371 | ]]> |
| 1372 | </programlisting> |
| 1373 | </informalexample> |
| 1374 | </para> |
| 1375 | |
| 1376 | <para> |
| 1377 | Now let's write the corresponding destructor for the resources |
| 1378 | above. The role of destructor is simple: disable the hardware |
| 1379 | (if already activated) and release the resources. So far, we |
| 1380 | have no hardware part, so the disabling is not written here. |
| 1381 | </para> |
| 1382 | |
| 1383 | <para> |
| 1384 | For releasing the resources, <quote>check-and-release</quote> |
| 1385 | method is a safer way. For the interrupt, do like this: |
| 1386 | |
| 1387 | <informalexample> |
| 1388 | <programlisting> |
| 1389 | <![CDATA[ |
| 1390 | if (chip->irq >= 0) |
| 1391 | free_irq(chip->irq, (void *)chip); |
| 1392 | ]]> |
| 1393 | </programlisting> |
| 1394 | </informalexample> |
| 1395 | |
| 1396 | Since the irq number can start from 0, you should initialize |
| 1397 | chip->irq with a negative value (e.g. -1), so that you can |
| 1398 | check the validity of the irq number as above. |
| 1399 | </para> |
| 1400 | |
| 1401 | <para> |
| 1402 | When you requested I/O ports or memory regions via |
| 1403 | <function>pci_request_region()</function> or |
| 1404 | <function>pci_request_regions()</function> like this example, |
| 1405 | release the resource(s) using the corresponding function, |
| 1406 | <function>pci_release_region()</function> or |
| 1407 | <function>pci_release_regions()</function>. |
| 1408 | |
| 1409 | <informalexample> |
| 1410 | <programlisting> |
| 1411 | <![CDATA[ |
| 1412 | pci_release_regions(chip->pci); |
| 1413 | ]]> |
| 1414 | </programlisting> |
| 1415 | </informalexample> |
| 1416 | </para> |
| 1417 | |
| 1418 | <para> |
| 1419 | When you requested manually via <function>request_region()</function> |
| 1420 | or <function>request_mem_region</function>, you can release it via |
| 1421 | <function>release_resource()</function>. Suppose that you keep |
| 1422 | the resource pointer returned from <function>request_region()</function> |
| 1423 | in chip->res_port, the release procedure looks like below: |
| 1424 | |
| 1425 | <informalexample> |
| 1426 | <programlisting> |
| 1427 | <![CDATA[ |
Takashi Iwai | b1d5776 | 2005-10-10 11:56:31 +0200 | [diff] [blame] | 1428 | release_and_free_resource(chip->res_port); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1429 | ]]> |
| 1430 | </programlisting> |
| 1431 | </informalexample> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1432 | </para> |
| 1433 | |
| 1434 | <para> |
| 1435 | Don't forget to call <function>pci_disable_device()</function> |
| 1436 | before all finished. |
| 1437 | </para> |
| 1438 | |
| 1439 | <para> |
| 1440 | And finally, release the chip-specific record. |
| 1441 | |
| 1442 | <informalexample> |
| 1443 | <programlisting> |
| 1444 | <![CDATA[ |
| 1445 | kfree(chip); |
| 1446 | ]]> |
| 1447 | </programlisting> |
| 1448 | </informalexample> |
| 1449 | </para> |
| 1450 | |
| 1451 | <para> |
| 1452 | Again, remember that you cannot |
| 1453 | set <parameter>__devexit</parameter> prefix for this destructor. |
| 1454 | </para> |
| 1455 | |
| 1456 | <para> |
| 1457 | We didn't implement the hardware-disabling part in the above. |
| 1458 | If you need to do this, please note that the destructor may be |
| 1459 | called even before the initialization of the chip is completed. |
| 1460 | It would be better to have a flag to skip the hardware-disabling |
| 1461 | if the hardware was not initialized yet. |
| 1462 | </para> |
| 1463 | |
| 1464 | <para> |
| 1465 | When the chip-data is assigned to the card using |
| 1466 | <function>snd_device_new()</function> with |
| 1467 | <constant>SNDRV_DEV_LOWLELVEL</constant> , its destructor is |
| 1468 | called at the last. That is, it is assured that all other |
| 1469 | components like PCMs and controls have been already released. |
| 1470 | You don't have to call stopping PCMs, etc. explicitly, but just |
| 1471 | stop the hardware in the low-level. |
| 1472 | </para> |
| 1473 | |
| 1474 | <para> |
| 1475 | The management of a memory-mapped region is almost as same as |
| 1476 | the management of an i/o port. You'll need three fields like |
| 1477 | the following: |
| 1478 | |
| 1479 | <informalexample> |
| 1480 | <programlisting> |
| 1481 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1482 | struct mychip { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1483 | .... |
| 1484 | unsigned long iobase_phys; |
| 1485 | void __iomem *iobase_virt; |
| 1486 | }; |
| 1487 | ]]> |
| 1488 | </programlisting> |
| 1489 | </informalexample> |
| 1490 | |
| 1491 | and the allocation would be like below: |
| 1492 | |
| 1493 | <informalexample> |
| 1494 | <programlisting> |
| 1495 | <![CDATA[ |
| 1496 | if ((err = pci_request_regions(pci, "My Chip")) < 0) { |
| 1497 | kfree(chip); |
| 1498 | return err; |
| 1499 | } |
| 1500 | chip->iobase_phys = pci_resource_start(pci, 0); |
| 1501 | chip->iobase_virt = ioremap_nocache(chip->iobase_phys, |
| 1502 | pci_resource_len(pci, 0)); |
| 1503 | ]]> |
| 1504 | </programlisting> |
| 1505 | </informalexample> |
| 1506 | |
| 1507 | and the corresponding destructor would be: |
| 1508 | |
| 1509 | <informalexample> |
| 1510 | <programlisting> |
| 1511 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1512 | static int snd_mychip_free(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1513 | { |
| 1514 | .... |
| 1515 | if (chip->iobase_virt) |
| 1516 | iounmap(chip->iobase_virt); |
| 1517 | .... |
| 1518 | pci_release_regions(chip->pci); |
| 1519 | .... |
| 1520 | } |
| 1521 | ]]> |
| 1522 | </programlisting> |
| 1523 | </informalexample> |
| 1524 | </para> |
| 1525 | |
| 1526 | </section> |
| 1527 | |
| 1528 | <section id="pci-resource-device-struct"> |
| 1529 | <title>Registration of Device Struct</title> |
| 1530 | <para> |
| 1531 | At some point, typically after calling <function>snd_device_new()</function>, |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1532 | you need to register the struct <structname>device</structname> of the chip |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1533 | you're handling for udev and co. ALSA provides a macro for compatibility with |
| 1534 | older kernels. Simply call like the following: |
| 1535 | <informalexample> |
| 1536 | <programlisting> |
| 1537 | <![CDATA[ |
| 1538 | snd_card_set_dev(card, &pci->dev); |
| 1539 | ]]> |
| 1540 | </programlisting> |
| 1541 | </informalexample> |
| 1542 | so that it stores the PCI's device pointer to the card. This will be |
| 1543 | referred by ALSA core functions later when the devices are registered. |
| 1544 | </para> |
| 1545 | <para> |
| 1546 | In the case of non-PCI, pass the proper device struct pointer of the BUS |
| 1547 | instead. (In the case of legacy ISA without PnP, you don't have to do |
| 1548 | anything.) |
| 1549 | </para> |
| 1550 | </section> |
| 1551 | |
| 1552 | <section id="pci-resource-entries"> |
| 1553 | <title>PCI Entries</title> |
| 1554 | <para> |
| 1555 | So far, so good. Let's finish the rest of missing PCI |
| 1556 | stuffs. At first, we need a |
| 1557 | <structname>pci_device_id</structname> table for this |
| 1558 | chipset. It's a table of PCI vendor/device ID number, and some |
| 1559 | masks. |
| 1560 | </para> |
| 1561 | |
| 1562 | <para> |
| 1563 | For example, |
| 1564 | |
| 1565 | <informalexample> |
| 1566 | <programlisting> |
| 1567 | <![CDATA[ |
| 1568 | static struct pci_device_id snd_mychip_ids[] = { |
| 1569 | { PCI_VENDOR_ID_FOO, PCI_DEVICE_ID_BAR, |
| 1570 | PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, }, |
| 1571 | .... |
| 1572 | { 0, } |
| 1573 | }; |
| 1574 | MODULE_DEVICE_TABLE(pci, snd_mychip_ids); |
| 1575 | ]]> |
| 1576 | </programlisting> |
| 1577 | </informalexample> |
| 1578 | </para> |
| 1579 | |
| 1580 | <para> |
| 1581 | The first and second fields of |
| 1582 | <structname>pci_device_id</structname> struct are the vendor and |
| 1583 | device IDs. If you have nothing special to filter the matching |
| 1584 | devices, you can use the rest of fields like above. The last |
| 1585 | field of <structname>pci_device_id</structname> struct is a |
| 1586 | private data for this entry. You can specify any value here, for |
| 1587 | example, to tell the type of different operations per each |
| 1588 | device IDs. Such an example is found in intel8x0 driver. |
| 1589 | </para> |
| 1590 | |
| 1591 | <para> |
| 1592 | The last entry of this list is the terminator. You must |
| 1593 | specify this all-zero entry. |
| 1594 | </para> |
| 1595 | |
| 1596 | <para> |
| 1597 | Then, prepare the <structname>pci_driver</structname> record: |
| 1598 | |
| 1599 | <informalexample> |
| 1600 | <programlisting> |
| 1601 | <![CDATA[ |
| 1602 | static struct pci_driver driver = { |
| 1603 | .name = "My Own Chip", |
| 1604 | .id_table = snd_mychip_ids, |
| 1605 | .probe = snd_mychip_probe, |
| 1606 | .remove = __devexit_p(snd_mychip_remove), |
| 1607 | }; |
| 1608 | ]]> |
| 1609 | </programlisting> |
| 1610 | </informalexample> |
| 1611 | </para> |
| 1612 | |
| 1613 | <para> |
| 1614 | The <structfield>probe</structfield> and |
| 1615 | <structfield>remove</structfield> functions are what we already |
| 1616 | defined in |
| 1617 | the previous sections. The <structfield>remove</structfield> should |
| 1618 | be defined with |
| 1619 | <function>__devexit_p()</function> macro, so that it's not |
| 1620 | defined for built-in (and non-hot-pluggable) case. The |
| 1621 | <structfield>name</structfield> |
| 1622 | field is the name string of this device. Note that you must not |
| 1623 | use a slash <quote>/</quote> in this string. |
| 1624 | </para> |
| 1625 | |
| 1626 | <para> |
| 1627 | And at last, the module entries: |
| 1628 | |
| 1629 | <informalexample> |
| 1630 | <programlisting> |
| 1631 | <![CDATA[ |
| 1632 | static int __init alsa_card_mychip_init(void) |
| 1633 | { |
Takashi Iwai | 01d25d4 | 2005-04-11 16:58:24 +0200 | [diff] [blame] | 1634 | return pci_register_driver(&driver); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1635 | } |
| 1636 | |
| 1637 | static void __exit alsa_card_mychip_exit(void) |
| 1638 | { |
| 1639 | pci_unregister_driver(&driver); |
| 1640 | } |
| 1641 | |
| 1642 | module_init(alsa_card_mychip_init) |
| 1643 | module_exit(alsa_card_mychip_exit) |
| 1644 | ]]> |
| 1645 | </programlisting> |
| 1646 | </informalexample> |
| 1647 | </para> |
| 1648 | |
| 1649 | <para> |
| 1650 | Note that these module entries are tagged with |
| 1651 | <parameter>__init</parameter> and |
| 1652 | <parameter>__exit</parameter> prefixes, not |
| 1653 | <parameter>__devinit</parameter> nor |
| 1654 | <parameter>__devexit</parameter>. |
| 1655 | </para> |
| 1656 | |
| 1657 | <para> |
| 1658 | Oh, one thing was forgotten. If you have no exported symbols, |
| 1659 | you need to declare it on 2.2 or 2.4 kernels (on 2.6 kernels |
| 1660 | it's not necessary, though). |
| 1661 | |
| 1662 | <informalexample> |
| 1663 | <programlisting> |
| 1664 | <![CDATA[ |
| 1665 | EXPORT_NO_SYMBOLS; |
| 1666 | ]]> |
| 1667 | </programlisting> |
| 1668 | </informalexample> |
| 1669 | |
| 1670 | That's all! |
| 1671 | </para> |
| 1672 | </section> |
| 1673 | </chapter> |
| 1674 | |
| 1675 | |
| 1676 | <!-- ****************************************************** --> |
| 1677 | <!-- PCM Interface --> |
| 1678 | <!-- ****************************************************** --> |
| 1679 | <chapter id="pcm-interface"> |
| 1680 | <title>PCM Interface</title> |
| 1681 | |
| 1682 | <section id="pcm-interface-general"> |
| 1683 | <title>General</title> |
| 1684 | <para> |
| 1685 | The PCM middle layer of ALSA is quite powerful and it is only |
| 1686 | necessary for each driver to implement the low-level functions |
| 1687 | to access its hardware. |
| 1688 | </para> |
| 1689 | |
| 1690 | <para> |
| 1691 | For accessing to the PCM layer, you need to include |
| 1692 | <filename><sound/pcm.h></filename> above all. In addition, |
| 1693 | <filename><sound/pcm_params.h></filename> might be needed |
| 1694 | if you access to some functions related with hw_param. |
| 1695 | </para> |
| 1696 | |
| 1697 | <para> |
| 1698 | Each card device can have up to four pcm instances. A pcm |
| 1699 | instance corresponds to a pcm device file. The limitation of |
| 1700 | number of instances comes only from the available bit size of |
| 1701 | the linux's device number. Once when 64bit device number is |
| 1702 | used, we'll have more available pcm instances. |
| 1703 | </para> |
| 1704 | |
| 1705 | <para> |
| 1706 | A pcm instance consists of pcm playback and capture streams, |
| 1707 | and each pcm stream consists of one or more pcm substreams. Some |
| 1708 | soundcard supports the multiple-playback function. For example, |
| 1709 | emu10k1 has a PCM playback of 32 stereo substreams. In this case, at |
| 1710 | each open, a free substream is (usually) automatically chosen |
| 1711 | and opened. Meanwhile, when only one substream exists and it was |
| 1712 | already opened, the succeeding open will result in the blocking |
| 1713 | or the error with <constant>EAGAIN</constant> according to the |
| 1714 | file open mode. But you don't have to know the detail in your |
| 1715 | driver. The PCM middle layer will take all such jobs. |
| 1716 | </para> |
| 1717 | </section> |
| 1718 | |
| 1719 | <section id="pcm-interface-example"> |
| 1720 | <title>Full Code Example</title> |
| 1721 | <para> |
| 1722 | The example code below does not include any hardware access |
| 1723 | routines but shows only the skeleton, how to build up the PCM |
| 1724 | interfaces. |
| 1725 | |
| 1726 | <example> |
| 1727 | <title>PCM Example Code</title> |
| 1728 | <programlisting> |
| 1729 | <![CDATA[ |
| 1730 | #include <sound/pcm.h> |
| 1731 | .... |
| 1732 | |
| 1733 | /* hardware definition */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1734 | static struct snd_pcm_hardware snd_mychip_playback_hw = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1735 | .info = (SNDRV_PCM_INFO_MMAP | |
| 1736 | SNDRV_PCM_INFO_INTERLEAVED | |
| 1737 | SNDRV_PCM_INFO_BLOCK_TRANSFER | |
| 1738 | SNDRV_PCM_INFO_MMAP_VALID), |
| 1739 | .formats = SNDRV_PCM_FMTBIT_S16_LE, |
| 1740 | .rates = SNDRV_PCM_RATE_8000_48000, |
| 1741 | .rate_min = 8000, |
| 1742 | .rate_max = 48000, |
| 1743 | .channels_min = 2, |
| 1744 | .channels_max = 2, |
| 1745 | .buffer_bytes_max = 32768, |
| 1746 | .period_bytes_min = 4096, |
| 1747 | .period_bytes_max = 32768, |
| 1748 | .periods_min = 1, |
| 1749 | .periods_max = 1024, |
| 1750 | }; |
| 1751 | |
| 1752 | /* hardware definition */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1753 | static struct snd_pcm_hardware snd_mychip_capture_hw = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1754 | .info = (SNDRV_PCM_INFO_MMAP | |
| 1755 | SNDRV_PCM_INFO_INTERLEAVED | |
| 1756 | SNDRV_PCM_INFO_BLOCK_TRANSFER | |
| 1757 | SNDRV_PCM_INFO_MMAP_VALID), |
| 1758 | .formats = SNDRV_PCM_FMTBIT_S16_LE, |
| 1759 | .rates = SNDRV_PCM_RATE_8000_48000, |
| 1760 | .rate_min = 8000, |
| 1761 | .rate_max = 48000, |
| 1762 | .channels_min = 2, |
| 1763 | .channels_max = 2, |
| 1764 | .buffer_bytes_max = 32768, |
| 1765 | .period_bytes_min = 4096, |
| 1766 | .period_bytes_max = 32768, |
| 1767 | .periods_min = 1, |
| 1768 | .periods_max = 1024, |
| 1769 | }; |
| 1770 | |
| 1771 | /* open callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1772 | static int snd_mychip_playback_open(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1773 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1774 | struct mychip *chip = snd_pcm_substream_chip(substream); |
| 1775 | struct snd_pcm_runtime *runtime = substream->runtime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1776 | |
| 1777 | runtime->hw = snd_mychip_playback_hw; |
| 1778 | // more hardware-initialization will be done here |
| 1779 | return 0; |
| 1780 | } |
| 1781 | |
| 1782 | /* close callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1783 | static int snd_mychip_playback_close(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1784 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1785 | struct mychip *chip = snd_pcm_substream_chip(substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1786 | // the hardware-specific codes will be here |
| 1787 | return 0; |
| 1788 | |
| 1789 | } |
| 1790 | |
| 1791 | /* open callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1792 | static int snd_mychip_capture_open(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1793 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1794 | struct mychip *chip = snd_pcm_substream_chip(substream); |
| 1795 | struct snd_pcm_runtime *runtime = substream->runtime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1796 | |
| 1797 | runtime->hw = snd_mychip_capture_hw; |
| 1798 | // more hardware-initialization will be done here |
| 1799 | return 0; |
| 1800 | } |
| 1801 | |
| 1802 | /* close callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1803 | static int snd_mychip_capture_close(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1804 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1805 | struct mychip *chip = snd_pcm_substream_chip(substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1806 | // the hardware-specific codes will be here |
| 1807 | return 0; |
| 1808 | |
| 1809 | } |
| 1810 | |
| 1811 | /* hw_params callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1812 | static int snd_mychip_pcm_hw_params(struct snd_pcm_substream *substream, |
| 1813 | struct snd_pcm_hw_params *hw_params) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1814 | { |
| 1815 | return snd_pcm_lib_malloc_pages(substream, |
| 1816 | params_buffer_bytes(hw_params)); |
| 1817 | } |
| 1818 | |
| 1819 | /* hw_free callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1820 | static int snd_mychip_pcm_hw_free(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1821 | { |
| 1822 | return snd_pcm_lib_free_pages(substream); |
| 1823 | } |
| 1824 | |
| 1825 | /* prepare callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1826 | static int snd_mychip_pcm_prepare(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1827 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1828 | struct mychip *chip = snd_pcm_substream_chip(substream); |
| 1829 | struct snd_pcm_runtime *runtime = substream->runtime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1830 | |
| 1831 | /* set up the hardware with the current configuration |
| 1832 | * for example... |
| 1833 | */ |
| 1834 | mychip_set_sample_format(chip, runtime->format); |
| 1835 | mychip_set_sample_rate(chip, runtime->rate); |
| 1836 | mychip_set_channels(chip, runtime->channels); |
Takashi Iwai | 0b7bed4 | 2006-03-02 15:35:55 +0100 | [diff] [blame] | 1837 | mychip_set_dma_setup(chip, runtime->dma_addr, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1838 | chip->buffer_size, |
| 1839 | chip->period_size); |
| 1840 | return 0; |
| 1841 | } |
| 1842 | |
| 1843 | /* trigger callback */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1844 | static int snd_mychip_pcm_trigger(struct snd_pcm_substream *substream, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1845 | int cmd) |
| 1846 | { |
| 1847 | switch (cmd) { |
| 1848 | case SNDRV_PCM_TRIGGER_START: |
| 1849 | // do something to start the PCM engine |
| 1850 | break; |
| 1851 | case SNDRV_PCM_TRIGGER_STOP: |
| 1852 | // do something to stop the PCM engine |
| 1853 | break; |
| 1854 | default: |
| 1855 | return -EINVAL; |
| 1856 | } |
| 1857 | } |
| 1858 | |
| 1859 | /* pointer callback */ |
| 1860 | static snd_pcm_uframes_t |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1861 | snd_mychip_pcm_pointer(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1862 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1863 | struct mychip *chip = snd_pcm_substream_chip(substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1864 | unsigned int current_ptr; |
| 1865 | |
| 1866 | /* get the current hardware pointer */ |
| 1867 | current_ptr = mychip_get_hw_pointer(chip); |
| 1868 | return current_ptr; |
| 1869 | } |
| 1870 | |
| 1871 | /* operators */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1872 | static struct snd_pcm_ops snd_mychip_playback_ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1873 | .open = snd_mychip_playback_open, |
| 1874 | .close = snd_mychip_playback_close, |
| 1875 | .ioctl = snd_pcm_lib_ioctl, |
| 1876 | .hw_params = snd_mychip_pcm_hw_params, |
| 1877 | .hw_free = snd_mychip_pcm_hw_free, |
| 1878 | .prepare = snd_mychip_pcm_prepare, |
| 1879 | .trigger = snd_mychip_pcm_trigger, |
| 1880 | .pointer = snd_mychip_pcm_pointer, |
| 1881 | }; |
| 1882 | |
| 1883 | /* operators */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1884 | static struct snd_pcm_ops snd_mychip_capture_ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1885 | .open = snd_mychip_capture_open, |
| 1886 | .close = snd_mychip_capture_close, |
| 1887 | .ioctl = snd_pcm_lib_ioctl, |
| 1888 | .hw_params = snd_mychip_pcm_hw_params, |
| 1889 | .hw_free = snd_mychip_pcm_hw_free, |
| 1890 | .prepare = snd_mychip_pcm_prepare, |
| 1891 | .trigger = snd_mychip_pcm_trigger, |
| 1892 | .pointer = snd_mychip_pcm_pointer, |
| 1893 | }; |
| 1894 | |
| 1895 | /* |
| 1896 | * definitions of capture are omitted here... |
| 1897 | */ |
| 1898 | |
| 1899 | /* create a pcm device */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1900 | static int __devinit snd_mychip_new_pcm(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1901 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1902 | struct snd_pcm *pcm; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1903 | int err; |
| 1904 | |
| 1905 | if ((err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1, |
| 1906 | &pcm)) < 0) |
| 1907 | return err; |
| 1908 | pcm->private_data = chip; |
| 1909 | strcpy(pcm->name, "My Chip"); |
| 1910 | chip->pcm = pcm; |
| 1911 | /* set operators */ |
| 1912 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, |
| 1913 | &snd_mychip_playback_ops); |
| 1914 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, |
| 1915 | &snd_mychip_capture_ops); |
| 1916 | /* pre-allocation of buffers */ |
| 1917 | /* NOTE: this may fail */ |
| 1918 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, |
| 1919 | snd_dma_pci_data(chip->pci), |
| 1920 | 64*1024, 64*1024); |
| 1921 | return 0; |
| 1922 | } |
| 1923 | ]]> |
| 1924 | </programlisting> |
| 1925 | </example> |
| 1926 | </para> |
| 1927 | </section> |
| 1928 | |
| 1929 | <section id="pcm-interface-constructor"> |
| 1930 | <title>Constructor</title> |
| 1931 | <para> |
| 1932 | A pcm instance is allocated by <function>snd_pcm_new()</function> |
| 1933 | function. It would be better to create a constructor for pcm, |
| 1934 | namely, |
| 1935 | |
| 1936 | <informalexample> |
| 1937 | <programlisting> |
| 1938 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1939 | static int __devinit snd_mychip_new_pcm(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1940 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1941 | struct snd_pcm *pcm; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1942 | int err; |
| 1943 | |
| 1944 | if ((err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1, |
| 1945 | &pcm)) < 0) |
| 1946 | return err; |
| 1947 | pcm->private_data = chip; |
| 1948 | strcpy(pcm->name, "My Chip"); |
| 1949 | chip->pcm = pcm; |
| 1950 | .... |
| 1951 | return 0; |
| 1952 | } |
| 1953 | ]]> |
| 1954 | </programlisting> |
| 1955 | </informalexample> |
| 1956 | </para> |
| 1957 | |
| 1958 | <para> |
| 1959 | The <function>snd_pcm_new()</function> function takes the four |
| 1960 | arguments. The first argument is the card pointer to which this |
| 1961 | pcm is assigned, and the second is the ID string. |
| 1962 | </para> |
| 1963 | |
| 1964 | <para> |
| 1965 | The third argument (<parameter>index</parameter>, 0 in the |
| 1966 | above) is the index of this new pcm. It begins from zero. When |
| 1967 | you will create more than one pcm instances, specify the |
| 1968 | different numbers in this argument. For example, |
| 1969 | <parameter>index</parameter> = 1 for the second PCM device. |
| 1970 | </para> |
| 1971 | |
| 1972 | <para> |
| 1973 | The fourth and fifth arguments are the number of substreams |
| 1974 | for playback and capture, respectively. Here both 1 are given in |
| 1975 | the above example. When no playback or no capture is available, |
| 1976 | pass 0 to the corresponding argument. |
| 1977 | </para> |
| 1978 | |
| 1979 | <para> |
| 1980 | If a chip supports multiple playbacks or captures, you can |
| 1981 | specify more numbers, but they must be handled properly in |
| 1982 | open/close, etc. callbacks. When you need to know which |
