| <?xml version="1.0" encoding="UTF-8"?> |
| <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" |
| "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []> |
| |
| <book id="LinuxDriversAPI"> |
| <bookinfo> |
| <title>Linux Device Drivers</title> |
| |
| <legalnotice> |
| <para> |
| This documentation is free software; you can redistribute |
| it and/or modify it under the terms of the GNU General Public |
| License as published by the Free Software Foundation; either |
| version 2 of the License, or (at your option) any later |
| version. |
| </para> |
| |
| <para> |
| This program is distributed in the hope that it will be |
| useful, but WITHOUT ANY WARRANTY; without even the implied |
| warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. |
| See the GNU General Public License for more details. |
| </para> |
| |
| <para> |
| You should have received a copy of the GNU General Public |
| License along with this program; if not, write to the Free |
| Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, |
| MA 02111-1307 USA |
| </para> |
| |
| <para> |
| For more details see the file COPYING in the source |
| distribution of Linux. |
| </para> |
| </legalnotice> |
| </bookinfo> |
| |
| <toc></toc> |
| |
| <chapter id="Basics"> |
| <title>Driver Basics</title> |
| <sect1><title>Driver Entry and Exit points</title> |
| !Iinclude/linux/init.h |
| </sect1> |
| |
| <sect1><title>Atomic and pointer manipulation</title> |
| !Iarch/x86/include/asm/atomic.h |
| </sect1> |
| |
| <sect1><title>Delaying, scheduling, and timer routines</title> |
| !Iinclude/linux/sched.h |
| !Ekernel/sched/core.c |
| !Ikernel/sched/cpupri.c |
| !Ikernel/sched/fair.c |
| !Iinclude/linux/completion.h |
| !Ekernel/time/timer.c |
| </sect1> |
| <sect1><title>Wait queues and Wake events</title> |
| !Iinclude/linux/wait.h |
| !Ekernel/sched/wait.c |
| </sect1> |
| <sect1><title>High-resolution timers</title> |
| !Iinclude/linux/ktime.h |
| !Iinclude/linux/hrtimer.h |
| !Ekernel/time/hrtimer.c |
| </sect1> |
| <sect1><title>Workqueues and Kevents</title> |
| !Iinclude/linux/workqueue.h |
| !Ekernel/workqueue.c |
| </sect1> |
| <sect1><title>Internal Functions</title> |
| !Ikernel/exit.c |
| !Ikernel/signal.c |
| !Iinclude/linux/kthread.h |
| !Ekernel/kthread.c |
| </sect1> |
| |
| <sect1><title>Kernel objects manipulation</title> |
| <!-- |
| X!Iinclude/linux/kobject.h |
| --> |
| !Elib/kobject.c |
| </sect1> |
| |
| <sect1><title>Kernel utility functions</title> |
| !Iinclude/linux/kernel.h |
| !Ekernel/printk/printk.c |
| !Ekernel/panic.c |
| !Ekernel/sys.c |
| !Ekernel/rcu/srcu.c |
| !Ekernel/rcu/tree.c |
| !Ekernel/rcu/tree_plugin.h |
| !Ekernel/rcu/update.c |
| </sect1> |
| |
| <sect1><title>Device Resource Management</title> |
| !Edrivers/base/devres.c |
| </sect1> |
| |
| </chapter> |
| |
| <chapter id="devdrivers"> |
| <title>Device drivers infrastructure</title> |
| <sect1><title>The Basic Device Driver-Model Structures </title> |
| !Iinclude/linux/device.h |
| </sect1> |
| <sect1><title>Device Drivers Base</title> |
| !Idrivers/base/init.c |
| !Edrivers/base/driver.c |
| !Edrivers/base/core.c |
| !Edrivers/base/syscore.c |
| !Edrivers/base/class.c |
| !Idrivers/base/node.c |
| !Edrivers/base/firmware_class.c |
| !Edrivers/base/transport_class.c |
| <!-- Cannot be included, because |
| attribute_container_add_class_device_adapter |
| and attribute_container_classdev_to_container |
| exceed allowed 44 characters maximum |
| X!Edrivers/base/attribute_container.c |
| --> |
| !Edrivers/base/dd.c |
| <!-- |
| X!Edrivers/base/interface.c |
| --> |
| !Iinclude/linux/platform_device.h |
| !Edrivers/base/platform.c |
| !Edrivers/base/bus.c |
| </sect1> |
| <sect1><title>Device Drivers DMA Management</title> |
| !Edrivers/dma-buf/dma-buf.c |
| !Edrivers/dma-buf/fence.c |
| !Edrivers/dma-buf/seqno-fence.c |
| !Iinclude/linux/fence.h |
| !Iinclude/linux/seqno-fence.h |
| !Edrivers/dma-buf/reservation.c |
| !Iinclude/linux/reservation.h |
| !Edrivers/base/dma-coherent.c |
| !Edrivers/base/dma-mapping.c |
| </sect1> |