| 1983 | substream you are referring to, then it can be obtained from |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1984 | struct <structname>snd_pcm_substream</structname> data passed to each callback |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1985 | as follows: |
| 1986 | |
| 1987 | <informalexample> |
| 1988 | <programlisting> |
| 1989 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 1990 | struct snd_pcm_substream *substream; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1991 | int index = substream->number; |
| 1992 | ]]> |
| 1993 | </programlisting> |
| 1994 | </informalexample> |
| 1995 | </para> |
| 1996 | |
| 1997 | <para> |
| 1998 | After the pcm is created, you need to set operators for each |
| 1999 | pcm stream. |
| 2000 | |
| 2001 | <informalexample> |
| 2002 | <programlisting> |
| 2003 | <![CDATA[ |
| 2004 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, |
| 2005 | &snd_mychip_playback_ops); |
| 2006 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, |
| 2007 | &snd_mychip_capture_ops); |
| 2008 | ]]> |
| 2009 | </programlisting> |
| 2010 | </informalexample> |
| 2011 | </para> |
| 2012 | |
| 2013 | <para> |
| 2014 | The operators are defined typically like this: |
| 2015 | |
| 2016 | <informalexample> |
| 2017 | <programlisting> |
| 2018 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2019 | static struct snd_pcm_ops snd_mychip_playback_ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2020 | .open = snd_mychip_pcm_open, |
| 2021 | .close = snd_mychip_pcm_close, |
| 2022 | .ioctl = snd_pcm_lib_ioctl, |
| 2023 | .hw_params = snd_mychip_pcm_hw_params, |
| 2024 | .hw_free = snd_mychip_pcm_hw_free, |
| 2025 | .prepare = snd_mychip_pcm_prepare, |
| 2026 | .trigger = snd_mychip_pcm_trigger, |
| 2027 | .pointer = snd_mychip_pcm_pointer, |
| 2028 | }; |
| 2029 | ]]> |
| 2030 | </programlisting> |
| 2031 | </informalexample> |
| 2032 | |
| 2033 | Each of callbacks is explained in the subsection |
| 2034 | <link linkend="pcm-interface-operators"><citetitle> |
| 2035 | Operators</citetitle></link>. |
| 2036 | </para> |
| 2037 | |
| 2038 | <para> |
| 2039 | After setting the operators, most likely you'd like to |
| 2040 | pre-allocate the buffer. For the pre-allocation, simply call |
| 2041 | the following: |
| 2042 | |
| 2043 | <informalexample> |
| 2044 | <programlisting> |
| 2045 | <![CDATA[ |
| 2046 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, |
| 2047 | snd_dma_pci_data(chip->pci), |
| 2048 | 64*1024, 64*1024); |
| 2049 | ]]> |
| 2050 | </programlisting> |
| 2051 | </informalexample> |
| 2052 | |
| 2053 | It will allocate up to 64kB buffer as default. The details of |
| 2054 | buffer management will be described in the later section <link |
| 2055 | linkend="buffer-and-memory"><citetitle>Buffer and Memory |
| 2056 | Management</citetitle></link>. |
| 2057 | </para> |
| 2058 | |
| 2059 | <para> |
| 2060 | Additionally, you can set some extra information for this pcm |
| 2061 | in pcm->info_flags. |
| 2062 | The available values are defined as |
| 2063 | <constant>SNDRV_PCM_INFO_XXX</constant> in |
| 2064 | <filename><sound/asound.h></filename>, which is used for |
| 2065 | the hardware definition (described later). When your soundchip |
| 2066 | supports only half-duplex, specify like this: |
| 2067 | |
| 2068 | <informalexample> |
| 2069 | <programlisting> |
| 2070 | <![CDATA[ |
| 2071 | pcm->info_flags = SNDRV_PCM_INFO_HALF_DUPLEX; |
| 2072 | ]]> |
| 2073 | </programlisting> |
| 2074 | </informalexample> |
| 2075 | </para> |
| 2076 | </section> |
| 2077 | |
| 2078 | <section id="pcm-interface-destructor"> |
| 2079 | <title>... And the Destructor?</title> |
| 2080 | <para> |
| 2081 | The destructor for a pcm instance is not always |
| 2082 | necessary. Since the pcm device will be released by the middle |
| 2083 | layer code automatically, you don't have to call destructor |
| 2084 | explicitly. |
| 2085 | </para> |
| 2086 | |
| 2087 | <para> |
| 2088 | The destructor would be necessary when you created some |
| 2089 | special records internally and need to release them. In such a |
| 2090 | case, set the destructor function to |
| 2091 | pcm->private_free: |
| 2092 | |
| 2093 | <example> |
| 2094 | <title>PCM Instance with a Destructor</title> |
| 2095 | <programlisting> |
| 2096 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2097 | static void mychip_pcm_free(struct snd_pcm *pcm) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2098 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2099 | struct mychip *chip = snd_pcm_chip(pcm); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2100 | /* free your own data */ |
| 2101 | kfree(chip->my_private_pcm_data); |
| 2102 | // do what you like else |
| 2103 | .... |
| 2104 | } |
| 2105 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2106 | static int __devinit snd_mychip_new_pcm(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2107 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2108 | struct snd_pcm *pcm; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2109 | .... |
| 2110 | /* allocate your own data */ |
| 2111 | chip->my_private_pcm_data = kmalloc(...); |
| 2112 | /* set the destructor */ |
| 2113 | pcm->private_data = chip; |
| 2114 | pcm->private_free = mychip_pcm_free; |
| 2115 | .... |
| 2116 | } |
| 2117 | ]]> |
| 2118 | </programlisting> |
| 2119 | </example> |
| 2120 | </para> |
| 2121 | </section> |
| 2122 | |
| 2123 | <section id="pcm-interface-runtime"> |
| 2124 | <title>Runtime Pointer - The Chest of PCM Information</title> |
| 2125 | <para> |
| 2126 | When the PCM substream is opened, a PCM runtime instance is |
| 2127 | allocated and assigned to the substream. This pointer is |
| 2128 | accessible via <constant>substream->runtime</constant>. |
| 2129 | This runtime pointer holds the various information; it holds |
| 2130 | the copy of hw_params and sw_params configurations, the buffer |
| 2131 | pointers, mmap records, spinlocks, etc. Almost everyhing you |
| 2132 | need for controlling the PCM can be found there. |
| 2133 | </para> |
| 2134 | |
| 2135 | <para> |
| 2136 | The definition of runtime instance is found in |
| 2137 | <filename><sound/pcm.h></filename>. Here is the |
| 2138 | copy from the file. |
| 2139 | <informalexample> |
| 2140 | <programlisting> |
| 2141 | <![CDATA[ |
| 2142 | struct _snd_pcm_runtime { |
| 2143 | /* -- Status -- */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2144 | struct snd_pcm_substream *trigger_master; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2145 | snd_timestamp_t trigger_tstamp; /* trigger timestamp */ |
| 2146 | int overrange; |
| 2147 | snd_pcm_uframes_t avail_max; |
| 2148 | snd_pcm_uframes_t hw_ptr_base; /* Position at buffer restart */ |
| 2149 | snd_pcm_uframes_t hw_ptr_interrupt; /* Position at interrupt time*/ |
| 2150 | |
| 2151 | /* -- HW params -- */ |
| 2152 | snd_pcm_access_t access; /* access mode */ |
| 2153 | snd_pcm_format_t format; /* SNDRV_PCM_FORMAT_* */ |
| 2154 | snd_pcm_subformat_t subformat; /* subformat */ |
| 2155 | unsigned int rate; /* rate in Hz */ |
| 2156 | unsigned int channels; /* channels */ |
| 2157 | snd_pcm_uframes_t period_size; /* period size */ |
| 2158 | unsigned int periods; /* periods */ |
| 2159 | snd_pcm_uframes_t buffer_size; /* buffer size */ |
| 2160 | unsigned int tick_time; /* tick time */ |
| 2161 | snd_pcm_uframes_t min_align; /* Min alignment for the format */ |
| 2162 | size_t byte_align; |
| 2163 | unsigned int frame_bits; |
| 2164 | unsigned int sample_bits; |
| 2165 | unsigned int info; |
| 2166 | unsigned int rate_num; |
| 2167 | unsigned int rate_den; |
| 2168 | |
| 2169 | /* -- SW params -- */ |
Takashi Iwai | 07799e7 | 2005-10-10 11:49:49 +0200 | [diff] [blame] | 2170 | struct timespec tstamp_mode; /* mmap timestamp is updated */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2171 | unsigned int period_step; |
| 2172 | unsigned int sleep_min; /* min ticks to sleep */ |
| 2173 | snd_pcm_uframes_t xfer_align; /* xfer size need to be a multiple */ |
| 2174 | snd_pcm_uframes_t start_threshold; |
| 2175 | snd_pcm_uframes_t stop_threshold; |
| 2176 | snd_pcm_uframes_t silence_threshold; /* Silence filling happens when |
| 2177 | noise is nearest than this */ |
| 2178 | snd_pcm_uframes_t silence_size; /* Silence filling size */ |
| 2179 | snd_pcm_uframes_t boundary; /* pointers wrap point */ |
| 2180 | |
| 2181 | snd_pcm_uframes_t silenced_start; |
| 2182 | snd_pcm_uframes_t silenced_size; |
| 2183 | |
| 2184 | snd_pcm_sync_id_t sync; /* hardware synchronization ID */ |
| 2185 | |
| 2186 | /* -- mmap -- */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2187 | volatile struct snd_pcm_mmap_status *status; |
| 2188 | volatile struct snd_pcm_mmap_control *control; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2189 | atomic_t mmap_count; |
| 2190 | |
| 2191 | /* -- locking / scheduling -- */ |
| 2192 | spinlock_t lock; |
| 2193 | wait_queue_head_t sleep; |
| 2194 | struct timer_list tick_timer; |
| 2195 | struct fasync_struct *fasync; |
| 2196 | |
| 2197 | /* -- private section -- */ |
| 2198 | void *private_data; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2199 | void (*private_free)(struct snd_pcm_runtime *runtime); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2200 | |
| 2201 | /* -- hardware description -- */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2202 | struct snd_pcm_hardware hw; |
| 2203 | struct snd_pcm_hw_constraints hw_constraints; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2204 | |
| 2205 | /* -- interrupt callbacks -- */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2206 | void (*transfer_ack_begin)(struct snd_pcm_substream *substream); |
| 2207 | void (*transfer_ack_end)(struct snd_pcm_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2208 | |
| 2209 | /* -- timer -- */ |
| 2210 | unsigned int timer_resolution; /* timer resolution */ |
| 2211 | |
| 2212 | /* -- DMA -- */ |
| 2213 | unsigned char *dma_area; /* DMA area */ |
| 2214 | dma_addr_t dma_addr; /* physical bus address (not accessible from main CPU) */ |
| 2215 | size_t dma_bytes; /* size of DMA area */ |
| 2216 | |
| 2217 | struct snd_dma_buffer *dma_buffer_p; /* allocated buffer */ |
| 2218 | |
| 2219 | #if defined(CONFIG_SND_PCM_OSS) || defined(CONFIG_SND_PCM_OSS_MODULE) |
| 2220 | /* -- OSS things -- */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2221 | struct snd_pcm_oss_runtime oss; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2222 | #endif |
| 2223 | }; |
| 2224 | ]]> |
| 2225 | </programlisting> |
| 2226 | </informalexample> |
| 2227 | </para> |
| 2228 | |
| 2229 | <para> |
| 2230 | For the operators (callbacks) of each sound driver, most of |
| 2231 | these records are supposed to be read-only. Only the PCM |
| 2232 | middle-layer changes / updates these info. The exceptions are |
| 2233 | the hardware description (hw), interrupt callbacks |
| 2234 | (transfer_ack_xxx), DMA buffer information, and the private |
| 2235 | data. Besides, if you use the standard buffer allocation |
| 2236 | method via <function>snd_pcm_lib_malloc_pages()</function>, |
| 2237 | you don't need to set the DMA buffer information by yourself. |
| 2238 | </para> |
| 2239 | |
| 2240 | <para> |
| 2241 | In the sections below, important records are explained. |
| 2242 | </para> |
| 2243 | |
| 2244 | <section id="pcm-interface-runtime-hw"> |
| 2245 | <title>Hardware Description</title> |
| 2246 | <para> |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2247 | The hardware descriptor (struct <structname>snd_pcm_hardware</structname>) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2248 | contains the definitions of the fundamental hardware |
| 2249 | configuration. Above all, you'll need to define this in |
| 2250 | <link linkend="pcm-interface-operators-open-callback"><citetitle> |
| 2251 | the open callback</citetitle></link>. |
| 2252 | Note that the runtime instance holds the copy of the |
| 2253 | descriptor, not the pointer to the existing descriptor. That |
| 2254 | is, in the open callback, you can modify the copied descriptor |
| 2255 | (<constant>runtime->hw</constant>) as you need. For example, if the maximum |
| 2256 | number of channels is 1 only on some chip models, you can |
| 2257 | still use the same hardware descriptor and change the |
| 2258 | channels_max later: |
| 2259 | <informalexample> |
| 2260 | <programlisting> |
| 2261 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2262 | struct snd_pcm_runtime *runtime = substream->runtime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2263 | ... |
| 2264 | runtime->hw = snd_mychip_playback_hw; /* common definition */ |
| 2265 | if (chip->model == VERY_OLD_ONE) |
| 2266 | runtime->hw.channels_max = 1; |
| 2267 | ]]> |
| 2268 | </programlisting> |
| 2269 | </informalexample> |
| 2270 | </para> |
| 2271 | |
| 2272 | <para> |
| 2273 | Typically, you'll have a hardware descriptor like below: |
| 2274 | <informalexample> |
| 2275 | <programlisting> |
| 2276 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2277 | static struct snd_pcm_hardware snd_mychip_playback_hw = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2278 | .info = (SNDRV_PCM_INFO_MMAP | |
| 2279 | SNDRV_PCM_INFO_INTERLEAVED | |
| 2280 | SNDRV_PCM_INFO_BLOCK_TRANSFER | |
| 2281 | SNDRV_PCM_INFO_MMAP_VALID), |
| 2282 | .formats = SNDRV_PCM_FMTBIT_S16_LE, |
| 2283 | .rates = SNDRV_PCM_RATE_8000_48000, |
| 2284 | .rate_min = 8000, |
| 2285 | .rate_max = 48000, |
| 2286 | .channels_min = 2, |
| 2287 | .channels_max = 2, |
| 2288 | .buffer_bytes_max = 32768, |
| 2289 | .period_bytes_min = 4096, |
| 2290 | .period_bytes_max = 32768, |
| 2291 | .periods_min = 1, |
| 2292 | .periods_max = 1024, |
| 2293 | }; |
| 2294 | ]]> |
| 2295 | </programlisting> |
| 2296 | </informalexample> |
| 2297 | </para> |
| 2298 | |
| 2299 | <para> |
| 2300 | <itemizedlist> |
| 2301 | <listitem><para> |
| 2302 | The <structfield>info</structfield> field contains the type and |
| 2303 | capabilities of this pcm. The bit flags are defined in |
| 2304 | <filename><sound/asound.h></filename> as |
| 2305 | <constant>SNDRV_PCM_INFO_XXX</constant>. Here, at least, you |
| 2306 | have to specify whether the mmap is supported and which |
| 2307 | interleaved format is supported. |
| 2308 | When the mmap is supported, add |
| 2309 | <constant>SNDRV_PCM_INFO_MMAP</constant> flag here. When the |
| 2310 | hardware supports the interleaved or the non-interleaved |
| 2311 | format, <constant>SNDRV_PCM_INFO_INTERLEAVED</constant> or |
| 2312 | <constant>SNDRV_PCM_INFO_NONINTERLEAVED</constant> flag must |
| 2313 | be set, respectively. If both are supported, you can set both, |
| 2314 | too. |
| 2315 | </para> |
| 2316 | |
| 2317 | <para> |
| 2318 | In the above example, <constant>MMAP_VALID</constant> and |
| 2319 | <constant>BLOCK_TRANSFER</constant> are specified for OSS mmap |
| 2320 | mode. Usually both are set. Of course, |
| 2321 | <constant>MMAP_VALID</constant> is set only if the mmap is |
| 2322 | really supported. |
| 2323 | </para> |
| 2324 | |
| 2325 | <para> |
| 2326 | The other possible flags are |
| 2327 | <constant>SNDRV_PCM_INFO_PAUSE</constant> and |
| 2328 | <constant>SNDRV_PCM_INFO_RESUME</constant>. The |
| 2329 | <constant>PAUSE</constant> bit means that the pcm supports the |
| 2330 | <quote>pause</quote> operation, while the |
| 2331 | <constant>RESUME</constant> bit means that the pcm supports |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 2332 | the full <quote>suspend/resume</quote> operation. |
| 2333 | If <constant>PAUSE</constant> flag is set, |
| 2334 | the <structfield>trigger</structfield> callback below |
| 2335 | must handle the corresponding (pause push/release) commands. |
| 2336 | The suspend/resume trigger commands can be defined even without |
| 2337 | <constant>RESUME</constant> flag. See <link |
| 2338 | linkend="power-management"><citetitle> |
| 2339 | Power Management</citetitle></link> section for details. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2340 | </para> |
| 2341 | |
| 2342 | <para> |
| 2343 | When the PCM substreams can be synchronized (typically, |
| 2344 | synchorinized start/stop of a playback and a capture streams), |
| 2345 | you can give <constant>SNDRV_PCM_INFO_SYNC_START</constant>, |
| 2346 | too. In this case, you'll need to check the linked-list of |
| 2347 | PCM substreams in the trigger callback. This will be |
| 2348 | described in the later section. |
| 2349 | </para> |
| 2350 | </listitem> |
| 2351 | |
| 2352 | <listitem> |
| 2353 | <para> |
| 2354 | <structfield>formats</structfield> field contains the bit-flags |
| 2355 | of supported formats (<constant>SNDRV_PCM_FMTBIT_XXX</constant>). |
| 2356 | If the hardware supports more than one format, give all or'ed |
| 2357 | bits. In the example above, the signed 16bit little-endian |
| 2358 | format is specified. |
| 2359 | </para> |
| 2360 | </listitem> |
| 2361 | |
| 2362 | <listitem> |
| 2363 | <para> |
| 2364 | <structfield>rates</structfield> field contains the bit-flags of |
| 2365 | supported rates (<constant>SNDRV_PCM_RATE_XXX</constant>). |
| 2366 | When the chip supports continuous rates, pass |
| 2367 | <constant>CONTINUOUS</constant> bit additionally. |
| 2368 | The pre-defined rate bits are provided only for typical |
| 2369 | rates. If your chip supports unconventional rates, you need to add |
| 2370 | <constant>KNOT</constant> bit and set up the hardware |
| 2371 | constraint manually (explained later). |
| 2372 | </para> |
| 2373 | </listitem> |
| 2374 | |
| 2375 | <listitem> |
| 2376 | <para> |
| 2377 | <structfield>rate_min</structfield> and |
| 2378 | <structfield>rate_max</structfield> define the minimal and |
| 2379 | maximal sample rate. This should correspond somehow to |
| 2380 | <structfield>rates</structfield> bits. |
| 2381 | </para> |
| 2382 | </listitem> |
| 2383 | |
| 2384 | <listitem> |
| 2385 | <para> |
| 2386 | <structfield>channel_min</structfield> and |
| 2387 | <structfield>channel_max</structfield> |
| 2388 | define, as you might already expected, the minimal and maximal |
| 2389 | number of channels. |
| 2390 | </para> |
| 2391 | </listitem> |
| 2392 | |
| 2393 | <listitem> |
| 2394 | <para> |
| 2395 | <structfield>buffer_bytes_max</structfield> defines the |
| 2396 | maximal buffer size in bytes. There is no |
| 2397 | <structfield>buffer_bytes_min</structfield> field, since |
| 2398 | it can be calculated from the minimal period size and the |
| 2399 | minimal number of periods. |
| 2400 | Meanwhile, <structfield>period_bytes_min</structfield> and |
| 2401 | define the minimal and maximal size of the period in bytes. |
| 2402 | <structfield>periods_max</structfield> and |
| 2403 | <structfield>periods_min</structfield> define the maximal and |
| 2404 | minimal number of periods in the buffer. |
| 2405 | </para> |
| 2406 | |
| 2407 | <para> |
| 2408 | The <quote>period</quote> is a term, that corresponds to |
| 2409 | fragment in the OSS world. The period defines the size at |
| 2410 | which the PCM interrupt is generated. This size strongly |
| 2411 | depends on the hardware. |
| 2412 | Generally, the smaller period size will give you more |
| 2413 | interrupts, that is, more controls. |
| 2414 | In the case of capture, this size defines the input latency. |
| 2415 | On the other hand, the whole buffer size defines the |
| 2416 | output latency for the playback direction. |
| 2417 | </para> |
| 2418 | </listitem> |
| 2419 | |
| 2420 | <listitem> |
| 2421 | <para> |
| 2422 | There is also a field <structfield>fifo_size</structfield>. |
| 2423 | This specifies the size of the hardware FIFO, but it's not |
| 2424 | used currently in the driver nor in the alsa-lib. So, you |
| 2425 | can ignore this field. |
| 2426 | </para> |
| 2427 | </listitem> |
| 2428 | </itemizedlist> |
| 2429 | </para> |
| 2430 | </section> |
| 2431 | |
| 2432 | <section id="pcm-interface-runtime-config"> |
| 2433 | <title>PCM Configurations</title> |
| 2434 | <para> |
| 2435 | Ok, let's go back again to the PCM runtime records. |
| 2436 | The most frequently referred records in the runtime instance are |
| 2437 | the PCM configurations. |
| 2438 | The PCM configurations are stored on runtime instance |
| 2439 | after the application sends <type>hw_params</type> data via |
| 2440 | alsa-lib. There are many fields copied from hw_params and |
| 2441 | sw_params structs. For example, |
| 2442 | <structfield>format</structfield> holds the format type |
| 2443 | chosen by the application. This field contains the enum value |
| 2444 | <constant>SNDRV_PCM_FORMAT_XXX</constant>. |
| 2445 | </para> |
| 2446 | |
| 2447 | <para> |
| 2448 | One thing to be noted is that the configured buffer and period |
| 2449 | sizes are stored in <quote>frames</quote> in the runtime |
| 2450 | In the ALSA world, 1 frame = channels * samples-size. |
| 2451 | For conversion between frames and bytes, you can use the |
| 2452 | helper functions, <function>frames_to_bytes()</function> and |
| 2453 | <function>bytes_to_frames()</function>. |
| 2454 | <informalexample> |
| 2455 | <programlisting> |
| 2456 | <![CDATA[ |
| 2457 | period_bytes = frames_to_bytes(runtime, runtime->period_size); |
| 2458 | ]]> |
| 2459 | </programlisting> |
| 2460 | </informalexample> |
| 2461 | </para> |
| 2462 | |
| 2463 | <para> |
| 2464 | Also, many software parameters (sw_params) are |
| 2465 | stored in frames, too. Please check the type of the field. |
| 2466 | <type>snd_pcm_uframes_t</type> is for the frames as unsigned |
| 2467 | integer while <type>snd_pcm_sframes_t</type> is for the frames |
| 2468 | as signed integer. |
| 2469 | </para> |
| 2470 | </section> |
| 2471 | |
| 2472 | <section id="pcm-interface-runtime-dma"> |
| 2473 | <title>DMA Buffer Information</title> |
| 2474 | <para> |
| 2475 | The DMA buffer is defined by the following four fields, |
| 2476 | <structfield>dma_area</structfield>, |
| 2477 | <structfield>dma_addr</structfield>, |
| 2478 | <structfield>dma_bytes</structfield> and |
| 2479 | <structfield>dma_private</structfield>. |
| 2480 | The <structfield>dma_area</structfield> holds the buffer |
| 2481 | pointer (the logical address). You can call |
| 2482 | <function>memcpy</function> from/to |
| 2483 | this pointer. Meanwhile, <structfield>dma_addr</structfield> |
| 2484 | holds the physical address of the buffer. This field is |
| 2485 | specified only when the buffer is a linear buffer. |
| 2486 | <structfield>dma_bytes</structfield> holds the size of buffer |
| 2487 | in bytes. <structfield>dma_private</structfield> is used for |
| 2488 | the ALSA DMA allocator. |
| 2489 | </para> |
| 2490 | |
| 2491 | <para> |
| 2492 | If you use a standard ALSA function, |
| 2493 | <function>snd_pcm_lib_malloc_pages()</function>, for |
| 2494 | allocating the buffer, these fields are set by the ALSA middle |
| 2495 | layer, and you should <emphasis>not</emphasis> change them by |
| 2496 | yourself. You can read them but not write them. |
| 2497 | On the other hand, if you want to allocate the buffer by |
| 2498 | yourself, you'll need to manage it in hw_params callback. |
| 2499 | At least, <structfield>dma_bytes</structfield> is mandatory. |
| 2500 | <structfield>dma_area</structfield> is necessary when the |
| 2501 | buffer is mmapped. If your driver doesn't support mmap, this |
| 2502 | field is not necessary. <structfield>dma_addr</structfield> |
| 2503 | is also not mandatory. You can use |
| 2504 | <structfield>dma_private</structfield> as you like, too. |
| 2505 | </para> |
| 2506 | </section> |
| 2507 | |
| 2508 | <section id="pcm-interface-runtime-status"> |
| 2509 | <title>Running Status</title> |
| 2510 | <para> |
| 2511 | The running status can be referred via <constant>runtime->status</constant>. |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2512 | This is the pointer to struct <structname>snd_pcm_mmap_status</structname> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2513 | record. For example, you can get the current DMA hardware |
| 2514 | pointer via <constant>runtime->status->hw_ptr</constant>. |
| 2515 | </para> |
| 2516 | |
| 2517 | <para> |
| 2518 | The DMA application pointer can be referred via |
| 2519 | <constant>runtime->control</constant>, which points |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2520 | struct <structname>snd_pcm_mmap_control</structname> record. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2521 | However, accessing directly to this value is not recommended. |
| 2522 | </para> |
| 2523 | </section> |
| 2524 | |
| 2525 | <section id="pcm-interface-runtime-private"> |
| 2526 | <title>Private Data</title> |
| 2527 | <para> |
| 2528 | You can allocate a record for the substream and store it in |
| 2529 | <constant>runtime->private_data</constant>. Usually, this |
| 2530 | done in |
| 2531 | <link linkend="pcm-interface-operators-open-callback"><citetitle> |
| 2532 | the open callback</citetitle></link>. |
| 2533 | Don't mix this with <constant>pcm->private_data</constant>. |
| 2534 | The <constant>pcm->private_data</constant> usually points the |
| 2535 | chip instance assigned statically at the creation of PCM, while the |
| 2536 | <constant>runtime->private_data</constant> points a dynamic |
| 2537 | data created at the PCM open callback. |
| 2538 | |
| 2539 | <informalexample> |
| 2540 | <programlisting> |
| 2541 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2542 | static int snd_xxx_open(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2543 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2544 | struct my_pcm_data *data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2545 | .... |
| 2546 | data = kmalloc(sizeof(*data), GFP_KERNEL); |
| 2547 | substream->runtime->private_data = data; |
| 2548 | .... |
| 2549 | } |
| 2550 | ]]> |
| 2551 | </programlisting> |
| 2552 | </informalexample> |
| 2553 | </para> |
| 2554 | |
| 2555 | <para> |
| 2556 | The allocated object must be released in |
| 2557 | <link linkend="pcm-interface-operators-open-callback"><citetitle> |
| 2558 | the close callback</citetitle></link>. |
| 2559 | </para> |
| 2560 | </section> |
| 2561 | |
| 2562 | <section id="pcm-interface-runtime-intr"> |
| 2563 | <title>Interrupt Callbacks</title> |
| 2564 | <para> |
| 2565 | The field <structfield>transfer_ack_begin</structfield> and |
| 2566 | <structfield>transfer_ack_end</structfield> are called at |
| 2567 | the beginning and the end of |
| 2568 | <function>snd_pcm_period_elapsed()</function>, respectively. |
| 2569 | </para> |
| 2570 | </section> |
| 2571 | |
| 2572 | </section> |
| 2573 | |
| 2574 | <section id="pcm-interface-operators"> |
| 2575 | <title>Operators</title> |
| 2576 | <para> |
| 2577 | OK, now let me explain the detail of each pcm callback |
| 2578 | (<parameter>ops</parameter>). In general, every callback must |
| 2579 | return 0 if successful, or a negative number with the error |
| 2580 | number such as <constant>-EINVAL</constant> at any |
| 2581 | error. |
| 2582 | </para> |
| 2583 | |
| 2584 | <para> |
| 2585 | The callback function takes at least the argument with |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2586 | <structname>snd_pcm_substream</structname> pointer. For retrieving the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2587 | chip record from the given substream instance, you can use the |
| 2588 | following macro. |
| 2589 | |
| 2590 | <informalexample> |
| 2591 | <programlisting> |
| 2592 | <![CDATA[ |
| 2593 | int xxx() { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2594 | struct mychip *chip = snd_pcm_substream_chip(substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2595 | .... |
| 2596 | } |
| 2597 | ]]> |
| 2598 | </programlisting> |
| 2599 | </informalexample> |
| 2600 | |
| 2601 | The macro reads <constant>substream->private_data</constant>, |
| 2602 | which is a copy of <constant>pcm->private_data</constant>. |
| 2603 | You can override the former if you need to assign different data |
| 2604 | records per PCM substream. For example, cmi8330 driver assigns |
| 2605 | different private_data for playback and capture directions, |
| 2606 | because it uses two different codecs (SB- and AD-compatible) for |
| 2607 | different directions. |
| 2608 | </para> |
| 2609 | |
| 2610 | <section id="pcm-interface-operators-open-callback"> |
| 2611 | <title>open callback</title> |
| 2612 | <para> |
| 2613 | <informalexample> |
| 2614 | <programlisting> |
| 2615 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2616 | static int snd_xxx_open(struct snd_pcm_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2617 | ]]> |
| 2618 | </programlisting> |
| 2619 | </informalexample> |
| 2620 | |
| 2621 | This is called when a pcm substream is opened. |
| 2622 | </para> |
| 2623 | |
| 2624 | <para> |
| 2625 | At least, here you have to initialize the runtime->hw |
| 2626 | record. Typically, this is done by like this: |
| 2627 | |
| 2628 | <informalexample> |
| 2629 | <programlisting> |
| 2630 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2631 | static int snd_xxx_open(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2632 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2633 | struct mychip *chip = snd_pcm_substream_chip(substream); |
| 2634 | struct snd_pcm_runtime *runtime = substream->runtime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2635 | |
| 2636 | runtime->hw = snd_mychip_playback_hw; |
| 2637 | return 0; |
| 2638 | } |
| 2639 | ]]> |
| 2640 | </programlisting> |
| 2641 | </informalexample> |
| 2642 | |
| 2643 | where <parameter>snd_mychip_playback_hw</parameter> is the |
| 2644 | pre-defined hardware description. |
| 2645 | </para> |
| 2646 | |
| 2647 | <para> |
| 2648 | You can allocate a private data in this callback, as described |
| 2649 | in <link linkend="pcm-interface-runtime-private"><citetitle> |
| 2650 | Private Data</citetitle></link> section. |
| 2651 | </para> |
| 2652 | |
| 2653 | <para> |
| 2654 | If the hardware configuration needs more constraints, set the |
| 2655 | hardware constraints here, too. |
| 2656 | See <link linkend="pcm-interface-constraints"><citetitle> |
| 2657 | Constraints</citetitle></link> for more details. |
| 2658 | </para> |
| 2659 | </section> |
| 2660 | |
| 2661 | <section id="pcm-interface-operators-close-callback"> |
| 2662 | <title>close callback</title> |
| 2663 | <para> |
| 2664 | <informalexample> |
| 2665 | <programlisting> |
| 2666 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2667 | static int snd_xxx_close(struct snd_pcm_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2668 | ]]> |
| 2669 | </programlisting> |
| 2670 | </informalexample> |
| 2671 | |
| 2672 | Obviously, this is called when a pcm substream is closed. |
| 2673 | </para> |
| 2674 | |
| 2675 | <para> |
| 2676 | Any private instance for a pcm substream allocated in the |
| 2677 | open callback will be released here. |
| 2678 | |
| 2679 | <informalexample> |
| 2680 | <programlisting> |
| 2681 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2682 | static int snd_xxx_close(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2683 | { |
| 2684 | .... |
| 2685 | kfree(substream->runtime->private_data); |
| 2686 | .... |
| 2687 | } |
| 2688 | ]]> |
| 2689 | </programlisting> |
| 2690 | </informalexample> |
| 2691 | </para> |
| 2692 | </section> |
| 2693 | |
| 2694 | <section id="pcm-interface-operators-ioctl-callback"> |
| 2695 | <title>ioctl callback</title> |
| 2696 | <para> |
| 2697 | This is used for any special action to pcm ioctls. But |
| 2698 | usually you can pass a generic ioctl callback, |
| 2699 | <function>snd_pcm_lib_ioctl</function>. |
| 2700 | </para> |
| 2701 | </section> |
| 2702 | |
| 2703 | <section id="pcm-interface-operators-hw-params-callback"> |
| 2704 | <title>hw_params callback</title> |
| 2705 | <para> |
| 2706 | <informalexample> |
| 2707 | <programlisting> |
| 2708 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2709 | static int snd_xxx_hw_params(struct snd_pcm_substream *substream, |
| 2710 | struct snd_pcm_hw_params *hw_params); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2711 | ]]> |
| 2712 | </programlisting> |
| 2713 | </informalexample> |
| 2714 | |
| 2715 | This and <structfield>hw_free</structfield> callbacks exist |
| 2716 | only on ALSA 0.9.x. |
| 2717 | </para> |
| 2718 | |
| 2719 | <para> |
| 2720 | This is called when the hardware parameter |
| 2721 | (<structfield>hw_params</structfield>) is set |
| 2722 | up by the application, |
| 2723 | that is, once when the buffer size, the period size, the |
| 2724 | format, etc. are defined for the pcm substream. |
| 2725 | </para> |
| 2726 | |
| 2727 | <para> |
| 2728 | Many hardware set-up should be done in this callback, |
| 2729 | including the allocation of buffers. |
| 2730 | </para> |
| 2731 | |
| 2732 | <para> |
| 2733 | Parameters to be initialized are retrieved by |
| 2734 | <function>params_xxx()</function> macros. For allocating a |
| 2735 | buffer, you can call a helper function, |
| 2736 | |
| 2737 | <informalexample> |
| 2738 | <programlisting> |
| 2739 | <![CDATA[ |
| 2740 | snd_pcm_lib_malloc_pages(substream, params_buffer_bytes(hw_params)); |
| 2741 | ]]> |
| 2742 | </programlisting> |
| 2743 | </informalexample> |
| 2744 | |
| 2745 | <function>snd_pcm_lib_malloc_pages()</function> is available |
| 2746 | only when the DMA buffers have been pre-allocated. |
| 2747 | See the section <link |
| 2748 | linkend="buffer-and-memory-buffer-types"><citetitle> |
| 2749 | Buffer Types</citetitle></link> for more details. |
| 2750 | </para> |
| 2751 | |
| 2752 | <para> |
| 2753 | Note that this and <structfield>prepare</structfield> callbacks |
| 2754 | may be called multiple times per initialization. |
| 2755 | For example, the OSS emulation may |
| 2756 | call these callbacks at each change via its ioctl. |
| 2757 | </para> |
| 2758 | |
| 2759 | <para> |
| 2760 | Thus, you need to take care not to allocate the same buffers |
| 2761 | many times, which will lead to memory leak! Calling the |
| 2762 | helper function above many times is OK. It will release the |
| 2763 | previous buffer automatically when it was already allocated. |
| 2764 | </para> |
| 2765 | |
| 2766 | <para> |
| 2767 | Another note is that this callback is non-atomic |
| 2768 | (schedulable). This is important, because the |
| 2769 | <structfield>trigger</structfield> callback |
| 2770 | is atomic (non-schedulable). That is, mutex or any |
| 2771 | schedule-related functions are not available in |
| 2772 | <structfield>trigger</structfield> callback. |
| 2773 | Please see the subsection |
| 2774 | <link linkend="pcm-interface-atomicity"><citetitle> |
| 2775 | Atomicity</citetitle></link> for details. |
| 2776 | </para> |
| 2777 | </section> |
| 2778 | |
| 2779 | <section id="pcm-interface-operators-hw-free-callback"> |
| 2780 | <title>hw_free callback</title> |
| 2781 | <para> |
| 2782 | <informalexample> |
| 2783 | <programlisting> |
| 2784 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2785 | static int snd_xxx_hw_free(struct snd_pcm_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2786 | ]]> |
| 2787 | </programlisting> |
| 2788 | </informalexample> |
| 2789 | </para> |
| 2790 | |
| 2791 | <para> |
| 2792 | This is called to release the resources allocated via |
| 2793 | <structfield>hw_params</structfield>. For example, releasing the |
| 2794 | buffer via |
| 2795 | <function>snd_pcm_lib_malloc_pages()</function> is done by |
| 2796 | calling the following: |
| 2797 | |
| 2798 | <informalexample> |
| 2799 | <programlisting> |
| 2800 | <![CDATA[ |
| 2801 | snd_pcm_lib_free_pages(substream); |
| 2802 | ]]> |
| 2803 | </programlisting> |
| 2804 | </informalexample> |
| 2805 | </para> |
| 2806 | |
| 2807 | <para> |
| 2808 | This function is always called before the close callback is called. |
| 2809 | Also, the callback may be called multiple times, too. |
| 2810 | Keep track whether the resource was already released. |
| 2811 | </para> |
| 2812 | </section> |
| 2813 | |
| 2814 | <section id="pcm-interface-operators-prepare-callback"> |
| 2815 | <title>prepare callback</title> |
| 2816 | <para> |
| 2817 | <informalexample> |
| 2818 | <programlisting> |
| 2819 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2820 | static int snd_xxx_prepare(struct snd_pcm_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2821 | ]]> |
| 2822 | </programlisting> |
| 2823 | </informalexample> |
| 2824 | </para> |
| 2825 | |
| 2826 | <para> |
| 2827 | This callback is called when the pcm is |
| 2828 | <quote>prepared</quote>. You can set the format type, sample |
| 2829 | rate, etc. here. The difference from |
| 2830 | <structfield>hw_params</structfield> is that the |
| 2831 | <structfield>prepare</structfield> callback will be called at each |
| 2832 | time |
| 2833 | <function>snd_pcm_prepare()</function> is called, i.e. when |
| 2834 | recovered after underruns, etc. |
| 2835 | </para> |
| 2836 | |
| 2837 | <para> |
| 2838 | Note that this callback became non-atomic since the recent version. |
Akinobu Mita | 0b28002 | 2006-03-26 01:38:58 -0800 | [diff] [blame] | 2839 | You can use schedule-related functions safely in this callback now. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2840 | </para> |
| 2841 | |
| 2842 | <para> |
| 2843 | In this and the following callbacks, you can refer to the |
| 2844 | values via the runtime record, |
| 2845 | substream->runtime. |
| 2846 | For example, to get the current |
| 2847 | rate, format or channels, access to |
| 2848 | runtime->rate, |
| 2849 | runtime->format or |
| 2850 | runtime->channels, respectively. |
| 2851 | The physical address of the allocated buffer is set to |
| 2852 | runtime->dma_area. The buffer and period sizes are |
| 2853 | in runtime->buffer_size and runtime->period_size, |
| 2854 | respectively. |
| 2855 | </para> |
| 2856 | |
| 2857 | <para> |
| 2858 | Be careful that this callback will be called many times at |
| 2859 | each set up, too. |
| 2860 | </para> |
| 2861 | </section> |
| 2862 | |
| 2863 | <section id="pcm-interface-operators-trigger-callback"> |
| 2864 | <title>trigger callback</title> |
| 2865 | <para> |
| 2866 | <informalexample> |
| 2867 | <programlisting> |
| 2868 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2869 | static int snd_xxx_trigger(struct snd_pcm_substream *substream, int cmd); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2870 | ]]> |
| 2871 | </programlisting> |
| 2872 | </informalexample> |
| 2873 | |
| 2874 | This is called when the pcm is started, stopped or paused. |
| 2875 | </para> |
| 2876 | |
| 2877 | <para> |
| 2878 | Which action is specified in the second argument, |
| 2879 | <constant>SNDRV_PCM_TRIGGER_XXX</constant> in |
| 2880 | <filename><sound/pcm.h></filename>. At least, |
| 2881 | <constant>START</constant> and <constant>STOP</constant> |
| 2882 | commands must be defined in this callback. |
| 2883 | |
| 2884 | <informalexample> |
| 2885 | <programlisting> |
| 2886 | <![CDATA[ |
| 2887 | switch (cmd) { |
| 2888 | case SNDRV_PCM_TRIGGER_START: |
| 2889 | // do something to start the PCM engine |
| 2890 | break; |
| 2891 | case SNDRV_PCM_TRIGGER_STOP: |
| 2892 | // do something to stop the PCM engine |
| 2893 | break; |
| 2894 | default: |
| 2895 | return -EINVAL; |
| 2896 | } |
| 2897 | ]]> |
| 2898 | </programlisting> |
| 2899 | </informalexample> |
| 2900 | </para> |
| 2901 | |
| 2902 | <para> |
| 2903 | When the pcm supports the pause operation (given in info |
| 2904 | field of the hardware table), <constant>PAUSE_PUSE</constant> |
| 2905 | and <constant>PAUSE_RELEASE</constant> commands must be |
| 2906 | handled here, too. The former is the command to pause the pcm, |
| 2907 | and the latter to restart the pcm again. |
| 2908 | </para> |
| 2909 | |
| 2910 | <para> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 2911 | When the pcm supports the suspend/resume operation, |
| 2912 | regardless of full or partial suspend/resume support, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2913 | <constant>SUSPEND</constant> and <constant>RESUME</constant> |
| 2914 | commands must be handled, too. |
| 2915 | These commands are issued when the power-management status is |
| 2916 | changed. Obviously, the <constant>SUSPEND</constant> and |
| 2917 | <constant>RESUME</constant> |
| 2918 | do suspend and resume of the pcm substream, and usually, they |
| 2919 | are identical with <constant>STOP</constant> and |
| 2920 | <constant>START</constant> commands, respectively. |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 2921 | See <link linkend="power-management"><citetitle> |
| 2922 | Power Management</citetitle></link> section for details. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2923 | </para> |
| 2924 | |
| 2925 | <para> |
| 2926 | As mentioned, this callback is atomic. You cannot call |
| 2927 | the function going to sleep. |
| 2928 | The trigger callback should be as minimal as possible, |
| 2929 | just really triggering the DMA. The other stuff should be |
| 2930 | initialized hw_params and prepare callbacks properly |
| 2931 | beforehand. |
| 2932 | </para> |
| 2933 | </section> |
| 2934 | |
| 2935 | <section id="pcm-interface-operators-pointer-callback"> |
| 2936 | <title>pointer callback</title> |
| 2937 | <para> |
| 2938 | <informalexample> |
| 2939 | <programlisting> |
| 2940 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 2941 | 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] | 2942 | ]]> |
| 2943 | </programlisting> |
| 2944 | </informalexample> |
| 2945 | |
| 2946 | This callback is called when the PCM middle layer inquires |
| 2947 | the current hardware position on the buffer. The position must |
| 2948 | be returned in frames (which was in bytes on ALSA 0.5.x), |
| 2949 | ranged from 0 to buffer_size - 1. |
| 2950 | </para> |
| 2951 | |
| 2952 | <para> |
| 2953 | This is called usually from the buffer-update routine in the |
| 2954 | pcm middle layer, which is invoked when |
| 2955 | <function>snd_pcm_period_elapsed()</function> is called in the |
| 2956 | interrupt routine. Then the pcm middle layer updates the |
| 2957 | position and calculates the available space, and wakes up the |
| 2958 | sleeping poll threads, etc. |
| 2959 | </para> |
| 2960 | |
| 2961 | <para> |
| 2962 | This callback is also atomic. |
| 2963 | </para> |
| 2964 | </section> |
| 2965 | |
| 2966 | <section id="pcm-interface-operators-copy-silence"> |
| 2967 | <title>copy and silence callbacks</title> |
| 2968 | <para> |
| 2969 | These callbacks are not mandatory, and can be omitted in |
| 2970 | most cases. These callbacks are used when the hardware buffer |
| 2971 | cannot be on the normal memory space. Some chips have their |
| 2972 | own buffer on the hardware which is not mappable. In such a |
| 2973 | case, you have to transfer the data manually from the memory |
| 2974 | buffer to the hardware buffer. Or, if the buffer is |
| 2975 | non-contiguous on both physical and virtual memory spaces, |
| 2976 | these callbacks must be defined, too. |
| 2977 | </para> |
| 2978 | |
| 2979 | <para> |
| 2980 | If these two callbacks are defined, copy and set-silence |
| 2981 | operations are done by them. The detailed will be described in |
| 2982 | the later section <link |
| 2983 | linkend="buffer-and-memory"><citetitle>Buffer and Memory |
| 2984 | Management</citetitle></link>. |
| 2985 | </para> |
| 2986 | </section> |
| 2987 | |
| 2988 | <section id="pcm-interface-operators-ack"> |
| 2989 | <title>ack callback</title> |
| 2990 | <para> |
| 2991 | This callback is also not mandatory. This callback is called |
| 2992 | when the appl_ptr is updated in read or write operations. |
| 2993 | Some drivers like emu10k1-fx and cs46xx need to track the |
| 2994 | current appl_ptr for the internal buffer, and this callback |
| 2995 | is useful only for such a purpose. |
| 2996 | </para> |
| 2997 | <para> |
| 2998 | This callback is atomic. |
| 2999 | </para> |
| 3000 | </section> |
| 3001 | |
| 3002 | <section id="pcm-interface-operators-page-callback"> |
| 3003 | <title>page callback</title> |
| 3004 | |
| 3005 | <para> |
| 3006 | This callback is also not mandatory. This callback is used |
| 3007 | mainly for the non-contiguous buffer. The mmap calls this |
| 3008 | callback to get the page address. Some examples will be |
| 3009 | explained in the later section <link |
| 3010 | linkend="buffer-and-memory"><citetitle>Buffer and Memory |
| 3011 | Management</citetitle></link>, too. |
| 3012 | </para> |
| 3013 | </section> |
| 3014 | </section> |
| 3015 | |
| 3016 | <section id="pcm-interface-interrupt-handler"> |
| 3017 | <title>Interrupt Handler</title> |
| 3018 | <para> |
| 3019 | The rest of pcm stuff is the PCM interrupt handler. The |
| 3020 | role of PCM interrupt handler in the sound driver is to update |
| 3021 | the buffer position and to tell the PCM middle layer when the |
| 3022 | buffer position goes across the prescribed period size. To |
| 3023 | inform this, call <function>snd_pcm_period_elapsed()</function> |
| 3024 | function. |
| 3025 | </para> |
| 3026 | |
| 3027 | <para> |
| 3028 | There are several types of sound chips to generate the interrupts. |
| 3029 | </para> |
| 3030 | |
| 3031 | <section id="pcm-interface-interrupt-handler-boundary"> |
| 3032 | <title>Interrupts at the period (fragment) boundary</title> |
| 3033 | <para> |
| 3034 | This is the most frequently found type: the hardware |
| 3035 | generates an interrupt at each period boundary. |
| 3036 | In this case, you can call |
| 3037 | <function>snd_pcm_period_elapsed()</function> at each |
| 3038 | interrupt. |
| 3039 | </para> |
| 3040 | |
| 3041 | <para> |
| 3042 | <function>snd_pcm_period_elapsed()</function> takes the |
| 3043 | substream pointer as its argument. Thus, you need to keep the |
| 3044 | substream pointer accessible from the chip instance. For |
| 3045 | example, define substream field in the chip record to hold the |
| 3046 | current running substream pointer, and set the pointer value |
| 3047 | at open callback (and reset at close callback). |
| 3048 | </para> |
| 3049 | |
| 3050 | <para> |
| 3051 | If you aquire a spinlock in the interrupt handler, and the |
| 3052 | lock is used in other pcm callbacks, too, then you have to |
| 3053 | release the lock before calling |
| 3054 | <function>snd_pcm_period_elapsed()</function>, because |
| 3055 | <function>snd_pcm_period_elapsed()</function> calls other pcm |
| 3056 | callbacks inside. |
| 3057 | </para> |
| 3058 | |
| 3059 | <para> |
| 3060 | A typical coding would be like: |
| 3061 | |
| 3062 | <example> |
| 3063 | <title>Interrupt Handler Case #1</title> |
| 3064 | <programlisting> |
| 3065 | <![CDATA[ |
| 3066 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id, |
| 3067 | struct pt_regs *regs) |
| 3068 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3069 | struct mychip *chip = dev_id; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3070 | spin_lock(&chip->lock); |
| 3071 | .... |
| 3072 | if (pcm_irq_invoked(chip)) { |
| 3073 | /* call updater, unlock before it */ |
| 3074 | spin_unlock(&chip->lock); |
| 3075 | snd_pcm_period_elapsed(chip->substream); |
| 3076 | spin_lock(&chip->lock); |
| 3077 | // acknowledge the interrupt if necessary |
| 3078 | } |
| 3079 | .... |
| 3080 | spin_unlock(&chip->lock); |
| 3081 | return IRQ_HANDLED; |
| 3082 | } |
| 3083 | ]]> |
| 3084 | </programlisting> |
| 3085 | </example> |
| 3086 | </para> |
| 3087 | </section> |
| 3088 | |
| 3089 | <section id="pcm-interface-interrupt-handler-timer"> |
| 3090 | <title>High-frequent timer interrupts</title> |
| 3091 | <para> |
| 3092 | This is the case when the hardware doesn't generate interrupts |
| 3093 | at the period boundary but do timer-interrupts at the fixed |
| 3094 | timer rate (e.g. es1968 or ymfpci drivers). |
| 3095 | In this case, you need to check the current hardware |
| 3096 | position and accumulates the processed sample length at each |
| 3097 | interrupt. When the accumulated size overcomes the period |
| 3098 | size, call |
| 3099 | <function>snd_pcm_period_elapsed()</function> and reset the |
| 3100 | accumulator. |
| 3101 | </para> |
| 3102 | |
| 3103 | <para> |
| 3104 | A typical coding would be like the following. |
| 3105 | |
| 3106 | <example> |
| 3107 | <title>Interrupt Handler Case #2</title> |
| 3108 | <programlisting> |
| 3109 | <![CDATA[ |
| 3110 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id, |
| 3111 | struct pt_regs *regs) |
| 3112 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3113 | struct mychip *chip = dev_id; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3114 | spin_lock(&chip->lock); |
| 3115 | .... |
| 3116 | if (pcm_irq_invoked(chip)) { |
| 3117 | unsigned int last_ptr, size; |
| 3118 | /* get the current hardware pointer (in frames) */ |
| 3119 | last_ptr = get_hw_ptr(chip); |
| 3120 | /* calculate the processed frames since the |
| 3121 | * last update |
| 3122 | */ |
| 3123 | if (last_ptr < chip->last_ptr) |
| 3124 | size = runtime->buffer_size + last_ptr |
| 3125 | - chip->last_ptr; |
| 3126 | else |
| 3127 | size = last_ptr - chip->last_ptr; |
| 3128 | /* remember the last updated point */ |
| 3129 | chip->last_ptr = last_ptr; |
| 3130 | /* accumulate the size */ |
| 3131 | chip->size += size; |
| 3132 | /* over the period boundary? */ |
| 3133 | if (chip->size >= runtime->period_size) { |
| 3134 | /* reset the accumulator */ |
| 3135 | chip->size %= runtime->period_size; |
| 3136 | /* call updater */ |