| <sect1><title>Device Drivers Power Management</title> |
| !Edrivers/base/power/main.c |
| </sect1> |
| <sect1><title>Device Drivers ACPI Support</title> |
| <!-- Internal functions only |
| X!Edrivers/acpi/sleep/main.c |
| X!Edrivers/acpi/sleep/wakeup.c |
| X!Edrivers/acpi/motherboard.c |
| X!Edrivers/acpi/bus.c |
| --> |
| !Edrivers/acpi/scan.c |
| !Idrivers/acpi/scan.c |
| <!-- No correct structured comments |
| X!Edrivers/acpi/pci_bind.c |
| --> |
| </sect1> |
| <sect1><title>Device drivers PnP support</title> |
| !Idrivers/pnp/core.c |
| <!-- No correct structured comments |
| X!Edrivers/pnp/system.c |
| --> |
| !Edrivers/pnp/card.c |
| !Idrivers/pnp/driver.c |
| !Edrivers/pnp/manager.c |
| !Edrivers/pnp/support.c |
| </sect1> |
| <sect1><title>Userspace IO devices</title> |
| !Edrivers/uio/uio.c |
| !Iinclude/linux/uio_driver.h |
| </sect1> |
| </chapter> |
| |
| <chapter id="parportdev"> |
| <title>Parallel Port Devices</title> |
| !Iinclude/linux/parport.h |
| !Edrivers/parport/ieee1284.c |
| !Edrivers/parport/share.c |
| !Idrivers/parport/daisy.c |
| </chapter> |
| |
| <chapter id="message_devices"> |
| <title>Message-based devices</title> |
| <sect1><title>Fusion message devices</title> |
| !Edrivers/message/fusion/mptbase.c |
| !Idrivers/message/fusion/mptbase.c |
| !Edrivers/message/fusion/mptscsih.c |
| !Idrivers/message/fusion/mptscsih.c |
| !Idrivers/message/fusion/mptctl.c |
| !Idrivers/message/fusion/mptspi.c |
| !Idrivers/message/fusion/mptfc.c |
| !Idrivers/message/fusion/mptlan.c |
| </sect1> |
| </chapter> |
| |
| <chapter id="snddev"> |
| <title>Sound Devices</title> |
| !Iinclude/sound/core.h |
| !Esound/sound_core.c |
| !Iinclude/sound/pcm.h |
| !Esound/core/pcm.c |
| !Esound/core/device.c |
| !Esound/core/info.c |
| !Esound/core/rawmidi.c |
| !Esound/core/sound.c |
| !Esound/core/memory.c |
| !Esound/core/pcm_memory.c |
| !Esound/core/init.c |
| !Esound/core/isadma.c |
| !Esound/core/control.c |
| !Esound/core/pcm_lib.c |
| !Esound/core/hwdep.c |
| !Esound/core/pcm_native.c |
| !Esound/core/memalloc.c |
| <!-- FIXME: Removed for now since no structured comments in source |
| X!Isound/sound_firmware.c |
| --> |
| </chapter> |
| |
| <chapter id="mediadev"> |
| <title>Media Devices</title> |
| |
| <sect1><title>Video2Linux devices</title> |
| !Iinclude/media/tuner.h |
| !Iinclude/media/tuner-types.h |
| !Iinclude/media/tveeprom.h |
| !Iinclude/media/v4l2-async.h |
| !Iinclude/media/v4l2-ctrls.h |
| !Iinclude/media/v4l2-dv-timings.h |
| !Iinclude/media/v4l2-event.h |
| !Iinclude/media/v4l2-flash-led-class.h |
| !Iinclude/media/v4l2-mc.h |
| !Iinclude/media/v4l2-mediabus.h |
| !Iinclude/media/v4l2-mem2mem.h |
| !Iinclude/media/v4l2-of.h |
| !Iinclude/media/v4l2-subdev.h |
| !Iinclude/media/videobuf2-core.h |
| !Iinclude/media/videobuf2-v4l2.h |
| !Iinclude/media/videobuf2-memops.h |
| </sect1> |
| <sect1><title>Digital TV (DVB) devices</title> |
| <sect1><title>Digital TV Common functions</title> |
| !Idrivers/media/dvb-core/dvb_math.h |
| !Idrivers/media/dvb-core/dvb_ringbuffer.h |
| !Idrivers/media/dvb-core/dvbdev.h |
| </sect1> |
| <sect1><title>Digital TV Frontend kABI</title> |
| !Pdrivers/media/dvb-core/dvb_frontend.h Digital TV Frontend |
| !Idrivers/media/dvb-core/dvb_frontend.h |
| </sect1> |
| <sect1><title>Digital TV Demux kABI</title> |
| !Pdrivers/media/dvb-core/demux.h Digital TV Demux |
| <sect1><title>Demux Callback API</title> |
| !Pdrivers/media/dvb-core/demux.h Demux Callback |
| </sect1> |
| !Idrivers/media/dvb-core/demux.h |
| </sect1> |
| <sect1><title>Digital TV Conditional Access kABI</title> |
| !Idrivers/media/dvb-core/dvb_ca_en50221.h |
| </sect1> |
| </sect1> |
| <sect1><title>Remote Controller devices</title> |
| !Iinclude/media/rc-core.h |
| !Iinclude/media/lirc_dev.h |
| </sect1> |
| <sect1><title>Media Controller devices</title> |
| !Pinclude/media/media-device.h Media Controller |
| !Iinclude/media/media-device.h |
| !Iinclude/media/media-devnode.h |
| !Iinclude/media/media-entity.h |
| </sect1> |
| |
| </chapter> |
| |
| <chapter id="uart16x50"> |
| <title>16x50 UART Driver</title> |
| !Edrivers/tty/serial/serial_core.c |
| !Edrivers/tty/serial/8250/8250_core.c |
| </chapter> |
| |
| <chapter id="fbdev"> |
| <title>Frame Buffer Library</title> |
| |
| <para> |
| The frame buffer drivers depend heavily on four data structures. |
| These structures are declared in include/linux/fb.h. They are |
| fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs. |
| The last three can be made available to and from userland. |
| </para> |
| |
| <para> |
| fb_info defines the current state of a particular video card. |
| Inside fb_info, there exists a fb_ops structure which is a |
| collection of needed functions to make fbdev and fbcon work. |
| fb_info is only visible to the kernel. |
| </para> |
| |
| <para> |
| fb_var_screeninfo is used to describe the features of a video card |
| that are user defined. With fb_var_screeninfo, things such as |
| depth and the resolution may be defined. |
| </para> |
| |
| <para> |
| The next structure is fb_fix_screeninfo. This defines the |
| properties of a card that are created when a mode is set and can't |
| be changed otherwise. A good example of this is the start of the |
| frame buffer memory. This "locks" the address of the frame buffer |
| memory, so that it cannot be changed or moved. |
| </para> |
| |
| <para> |
| The last structure is fb_monospecs. In the old API, there was |
| little importance for fb_monospecs. This allowed for forbidden things |
| such as setting a mode of 800x600 on a fix frequency monitor. With |
| the new API, fb_monospecs prevents such things, and if used |
| correctly, can prevent a monitor from being cooked. fb_monospecs |
| will not be useful until kernels 2.5.x. |
| </para> |
| |
| <sect1><title>Frame Buffer Memory</title> |
| !Edrivers/video/fbdev/core/fbmem.c |
| </sect1> |
| <!-- |
| <sect1><title>Frame Buffer Console</title> |
| X!Edrivers/video/console/fbcon.c |
| </sect1> |
| --> |
| <sect1><title>Frame Buffer Colormap</title> |
| !Edrivers/video/fbdev/core/fbcmap.c |
| </sect1> |
| <!-- FIXME: |
| drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment |
| out until somebody adds docs. KAO |
| <sect1><title>Frame Buffer Generic Functions</title> |
| X!Idrivers/video/fbgen.c |
| </sect1> |
| KAO --> |
| <sect1><title>Frame Buffer Video Mode Database</title> |
| !Idrivers/video/fbdev/core/modedb.c |
| !Edrivers/video/fbdev/core/modedb.c |
| </sect1> |
| <sect1><title>Frame Buffer Macintosh Video Mode Database</title> |
| !Edrivers/video/fbdev/macmodes.c |
| </sect1> |
| <sect1><title>Frame Buffer Fonts</title> |
| <para> |
| Refer to the file lib/fonts/fonts.c for more information. |
| </para> |
| <!-- FIXME: Removed for now since no structured comments in source |
| X!Ilib/fonts/fonts.c |
| --> |
| </sect1> |
| </chapter> |
| |
| <chapter id="input_subsystem"> |
| <title>Input Subsystem</title> |
| <sect1><title>Input core</title> |
| !Iinclude/linux/input.h |
| !Edrivers/input/input.c |
| !Edrivers/input/ff-core.c |
| !Edrivers/input/ff-memless.c |
| </sect1> |
| <sect1><title>Multitouch Library</title> |
| !Iinclude/linux/input/mt.h |
| !Edrivers/input/input-mt.c |
| </sect1> |
| <sect1><title>Polled input devices</title> |
| !Iinclude/linux/input-polldev.h |
| !Edrivers/input/input-polldev.c |
| </sect1> |
| <sect1><title>Matrix keyboars/keypads</title> |
| !Iinclude/linux/input/matrix_keypad.h |
| </sect1> |
| <sect1><title>Sparse keymap support</title> |
| !Iinclude/linux/input/sparse-keymap.h |
| !Edrivers/input/sparse-keymap.c |
| </sect1> |
| </chapter> |
| |
| <chapter id="spi"> |
| <title>Serial Peripheral Interface (SPI)</title> |
| <para> |
| SPI is the "Serial Peripheral Interface", widely used with |
| embedded systems because it is a simple and efficient |
| interface: basically a multiplexed shift register. |
| Its three signal wires hold a clock (SCK, often in the range |
| of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and |
| a "Master In, Slave Out" (MISO) data line. |
| SPI is a full duplex protocol; for each bit shifted out the |