| 3137 | spin_unlock(&chip->lock); |
| 3138 | snd_pcm_period_elapsed(substream); |
| 3139 | spin_lock(&chip->lock); |
| 3140 | } |
| 3141 | // acknowledge the interrupt if necessary |
| 3142 | } |
| 3143 | .... |
| 3144 | spin_unlock(&chip->lock); |
| 3145 | return IRQ_HANDLED; |
| 3146 | } |
| 3147 | ]]> |
| 3148 | </programlisting> |
| 3149 | </example> |
| 3150 | </para> |
| 3151 | </section> |
| 3152 | |
| 3153 | <section id="pcm-interface-interrupt-handler-both"> |
| 3154 | <title>On calling <function>snd_pcm_period_elapsed()</function></title> |
| 3155 | <para> |
| 3156 | In both cases, even if more than one period are elapsed, you |
| 3157 | don't have to call |
| 3158 | <function>snd_pcm_period_elapsed()</function> many times. Call |
| 3159 | only once. And the pcm layer will check the current hardware |
| 3160 | pointer and update to the latest status. |
| 3161 | </para> |
| 3162 | </section> |
| 3163 | </section> |
| 3164 | |
| 3165 | <section id="pcm-interface-atomicity"> |
| 3166 | <title>Atomicity</title> |
| 3167 | <para> |
| 3168 | One of the most important (and thus difficult to debug) problem |
| 3169 | on the kernel programming is the race condition. |
| 3170 | On linux kernel, usually it's solved via spin-locks or |
| 3171 | semaphores. In general, if the race condition may |
| 3172 | happen in the interrupt handler, it's handled as atomic, and you |
| 3173 | have to use spinlock for protecting the critical session. If it |
| 3174 | never happens in the interrupt and it may take relatively long |
| 3175 | time, you should use semaphore. |
| 3176 | </para> |
| 3177 | |
| 3178 | <para> |
| 3179 | As already seen, some pcm callbacks are atomic and some are |
| 3180 | not. For example, <parameter>hw_params</parameter> callback is |
| 3181 | non-atomic, while <parameter>trigger</parameter> callback is |
| 3182 | atomic. This means, the latter is called already in a spinlock |
| 3183 | held by the PCM middle layer. Please take this atomicity into |
| 3184 | account when you use a spinlock or a semaphore in the callbacks. |
| 3185 | </para> |
| 3186 | |
| 3187 | <para> |
| 3188 | In the atomic callbacks, you cannot use functions which may call |
| 3189 | <function>schedule</function> or go to |
| 3190 | <function>sleep</function>. The semaphore and mutex do sleep, |
| 3191 | and hence they cannot be used inside the atomic callbacks |
| 3192 | (e.g. <parameter>trigger</parameter> callback). |
| 3193 | For taking a certain delay in such a callback, please use |
| 3194 | <function>udelay()</function> or <function>mdelay()</function>. |
| 3195 | </para> |
| 3196 | |
| 3197 | <para> |
| 3198 | All three atomic callbacks (trigger, pointer, and ack) are |
| 3199 | called with local interrupts disabled. |
| 3200 | </para> |
| 3201 | |
| 3202 | </section> |
| 3203 | <section id="pcm-interface-constraints"> |
| 3204 | <title>Constraints</title> |
| 3205 | <para> |
| 3206 | If your chip supports unconventional sample rates, or only the |
| 3207 | limited samples, you need to set a constraint for the |
| 3208 | condition. |
| 3209 | </para> |
| 3210 | |
| 3211 | <para> |
| 3212 | For example, in order to restrict the sample rates in the some |
| 3213 | supported values, use |
| 3214 | <function>snd_pcm_hw_constraint_list()</function>. |
| 3215 | You need to call this function in the open callback. |
| 3216 | |
| 3217 | <example> |
| 3218 | <title>Example of Hardware Constraints</title> |
| 3219 | <programlisting> |
| 3220 | <![CDATA[ |
| 3221 | static unsigned int rates[] = |
| 3222 | {4000, 10000, 22050, 44100}; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3223 | static struct snd_pcm_hw_constraint_list constraints_rates = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3224 | .count = ARRAY_SIZE(rates), |
| 3225 | .list = rates, |
| 3226 | .mask = 0, |
| 3227 | }; |
| 3228 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3229 | static int snd_mychip_pcm_open(struct snd_pcm_substream *substream) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3230 | { |
| 3231 | int err; |
| 3232 | .... |
| 3233 | err = snd_pcm_hw_constraint_list(substream->runtime, 0, |
| 3234 | SNDRV_PCM_HW_PARAM_RATE, |
| 3235 | &constraints_rates); |
| 3236 | if (err < 0) |
| 3237 | return err; |
| 3238 | .... |
| 3239 | } |
| 3240 | ]]> |
| 3241 | </programlisting> |
| 3242 | </example> |
| 3243 | </para> |
| 3244 | |
| 3245 | <para> |
| 3246 | There are many different constraints. |
| 3247 | Look in <filename>sound/pcm.h</filename> for a complete list. |
| 3248 | You can even define your own constraint rules. |
| 3249 | For example, let's suppose my_chip can manage a substream of 1 channel |
| 3250 | if and only if the format is S16_LE, otherwise it supports any format |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3251 | specified in the <structname>snd_pcm_hardware</structname> stucture (or in any |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3252 | other constraint_list). You can build a rule like this: |
| 3253 | |
| 3254 | <example> |
| 3255 | <title>Example of Hardware Constraints for Channels</title> |
| 3256 | <programlisting> |
| 3257 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3258 | static int hw_rule_format_by_channels(struct snd_pcm_hw_params *params, |
| 3259 | struct snd_pcm_hw_rule *rule) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3260 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3261 | struct snd_interval *c = hw_param_interval(params, |
| 3262 | SNDRV_PCM_HW_PARAM_CHANNELS); |
| 3263 | struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT); |
| 3264 | struct snd_mask fmt; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3265 | |
| 3266 | snd_mask_any(&fmt); /* Init the struct */ |
| 3267 | if (c->min < 2) { |
| 3268 | fmt.bits[0] &= SNDRV_PCM_FMTBIT_S16_LE; |
| 3269 | return snd_mask_refine(f, &fmt); |
| 3270 | } |
| 3271 | return 0; |
| 3272 | } |
| 3273 | ]]> |
| 3274 | </programlisting> |
| 3275 | </example> |
| 3276 | </para> |
| 3277 | |
| 3278 | <para> |
| 3279 | Then you need to call this function to add your rule: |
| 3280 | |
| 3281 | <informalexample> |
| 3282 | <programlisting> |
| 3283 | <![CDATA[ |
| 3284 | snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS, |
| 3285 | hw_rule_channels_by_format, 0, SNDRV_PCM_HW_PARAM_FORMAT, |
| 3286 | -1); |
| 3287 | ]]> |
| 3288 | </programlisting> |
| 3289 | </informalexample> |
| 3290 | </para> |
| 3291 | |
| 3292 | <para> |
| 3293 | The rule function is called when an application sets the number of |
| 3294 | channels. But an application can set the format before the number of |
| 3295 | channels. Thus you also need to define the inverse rule: |
| 3296 | |
| 3297 | <example> |
| 3298 | <title>Example of Hardware Constraints for Channels</title> |
| 3299 | <programlisting> |
| 3300 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3301 | static int hw_rule_channels_by_format(struct snd_pcm_hw_params *params, |
| 3302 | struct snd_pcm_hw_rule *rule) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3303 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3304 | struct snd_interval *c = hw_param_interval(params, |
| 3305 | SNDRV_PCM_HW_PARAM_CHANNELS); |
| 3306 | struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT); |
| 3307 | struct snd_interval ch; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3308 | |
| 3309 | snd_interval_any(&ch); |
| 3310 | if (f->bits[0] == SNDRV_PCM_FMTBIT_S16_LE) { |
| 3311 | ch.min = ch.max = 1; |
| 3312 | ch.integer = 1; |
| 3313 | return snd_interval_refine(c, &ch); |
| 3314 | } |
| 3315 | return 0; |
| 3316 | } |
| 3317 | ]]> |
| 3318 | </programlisting> |
| 3319 | </example> |
| 3320 | </para> |
| 3321 | |
| 3322 | <para> |
| 3323 | ...and in the open callback: |
| 3324 | <informalexample> |
| 3325 | <programlisting> |
| 3326 | <![CDATA[ |
| 3327 | snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_FORMAT, |
| 3328 | hw_rule_format_by_channels, 0, SNDRV_PCM_HW_PARAM_CHANNELS, |
| 3329 | -1); |
| 3330 | ]]> |
| 3331 | </programlisting> |
| 3332 | </informalexample> |
| 3333 | </para> |
| 3334 | |
| 3335 | <para> |
| 3336 | I won't explain more details here, rather I |
| 3337 | would like to say, <quote>Luke, use the source.</quote> |
| 3338 | </para> |
| 3339 | </section> |
| 3340 | |
| 3341 | </chapter> |
| 3342 | |
| 3343 | |
| 3344 | <!-- ****************************************************** --> |
| 3345 | <!-- Control Interface --> |
| 3346 | <!-- ****************************************************** --> |
| 3347 | <chapter id="control-interface"> |
| 3348 | <title>Control Interface</title> |
| 3349 | |
| 3350 | <section id="control-interface-general"> |
| 3351 | <title>General</title> |
| 3352 | <para> |
| 3353 | The control interface is used widely for many switches, |
| 3354 | sliders, etc. which are accessed from the user-space. Its most |
| 3355 | important use is the mixer interface. In other words, on ALSA |
| 3356 | 0.9.x, all the mixer stuff is implemented on the control kernel |
| 3357 | API (while there was an independent mixer kernel API on 0.5.x). |
| 3358 | </para> |
| 3359 | |
| 3360 | <para> |
| 3361 | ALSA has a well-defined AC97 control module. If your chip |
| 3362 | supports only the AC97 and nothing else, you can skip this |
| 3363 | section. |
| 3364 | </para> |
| 3365 | |
| 3366 | <para> |
| 3367 | The control API is defined in |
| 3368 | <filename><sound/control.h></filename>. |
| 3369 | Include this file if you add your own controls. |
| 3370 | </para> |
| 3371 | </section> |
| 3372 | |
| 3373 | <section id="control-interface-definition"> |
| 3374 | <title>Definition of Controls</title> |
| 3375 | <para> |
| 3376 | For creating a new control, you need to define the three |
| 3377 | callbacks: <structfield>info</structfield>, |
| 3378 | <structfield>get</structfield> and |
| 3379 | <structfield>put</structfield>. Then, define a |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3380 | struct <structname>snd_kcontrol_new</structname> record, such as: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3381 | |
| 3382 | <example> |
| 3383 | <title>Definition of a Control</title> |
| 3384 | <programlisting> |
| 3385 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3386 | static struct snd_kcontrol_new my_control __devinitdata = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3387 | .iface = SNDRV_CTL_ELEM_IFACE_MIXER, |
| 3388 | .name = "PCM Playback Switch", |
| 3389 | .index = 0, |
| 3390 | .access = SNDRV_CTL_ELEM_ACCESS_READWRITE, |
Takashi Iwai | 0b7bed4 | 2006-03-02 15:35:55 +0100 | [diff] [blame] | 3391 | .private_value = 0xffff, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3392 | .info = my_control_info, |
| 3393 | .get = my_control_get, |
| 3394 | .put = my_control_put |
| 3395 | }; |
| 3396 | ]]> |
| 3397 | </programlisting> |
| 3398 | </example> |
| 3399 | </para> |
| 3400 | |
| 3401 | <para> |
| 3402 | Most likely the control is created via |
| 3403 | <function>snd_ctl_new1()</function>, and in such a case, you can |
| 3404 | add <parameter>__devinitdata</parameter> prefix to the |
| 3405 | definition like above. |
| 3406 | </para> |
| 3407 | |
| 3408 | <para> |
| 3409 | The <structfield>iface</structfield> field specifies the type of |
Clemens Ladisch | 67ed416 | 2005-07-29 15:32:58 +0200 | [diff] [blame] | 3410 | the control, <constant>SNDRV_CTL_ELEM_IFACE_XXX</constant>, which |
| 3411 | is usually <constant>MIXER</constant>. |
| 3412 | Use <constant>CARD</constant> for global controls that are not |
| 3413 | logically part of the mixer. |
| 3414 | If the control is closely associated with some specific device on |
| 3415 | the sound card, use <constant>HWDEP</constant>, |
| 3416 | <constant>PCM</constant>, <constant>RAWMIDI</constant>, |
| 3417 | <constant>TIMER</constant>, or <constant>SEQUENCER</constant>, and |
| 3418 | specify the device number with the |
| 3419 | <structfield>device</structfield> and |
| 3420 | <structfield>subdevice</structfield> fields. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3421 | </para> |
| 3422 | |
| 3423 | <para> |
| 3424 | The <structfield>name</structfield> is the name identifier |
| 3425 | string. On ALSA 0.9.x, the control name is very important, |
| 3426 | because its role is classified from its name. There are |
| 3427 | pre-defined standard control names. The details are described in |
| 3428 | the subsection |
| 3429 | <link linkend="control-interface-control-names"><citetitle> |
| 3430 | Control Names</citetitle></link>. |
| 3431 | </para> |
| 3432 | |
| 3433 | <para> |
| 3434 | The <structfield>index</structfield> field holds the index number |
| 3435 | of this control. If there are several different controls with |
| 3436 | the same name, they can be distinguished by the index |
| 3437 | number. This is the case when |
| 3438 | several codecs exist on the card. If the index is zero, you can |
| 3439 | omit the definition above. |
| 3440 | </para> |
| 3441 | |
| 3442 | <para> |
| 3443 | The <structfield>access</structfield> field contains the access |
| 3444 | type of this control. Give the combination of bit masks, |
| 3445 | <constant>SNDRV_CTL_ELEM_ACCESS_XXX</constant>, there. |
| 3446 | The detailed will be explained in the subsection |
| 3447 | <link linkend="control-interface-access-flags"><citetitle> |
| 3448 | Access Flags</citetitle></link>. |
| 3449 | </para> |
| 3450 | |
| 3451 | <para> |
Takashi Iwai | 0b7bed4 | 2006-03-02 15:35:55 +0100 | [diff] [blame] | 3452 | The <structfield>private_value</structfield> field contains |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3453 | an arbitrary long integer value for this record. When using |
| 3454 | generic <structfield>info</structfield>, |
| 3455 | <structfield>get</structfield> and |
| 3456 | <structfield>put</structfield> callbacks, you can pass a value |
| 3457 | through this field. If several small numbers are necessary, you can |
| 3458 | combine them in bitwise. Or, it's possible to give a pointer |
| 3459 | (casted to unsigned long) of some record to this field, too. |
| 3460 | </para> |
| 3461 | |
| 3462 | <para> |
| 3463 | The other three are |
| 3464 | <link linkend="control-interface-callbacks"><citetitle> |
| 3465 | callback functions</citetitle></link>. |
| 3466 | </para> |
| 3467 | </section> |
| 3468 | |
| 3469 | <section id="control-interface-control-names"> |
| 3470 | <title>Control Names</title> |
| 3471 | <para> |
| 3472 | There are some standards for defining the control names. A |
| 3473 | control is usually defined from the three parts as |
| 3474 | <quote>SOURCE DIRECTION FUNCTION</quote>. |
| 3475 | </para> |
| 3476 | |
| 3477 | <para> |
| 3478 | The first, <constant>SOURCE</constant>, specifies the source |
| 3479 | of the control, and is a string such as <quote>Master</quote>, |
| 3480 | <quote>PCM</quote>, <quote>CD</quote> or |
| 3481 | <quote>Line</quote>. There are many pre-defined sources. |
| 3482 | </para> |
| 3483 | |
| 3484 | <para> |
| 3485 | The second, <constant>DIRECTION</constant>, is one of the |
| 3486 | following strings according to the direction of the control: |
| 3487 | <quote>Playback</quote>, <quote>Capture</quote>, <quote>Bypass |
| 3488 | Playback</quote> and <quote>Bypass Capture</quote>. Or, it can |
| 3489 | be omitted, meaning both playback and capture directions. |
| 3490 | </para> |
| 3491 | |
| 3492 | <para> |
| 3493 | The third, <constant>FUNCTION</constant>, is one of the |
| 3494 | following strings according to the function of the control: |
| 3495 | <quote>Switch</quote>, <quote>Volume</quote> and |
| 3496 | <quote>Route</quote>. |
| 3497 | </para> |
| 3498 | |
| 3499 | <para> |
| 3500 | The example of control names are, thus, <quote>Master Capture |
| 3501 | Switch</quote> or <quote>PCM Playback Volume</quote>. |
| 3502 | </para> |
| 3503 | |
| 3504 | <para> |
| 3505 | There are some exceptions: |
| 3506 | </para> |
| 3507 | |
| 3508 | <section id="control-interface-control-names-global"> |
| 3509 | <title>Global capture and playback</title> |
| 3510 | <para> |
| 3511 | <quote>Capture Source</quote>, <quote>Capture Switch</quote> |
| 3512 | and <quote>Capture Volume</quote> are used for the global |
| 3513 | capture (input) source, switch and volume. Similarly, |
| 3514 | <quote>Playback Switch</quote> and <quote>Playback |
| 3515 | Volume</quote> are used for the global output gain switch and |
| 3516 | volume. |
| 3517 | </para> |
| 3518 | </section> |
| 3519 | |
| 3520 | <section id="control-interface-control-names-tone"> |
| 3521 | <title>Tone-controls</title> |
| 3522 | <para> |
| 3523 | tone-control switch and volumes are specified like |
| 3524 | <quote>Tone Control - XXX</quote>, e.g. <quote>Tone Control - |
| 3525 | Switch</quote>, <quote>Tone Control - Bass</quote>, |
| 3526 | <quote>Tone Control - Center</quote>. |
| 3527 | </para> |
| 3528 | </section> |
| 3529 | |
| 3530 | <section id="control-interface-control-names-3d"> |
| 3531 | <title>3D controls</title> |
| 3532 | <para> |
| 3533 | 3D-control switches and volumes are specified like <quote>3D |
| 3534 | Control - XXX</quote>, e.g. <quote>3D Control - |
| 3535 | Switch</quote>, <quote>3D Control - Center</quote>, <quote>3D |
| 3536 | Control - Space</quote>. |
| 3537 | </para> |
| 3538 | </section> |
| 3539 | |
| 3540 | <section id="control-interface-control-names-mic"> |
| 3541 | <title>Mic boost</title> |
| 3542 | <para> |
| 3543 | Mic-boost switch is set as <quote>Mic Boost</quote> or |
| 3544 | <quote>Mic Boost (6dB)</quote>. |
| 3545 | </para> |
| 3546 | |
| 3547 | <para> |
| 3548 | More precise information can be found in |
| 3549 | <filename>Documentation/sound/alsa/ControlNames.txt</filename>. |
| 3550 | </para> |
| 3551 | </section> |
| 3552 | </section> |
| 3553 | |
| 3554 | <section id="control-interface-access-flags"> |
| 3555 | <title>Access Flags</title> |
| 3556 | |
| 3557 | <para> |
| 3558 | The access flag is the bit-flags which specifies the access type |
| 3559 | of the given control. The default access type is |
| 3560 | <constant>SNDRV_CTL_ELEM_ACCESS_READWRITE</constant>, |
| 3561 | which means both read and write are allowed to this control. |
| 3562 | When the access flag is omitted (i.e. = 0), it is |
| 3563 | regarded as <constant>READWRITE</constant> access as default. |
| 3564 | </para> |
| 3565 | |
| 3566 | <para> |
| 3567 | When the control is read-only, pass |
| 3568 | <constant>SNDRV_CTL_ELEM_ACCESS_READ</constant> instead. |
| 3569 | In this case, you don't have to define |
| 3570 | <structfield>put</structfield> callback. |
| 3571 | Similarly, when the control is write-only (although it's a rare |
| 3572 | case), you can use <constant>WRITE</constant> flag instead, and |
| 3573 | you don't need <structfield>get</structfield> callback. |
| 3574 | </para> |
| 3575 | |
| 3576 | <para> |
| 3577 | If the control value changes frequently (e.g. the VU meter), |
| 3578 | <constant>VOLATILE</constant> flag should be given. This means |
| 3579 | that the control may be changed without |
| 3580 | <link linkend="control-interface-change-notification"><citetitle> |
| 3581 | notification</citetitle></link>. Applications should poll such |
| 3582 | a control constantly. |
| 3583 | </para> |
| 3584 | |
| 3585 | <para> |
| 3586 | When the control is inactive, set |
| 3587 | <constant>INACTIVE</constant> flag, too. |
| 3588 | There are <constant>LOCK</constant> and |
| 3589 | <constant>OWNER</constant> flags for changing the write |
| 3590 | permissions. |
| 3591 | </para> |
| 3592 | |
| 3593 | </section> |
| 3594 | |
| 3595 | <section id="control-interface-callbacks"> |
| 3596 | <title>Callbacks</title> |
| 3597 | |
| 3598 | <section id="control-interface-callbacks-info"> |
| 3599 | <title>info callback</title> |
| 3600 | <para> |
| 3601 | The <structfield>info</structfield> callback is used to get |
| 3602 | the detailed information of this control. This must store the |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3603 | values of the given struct <structname>snd_ctl_elem_info</structname> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3604 | object. For example, for a boolean control with a single |
| 3605 | element will be: |
| 3606 | |
| 3607 | <example> |
| 3608 | <title>Example of info callback</title> |
| 3609 | <programlisting> |
| 3610 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3611 | static int snd_myctl_info(struct snd_kcontrol *kcontrol, |
| 3612 | struct snd_ctl_elem_info *uinfo) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3613 | { |
| 3614 | uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN; |
| 3615 | uinfo->count = 1; |
| 3616 | uinfo->value.integer.min = 0; |
| 3617 | uinfo->value.integer.max = 1; |
| 3618 | return 0; |
| 3619 | } |
| 3620 | ]]> |
| 3621 | </programlisting> |
| 3622 | </example> |
| 3623 | </para> |
| 3624 | |
| 3625 | <para> |
| 3626 | The <structfield>type</structfield> field specifies the type |
| 3627 | of the control. There are <constant>BOOLEAN</constant>, |
| 3628 | <constant>INTEGER</constant>, <constant>ENUMERATED</constant>, |
| 3629 | <constant>BYTES</constant>, <constant>IEC958</constant> and |
| 3630 | <constant>INTEGER64</constant>. The |
| 3631 | <structfield>count</structfield> field specifies the |
| 3632 | number of elements in this control. For example, a stereo |
| 3633 | volume would have count = 2. The |
| 3634 | <structfield>value</structfield> field is a union, and |
| 3635 | the values stored are depending on the type. The boolean and |
| 3636 | integer are identical. |
| 3637 | </para> |
| 3638 | |
| 3639 | <para> |
| 3640 | The enumerated type is a bit different from others. You'll |
| 3641 | need to set the string for the currently given item index. |
| 3642 | |
| 3643 | <informalexample> |
| 3644 | <programlisting> |
| 3645 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3646 | static int snd_myctl_info(struct snd_kcontrol *kcontrol, |
| 3647 | struct snd_ctl_elem_info *uinfo) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3648 | { |
| 3649 | static char *texts[4] = { |
| 3650 | "First", "Second", "Third", "Fourth" |
| 3651 | }; |
| 3652 | uinfo->type = SNDRV_CTL_ELEM_TYPE_ENUMERATED; |
| 3653 | uinfo->count = 1; |
| 3654 | uinfo->value.enumerated.items = 4; |
| 3655 | if (uinfo->value.enumerated.item > 3) |
| 3656 | uinfo->value.enumerated.item = 3; |
| 3657 | strcpy(uinfo->value.enumerated.name, |
| 3658 | texts[uinfo->value.enumerated.item]); |
| 3659 | return 0; |
| 3660 | } |
| 3661 | ]]> |
| 3662 | </programlisting> |
| 3663 | </informalexample> |
| 3664 | </para> |
| 3665 | </section> |
| 3666 | |
| 3667 | <section id="control-interface-callbacks-get"> |
| 3668 | <title>get callback</title> |
| 3669 | |
| 3670 | <para> |
| 3671 | This callback is used to read the current value of the |
| 3672 | control and to return to the user-space. |
| 3673 | </para> |
| 3674 | |
| 3675 | <para> |
| 3676 | For example, |
| 3677 | |
| 3678 | <example> |
| 3679 | <title>Example of get callback</title> |
| 3680 | <programlisting> |
| 3681 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3682 | static int snd_myctl_get(struct snd_kcontrol *kcontrol, |
| 3683 | struct snd_ctl_elem_value *ucontrol) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3684 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3685 | struct mychip *chip = snd_kcontrol_chip(kcontrol); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3686 | ucontrol->value.integer.value[0] = get_some_value(chip); |
| 3687 | return 0; |
| 3688 | } |
| 3689 | ]]> |
| 3690 | </programlisting> |
| 3691 | </example> |
| 3692 | </para> |
| 3693 | |
| 3694 | <para> |
| 3695 | Here, the chip instance is retrieved via |
| 3696 | <function>snd_kcontrol_chip()</function> macro. This macro |
Takashi Iwai | 063859c | 2005-10-14 17:17:02 +0200 | [diff] [blame] | 3697 | just accesses to kcontrol->private_data. The |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3698 | kcontrol->private_data field is |
| 3699 | given as the argument of <function>snd_ctl_new()</function> |
| 3700 | (see the later subsection |
| 3701 | <link linkend="control-interface-constructor"><citetitle>Constructor</citetitle></link>). |
| 3702 | </para> |
| 3703 | |
| 3704 | <para> |
| 3705 | The <structfield>value</structfield> field is depending on |
| 3706 | the type of control as well as on info callback. For example, |
| 3707 | the sb driver uses this field to store the register offset, |
| 3708 | the bit-shift and the bit-mask. The |
| 3709 | <structfield>private_value</structfield> is set like |
| 3710 | <informalexample> |
| 3711 | <programlisting> |
| 3712 | <![CDATA[ |
| 3713 | .private_value = reg | (shift << 16) | (mask << 24) |
| 3714 | ]]> |
| 3715 | </programlisting> |
| 3716 | </informalexample> |
| 3717 | and is retrieved in callbacks like |
| 3718 | <informalexample> |
| 3719 | <programlisting> |
| 3720 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3721 | static int snd_sbmixer_get_single(struct snd_kcontrol *kcontrol, |
| 3722 | struct snd_ctl_elem_value *ucontrol) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3723 | { |
| 3724 | int reg = kcontrol->private_value & 0xff; |
| 3725 | int shift = (kcontrol->private_value >> 16) & 0xff; |
| 3726 | int mask = (kcontrol->private_value >> 24) & 0xff; |
| 3727 | .... |
| 3728 | } |
| 3729 | ]]> |
| 3730 | </programlisting> |
| 3731 | </informalexample> |
| 3732 | </para> |
| 3733 | |
| 3734 | <para> |
| 3735 | In <structfield>get</structfield> callback, you have to fill all the elements if the |
| 3736 | control has more than one elements, |
| 3737 | i.e. <structfield>count</structfield> > 1. |
| 3738 | In the example above, we filled only one element |
| 3739 | (<structfield>value.integer.value[0]</structfield>) since it's |
| 3740 | assumed as <structfield>count</structfield> = 1. |
| 3741 | </para> |
| 3742 | </section> |
| 3743 | |
| 3744 | <section id="control-interface-callbacks-put"> |
| 3745 | <title>put callback</title> |
| 3746 | |
| 3747 | <para> |
| 3748 | This callback is used to write a value from the user-space. |
| 3749 | </para> |
| 3750 | |
| 3751 | <para> |
| 3752 | For example, |
| 3753 | |
| 3754 | <example> |
| 3755 | <title>Example of put callback</title> |
| 3756 | <programlisting> |
| 3757 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3758 | static int snd_myctl_put(struct snd_kcontrol *kcontrol, |
| 3759 | struct snd_ctl_elem_value *ucontrol) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3760 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3761 | struct mychip *chip = snd_kcontrol_chip(kcontrol); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3762 | int changed = 0; |
| 3763 | if (chip->current_value != |
| 3764 | ucontrol->value.integer.value[0]) { |
| 3765 | change_current_value(chip, |
| 3766 | ucontrol->value.integer.value[0]); |
| 3767 | changed = 1; |
| 3768 | } |
| 3769 | return changed; |
| 3770 | } |
| 3771 | ]]> |
| 3772 | </programlisting> |
| 3773 | </example> |
| 3774 | |
| 3775 | As seen above, you have to return 1 if the value is |
| 3776 | changed. If the value is not changed, return 0 instead. |
| 3777 | If any fatal error happens, return a negative error code as |
| 3778 | usual. |
| 3779 | </para> |
| 3780 | |
| 3781 | <para> |
| 3782 | Like <structfield>get</structfield> callback, |
| 3783 | when the control has more than one elements, |
| 3784 | all elemehts must be evaluated in this callback, too. |
| 3785 | </para> |
| 3786 | </section> |
| 3787 | |
| 3788 | <section id="control-interface-callbacks-all"> |
| 3789 | <title>Callbacks are not atomic</title> |
| 3790 | <para> |
| 3791 | All these three callbacks are basically not atomic. |
| 3792 | </para> |
| 3793 | </section> |
| 3794 | </section> |
| 3795 | |
| 3796 | <section id="control-interface-constructor"> |
| 3797 | <title>Constructor</title> |
| 3798 | <para> |
| 3799 | When everything is ready, finally we can create a new |
| 3800 | control. For creating a control, there are two functions to be |
| 3801 | called, <function>snd_ctl_new1()</function> and |
| 3802 | <function>snd_ctl_add()</function>. |
| 3803 | </para> |
| 3804 | |
| 3805 | <para> |
| 3806 | In the simplest way, you can do like this: |
| 3807 | |
| 3808 | <informalexample> |
| 3809 | <programlisting> |
| 3810 | <![CDATA[ |
| 3811 | if ((err = snd_ctl_add(card, snd_ctl_new1(&my_control, chip))) < 0) |
| 3812 | return err; |
| 3813 | ]]> |
| 3814 | </programlisting> |
| 3815 | </informalexample> |
| 3816 | |
| 3817 | where <parameter>my_control</parameter> is the |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3818 | struct <structname>snd_kcontrol_new</structname> object defined above, and chip |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3819 | is the object pointer to be passed to |
| 3820 | kcontrol->private_data |
| 3821 | which can be referred in callbacks. |
| 3822 | </para> |
| 3823 | |
| 3824 | <para> |
| 3825 | <function>snd_ctl_new1()</function> allocates a new |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3826 | <structname>snd_kcontrol</structname> instance (that's why the definition |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3827 | of <parameter>my_control</parameter> can be with |
| 3828 | <parameter>__devinitdata</parameter> |
| 3829 | prefix), and <function>snd_ctl_add</function> assigns the given |
| 3830 | control component to the card. |
| 3831 | </para> |
| 3832 | </section> |
| 3833 | |
| 3834 | <section id="control-interface-change-notification"> |
| 3835 | <title>Change Notification</title> |
| 3836 | <para> |
| 3837 | If you need to change and update a control in the interrupt |
| 3838 | routine, you can call <function>snd_ctl_notify()</function>. For |
| 3839 | example, |
| 3840 | |
| 3841 | <informalexample> |
| 3842 | <programlisting> |
| 3843 | <![CDATA[ |
| 3844 | snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, id_pointer); |
| 3845 | ]]> |
| 3846 | </programlisting> |
| 3847 | </informalexample> |
| 3848 | |
| 3849 | This function takes the card pointer, the event-mask, and the |
| 3850 | control id pointer for the notification. The event-mask |
| 3851 | specifies the types of notification, for example, in the above |
| 3852 | example, the change of control values is notified. |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3853 | 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] | 3854 | to be notified. |
| 3855 | You can find some examples in <filename>es1938.c</filename> or |
| 3856 | <filename>es1968.c</filename> for hardware volume interrupts. |
| 3857 | </para> |
| 3858 | </section> |
| 3859 | |
| 3860 | </chapter> |
| 3861 | |
| 3862 | |
| 3863 | <!-- ****************************************************** --> |
| 3864 | <!-- API for AC97 Codec --> |
| 3865 | <!-- ****************************************************** --> |
| 3866 | <chapter id="api-ac97"> |
| 3867 | <title>API for AC97 Codec</title> |
| 3868 | |
| 3869 | <section> |
| 3870 | <title>General</title> |
| 3871 | <para> |
| 3872 | The ALSA AC97 codec layer is a well-defined one, and you don't |
| 3873 | have to write many codes to control it. Only low-level control |
| 3874 | routines are necessary. The AC97 codec API is defined in |
| 3875 | <filename><sound/ac97_codec.h></filename>. |
| 3876 | </para> |
| 3877 | </section> |
| 3878 | |
| 3879 | <section id="api-ac97-example"> |
| 3880 | <title>Full Code Example</title> |
| 3881 | <para> |
| 3882 | <example> |
| 3883 | <title>Example of AC97 Interface</title> |
| 3884 | <programlisting> |
| 3885 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3886 | struct mychip { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3887 | .... |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3888 | struct snd_ac97 *ac97; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3889 | .... |
| 3890 | }; |
| 3891 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3892 | static unsigned short snd_mychip_ac97_read(struct snd_ac97 *ac97, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3893 | unsigned short reg) |
| 3894 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3895 | struct mychip *chip = ac97->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3896 | .... |
| 3897 | // read a register value here from the codec |
| 3898 | return the_register_value; |
| 3899 | } |
| 3900 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3901 | static void snd_mychip_ac97_write(struct snd_ac97 *ac97, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3902 | unsigned short reg, unsigned short val) |
| 3903 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3904 | struct mychip *chip = ac97->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3905 | .... |
| 3906 | // write the given register value to the codec |
| 3907 | } |
| 3908 | |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3909 | static int snd_mychip_ac97(struct mychip *chip) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3910 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3911 | struct snd_ac97_bus *bus; |
| 3912 | struct snd_ac97_template ac97; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3913 | int err; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3914 | static struct snd_ac97_bus_ops ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3915 | .write = snd_mychip_ac97_write, |
| 3916 | .read = snd_mychip_ac97_read, |
| 3917 | }; |
| 3918 | |
| 3919 | if ((err = snd_ac97_bus(chip->card, 0, &ops, NULL, &bus)) < 0) |
| 3920 | return err; |
| 3921 | memset(&ac97, 0, sizeof(ac97)); |
| 3922 | ac97.private_data = chip; |
| 3923 | return snd_ac97_mixer(bus, &ac97, &chip->ac97); |
| 3924 | } |
| 3925 | |
| 3926 | ]]> |
| 3927 | </programlisting> |
| 3928 | </example> |
| 3929 | </para> |
| 3930 | </section> |
| 3931 | |
| 3932 | <section id="api-ac97-constructor"> |
| 3933 | <title>Constructor</title> |
| 3934 | <para> |
| 3935 | For creating an ac97 instance, first call <function>snd_ac97_bus</function> |
| 3936 | with an <type>ac97_bus_ops_t</type> record with callback functions. |
| 3937 | |
| 3938 | <informalexample> |
| 3939 | <programlisting> |
| 3940 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3941 | struct snd_ac97_bus *bus; |
| 3942 | static struct snd_ac97_bus_ops ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3943 | .write = snd_mychip_ac97_write, |
| 3944 | .read = snd_mychip_ac97_read, |
| 3945 | }; |
| 3946 | |
| 3947 | snd_ac97_bus(card, 0, &ops, NULL, &pbus); |
| 3948 | ]]> |
| 3949 | </programlisting> |
| 3950 | </informalexample> |
| 3951 | |
| 3952 | The bus record is shared among all belonging ac97 instances. |
| 3953 | </para> |
| 3954 | |
| 3955 | <para> |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3956 | And then call <function>snd_ac97_mixer()</function> with an |
| 3957 | struct <structname>snd_ac97_template</structname> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3958 | record together with the bus pointer created above. |
| 3959 | |
| 3960 | <informalexample> |
| 3961 | <programlisting> |
| 3962 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 3963 | struct snd_ac97_template ac97; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3964 | int err; |
| 3965 | |
| 3966 | memset(&ac97, 0, sizeof(ac97)); |
| 3967 | ac97.private_data = chip; |
| 3968 | snd_ac97_mixer(bus, &ac97, &chip->ac97); |
| 3969 | ]]> |
| 3970 | </programlisting> |
| 3971 | </informalexample> |
| 3972 | |
| 3973 | where chip->ac97 is the pointer of a newly created |
| 3974 | <type>ac97_t</type> instance. |
| 3975 | In this case, the chip pointer is set as the private data, so that |
| 3976 | the read/write callback functions can refer to this chip instance. |
| 3977 | This instance is not necessarily stored in the chip |
| 3978 | record. When you need to change the register values from the |
| 3979 | driver, or need the suspend/resume of ac97 codecs, keep this |
| 3980 | pointer to pass to the corresponding functions. |
| 3981 | </para> |
| 3982 | </section> |
| 3983 | |
| 3984 | <section id="api-ac97-callbacks"> |
| 3985 | <title>Callbacks</title> |
| 3986 | <para> |
| 3987 | The standard callbacks are <structfield>read</structfield> and |
| 3988 | <structfield>write</structfield>. Obviously they |
| 3989 | correspond to the functions for read and write accesses to the |
| 3990 | hardware low-level codes. |
| 3991 | </para> |
| 3992 | |
| 3993 | <para> |
| 3994 | The <structfield>read</structfield> callback returns the |
| 3995 | register value specified in the argument. |
| 3996 | |
| 3997 | <informalexample> |
| 3998 | <programlisting> |
| 3999 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4000 | static unsigned short snd_mychip_ac97_read(struct snd_ac97 *ac97, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4001 | unsigned short reg) |
| 4002 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4003 | struct mychip *chip = ac97->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4004 | .... |
| 4005 | return the_register_value; |
| 4006 | } |
| 4007 | ]]> |
| 4008 | </programlisting> |
| 4009 | </informalexample> |
| 4010 | |
| 4011 | Here, the chip can be cast from ac97->private_data. |
| 4012 | </para> |
| 4013 | |
| 4014 | <para> |
| 4015 | Meanwhile, the <structfield>write</structfield> callback is |
| 4016 | used to set the register value. |
| 4017 | |
| 4018 | <informalexample> |
| 4019 | <programlisting> |
| 4020 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4021 | static void snd_mychip_ac97_write(struct snd_ac97 *ac97, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4022 | unsigned short reg, unsigned short val) |
| 4023 | ]]> |
| 4024 | </programlisting> |
| 4025 | </informalexample> |
| 4026 | </para> |
| 4027 | |
| 4028 | <para> |
| 4029 | These callbacks are non-atomic like the callbacks of control API. |
| 4030 | </para> |
| 4031 | |
| 4032 | <para> |
| 4033 | There are also other callbacks: |
| 4034 | <structfield>reset</structfield>, |
| 4035 | <structfield>wait</structfield> and |
| 4036 | <structfield>init</structfield>. |
| 4037 | </para> |
| 4038 | |
| 4039 | <para> |
| 4040 | The <structfield>reset</structfield> callback is used to reset |
| 4041 | the codec. If the chip requires a special way of reset, you can |
| 4042 | define this callback. |
| 4043 | </para> |
| 4044 | |
| 4045 | <para> |
| 4046 | The <structfield>wait</structfield> callback is used for a |
| 4047 | certain wait at the standard initialization of the codec. If the |
| 4048 | chip requires the extra wait-time, define this callback. |
| 4049 | </para> |
| 4050 | |
| 4051 | <para> |
| 4052 | The <structfield>init</structfield> callback is used for |
| 4053 | additional initialization of the codec. |
| 4054 | </para> |
| 4055 | </section> |
| 4056 | |
| 4057 | <section id="api-ac97-updating-registers"> |
| 4058 | <title>Updating Registers in The Driver</title> |
| 4059 | <para> |
| 4060 | If you need to access to the codec from the driver, you can |
| 4061 | call the following functions: |
| 4062 | <function>snd_ac97_write()</function>, |
| 4063 | <function>snd_ac97_read()</function>, |
| 4064 | <function>snd_ac97_update()</function> and |
| 4065 | <function>snd_ac97_update_bits()</function>. |
| 4066 | </para> |
| 4067 | |
| 4068 | <para> |
| 4069 | Both <function>snd_ac97_write()</function> and |
| 4070 | <function>snd_ac97_update()</function> functions are used to |
| 4071 | set a value to the given register |
| 4072 | (<constant>AC97_XXX</constant>). The difference between them is |
| 4073 | that <function>snd_ac97_update()</function> doesn't write a |
| 4074 | value if the given value has been already set, while |
| 4075 | <function>snd_ac97_write()</function> always rewrites the |
| 4076 | value. |
| 4077 | |
| 4078 | <informalexample> |
| 4079 | <programlisting> |
| 4080 | <![CDATA[ |
| 4081 | snd_ac97_write(ac97, AC97_MASTER, 0x8080); |
| 4082 | snd_ac97_update(ac97, AC97_MASTER, 0x8080); |
| 4083 | ]]> |
| 4084 | </programlisting> |
| 4085 | </informalexample> |
| 4086 | </para> |
| 4087 | |
| 4088 | <para> |
| 4089 | <function>snd_ac97_read()</function> is used to read the value |
| 4090 | of the given register. For example, |
| 4091 | |
| 4092 | <informalexample> |
| 4093 | <programlisting> |
| 4094 | <![CDATA[ |
| 4095 | value = snd_ac97_read(ac97, AC97_MASTER); |
| 4096 | ]]> |
| 4097 | </programlisting> |
| 4098 | </informalexample> |
| 4099 | </para> |
| 4100 | |
| 4101 | <para> |
| 4102 | <function>snd_ac97_update_bits()</function> is used to update |
| 4103 | some bits of the given register. |
| 4104 | |
| 4105 | <informalexample> |
| 4106 | <programlisting> |
| 4107 | <![CDATA[ |
| 4108 | snd_ac97_update_bits(ac97, reg, mask, value); |
| 4109 | ]]> |
| 4110 | </programlisting> |
| 4111 | </informalexample> |
| 4112 | </para> |
| 4113 | |
| 4114 | <para> |
| 4115 | Also, there is a function to change the sample rate (of a |
| 4116 | certain register such as |
| 4117 | <constant>AC97_PCM_FRONT_DAC_RATE</constant>) when VRA or |
| 4118 | DRA is supported by the codec: |
| 4119 | <function>snd_ac97_set_rate()</function>. |
| 4120 | |
| 4121 | <informalexample> |
| 4122 | <programlisting> |
| 4123 | <![CDATA[ |
| 4124 | snd_ac97_set_rate(ac97, AC97_PCM_FRONT_DAC_RATE, 44100); |
| 4125 | ]]> |
| 4126 | </programlisting> |
| 4127 | </informalexample> |
| 4128 | </para> |
| 4129 | |
| 4130 | <para> |
| 4131 | The following registers are available for setting the rate: |
| 4132 | <constant>AC97_PCM_MIC_ADC_RATE</constant>, |
| 4133 | <constant>AC97_PCM_FRONT_DAC_RATE</constant>, |
| 4134 | <constant>AC97_PCM_LR_ADC_RATE</constant>, |
| 4135 | <constant>AC97_SPDIF</constant>. When the |
| 4136 | <constant>AC97_SPDIF</constant> is specified, the register is |
| 4137 | not really changed but the corresponding IEC958 status bits will |
| 4138 | be updated. |
| 4139 | </para> |
| 4140 | </section> |
| 4141 | |
| 4142 | <section id="api-ac97-clock-adjustment"> |
| 4143 | <title>Clock Adjustment</title> |
| 4144 | <para> |
| 4145 | On some chip, the clock of the codec isn't 48000 but using a |
| 4146 | PCI clock (to save a quartz!). In this case, change the field |
| 4147 | bus->clock to the corresponding |
| 4148 | value. For example, intel8x0 |
| 4149 | and es1968 drivers have the auto-measurement function of the |
| 4150 | clock. |
| 4151 | </para> |
| 4152 | </section> |
| 4153 | |
| 4154 | <section id="api-ac97-proc-files"> |
| 4155 | <title>Proc Files</title> |
| 4156 | <para> |
| 4157 | The ALSA AC97 interface will create a proc file such as |
| 4158 | <filename>/proc/asound/card0/codec97#0/ac97#0-0</filename> and |
| 4159 | <filename>ac97#0-0+regs</filename>. You can refer to these files to |
| 4160 | see the current status and registers of the codec. |
| 4161 | </para> |
| 4162 | </section> |
| 4163 | |
| 4164 | <section id="api-ac97-multiple-codecs"> |
| 4165 | <title>Multiple Codecs</title> |
| 4166 | <para> |
| 4167 | When there are several codecs on the same card, you need to |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4168 | call <function>snd_ac97_mixer()</function> multiple times with |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4169 | ac97.num=1 or greater. The <structfield>num</structfield> field |
| 4170 | specifies the codec |
| 4171 | number. |
| 4172 | </para> |
| 4173 | |
| 4174 | <para> |
| 4175 | If you have set up multiple codecs, you need to either write |
| 4176 | different callbacks for each codec or check |
| 4177 | ac97->num in the |
| 4178 | callback routines. |
| 4179 | </para> |
| 4180 | </section> |
| 4181 | |
| 4182 | </chapter> |
| 4183 | |
| 4184 | |
| 4185 | <!-- ****************************************************** --> |
| 4186 | <!-- MIDI (MPU401-UART) Interface --> |
| 4187 | <!-- ****************************************************** --> |
| 4188 | <chapter id="midi-interface"> |
| 4189 | <title>MIDI (MPU401-UART) Interface</title> |
| 4190 | |
| 4191 | <section id="midi-interface-general"> |
| 4192 | <title>General</title> |
| 4193 | <para> |
| 4194 | Many soundcards have built-in MIDI (MPU401-UART) |
| 4195 | interfaces. When the soundcard supports the standard MPU401-UART |
| 4196 | interface, most likely you can use the ALSA MPU401-UART API. The |
| 4197 | MPU401-UART API is defined in |
| 4198 | <filename><sound/mpu401.h></filename>. |
| 4199 | </para> |
| 4200 | |
| 4201 | <para> |
| 4202 | Some soundchips have similar but a little bit different |
| 4203 | implementation of mpu401 stuff. For example, emu10k1 has its own |
| 4204 | mpu401 routines. |
| 4205 | </para> |
| 4206 | </section> |
| 4207 | |
| 4208 | <section id="midi-interface-constructor"> |
| 4209 | <title>Constructor</title> |
| 4210 | <para> |
| 4211 | For creating a rawmidi object, call |
| 4212 | <function>snd_mpu401_uart_new()</function>. |
| 4213 | |
| 4214 | <informalexample> |
| 4215 | <programlisting> |
| 4216 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4217 | struct snd_rawmidi *rmidi; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4218 | snd_mpu401_uart_new(card, 0, MPU401_HW_MPU401, port, integrated, |
| 4219 | irq, irq_flags, &rmidi); |
| 4220 | ]]> |
| 4221 | </programlisting> |
| 4222 | </informalexample> |
| 4223 | </para> |
| 4224 | |
| 4225 | <para> |
| 4226 | The first argument is the card pointer, and the second is the |
| 4227 | index of this component. You can create up to 8 rawmidi |
| 4228 | devices. |
| 4229 | </para> |
| 4230 | |
| 4231 | <para> |
| 4232 | The third argument is the type of the hardware, |
| 4233 | <constant>MPU401_HW_XXX</constant>. If it's not a special one, |
| 4234 | you can use <constant>MPU401_HW_MPU401</constant>. |
| 4235 | </para> |
| 4236 | |
| 4237 | <para> |
| 4238 | The 4th argument is the i/o port address. Many |
| 4239 | backward-compatible MPU401 has an i/o port such as 0x330. Or, it |
| 4240 | might be a part of its own PCI i/o region. It depends on the |
| 4241 | chip design. |
| 4242 | </para> |
| 4243 | |
| 4244 | <para> |
| 4245 | When the i/o port address above is a part of the PCI i/o |
| 4246 | region, the MPU401 i/o port might have been already allocated |
| 4247 | (reserved) by the driver itself. In such a case, pass non-zero |
| 4248 | to the 5th argument |
| 4249 | (<parameter>integrated</parameter>). Otherwise, pass 0 to it, |
| 4250 | and |
| 4251 | the mpu401-uart layer will allocate the i/o ports by itself. |
| 4252 | </para> |
| 4253 | |
| 4254 | <para> |
| 4255 | Usually, the port address corresponds to the command port and |
| 4256 | port + 1 corresponds to the data port. If not, you may change |
| 4257 | the <structfield>cport</structfield> field of |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4258 | struct <structname>snd_mpu401</structname> manually |
| 4259 | afterward. However, <structname>snd_mpu401</structname> pointer is not |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4260 | returned explicitly by |
| 4261 | <function>snd_mpu401_uart_new()</function>. You need to cast |
| 4262 | rmidi->private_data to |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4263 | <structname>snd_mpu401</structname> explicitly, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4264 | |
| 4265 | <informalexample> |
| 4266 | <programlisting> |
| 4267 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4268 | struct snd_mpu401 *mpu; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4269 | mpu = rmidi->private_data; |
| 4270 | ]]> |
| 4271 | </programlisting> |
| 4272 | </informalexample> |
| 4273 | |
| 4274 | and reset the cport as you like: |
| 4275 | |
| 4276 | <informalexample> |
| 4277 | <programlisting> |
| 4278 | <![CDATA[ |
| 4279 | mpu->cport = my_own_control_port; |
| 4280 | ]]> |
| 4281 | </programlisting> |
| 4282 | </informalexample> |
| 4283 | </para> |
| 4284 | |
| 4285 | <para> |
| 4286 | The 6th argument specifies the irq number for UART. If the irq |
| 4287 | is already allocated, pass 0 to the 7th argument |
| 4288 | (<parameter>irq_flags</parameter>). Otherwise, pass the flags |
| 4289 | for irq allocation |
| 4290 | (<constant>SA_XXX</constant> bits) to it, and the irq will be |
| 4291 | reserved by the mpu401-uart layer. If the card doesn't generates |
| 4292 | UART interrupts, pass -1 as the irq number. Then a timer |
| 4293 | interrupt will be invoked for polling. |
| 4294 | </para> |
| 4295 | </section> |
| 4296 | |
| 4297 | <section id="midi-interface-interrupt-handler"> |
| 4298 | <title>Interrupt Handler</title> |
| 4299 | <para> |
| 4300 | When the interrupt is allocated in |
| 4301 | <function>snd_mpu401_uart_new()</function>, the private |
| 4302 | interrupt handler is used, hence you don't have to do nothing |
| 4303 | else than creating the mpu401 stuff. Otherwise, you have to call |
| 4304 | <function>snd_mpu401_uart_interrupt()</function> explicitly when |
| 4305 | a UART interrupt is invoked and checked in your own interrupt |
| 4306 | handler. |
| 4307 | </para> |
| 4308 | |
| 4309 | <para> |
| 4310 | In this case, you need to pass the private_data of the |
| 4311 | returned rawmidi object from |
| 4312 | <function>snd_mpu401_uart_new()</function> as the second |
| 4313 | argument of <function>snd_mpu401_uart_interrupt()</function>. |
| 4314 | |
| 4315 | <informalexample> |
| 4316 | <programlisting> |
| 4317 | <![CDATA[ |
| 4318 | snd_mpu401_uart_interrupt(irq, rmidi->private_data, regs); |
| 4319 | ]]> |
| 4320 | </programlisting> |
| 4321 | </informalexample> |
| 4322 | </para> |
| 4323 | </section> |
| 4324 | |
| 4325 | </chapter> |
| 4326 | |
| 4327 | |
| 4328 | <!-- ****************************************************** --> |
| 4329 | <!-- RawMIDI Interface --> |
| 4330 | <!-- ****************************************************** --> |
| 4331 | <chapter id="rawmidi-interface"> |
| 4332 | <title>RawMIDI Interface</title> |
| 4333 | |
| 4334 | <section id="rawmidi-interface-overview"> |
| 4335 | <title>Overview</title> |
| 4336 | |
| 4337 | <para> |
| 4338 | The raw MIDI interface is used for hardware MIDI ports that can |
| 4339 | be accessed as a byte stream. It is not used for synthesizer |
| 4340 | chips that do not directly understand MIDI. |
| 4341 | </para> |
| 4342 | |
| 4343 | <para> |
| 4344 | ALSA handles file and buffer management. All you have to do is |
| 4345 | to write some code to move data between the buffer and the |
| 4346 | hardware. |
| 4347 | </para> |
| 4348 | |
| 4349 | <para> |
| 4350 | The rawmidi API is defined in |
| 4351 | <filename><sound/rawmidi.h></filename>. |
| 4352 | </para> |
| 4353 | </section> |
| 4354 | |
| 4355 | <section id="rawmidi-interface-constructor"> |
| 4356 | <title>Constructor</title> |
| 4357 | |
| 4358 | <para> |
| 4359 | To create a rawmidi device, call the |
| 4360 | <function>snd_rawmidi_new</function> function: |
| 4361 | <informalexample> |
| 4362 | <programlisting> |
| 4363 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4364 | struct snd_rawmidi *rmidi; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4365 | err = snd_rawmidi_new(chip->card, "MyMIDI", 0, outs, ins, &rmidi); |
| 4366 | if (err < 0) |
| 4367 | return err; |
| 4368 | rmidi->private_data = chip; |
| 4369 | strcpy(rmidi->name, "My MIDI"); |
| 4370 | rmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT | |
| 4371 | SNDRV_RAWMIDI_INFO_INPUT | |
| 4372 | SNDRV_RAWMIDI_INFO_DUPLEX; |
| 4373 | ]]> |
| 4374 | </programlisting> |
| 4375 | </informalexample> |
| 4376 | </para> |
| 4377 | |
| 4378 | <para> |
| 4379 | The first argument is the card pointer, the second argument is |
| 4380 | the ID string. |
| 4381 | </para> |
| 4382 | |
| 4383 | <para> |
| 4384 | The third argument is the index of this component. You can |
| 4385 | create up to 8 rawmidi devices. |
| 4386 | </para> |
| 4387 | |
| 4388 | <para> |
| 4389 | The fourth and fifth arguments are the number of output and |
| 4390 | input substreams, respectively, of this device. (A substream is |
| 4391 | the equivalent of a MIDI port.) |
| 4392 | </para> |
| 4393 | |
| 4394 | <para> |
| 4395 | Set the <structfield>info_flags</structfield> field to specify |
| 4396 | the capabilities of the device. |
| 4397 | Set <constant>SNDRV_RAWMIDI_INFO_OUTPUT</constant> if there is |
| 4398 | at least one output port, |
| 4399 | <constant>SNDRV_RAWMIDI_INFO_INPUT</constant> if there is at |
| 4400 | least one input port, |
| 4401 | and <constant>SNDRV_RAWMIDI_INFO_DUPLEX</constant> if the device |
| 4402 | can handle output and input at the same time. |
| 4403 | </para> |
| 4404 | |
| 4405 | <para> |
| 4406 | After the rawmidi device is created, you need to set the |
| 4407 | operators (callbacks) for each substream. There are helper |
| 4408 | functions to set the operators for all substream of a device: |
| 4409 | <informalexample> |
| 4410 | <programlisting> |
| 4411 | <![CDATA[ |
| 4412 | snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, &snd_mymidi_output_ops); |
| 4413 | snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT, &snd_mymidi_input_ops); |
| 4414 | ]]> |
| 4415 | </programlisting> |
| 4416 | </informalexample> |
| 4417 | </para> |
| 4418 | |
| 4419 | <para> |
| 4420 | The operators are usually defined like this: |
| 4421 | <informalexample> |
| 4422 | <programlisting> |
| 4423 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4424 | static struct snd_rawmidi_ops snd_mymidi_output_ops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4425 | .open = snd_mymidi_output_open, |
| 4426 | .close = snd_mymidi_output_close, |
| 4427 | .trigger = snd_mymidi_output_trigger, |
| 4428 | }; |
| 4429 | ]]> |
| 4430 | </programlisting> |
| 4431 | </informalexample> |
| 4432 | These callbacks are explained in the <link |
| 4433 | linkend="rawmidi-interface-callbacks"><citetitle>Callbacks</citetitle></link> |
| 4434 | section. |
| 4435 | </para> |
| 4436 | |
| 4437 | <para> |
| 4438 | If there is more than one substream, you should give each one a |
| 4439 | unique name: |
| 4440 | <informalexample> |
| 4441 | <programlisting> |
| 4442 | <![CDATA[ |
| 4443 | struct list_head *list; |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4444 | struct snd_rawmidi_substream *substream; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4445 | list_for_each(list, &rmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT].substreams) { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4446 | substream = list_entry(list, struct snd_rawmidi_substream, list); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4447 | sprintf(substream->name, "My MIDI Port %d", substream->number + 1); |
| 4448 | } |
| 4449 | /* same for SNDRV_RAWMIDI_STREAM_INPUT */ |
| 4450 | ]]> |
| 4451 | </programlisting> |
| 4452 | </informalexample> |
| 4453 | </para> |
| 4454 | </section> |
| 4455 | |
| 4456 | <section id="rawmidi-interface-callbacks"> |
| 4457 | <title>Callbacks</title> |
| 4458 | |
| 4459 | <para> |
| 4460 | In all callbacks, the private data that you've set for the |
| 4461 | rawmidi device can be accessed as |
| 4462 | substream->rmidi->private_data. |
| 4463 | <!-- <code> isn't available before DocBook 4.3 --> |
| 4464 | </para> |
| 4465 | |
| 4466 | <para> |
| 4467 | If there is more than one port, your callbacks can determine the |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4468 | port index from the struct snd_rawmidi_substream data passed to each |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4469 | callback: |
| 4470 | <informalexample> |
| 4471 | <programlisting> |
| 4472 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4473 | struct snd_rawmidi_substream *substream; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4474 | int index = substream->number; |
| 4475 | ]]> |
| 4476 | </programlisting> |
| 4477 | </informalexample> |
| 4478 | </para> |
| 4479 | |
| 4480 | <section id="rawmidi-interface-op-open"> |
| 4481 | <title><function>open</function> callback</title> |
| 4482 | |
| 4483 | <informalexample> |
| 4484 | <programlisting> |
| 4485 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4486 | static int snd_xxx_open(struct snd_rawmidi_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4487 | ]]> |
| 4488 | </programlisting> |
| 4489 | </informalexample> |
| 4490 | |
| 4491 | <para> |
| 4492 | This is called when a substream is opened. |
| 4493 | You can initialize the hardware here, but you should not yet |
| 4494 | start transmitting/receiving data. |
| 4495 | </para> |
| 4496 | </section> |
| 4497 | |
| 4498 | <section id="rawmidi-interface-op-close"> |
| 4499 | <title><function>close</function> callback</title> |
| 4500 | |
| 4501 | <informalexample> |
| 4502 | <programlisting> |
| 4503 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4504 | static int snd_xxx_close(struct snd_rawmidi_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4505 | ]]> |
| 4506 | </programlisting> |
| 4507 | </informalexample> |
| 4508 | |
| 4509 | <para> |
| 4510 | Guess what. |
| 4511 | </para> |
| 4512 | |
| 4513 | <para> |
| 4514 | The <function>open</function> and <function>close</function> |
| 4515 | callbacks of a rawmidi device are serialized with a mutex, |
| 4516 | and can sleep. |
| 4517 | </para> |
| 4518 | </section> |
| 4519 | |
| 4520 | <section id="rawmidi-interface-op-trigger-out"> |
| 4521 | <title><function>trigger</function> callback for output |
| 4522 | substreams</title> |
| 4523 | |
| 4524 | <informalexample> |
| 4525 | <programlisting> |
| 4526 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4527 | 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] | 4528 | ]]> |
| 4529 | </programlisting> |
| 4530 | </informalexample> |
| 4531 | |
| 4532 | <para> |
| 4533 | This is called with a nonzero <parameter>up</parameter> |
| 4534 | parameter when there is some data in the substream buffer that |
| 4535 | must be transmitted. |
| 4536 | </para> |
| 4537 | |
| 4538 | <para> |
| 4539 | To read data from the buffer, call |
| 4540 | <function>snd_rawmidi_transmit_peek</function>. It will |
| 4541 | return the number of bytes that have been read; this will be |
| 4542 | less than the number of bytes requested when there is no more |
| 4543 | data in the buffer. |
| 4544 | After the data has been transmitted successfully, call |
| 4545 | <function>snd_rawmidi_transmit_ack</function> to remove the |
| 4546 | data from the substream buffer: |
| 4547 | <informalexample> |
| 4548 | <programlisting> |
| 4549 | <![CDATA[ |
| 4550 | unsigned char data; |
| 4551 | while (snd_rawmidi_transmit_peek(substream, &data, 1) == 1) { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4552 | if (snd_mychip_try_to_transmit(data)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4553 | snd_rawmidi_transmit_ack(substream, 1); |
| 4554 | else |
| 4555 | break; /* hardware FIFO full */ |
| 4556 | } |
| 4557 | ]]> |
| 4558 | </programlisting> |
| 4559 | </informalexample> |
| 4560 | </para> |
| 4561 | |
| 4562 | <para> |
| 4563 | If you know beforehand that the hardware will accept data, you |
| 4564 | can use the <function>snd_rawmidi_transmit</function> function |
| 4565 | which reads some data and removes it from the buffer at once: |
| 4566 | <informalexample> |
| 4567 | <programlisting> |
| 4568 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4569 | while (snd_mychip_transmit_possible()) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4570 | unsigned char data; |
| 4571 | if (snd_rawmidi_transmit(substream, &data, 1) != 1) |
| 4572 | break; /* no more data */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4573 | snd_mychip_transmit(data); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4574 | } |
| 4575 | ]]> |
| 4576 | </programlisting> |
| 4577 | </informalexample> |
| 4578 | </para> |
| 4579 | |
| 4580 | <para> |
| 4581 | If you know beforehand how many bytes you can accept, you can |
| 4582 | use a buffer size greater than one with the |
| 4583 | <function>snd_rawmidi_transmit*</function> functions. |
| 4584 | </para> |
| 4585 | |
| 4586 | <para> |
| 4587 | The <function>trigger</function> callback must not sleep. If |
| 4588 | the hardware FIFO is full before the substream buffer has been |
| 4589 | emptied, you have to continue transmitting data later, either |
| 4590 | in an interrupt handler, or with a timer if the hardware |
| 4591 | doesn't have a MIDI transmit interrupt. |
| 4592 | </para> |
| 4593 | |
| 4594 | <para> |
| 4595 | The <function>trigger</function> callback is called with a |
| 4596 | zero <parameter>up</parameter> parameter when the transmission |
| 4597 | of data should be aborted. |
| 4598 | </para> |
| 4599 | </section> |
| 4600 | |
| 4601 | <section id="rawmidi-interface-op-trigger-in"> |
| 4602 | <title><function>trigger</function> callback for input |
| 4603 | substreams</title> |
| 4604 | |
| 4605 | <informalexample> |
| 4606 | <programlisting> |
| 4607 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4608 | 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] | 4609 | ]]> |
| 4610 | </programlisting> |
| 4611 | </informalexample> |
| 4612 | |
| 4613 | <para> |
| 4614 | This is called with a nonzero <parameter>up</parameter> |
| 4615 | parameter to enable receiving data, or with a zero |
| 4616 | <parameter>up</parameter> parameter do disable receiving data. |
| 4617 | </para> |
| 4618 | |
| 4619 | <para> |
| 4620 | The <function>trigger</function> callback must not sleep; the |
| 4621 | actual reading of data from the device is usually done in an |
| 4622 | interrupt handler. |
| 4623 | </para> |
| 4624 | |
| 4625 | <para> |
| 4626 | When data reception is enabled, your interrupt handler should |
| 4627 | call <function>snd_rawmidi_receive</function> for all received |
| 4628 | data: |
| 4629 | <informalexample> |
| 4630 | <programlisting> |
| 4631 | <![CDATA[ |
| 4632 | void snd_mychip_midi_interrupt(...) |
| 4633 | { |
| 4634 | while (mychip_midi_available()) { |
| 4635 | unsigned char data; |
| 4636 | data = mychip_midi_read(); |
| 4637 | snd_rawmidi_receive(substream, &data, 1); |
| 4638 | } |
| 4639 | } |
| 4640 | ]]> |
| 4641 | </programlisting> |
| 4642 | </informalexample> |
| 4643 | </para> |
| 4644 | </section> |
| 4645 | |
| 4646 | <section id="rawmidi-interface-op-drain"> |
| 4647 | <title><function>drain</function> callback</title> |
| 4648 | |
| 4649 | <informalexample> |
| 4650 | <programlisting> |
| 4651 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4652 | static void snd_xxx_drain(struct snd_rawmidi_substream *substream); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4653 | ]]> |
| 4654 | </programlisting> |
| 4655 | </informalexample> |
| 4656 | |
| 4657 | <para> |
| 4658 | This is only used with output substreams. This function should wait |
| 4659 | until all data read from the substream buffer has been transmitted. |
| 4660 | This ensures that the device can be closed and the driver unloaded |
| 4661 | without losing data. |
| 4662 | </para> |
| 4663 | |
| 4664 | <para> |
| 4665 | This callback is optional. If you do not set |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4666 | <structfield>drain</structfield> in the struct snd_rawmidi_ops |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4667 | structure, ALSA will simply wait for 50 milliseconds |
| 4668 | instead. |
| 4669 | </para> |
| 4670 | </section> |
| 4671 | </section> |
| 4672 | |
| 4673 | </chapter> |
| 4674 | |
| 4675 | |
| 4676 | <!-- ****************************************************** --> |
| 4677 | <!-- Miscellaneous Devices --> |
| 4678 | <!-- ****************************************************** --> |
| 4679 | <chapter id="misc-devices"> |
| 4680 | <title>Miscellaneous Devices</title> |
| 4681 | |
| 4682 | <section id="misc-devices-opl3"> |
| 4683 | <title>FM OPL3</title> |
| 4684 | <para> |
| 4685 | The FM OPL3 is still used on many chips (mainly for backward |
| 4686 | compatibility). ALSA has a nice OPL3 FM control layer, too. The |
| 4687 | OPL3 API is defined in |
| 4688 | <filename><sound/opl3.h></filename>. |
| 4689 | </para> |
| 4690 | |
| 4691 | <para> |
| 4692 | FM registers can be directly accessed through direct-FM API, |
| 4693 | defined in <filename><sound/asound_fm.h></filename>. In |
| 4694 | ALSA native mode, FM registers are accessed through |
| 4695 | Hardware-Dependant Device direct-FM extension API, whereas in |
| 4696 | OSS compatible mode, FM registers can be accessed with OSS |
| 4697 | direct-FM compatible API on <filename>/dev/dmfmX</filename> device. |
| 4698 | </para> |
| 4699 | |
| 4700 | <para> |
| 4701 | For creating the OPL3 component, you have two functions to |
| 4702 | call. The first one is a constructor for <type>opl3_t</type> |
| 4703 | instance. |
| 4704 | |
| 4705 | <informalexample> |
| 4706 | <programlisting> |
| 4707 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4708 | struct snd_opl3 *opl3; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4709 | snd_opl3_create(card, lport, rport, OPL3_HW_OPL3_XXX, |
| 4710 | integrated, &opl3); |
| 4711 | ]]> |
| 4712 | </programlisting> |
| 4713 | </informalexample> |
| 4714 | </para> |
| 4715 | |
| 4716 | <para> |
| 4717 | The first argument is the card pointer, the second one is the |
| 4718 | left port address, and the third is the right port address. In |
| 4719 | most cases, the right port is placed at the left port + 2. |
| 4720 | </para> |
| 4721 | |
| 4722 | <para> |
| 4723 | The fourth argument is the hardware type. |
| 4724 | </para> |
| 4725 | |
| 4726 | <para> |
| 4727 | When the left and right ports have been already allocated by |
| 4728 | the card driver, pass non-zero to the fifth argument |
| 4729 | (<parameter>integrated</parameter>). Otherwise, opl3 module will |
| 4730 | allocate the specified ports by itself. |
| 4731 | </para> |
| 4732 | |
| 4733 | <para> |
| 4734 | When the accessing to the hardware requires special method |
| 4735 | instead of the standard I/O access, you can create opl3 instance |
| 4736 | separately with <function>snd_opl3_new()</function>. |
| 4737 | |
| 4738 | <informalexample> |
| 4739 | <programlisting> |
| 4740 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4741 | struct snd_opl3 *opl3; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4742 | snd_opl3_new(card, OPL3_HW_OPL3_XXX, &opl3); |
| 4743 | ]]> |
| 4744 | </programlisting> |
| 4745 | </informalexample> |
| 4746 | </para> |
| 4747 | |
| 4748 | <para> |
| 4749 | Then set <structfield>command</structfield>, |
| 4750 | <structfield>private_data</structfield> and |
| 4751 | <structfield>private_free</structfield> for the private |
| 4752 | access function, the private data and the destructor. |
| 4753 | The l_port and r_port are not necessarily set. Only the |
| 4754 | command must be set properly. You can retrieve the data |
| 4755 | from opl3->private_data field. |
| 4756 | </para> |
| 4757 | |
| 4758 | <para> |
| 4759 | After creating the opl3 instance via <function>snd_opl3_new()</function>, |
| 4760 | call <function>snd_opl3_init()</function> to initialize the chip to the |
| 4761 | proper state. Note that <function>snd_opl3_create()</function> always |
| 4762 | calls it internally. |
| 4763 | </para> |
| 4764 | |
| 4765 | <para> |
| 4766 | If the opl3 instance is created successfully, then create a |
| 4767 | hwdep device for this opl3. |
| 4768 | |
| 4769 | <informalexample> |
| 4770 | <programlisting> |
| 4771 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4772 | struct snd_hwdep *opl3hwdep; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4773 | snd_opl3_hwdep_new(opl3, 0, 1, &opl3hwdep); |
| 4774 | ]]> |
| 4775 | </programlisting> |
| 4776 | </informalexample> |
| 4777 | </para> |
| 4778 | |
| 4779 | <para> |
| 4780 | The first argument is the <type>opl3_t</type> instance you |
| 4781 | created, and the second is the index number, usually 0. |
| 4782 | </para> |
| 4783 | |
| 4784 | <para> |
| 4785 | The third argument is the index-offset for the sequencer |
| 4786 | client assigned to the OPL3 port. When there is an MPU401-UART, |
| 4787 | give 1 for here (UART always takes 0). |
| 4788 | </para> |
| 4789 | </section> |
| 4790 | |
| 4791 | <section id="misc-devices-hardware-dependent"> |
| 4792 | <title>Hardware-Dependent Devices</title> |
| 4793 | <para> |
| 4794 | Some chips need the access from the user-space for special |
| 4795 | controls or for loading the micro code. In such a case, you can |
| 4796 | create a hwdep (hardware-dependent) device. The hwdep API is |
| 4797 | defined in <filename><sound/hwdep.h></filename>. You can |
| 4798 | find examples in opl3 driver or |
| 4799 | <filename>isa/sb/sb16_csp.c</filename>. |
| 4800 | </para> |
| 4801 | |
| 4802 | <para> |
| 4803 | Creation of the <type>hwdep</type> instance is done via |
| 4804 | <function>snd_hwdep_new()</function>. |
| 4805 | |
| 4806 | <informalexample> |
| 4807 | <programlisting> |
| 4808 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4809 | struct snd_hwdep *hw; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4810 | snd_hwdep_new(card, "My HWDEP", 0, &hw); |
| 4811 | ]]> |
| 4812 | </programlisting> |
| 4813 | </informalexample> |
| 4814 | |
| 4815 | where the third argument is the index number. |
| 4816 | </para> |
| 4817 | |
| 4818 | <para> |
| 4819 | You can then pass any pointer value to the |
| 4820 | <parameter>private_data</parameter>. |
| 4821 | If you assign a private data, you should define the |
| 4822 | destructor, too. The destructor function is set to |
| 4823 | <structfield>private_free</structfield> field. |
| 4824 | |
| 4825 | <informalexample> |
| 4826 | <programlisting> |
| 4827 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4828 | struct mydata *p = kmalloc(sizeof(*p), GFP_KERNEL); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4829 | hw->private_data = p; |
| 4830 | hw->private_free = mydata_free; |
| 4831 | ]]> |
| 4832 | </programlisting> |
| 4833 | </informalexample> |
| 4834 | |
| 4835 | and the implementation of destructor would be: |
| 4836 | |
| 4837 | <informalexample> |
| 4838 | <programlisting> |
| 4839 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4840 | static void mydata_free(struct snd_hwdep *hw) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4841 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 4842 | struct mydata *p = hw->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4843 | kfree(p); |
| 4844 | } |
| 4845 | ]]> |
| 4846 | </programlisting> |
| 4847 | </informalexample> |
| 4848 | </para> |
| 4849 | |
| 4850 | <para> |
| 4851 | The arbitrary file operations can be defined for this |
| 4852 | instance. The file operators are defined in |
| 4853 | <parameter>ops</parameter> table. For example, assume that |
| 4854 | this chip needs an ioctl. |
| 4855 | |
| 4856 | <informalexample> |
| 4857 | <programlisting> |
| 4858 | <![CDATA[ |
| 4859 | hw->ops.open = mydata_open; |
| 4860 | hw->ops.ioctl = mydata_ioctl; |
| 4861 | hw->ops.release = mydata_release; |
| 4862 | ]]> |
| 4863 | </programlisting> |
| 4864 | </informalexample> |
| 4865 | |
| 4866 | And implement the callback functions as you like. |
| 4867 | </para> |
| 4868 | </section> |
| 4869 | |
| 4870 | <section id="misc-devices-IEC958"> |
| 4871 | <title>IEC958 (S/PDIF)</title> |
| 4872 | <para> |
| 4873 | Usually the controls for IEC958 devices are implemented via |
| 4874 | control interface. There is a macro to compose a name string for |
| 4875 | IEC958 controls, <function>SNDRV_CTL_NAME_IEC958()</function> |
| 4876 | defined in <filename><include/asound.h></filename>. |
| 4877 | </para> |
| 4878 | |
| 4879 | <para> |
| 4880 | There are some standard controls for IEC958 status bits. These |
| 4881 | controls use the type <type>SNDRV_CTL_ELEM_TYPE_IEC958</type>, |
| 4882 | and the size of element is fixed as 4 bytes array |
| 4883 | (value.iec958.status[x]). For <structfield>info</structfield> |
| 4884 | callback, you don't specify |
| 4885 | the value field for this type (the count field must be set, |
| 4886 | though). |
| 4887 | </para> |
| 4888 | |
| 4889 | <para> |
| 4890 | <quote>IEC958 Playback Con Mask</quote> is used to return the |
| 4891 | bit-mask for the IEC958 status bits of consumer mode. Similarly, |
| 4892 | <quote>IEC958 Playback Pro Mask</quote> returns the bitmask for |
| 4893 | professional mode. They are read-only controls, and are defined |
| 4894 | as MIXER controls (iface = |
| 4895 | <constant>SNDRV_CTL_ELEM_IFACE_MIXER</constant>). |
| 4896 | </para> |
| 4897 | |
| 4898 | <para> |
| 4899 | Meanwhile, <quote>IEC958 Playback Default</quote> control is |
| 4900 | defined for getting and setting the current default IEC958 |
| 4901 | bits. Note that this one is usually defined as a PCM control |
| 4902 | (iface = <constant>SNDRV_CTL_ELEM_IFACE_PCM</constant>), |
| 4903 | although in some places it's defined as a MIXER control. |
| 4904 | </para> |
| 4905 | |
| 4906 | <para> |
| 4907 | In addition, you can define the control switches to |
| 4908 | enable/disable or to set the raw bit mode. The implementation |
| 4909 | will depend on the chip, but the control should be named as |
| 4910 | <quote>IEC958 xxx</quote>, preferably using |
| 4911 | <function>SNDRV_CTL_NAME_IEC958()</function> macro. |
| 4912 | </para> |
| 4913 | |
| 4914 | <para> |
| 4915 | You can find several cases, for example, |
| 4916 | <filename>pci/emu10k1</filename>, |
| 4917 | <filename>pci/ice1712</filename>, or |
| 4918 | <filename>pci/cmipci.c</filename>. |
| 4919 | </para> |
| 4920 | </section> |
| 4921 | |
| 4922 | </chapter> |
| 4923 | |
| 4924 | |
| 4925 | <!-- ****************************************************** --> |
| 4926 | <!-- Buffer and Memory Management --> |
| 4927 | <!-- ****************************************************** --> |
| 4928 | <chapter id="buffer-and-memory"> |
| 4929 | <title>Buffer and Memory Management</title> |
| 4930 | |
| 4931 | <section id="buffer-and-memory-buffer-types"> |
| 4932 | <title>Buffer Types</title> |
| 4933 | <para> |
| 4934 | ALSA provides several different buffer allocation functions |
| 4935 | depending on the bus and the architecture. All these have a |
| 4936 | consistent API. The allocation of physically-contiguous pages is |
| 4937 | done via |
| 4938 | <function>snd_malloc_xxx_pages()</function> function, where xxx |
| 4939 | is the bus type. |
| 4940 | </para> |
| 4941 | |
| 4942 | <para> |
| 4943 | The allocation of pages with fallback is |
| 4944 | <function>snd_malloc_xxx_pages_fallback()</function>. This |
| 4945 | function tries to allocate the specified pages but if the pages |
| 4946 | are not available, it tries to reduce the page sizes until the |
| 4947 | enough space is found. |
| 4948 | </para> |
| 4949 | |
| 4950 | <para> |
| 4951 | For releasing the space, call |
| 4952 | <function>snd_free_xxx_pages()</function> function. |
| 4953 | </para> |
| 4954 | |
| 4955 | <para> |
| 4956 | Usually, ALSA drivers try to allocate and reserve |
| 4957 | a large contiguous physical space |
| 4958 | at the time the module is loaded for the later use. |
| 4959 | This is called <quote>pre-allocation</quote>. |
| 4960 | As already written, you can call the following function at the |
| 4961 | construction of pcm instance (in the case of PCI bus). |
| 4962 | |
| 4963 | <informalexample> |
| 4964 | <programlisting> |
| 4965 | <![CDATA[ |
| 4966 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, |
| 4967 | snd_dma_pci_data(pci), size, max); |
| 4968 | ]]> |
| 4969 | </programlisting> |
| 4970 | </informalexample> |
| 4971 | |
| 4972 | where <parameter>size</parameter> is the byte size to be |
| 4973 | pre-allocated and the <parameter>max</parameter> is the maximal |
| 4974 | size to be changed via <filename>prealloc</filename> proc file. |
| 4975 | The allocator will try to get as large area as possible |
| 4976 | within the given size. |
| 4977 | </para> |
| 4978 | |
| 4979 | <para> |
| 4980 | The second argument (type) and the third argument (device pointer) |
| 4981 | are dependent on the bus. |
| 4982 | In the case of ISA bus, pass <function>snd_dma_isa_data()</function> |
| 4983 | as the third argument with <constant>SNDRV_DMA_TYPE_DEV</constant> type. |
| 4984 | For the continuous buffer unrelated to the bus can be pre-allocated |
| 4985 | with <constant>SNDRV_DMA_TYPE_CONTINUOUS</constant> type and the |
| 4986 | <function>snd_dma_continuous_data(GFP_KERNEL)</function> device pointer, |
| 4987 | whereh <constant>GFP_KERNEL</constant> is the kernel allocation flag to |
| 4988 | use. For the SBUS, <constant>SNDRV_DMA_TYPE_SBUS</constant> and |
| 4989 | <function>snd_dma_sbus_data(sbus_dev)</function> are used instead. |
| 4990 | For the PCI scatter-gather buffers, use |
| 4991 | <constant>SNDRV_DMA_TYPE_DEV_SG</constant> with |
| 4992 | <function>snd_dma_pci_data(pci)</function> |
| 4993 | (see the section |
| 4994 | <link linkend="buffer-and-memory-non-contiguous"><citetitle>Non-Contiguous Buffers |
| 4995 | </citetitle></link>). |
| 4996 | </para> |
| 4997 | |
| 4998 | <para> |
| 4999 | Once when the buffer is pre-allocated, you can use the |
| 5000 | allocator in the <structfield>hw_params</structfield> callback |
| 5001 | |
| 5002 | <informalexample> |
| 5003 | <programlisting> |
| 5004 | <![CDATA[ |
| 5005 | snd_pcm_lib_malloc_pages(substream, size); |
| 5006 | ]]> |
| 5007 | </programlisting> |
| 5008 | </informalexample> |
| 5009 | |
| 5010 | Note that you have to pre-allocate to use this function. |
| 5011 | </para> |
| 5012 | </section> |
| 5013 | |
| 5014 | <section id="buffer-and-memory-external-hardware"> |
| 5015 | <title>External Hardware Buffers</title> |
| 5016 | <para> |
| 5017 | Some chips have their own hardware buffers and the DMA |
| 5018 | transfer from the host memory is not available. In such a case, |
| 5019 | you need to either 1) copy/set the audio data directly to the |
| 5020 | external hardware buffer, or 2) make an intermediate buffer and |
| 5021 | copy/set the data from it to the external hardware buffer in |
| 5022 | interrupts (or in tasklets, preferably). |
| 5023 | </para> |
| 5024 | |
| 5025 | <para> |
| 5026 | The first case works fine if the external hardware buffer is enough |
| 5027 | large. This method doesn't need any extra buffers and thus is |
| 5028 | more effective. You need to define the |
| 5029 | <structfield>copy</structfield> and |
| 5030 | <structfield>silence</structfield> callbacks for |
| 5031 | the data transfer. However, there is a drawback: it cannot |
| 5032 | be mmapped. The examples are GUS's GF1 PCM or emu8000's |
| 5033 | wavetable PCM. |
| 5034 | </para> |
| 5035 | |
| 5036 | <para> |
| 5037 | The second case allows the mmap of the buffer, although you have |
| 5038 | to handle an interrupt or a tasklet for transferring the data |
| 5039 | from the intermediate buffer to the hardware buffer. You can find an |
| 5040 | example in vxpocket driver. |
| 5041 | </para> |
| 5042 | |
| 5043 | <para> |
| 5044 | Another case is that the chip uses a PCI memory-map |
| 5045 | region for the buffer instead of the host memory. In this case, |
| 5046 | mmap is available only on certain architectures like intel. In |
| 5047 | non-mmap mode, the data cannot be transferred as the normal |
| 5048 | way. Thus you need to define <structfield>copy</structfield> and |
| 5049 | <structfield>silence</structfield> callbacks as well |
| 5050 | as in the cases above. The examples are found in |
| 5051 | <filename>rme32.c</filename> and <filename>rme96.c</filename>. |
| 5052 | </para> |
| 5053 | |
| 5054 | <para> |
| 5055 | The implementation of <structfield>copy</structfield> and |
| 5056 | <structfield>silence</structfield> callbacks depends upon |
| 5057 | whether the hardware supports interleaved or non-interleaved |
| 5058 | samples. The <structfield>copy</structfield> callback is |
| 5059 | defined like below, a bit |
| 5060 | differently depending whether the direction is playback or |
| 5061 | capture: |
| 5062 | |
| 5063 | <informalexample> |
| 5064 | <programlisting> |
| 5065 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5066 | static int playback_copy(struct snd_pcm_substream *substream, int channel, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5067 | snd_pcm_uframes_t pos, void *src, snd_pcm_uframes_t count); |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5068 | static int capture_copy(struct snd_pcm_substream *substream, int channel, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5069 | snd_pcm_uframes_t pos, void *dst, snd_pcm_uframes_t count); |
| 5070 | ]]> |
| 5071 | </programlisting> |
| 5072 | </informalexample> |
| 5073 | </para> |
| 5074 | |
| 5075 | <para> |
| 5076 | In the case of interleaved samples, the second argument |
| 5077 | (<parameter>channel</parameter>) is not used. The third argument |
| 5078 | (<parameter>pos</parameter>) points the |
| 5079 | current position offset in frames. |
| 5080 | </para> |
| 5081 | |
| 5082 | <para> |
| 5083 | The meaning of the fourth argument is different between |
| 5084 | playback and capture. For playback, it holds the source data |
| 5085 | pointer, and for capture, it's the destination data pointer. |
| 5086 | </para> |
| 5087 | |
| 5088 | <para> |
| 5089 | The last argument is the number of frames to be copied. |
| 5090 | </para> |
| 5091 | |
| 5092 | <para> |
| 5093 | What you have to do in this callback is again different |
| 5094 | between playback and capture directions. In the case of |
| 5095 | playback, you do: copy the given amount of data |
| 5096 | (<parameter>count</parameter>) at the specified pointer |
| 5097 | (<parameter>src</parameter>) to the specified offset |
| 5098 | (<parameter>pos</parameter>) on the hardware buffer. When |
| 5099 | coded like memcpy-like way, the copy would be like: |
| 5100 | |
| 5101 | <informalexample> |
| 5102 | <programlisting> |
| 5103 | <![CDATA[ |
| 5104 | my_memcpy(my_buffer + frames_to_bytes(runtime, pos), src, |
| 5105 | frames_to_bytes(runtime, count)); |
| 5106 | ]]> |
| 5107 | </programlisting> |
| 5108 | </informalexample> |
| 5109 | </para> |
| 5110 | |
| 5111 | <para> |
| 5112 | For the capture direction, you do: copy the given amount of |
| 5113 | data (<parameter>count</parameter>) at the specified offset |
| 5114 | (<parameter>pos</parameter>) on the hardware buffer to the |
| 5115 | specified pointer (<parameter>dst</parameter>). |
| 5116 | |
| 5117 | <informalexample> |
| 5118 | <programlisting> |
| 5119 | <![CDATA[ |
| 5120 | my_memcpy(dst, my_buffer + frames_to_bytes(runtime, pos), |
| 5121 | frames_to_bytes(runtime, count)); |
| 5122 | ]]> |
| 5123 | </programlisting> |
| 5124 | </informalexample> |
| 5125 | |
| 5126 | Note that both of the position and the data amount are given |
| 5127 | in frames. |
| 5128 | </para> |
| 5129 | |
| 5130 | <para> |
| 5131 | In the case of non-interleaved samples, the implementation |
| 5132 | will be a bit more complicated. |
| 5133 | </para> |
| 5134 | |
| 5135 | <para> |
| 5136 | You need to check the channel argument, and if it's -1, copy |
| 5137 | the whole channels. Otherwise, you have to copy only the |
| 5138 | specified channel. Please check |
| 5139 | <filename>isa/gus/gus_pcm.c</filename> as an example. |
| 5140 | </para> |
| 5141 | |
| 5142 | <para> |
| 5143 | The <structfield>silence</structfield> callback is also |
| 5144 | implemented in a similar way. |
| 5145 | |
| 5146 | <informalexample> |
| 5147 | <programlisting> |
| 5148 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5149 | static int silence(struct snd_pcm_substream *substream, int channel, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5150 | snd_pcm_uframes_t pos, snd_pcm_uframes_t count); |
| 5151 | ]]> |
| 5152 | </programlisting> |
| 5153 | </informalexample> |
| 5154 | </para> |
| 5155 | |
| 5156 | <para> |
| 5157 | The meanings of arguments are identical with the |
| 5158 | <structfield>copy</structfield> |
| 5159 | callback, although there is no <parameter>src/dst</parameter> |
| 5160 | argument. In the case of interleaved samples, the channel |
| 5161 | argument has no meaning, as well as on |
| 5162 | <structfield>copy</structfield> callback. |
| 5163 | </para> |
| 5164 | |
| 5165 | <para> |
| 5166 | The role of <structfield>silence</structfield> callback is to |
| 5167 | set the given amount |
| 5168 | (<parameter>count</parameter>) of silence data at the |
| 5169 | specified offset (<parameter>pos</parameter>) on the hardware |
| 5170 | buffer. Suppose that the data format is signed (that is, the |
| 5171 | silent-data is 0), and the implementation using a memset-like |
| 5172 | function would be like: |
| 5173 | |
| 5174 | <informalexample> |
| 5175 | <programlisting> |
| 5176 | <![CDATA[ |
| 5177 | my_memcpy(my_buffer + frames_to_bytes(runtime, pos), 0, |
| 5178 | frames_to_bytes(runtime, count)); |
| 5179 | ]]> |
| 5180 | </programlisting> |
| 5181 | </informalexample> |
| 5182 | </para> |
| 5183 | |
| 5184 | <para> |
| 5185 | In the case of non-interleaved samples, again, the |
| 5186 | implementation becomes a bit more complicated. See, for example, |
| 5187 | <filename>isa/gus/gus_pcm.c</filename>. |
| 5188 | </para> |
| 5189 | </section> |
| 5190 | |
| 5191 | <section id="buffer-and-memory-non-contiguous"> |
| 5192 | <title>Non-Contiguous Buffers</title> |
| 5193 | <para> |
| 5194 | If your hardware supports the page table like emu10k1 or the |
| 5195 | buffer descriptors like via82xx, you can use the scatter-gather |
| 5196 | (SG) DMA. ALSA provides an interface for handling SG-buffers. |
| 5197 | The API is provided in <filename><sound/pcm.h></filename>. |
| 5198 | </para> |
| 5199 | |
| 5200 | <para> |
| 5201 | For creating the SG-buffer handler, call |
| 5202 | <function>snd_pcm_lib_preallocate_pages()</function> or |
| 5203 | <function>snd_pcm_lib_preallocate_pages_for_all()</function> |
| 5204 | with <constant>SNDRV_DMA_TYPE_DEV_SG</constant> |
| 5205 | in the PCM constructor like other PCI pre-allocator. |
| 5206 | You need to pass the <function>snd_dma_pci_data(pci)</function>, |
| 5207 | where pci is the struct <structname>pci_dev</structname> pointer |
| 5208 | of the chip as well. |
Giuliano Pochini | 44275f1 | 2006-01-27 12:02:05 +0100 | [diff] [blame] | 5209 | The <type>struct snd_sg_buf</type> instance is created as |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5210 | substream->dma_private. You can cast |
| 5211 | the pointer like: |
| 5212 | |
| 5213 | <informalexample> |
| 5214 | <programlisting> |
| 5215 | <![CDATA[ |
Giuliano Pochini | 44275f1 | 2006-01-27 12:02:05 +0100 | [diff] [blame] | 5216 | struct snd_sg_buf *sgbuf = (struct snd_sg_buf *)substream->dma_private; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5217 | ]]> |
| 5218 | </programlisting> |
| 5219 | </informalexample> |
| 5220 | </para> |
| 5221 | |
| 5222 | <para> |
| 5223 | Then call <function>snd_pcm_lib_malloc_pages()</function> |
| 5224 | in <structfield>hw_params</structfield> callback |
| 5225 | as well as in the case of normal PCI buffer. |
| 5226 | The SG-buffer handler will allocate the non-contiguous kernel |
| 5227 | pages of the given size and map them onto the virtually contiguous |
| 5228 | memory. The virtual pointer is addressed in runtime->dma_area. |
| 5229 | The physical address (runtime->dma_addr) is set to zero, |
| 5230 | because the buffer is physically non-contigous. |
| 5231 | The physical address table is set up in sgbuf->table. |
| 5232 | You can get the physical address at a certain offset via |
| 5233 | <function>snd_pcm_sgbuf_get_addr()</function>. |
| 5234 | </para> |
| 5235 | |
| 5236 | <para> |
| 5237 | When a SG-handler is used, you need to set |
| 5238 | <function>snd_pcm_sgbuf_ops_page</function> as |
| 5239 | the <structfield>page</structfield> callback. |
| 5240 | (See <link linkend="pcm-interface-operators-page-callback"> |
| 5241 | <citetitle>page callback section</citetitle></link>.) |
| 5242 | </para> |
| 5243 | |
| 5244 | <para> |
| 5245 | For releasing the data, call |
| 5246 | <function>snd_pcm_lib_free_pages()</function> in the |
| 5247 | <structfield>hw_free</structfield> callback as usual. |
| 5248 | </para> |
| 5249 | </section> |
| 5250 | |
| 5251 | <section id="buffer-and-memory-vmalloced"> |
| 5252 | <title>Vmalloc'ed Buffers</title> |
| 5253 | <para> |
| 5254 | It's possible to use a buffer allocated via |
| 5255 | <function>vmalloc</function>, for example, for an intermediate |
| 5256 | buffer. Since the allocated pages are not contiguous, you need |
| 5257 | to set the <structfield>page</structfield> callback to obtain |
| 5258 | the physical address at every offset. |
| 5259 | </para> |
| 5260 | |
| 5261 | <para> |
| 5262 | The implementation of <structfield>page</structfield> callback |
| 5263 | would be like this: |
| 5264 | |
| 5265 | <informalexample> |
| 5266 | <programlisting> |
| 5267 | <![CDATA[ |
| 5268 | #include <linux/vmalloc.h> |
| 5269 | |
| 5270 | /* get the physical page pointer on the given offset */ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5271 | static struct page *mychip_page(struct snd_pcm_substream *substream, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5272 | unsigned long offset) |
| 5273 | { |
| 5274 | void *pageptr = substream->runtime->dma_area + offset; |
| 5275 | return vmalloc_to_page(pageptr); |
| 5276 | } |
| 5277 | ]]> |
| 5278 | </programlisting> |
| 5279 | </informalexample> |
| 5280 | </para> |
| 5281 | </section> |
| 5282 | |
| 5283 | </chapter> |
| 5284 | |
| 5285 | |
| 5286 | <!-- ****************************************************** --> |
| 5287 | <!-- Proc Interface --> |
| 5288 | <!-- ****************************************************** --> |
| 5289 | <chapter id="proc-interface"> |
| 5290 | <title>Proc Interface</title> |
| 5291 | <para> |
| 5292 | ALSA provides an easy interface for procfs. The proc files are |
| 5293 | very useful for debugging. I recommend you set up proc files if |
| 5294 | you write a driver and want to get a running status or register |
| 5295 | dumps. The API is found in |
| 5296 | <filename><sound/info.h></filename>. |
| 5297 | </para> |
| 5298 | |
| 5299 | <para> |
| 5300 | For creating a proc file, call |
| 5301 | <function>snd_card_proc_new()</function>. |
| 5302 | |
| 5303 | <informalexample> |
| 5304 | <programlisting> |
| 5305 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5306 | struct snd_info_entry *entry; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5307 | int err = snd_card_proc_new(card, "my-file", &entry); |
| 5308 | ]]> |
| 5309 | </programlisting> |
| 5310 | </informalexample> |
| 5311 | |
| 5312 | where the second argument specifies the proc-file name to be |
| 5313 | created. The above example will create a file |
| 5314 | <filename>my-file</filename> under the card directory, |
| 5315 | e.g. <filename>/proc/asound/card0/my-file</filename>. |
| 5316 | </para> |
| 5317 | |
| 5318 | <para> |
| 5319 | Like other components, the proc entry created via |
| 5320 | <function>snd_card_proc_new()</function> will be registered and |
| 5321 | released automatically in the card registration and release |
| 5322 | functions. |
| 5323 | </para> |
| 5324 | |
| 5325 | <para> |
| 5326 | When the creation is successful, the function stores a new |
| 5327 | instance at the pointer given in the third argument. |
| 5328 | It is initialized as a text proc file for read only. For using |
| 5329 | this proc file as a read-only text file as it is, set the read |
| 5330 | callback with a private data via |
| 5331 | <function>snd_info_set_text_ops()</function>. |
| 5332 | |
| 5333 | <informalexample> |
| 5334 | <programlisting> |
| 5335 | <![CDATA[ |
| 5336 | snd_info_set_text_ops(entry, chip, read_size, my_proc_read); |
| 5337 | ]]> |
| 5338 | </programlisting> |
| 5339 | </informalexample> |
| 5340 | |
| 5341 | where the second argument (<parameter>chip</parameter>) is the |
| 5342 | private data to be used in the callbacks. The third parameter |
| 5343 | specifies the read buffer size and the fourth |
| 5344 | (<parameter>my_proc_read</parameter>) is the callback function, which |
| 5345 | is defined like |
| 5346 | |
| 5347 | <informalexample> |
| 5348 | <programlisting> |
| 5349 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5350 | static void my_proc_read(struct snd_info_entry *entry, |
| 5351 | struct snd_info_buffer *buffer); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5352 | ]]> |
| 5353 | </programlisting> |
| 5354 | </informalexample> |
| 5355 | |
| 5356 | </para> |
| 5357 | |
| 5358 | <para> |
| 5359 | In the read callback, use <function>snd_iprintf()</function> for |
| 5360 | output strings, which works just like normal |
| 5361 | <function>printf()</function>. For example, |
| 5362 | |
| 5363 | <informalexample> |
| 5364 | <programlisting> |
| 5365 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5366 | static void my_proc_read(struct snd_info_entry *entry, |
| 5367 | struct snd_info_buffer *buffer) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5368 | { |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5369 | struct my_chip *chip = entry->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5370 | |
| 5371 | snd_iprintf(buffer, "This is my chip!\n"); |
| 5372 | snd_iprintf(buffer, "Port = %ld\n", chip->port); |
| 5373 | } |
| 5374 | ]]> |
| 5375 | </programlisting> |
| 5376 | </informalexample> |
| 5377 | </para> |
| 5378 | |
| 5379 | <para> |
| 5380 | The file permission can be changed afterwards. As default, it's |
| 5381 | set as read only for all users. If you want to add the write |
| 5382 | permission to the user (root as default), set like below: |
| 5383 | |
| 5384 | <informalexample> |
| 5385 | <programlisting> |
| 5386 | <![CDATA[ |
| 5387 | entry->mode = S_IFREG | S_IRUGO | S_IWUSR; |
| 5388 | ]]> |
| 5389 | </programlisting> |
| 5390 | </informalexample> |
| 5391 | |
| 5392 | and set the write buffer size and the callback |
| 5393 | |
| 5394 | <informalexample> |
| 5395 | <programlisting> |
| 5396 | <![CDATA[ |
| 5397 | entry->c.text.write_size = 256; |
| 5398 | entry->c.text.write = my_proc_write; |
| 5399 | ]]> |
| 5400 | </programlisting> |
| 5401 | </informalexample> |
| 5402 | </para> |
| 5403 | |
| 5404 | <para> |
| 5405 | The buffer size for read is set to 1024 implicitly by |
| 5406 | <function>snd_info_set_text_ops()</function>. It should suffice |
| 5407 | in most cases (the size will be aligned to |
| 5408 | <constant>PAGE_SIZE</constant> anyway), but if you need to handle |
| 5409 | very large text files, you can set it explicitly, too. |
| 5410 | |
| 5411 | <informalexample> |
| 5412 | <programlisting> |
| 5413 | <![CDATA[ |
| 5414 | entry->c.text.read_size = 65536; |
| 5415 | ]]> |
| 5416 | </programlisting> |
| 5417 | </informalexample> |
| 5418 | </para> |
| 5419 | |
| 5420 | <para> |
| 5421 | For the write callback, you can use |
| 5422 | <function>snd_info_get_line()</function> to get a text line, and |
| 5423 | <function>snd_info_get_str()</function> to retrieve a string from |
| 5424 | the line. Some examples are found in |
| 5425 | <filename>core/oss/mixer_oss.c</filename>, core/oss/and |
| 5426 | <filename>pcm_oss.c</filename>. |
| 5427 | </para> |
| 5428 | |
| 5429 | <para> |
| 5430 | For a raw-data proc-file, set the attributes like the following: |
| 5431 | |
| 5432 | <informalexample> |
| 5433 | <programlisting> |
| 5434 | <![CDATA[ |
| 5435 | static struct snd_info_entry_ops my_file_io_ops = { |
| 5436 | .read = my_file_io_read, |
| 5437 | }; |
| 5438 | |
| 5439 | entry->content = SNDRV_INFO_CONTENT_DATA; |
| 5440 | entry->private_data = chip; |
| 5441 | entry->c.ops = &my_file_io_ops; |
| 5442 | entry->size = 4096; |
| 5443 | entry->mode = S_IFREG | S_IRUGO; |
| 5444 | ]]> |
| 5445 | </programlisting> |
| 5446 | </informalexample> |
| 5447 | </para> |
| 5448 | |
| 5449 | <para> |
| 5450 | The callback is much more complicated than the text-file |
| 5451 | version. You need to use a low-level i/o functions such as |
| 5452 | <function>copy_from/to_user()</function> to transfer the |
| 5453 | data. |
| 5454 | |
| 5455 | <informalexample> |
| 5456 | <programlisting> |
| 5457 | <![CDATA[ |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5458 | static long my_file_io_read(struct snd_info_entry *entry, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5459 | void *file_private_data, |
| 5460 | struct file *file, |
| 5461 | char *buf, |
| 5462 | unsigned long count, |
| 5463 | unsigned long pos) |
| 5464 | { |
| 5465 | long size = count; |
| 5466 | if (pos + size > local_max_size) |
| 5467 | size = local_max_size - pos; |
| 5468 | if (copy_to_user(buf, local_data + pos, size)) |
| 5469 | return -EFAULT; |
| 5470 | return size; |
| 5471 | } |
| 5472 | ]]> |
| 5473 | </programlisting> |
| 5474 | </informalexample> |
| 5475 | </para> |
| 5476 | |
| 5477 | </chapter> |
| 5478 | |
| 5479 | |
| 5480 | <!-- ****************************************************** --> |
| 5481 | <!-- Power Management --> |
| 5482 | <!-- ****************************************************** --> |
| 5483 | <chapter id="power-management"> |
| 5484 | <title>Power Management</title> |
| 5485 | <para> |
| 5486 | If the chip is supposed to work with with suspend/resume |
| 5487 | functions, you need to add the power-management codes to the |
| 5488 | driver. The additional codes for the power-management should be |
| 5489 | <function>ifdef</function>'ed with |
| 5490 | <constant>CONFIG_PM</constant>. |
| 5491 | </para> |
| 5492 | |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5493 | <para> |
| 5494 | If the driver supports the suspend/resume |
| 5495 | <emphasis>fully</emphasis>, that is, the device can be |
| 5496 | properly resumed to the status at the suspend is called, |
| 5497 | you can set <constant>SNDRV_PCM_INFO_RESUME</constant> flag |
| 5498 | to pcm info field. Usually, this is possible when the |
| 5499 | registers of ths chip can be safely saved and restored to the |
| 5500 | RAM. If this is set, the trigger callback is called with |
| 5501 | <constant>SNDRV_PCM_TRIGGER_RESUME</constant> after resume |
| 5502 | callback is finished. |
| 5503 | </para> |
| 5504 | |
| 5505 | <para> |
| 5506 | Even if the driver doesn't support PM fully but only the |
| 5507 | partial suspend/resume is possible, it's still worthy to |
| 5508 | implement suspend/resume callbacks. In such a case, applications |
| 5509 | would reset the status by calling |
| 5510 | <function>snd_pcm_prepare()</function> and restart the stream |
| 5511 | appropriately. Hence, you can define suspend/resume callbacks |
| 5512 | below but don't set <constant>SNDRV_PCM_INFO_RESUME</constant> |
| 5513 | info flag to the PCM. |
| 5514 | </para> |
| 5515 | |
| 5516 | <para> |
| 5517 | Note that the trigger with SUSPEND can be always called when |
| 5518 | <function>snd_pcm_suspend_all</function> is called, |
| 5519 | regardless of <constant>SNDRV_PCM_INFO_RESUME</constant> flag. |
| 5520 | The <constant>RESUME</constant> flag affects only the behavior |
| 5521 | of <function>snd_pcm_resume()</function>. |
| 5522 | (Thus, in theory, |
| 5523 | <constant>SNDRV_PCM_TRIGGER_RESUME</constant> isn't needed |
| 5524 | to be handled in the trigger callback when no |
| 5525 | <constant>SNDRV_PCM_INFO_RESUME</constant> flag is set. But, |
| 5526 | it's better to keep it for compatibility reason.) |
| 5527 | </para> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5528 | <para> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5529 | In the earlier version of ALSA drivers, a common |
| 5530 | power-management layer was provided, but it has been removed. |
| 5531 | The driver needs to define the suspend/resume hooks according to |
| 5532 | the bus the device is assigned. In the case of PCI driver, the |
| 5533 | callbacks look like below: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5534 | |
| 5535 | <informalexample> |
| 5536 | <programlisting> |
| 5537 | <![CDATA[ |
| 5538 | #ifdef CONFIG_PM |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5539 | 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] | 5540 | { |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5541 | .... /* do things for suspsend */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5542 | return 0; |
| 5543 | } |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5544 | static int snd_my_resume(struct pci_dev *pci) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5545 | { |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5546 | .... /* do things for suspsend */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5547 | return 0; |
| 5548 | } |
| 5549 | #endif |
| 5550 | ]]> |
| 5551 | </programlisting> |
| 5552 | </informalexample> |
| 5553 | </para> |
| 5554 | |
| 5555 | <para> |
| 5556 | The scheme of the real suspend job is as following. |
| 5557 | |
| 5558 | <orderedlist> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5559 | <listitem><para>Retrieve the card and the chip data.</para></listitem> |
| 5560 | <listitem><para>Call <function>snd_power_change_state()</function> with |
| 5561 | <constant>SNDRV_CTL_POWER_D3hot</constant> to change the |
| 5562 | power status.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5563 | <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] | 5564 | <listitem><para>If AC97 codecs are used, call |
| 5565 | <function>snd_ac97_resume()</function> for each codec.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5566 | <listitem><para>Save the register values if necessary.</para></listitem> |
| 5567 | <listitem><para>Stop the hardware if necessary.</para></listitem> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5568 | <listitem><para>Disable the PCI device by calling |
| 5569 | <function>pci_disable_device()</function>. Then, call |
| 5570 | <function>pci_save_state()</function> at last.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5571 | </orderedlist> |
| 5572 | </para> |
| 5573 | |
| 5574 | <para> |
| 5575 | A typical code would be like: |
| 5576 | |
| 5577 | <informalexample> |
| 5578 | <programlisting> |
| 5579 | <![CDATA[ |
Alexey Dobriyan | 32357988 | 2006-01-15 02:12:54 +0100 | [diff] [blame] | 5580 | static int mychip_suspend(struct pci_dev *pci, pm_message_t state) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5581 | { |
| 5582 | /* (1) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5583 | struct snd_card *card = pci_get_drvdata(pci); |
| 5584 | struct mychip *chip = card->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5585 | /* (2) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5586 | snd_power_change_state(card, SNDRV_CTL_POWER_D3hot); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5587 | /* (3) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5588 | snd_pcm_suspend_all(chip->pcm); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5589 | /* (4) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5590 | snd_ac97_suspend(chip->ac97); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5591 | /* (5) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5592 | snd_mychip_save_registers(chip); |
| 5593 | /* (6) */ |
| 5594 | snd_mychip_stop_hardware(chip); |
| 5595 | /* (7) */ |
| 5596 | pci_disable_device(pci); |
| 5597 | pci_save_state(pci); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5598 | return 0; |
| 5599 | } |
| 5600 | ]]> |
| 5601 | </programlisting> |
| 5602 | </informalexample> |
| 5603 | </para> |
| 5604 | |
| 5605 | <para> |
| 5606 | The scheme of the real resume job is as following. |
| 5607 | |
| 5608 | <orderedlist> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5609 | <listitem><para>Retrieve the card and the chip data.</para></listitem> |
| 5610 | <listitem><para>Set up PCI. First, call <function>pci_restore_state()</function>. |
| 5611 | Then enable the pci device again by calling <function>pci_enable_device()</function>. |
| 5612 | Call <function>pci_set_master()</function> if necessary, too.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5613 | <listitem><para>Re-initialize the chip.</para></listitem> |
| 5614 | <listitem><para>Restore the saved registers if necessary.</para></listitem> |
| 5615 | <listitem><para>Resume the mixer, e.g. calling |
| 5616 | <function>snd_ac97_resume()</function>.</para></listitem> |
| 5617 | <listitem><para>Restart the hardware (if any).</para></listitem> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5618 | <listitem><para>Call <function>snd_power_change_state()</function> with |
| 5619 | <constant>SNDRV_CTL_POWER_D0</constant> to notify the processes.</para></listitem> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5620 | </orderedlist> |
| 5621 | </para> |
| 5622 | |
| 5623 | <para> |
| 5624 | A typical code would be like: |
| 5625 | |
| 5626 | <informalexample> |
| 5627 | <programlisting> |
| 5628 | <![CDATA[ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5629 | static int mychip_resume(struct pci_dev *pci) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5630 | { |
| 5631 | /* (1) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5632 | struct snd_card *card = pci_get_drvdata(pci); |
| 5633 | struct mychip *chip = card->private_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5634 | /* (2) */ |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5635 | pci_restore_state(pci); |
| 5636 | pci_enable_device(pci); |
| 5637 | pci_set_master(pci); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5638 | /* (3) */ |
| 5639 | snd_mychip_reinit_chip(chip); |
| 5640 | /* (4) */ |
| 5641 | snd_mychip_restore_registers(chip); |
| 5642 | /* (5) */ |
| 5643 | snd_ac97_resume(chip->ac97); |
| 5644 | /* (6) */ |
| 5645 | snd_mychip_restart_chip(chip); |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5646 | /* (7) */ |
| 5647 | snd_power_change_state(card, SNDRV_CTL_POWER_D0); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5648 | return 0; |
| 5649 | } |
| 5650 | ]]> |
| 5651 | </programlisting> |
| 5652 | </informalexample> |
| 5653 | </para> |
| 5654 | |
| 5655 | <para> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5656 | As shown in the above, it's better to save registers after |
| 5657 | suspending the PCM operations via |
| 5658 | <function>snd_pcm_suspend_all()</function> or |
| 5659 | <function>snd_pcm_suspend()</function>. It means that the PCM |
| 5660 | streams are already stoppped when the register snapshot is |
| 5661 | taken. But, remind that you don't have to restart the PCM |
| 5662 | stream in the resume callback. It'll be restarted via |
| 5663 | trigger call with <constant>SNDRV_PCM_TRIGGER_RESUME</constant> |
| 5664 | when necessary. |
| 5665 | </para> |
| 5666 | |
| 5667 | <para> |
| 5668 | OK, we have all callbacks now. Let's set them up. In the |
| 5669 | initialization of the card, make sure that you can get the chip |
| 5670 | data from the card instance, typically via |
| 5671 | <structfield>private_data</structfield> field, in case you |
| 5672 | created the chip data individually. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5673 | |
| 5674 | <informalexample> |
| 5675 | <programlisting> |
| 5676 | <![CDATA[ |
| 5677 | static int __devinit snd_mychip_probe(struct pci_dev *pci, |
| 5678 | const struct pci_device_id *pci_id) |
| 5679 | { |
| 5680 | .... |
Takashi Iwai | 446ab5f | 2005-11-17 15:12:54 +0100 | [diff] [blame] | 5681 | struct snd_card *card; |
| 5682 | struct mychip *chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5683 | .... |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5684 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, NULL); |
| 5685 | .... |
| 5686 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
| 5687 | .... |
| 5688 | card->private_data = chip; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5689 | .... |
| 5690 | } |
| 5691 | ]]> |
| 5692 | </programlisting> |
| 5693 | </informalexample> |
| 5694 | |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5695 | When you created the chip data with |
| 5696 | <function>snd_card_new()</function>, it's anyway accessible |
| 5697 | via <structfield>private_data</structfield> field. |
| 5698 | |
| 5699 | <informalexample> |
| 5700 | <programlisting> |
| 5701 | <![CDATA[ |
| 5702 | static int __devinit snd_mychip_probe(struct pci_dev *pci, |
| 5703 | const struct pci_device_id *pci_id) |
| 5704 | { |
| 5705 | .... |
| 5706 | struct snd_card *card; |
| 5707 | struct mychip *chip; |
| 5708 | .... |
| 5709 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, |
| 5710 | sizeof(struct mychip)); |
| 5711 | .... |
| 5712 | chip = card->private_data; |
| 5713 | .... |
| 5714 | } |
| 5715 | ]]> |
| 5716 | </programlisting> |
| 5717 | </informalexample> |
| 5718 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5719 | </para> |
| 5720 | |
| 5721 | <para> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5722 | If you need a space for saving the registers, allocate the |
| 5723 | buffer for it here, too, since it would be fatal |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5724 | if you cannot allocate a memory in the suspend phase. |
| 5725 | The allocated buffer should be released in the corresponding |
| 5726 | destructor. |
| 5727 | </para> |
| 5728 | |
| 5729 | <para> |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5730 | And next, set suspend/resume callbacks to the pci_driver. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5731 | |
| 5732 | <informalexample> |
| 5733 | <programlisting> |
| 5734 | <![CDATA[ |
| 5735 | static struct pci_driver driver = { |
| 5736 | .name = "My Chip", |
| 5737 | .id_table = snd_my_ids, |
| 5738 | .probe = snd_my_probe, |
| 5739 | .remove = __devexit_p(snd_my_remove), |
Takashi Iwai | 5fe76e4 | 2005-11-17 17:26:09 +0100 | [diff] [blame] | 5740 | #ifdef CONFIG_PM |
| 5741 | .suspend = snd_my_suspend, |
| 5742 | .resume = snd_my_resume, |
| 5743 | #endif |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 5744 | }; |
| 5745 | ]]> |
| 5746 | </programlisting> |
| 5747 | </informalexample> |
| 5748 | </para> |
| 5749 | |
| 5750 | </chapter> |
| 5751 | |
| 5752 | |
| 5753 | <!-- ****************************************************** --> |
| 5754 | <!-- Module Parameters --> |
| 5755 | <!-- ****************************************************** --> |
| 5756 | <chapter id="module-parameters"> |
| 5757 | <title>Module Parameters</title> |
| 5758 | <para> |
| 5759 | There are standard module options for ALSA. At least, each |
| 5760 | module should have <parameter>index</parameter>, |
| 5761 | <parameter>id</parameter> and <parameter>enable</parameter> |
| 5762 | options. |
| 5763 | </para> |
| 5764 | |
| 5765 | <para> |
| 5766 | If the module supports multiple cards (usually up to |
| 5767 | 8 = <constant>SNDRV_CARDS</constant> cards), they should be |
| 5768 | arrays. The default initial values are defined already as |
| 5769 | constants for ease of programming: |
| 5770 | |
| 5771 | <informalexample> |
| 5772 | <programlisting> |
| 5773 | <![CDATA[ |
| 5774 | static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX; |
| 5775 | static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR; |
| 5776 | static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP; |
| 5777 | ]]> |
| 5778 | </programlisting> |
| 5779 | </informalexample> |
| 5780 | </para> |
| 5781 | |
| 5782 | <para> |
| 5783 | If the module supports only a single card, they could be single |
| 5784 | variables, instead. <parameter>enable</parameter> option is not |
| 5785 | always necessary in this case, but it wouldn't be so bad to have a |
| 5786 | dummy option for compatibility. |
| 5787 | </para> |
| 5788 | |
| 5789 | <para> |
| 5790 | The module parameters must be declared with the standard |
| 5791 | <function>module_param()()</function>, |
| 5792 | <function>module_param_array()()</function> and |
| 5793 | <function>MODULE_PARM_DESC()</function> macros. |
| 5794 | </para> |
| 5795 | |
| 5796 | <para> |
| 5797 | The typical coding would be like below: |
| 5798 | |
| 5799 | <informalexample> |
| 5800 | <programlisting> |
| 5801 | <![CDATA[ |
| 5802 | #define CARD_NAME "My Chip" |
| 5803 | |
| 5804 | module_param_array(index, int, NULL, 0444); |
| 5805 | MODULE_PARM_DESC(index, "Index value for " CARD_NAME " soundcard."); |
| 5806 | module_param_array(id, charp, NULL, 0444); |
| 5807 | MODULE_PARM_DESC(id, "ID string for " CARD_NAME " soundcard."); |
| 5808 | module_param_array(enable, bool, NULL, 0444); |
| 5809 | MODULE_PARM_DESC(enable, "Enable " CARD_NAME " soundcard."); |
| 5810 | ]]> |
| 5811 | </programlisting> |
| 5812 | </informalexample> |
| 5813 | </para> |
| 5814 | |
| 5815 | <para> |
| 5816 | Also, don't forget to define the module description, classes, |
| 5817 | license and devices. Especially, the recent modprobe requires to |
| 5818 | define the module license as GPL, etc., otherwise the system is |
| 5819 | shown as <quote>tainted</quote>. |
| 5820 | |
| 5821 | <informalexample> |
| 5822 | <programlisting> |
| 5823 | <![CDATA[ |
| 5824 | MODULE_DESCRIPTION("My Chip"); |
| 5825 | MODULE_LICENSE("GPL"); |
| 5826 | MODULE_SUPPORTED_DEVICE("{{Vendor,My Chip Name}}"); |
| 5827 | ]]> |
| 5828 | </programlisting> |
| 5829 | </informalexample> |
| 5830 | </para> |
| 5831 | |
| 5832 | </chapter> |
| 5833 | |
| 5834 | |
| 5835 | <!-- ****************************************************** --> |
| 5836 | <!-- How To Put Your Driver --> |
| 5837 | <!-- ****************************************************** --> |
| 5838 | <chapter id="how-to-put-your-driver"> |
| 5839 | <title>How To Put Your Driver Into ALSA Tree</title> |
| 5840 | <section> |
| 5841 | <title>General</title> |
| 5842 | <para> |
| 5843 | So far, you've learned how to write the driver codes. |
| 5844 | And you might have a question now: how to put my own |
| 5845 | driver into the ALSA driver tree? |
| 5846 | Here (finally :) the standard procedure is described briefly. |
| 5847 | </para> |
| 5848 | |
| 5849 | <para> |
| 5850 | Suppose that you'll create a new PCI driver for the card |
| 5851 | <quote>xyz</quote>. The card module name would be |
| 5852 | snd-xyz. The new driver is usually put into alsa-driver |
| 5853 | tree, <filename>alsa-driver/pci</filename> directory in |
| 5854 | the case of PCI cards. |
| 5855 | Then the driver is evaluated, audited and tested |
| 5856 | by developers and users. After a certain time, the driver |
| 5857 | will go to alsa-kernel tree (to the corresponding directory, |
| 5858 | such as <filename>alsa-kernel/pci</filename>) and eventually |
| 5859 | integrated into Linux 2.6 tree (the directory would be |
| 5860 | <filename>linux/sound/pci</filename>). |
| 5861 | </para> |
| 5862 | |
| 5863 | <para> |
| 5864 | In the following sections, the driver code is supposed |
| 5865 | to be put into alsa-driver tree. The two cases are assumed: |
| 5866 | a driver consisting of a single source file and one consisting |
| 5867 | of several source files. |
| 5868 | </para> |
| 5869 | </section> |
| 5870 | |
| 5871 | <section> |
| 5872 | <title>Driver with A Single Source File</title> |
| 5873 | <para> |
| 5874 | <orderedlist> |
| 5875 | <listitem> |
| 5876 | <para> |
| 5877 | Modify alsa-driver/pci/Makefile |
| 5878 | </para> |
| 5879 | |
| 5880 | <para> |
| 5881 | Suppose you have a file xyz.c. Add the following |
| 5882 | two lines |
| 5883 | <informalexample> |
| 5884 | <programlisting> |
| 5885 | <![CDATA[ |
| 5886 | snd-xyz-objs := xyz.o |
| 5887 | obj-$(CONFIG_SND_XYZ) += snd-xyz.o |
| 5888 | ]]> |
| 5889 | </programlisting> |
| 5890 | </informalexample> |
| 5891 | </para> |
| 5892 | </listitem> |
| 5893 | |
| 5894 | <listitem> |
| 5895 | <para> |
| 5896 | Create the Kconfig entry |
| 5897 | </para> |
| 5898 | |
| 5899 | <para> |
| 5900 | Add the new entry of Kconfig for your xyz driver. |
| 5901 | <informalexample> |
| 5902 | <programlisting> |
| 5903 | <![CDATA[ |
| 5904 | config SND_XYZ |
| 5905 | tristate "Foobar XYZ" |
| 5906 | depends on SND |
| 5907 | select SND_PCM |
| 5908 | help |
| 5909 | Say Y here to include support for Foobar XYZ soundcard. |
| 5910 | |
| 5911 | To compile this driver as a module, choose M here: the module |
| 5912 | will be called snd-xyz. |
| 5913 | ]]> |
| 5914 | </programlisting> |
| 5915 | </informalexample> |
| 5916 | |
| 5917 | the line, select SND_PCM, specifies that the driver xyz supports |
| 5918 | PCM. In addition to SND_PCM, the following components are |
| 5919 | supported for select command: |
| 5920 | SND_RAWMIDI, SND_TIMER, SND_HWDEP, SND_MPU401_UART, |
| 5921 | SND_OPL3_LIB, SND_OPL4_LIB, SND_VX_LIB, SND_AC97_CODEC. |
| 5922 | Add the select command for each supported component. |
| 5923 | </para> |
| 5924 | |
| 5925 | <para> |
| 5926 | Note that some selections imply the lowlevel selections. |
| 5927 | For example, PCM includes TIMER, MPU401_UART includes RAWMIDI, |
| 5928 | AC97_CODEC includes PCM, and OPL3_LIB includes HWDEP. |
| 5929 | You don't need to give the lowlevel selections again. |
| 5930 | </para> |
| 5931 | |
| 5932 | <para> |
| 5933 | For the details of Kconfig script, refer to the kbuild |
| 5934 | documentation. |
| 5935 | </para> |
| 5936 | |
| 5937 | </listitem> |
| 5938 | |
| 5939 | <listitem> |
| 5940 | <para> |
| 5941 | Run cvscompile script to re-generate the configure script and |
| 5942 | build the whole stuff again. |
| 5943 | </para> |
| 5944 | </listitem> |
| 5945 | </orderedlist> |
| 5946 | </para> |
| 5947 | </section> |
| 5948 | |
| 5949 | <section> |
| 5950 | <title>Drivers with Several Source Files</title> |
| 5951 | <para> |
| 5952 | Suppose that the driver snd-xyz have several source files. |
| 5953 | They are located in the new subdirectory, |
| 5954 | pci/xyz. |
| 5955 | |
| 5956 | <orderedlist> |
| 5957 | <listitem> |
| 5958 | <para> |
| 5959 | Add a new directory (<filename>xyz</filename>) in |
| 5960 | <filename>alsa-driver/pci/Makefile</filename> like below |
| 5961 | |
| 5962 | <informalexample> |
| 5963 | <programlisting> |
| 5964 | <![CDATA[ |
| 5965 | obj-$(CONFIG_SND) += xyz/ |
| 5966 | ]]> |
| 5967 | </programlisting> |
| 5968 | </informalexample> |
| 5969 | </para> |
| 5970 | </listitem> |
| 5971 | |
| 5972 | <listitem> |
| 5973 | <para> |
| 5974 | Under the directory <filename>xyz</filename>, create a Makefile |
| 5975 | |
| 5976 | <example> |
| 5977 | <title>Sample Makefile for a driver xyz</title> |
| 5978 | <programlisting> |
| 5979 | <![CDATA[ |
| 5980 | ifndef SND_TOPDIR |
| 5981 | SND_TOPDIR=../.. |
| 5982 | endif |
| 5983 | |
| 5984 | include $(SND_TOPDIR)/toplevel.config |
| 5985 | include $(SND_TOPDIR)/Makefile.conf |
| 5986 | |
| 5987 | snd-xyz-objs := xyz.o abc.o def.o |
| 5988 | |
| 5989 | obj-$(CONFIG_SND_XYZ) += snd-xyz.o |
| 5990 | |
| 5991 | include $(SND_TOPDIR)/Rules.make |
| 5992 | ]]> |
| 5993 | </programlisting> |
| 5994 | </example> |
| 5995 | </para> |
| 5996 | </listitem> |
| 5997 | |
| 5998 | <listitem> |
| 5999 | <para> |
| 6000 | Create the Kconfig entry |
| 6001 | </para> |
| 6002 | |
| 6003 | <para> |
| 6004 | This procedure is as same as in the last section. |
| 6005 | </para> |
| 6006 | </listitem> |
| 6007 | |
| 6008 | <listitem> |
| 6009 | <para> |
| 6010 | Run cvscompile script to re-generate the configure script and |
| 6011 | build the whole stuff again. |
| 6012 | </para> |
| 6013 | </listitem> |
| 6014 | </orderedlist> |
| 6015 | </para> |
| 6016 | </section> |
| 6017 | |
| 6018 | </chapter> |
| 6019 | |
| 6020 | <!-- ****************************************************** --> |
| 6021 | <!-- Useful Functions --> |
| 6022 | <!-- ****************************************************** --> |
| 6023 | <chapter id="useful-functions"> |
| 6024 | <title>Useful Functions</title> |
| 6025 | |
| 6026 | <section id="useful-functions-snd-printk"> |
| 6027 | <title><function>snd_printk()</function> and friends</title> |
| 6028 | <para> |
| 6029 | ALSA provides a verbose version of |
| 6030 | <function>printk()</function> function. If a kernel config |
| 6031 | <constant>CONFIG_SND_VERBOSE_PRINTK</constant> is set, this |
| 6032 | function prints the given message together with the file name |
| 6033 | and the line of the caller. The <constant>KERN_XXX</constant> |
| 6034 | prefix is processed as |
| 6035 | well as the original <function>printk()</function> does, so it's |
| 6036 | recommended to add this prefix, e.g. |
| 6037 | |
| 6038 | <informalexample> |
| 6039 | <programlisting> |
| 6040 | <![CDATA[ |
| 6041 | snd_printk(KERN_ERR "Oh my, sorry, it's extremely bad!\n"); |
| 6042 | ]]> |
| 6043 | </programlisting> |
| 6044 | </informalexample> |
| 6045 | </para> |
| 6046 | |
| 6047 | <para> |
| 6048 | There are also <function>printk()</function>'s for |
| 6049 | debugging. <function>snd_printd()</function> can be used for |
| 6050 | general debugging purposes. If |
| 6051 | <constant>CONFIG_SND_DEBUG</constant> is set, this function is |
| 6052 | compiled, and works just like |
| 6053 | <function>snd_printk()</function>. If the ALSA is compiled |
| 6054 | without the debugging flag, it's ignored. |
| 6055 | </para> |
| 6056 | |
| 6057 | <para> |
| 6058 | <function>snd_printdd()</function> is compiled in only when |
| 6059 | <constant>CONFIG_SND_DEBUG_DETECT</constant> is set. Please note |
| 6060 | that <constant>DEBUG_DETECT</constant> is not set as default |
| 6061 | even if you configure the alsa-driver with |
| 6062 | <option>--with-debug=full</option> option. You need to give |
| 6063 | explicitly <option>--with-debug=detect</option> option instead. |
| 6064 | </para> |
| 6065 | </section> |
| 6066 | |
| 6067 | <section id="useful-functions-snd-assert"> |
| 6068 | <title><function>snd_assert()</function></title> |
| 6069 | <para> |
| 6070 | <function>snd_assert()</function> macro is similar with the |
| 6071 | normal <function>assert()</function> macro. For example, |
| 6072 | |
| 6073 | <informalexample> |
| 6074 | <programlisting> |
| 6075 | <![CDATA[ |
| 6076 | snd_assert(pointer != NULL, return -EINVAL); |
| 6077 | ]]> |
| 6078 | </programlisting> |
| 6079 | </informalexample> |
| 6080 | </para> |
| 6081 | |
| 6082 | <para> |
| 6083 | The first argument is the expression to evaluate, and the |
| 6084 | second argument is the action if it fails. When |
| 6085 | <constant>CONFIG_SND_DEBUG</constant>, is set, it will show an |
Takashi Iwai | 7c22f1a | 2005-10-10 11:46:31 +0200 | [diff] [blame] | 6086 | error message such as <computeroutput>BUG? (xxx)</computeroutput> |
| 6087 | together with stack trace. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6088 | </para> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6089 | <para> |
Takashi Iwai | 7c22f1a | 2005-10-10 11:46:31 +0200 | [diff] [blame] | 6090 | When no debug flag is set, this macro is ignored. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6091 | </para> |
| 6092 | </section> |
| 6093 | |
| 6094 | <section id="useful-functions-snd-bug"> |
| 6095 | <title><function>snd_BUG()</function></title> |
| 6096 | <para> |
Takashi Iwai | 7c22f1a | 2005-10-10 11:46:31 +0200 | [diff] [blame] | 6097 | It shows <computeroutput>BUG?</computeroutput> message and |
| 6098 | stack trace as well as <function>snd_assert</function> at the point. |
| 6099 | It's useful to show that a fatal error happens there. |
| 6100 | </para> |
| 6101 | <para> |
| 6102 | When no debug flag is set, this macro is ignored. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6103 | </para> |
| 6104 | </section> |
| 6105 | </chapter> |
| 6106 | |
| 6107 | |
| 6108 | <!-- ****************************************************** --> |
| 6109 | <!-- Acknowledgments --> |
| 6110 | <!-- ****************************************************** --> |
| 6111 | <chapter id="acknowledments"> |
| 6112 | <title>Acknowledgments</title> |
| 6113 | <para> |
| 6114 | I would like to thank Phil Kerr for his help for improvement and |
| 6115 | corrections of this document. |
| 6116 | </para> |
| 6117 | <para> |
| 6118 | Kevin Conder reformatted the original plain-text to the |
| 6119 | DocBook format. |
| 6120 | </para> |
| 6121 | <para> |
| 6122 | Giuliano Pochini corrected typos and contributed the example codes |
| 6123 | in the hardware constraints section. |
| 6124 | </para> |
| 6125 | </chapter> |
| 6126 | |
| 6127 | |
| 6128 | </book> |