| MOSI line (one per clock) another is shifted in on the MISO line. |
| Those bits are assembled into words of various sizes on the |
| way to and from system memory. |
| An additional chipselect line is usually active-low (nCS); |
| four signals are normally used for each peripheral, plus |
| sometimes an interrupt. |
| </para> |
| <para> |
| The SPI bus facilities listed here provide a generalized |
| interface to declare SPI busses and devices, manage them |
| according to the standard Linux driver model, and perform |
| input/output operations. |
| At this time, only "master" side interfaces are supported, |
| where Linux talks to SPI peripherals and does not implement |
| such a peripheral itself. |
| (Interfaces to support implementing SPI slaves would |
| necessarily look different.) |
| </para> |
| <para> |
| The programming interface is structured around two kinds of driver, |
| and two kinds of device. |
| A "Controller Driver" abstracts the controller hardware, which may |
| be as simple as a set of GPIO pins or as complex as a pair of FIFOs |
| connected to dual DMA engines on the other side of the SPI shift |
| register (maximizing throughput). Such drivers bridge between |
| whatever bus they sit on (often the platform bus) and SPI, and |
| expose the SPI side of their device as a |
| <structname>struct spi_master</structname>. |
| SPI devices are children of that master, represented as a |
| <structname>struct spi_device</structname> and manufactured from |
| <structname>struct spi_board_info</structname> descriptors which |
| are usually provided by board-specific initialization code. |
| A <structname>struct spi_driver</structname> is called a |
| "Protocol Driver", and is bound to a spi_device using normal |
| driver model calls. |
| </para> |
| <para> |
| The I/O model is a set of queued messages. Protocol drivers |
| submit one or more <structname>struct spi_message</structname> |
| objects, which are processed and completed asynchronously. |
| (There are synchronous wrappers, however.) Messages are |
| built from one or more <structname>struct spi_transfer</structname> |
| objects, each of which wraps a full duplex SPI transfer. |
| A variety of protocol tweaking options are needed, because |
| different chips adopt very different policies for how they |
| use the bits transferred with SPI. |
| </para> |
| !Iinclude/linux/spi/spi.h |
| !Fdrivers/spi/spi.c spi_register_board_info |
| !Edrivers/spi/spi.c |
| </chapter> |
| |
| <chapter id="i2c"> |
| <title>I<superscript>2</superscript>C and SMBus Subsystem</title> |
| |
| <para> |
| I<superscript>2</superscript>C (or without fancy typography, "I2C") |
| is an acronym for the "Inter-IC" bus, a simple bus protocol which is |
| widely used where low data rate communications suffice. |
| Since it's also a licensed trademark, some vendors use another |
| name (such as "Two-Wire Interface", TWI) for the same bus. |
| I2C only needs two signals (SCL for clock, SDA for data), conserving |
| board real estate and minimizing signal quality issues. |
| Most I2C devices use seven bit addresses, and bus speeds of up |
| to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet |
| found wide use. |
| I2C is a multi-master bus; open drain signaling is used to |
| arbitrate between masters, as well as to handshake and to |
| synchronize clocks from slower clients. |
| </para> |
| |
| <para> |
| The Linux I2C programming interfaces support only the master |
| side of bus interactions, not the slave side. |
| The programming interface is structured around two kinds of driver, |
| and two kinds of device. |
| An I2C "Adapter Driver" abstracts the controller hardware; it binds |
| to a physical device (perhaps a PCI device or platform_device) and |
| exposes a <structname>struct i2c_adapter</structname> representing |
| each I2C bus segment it manages. |
| On each I2C bus segment will be I2C devices represented by a |
| <structname>struct i2c_client</structname>. Those devices will |
| be bound to a <structname>struct i2c_driver</structname>, |
| which should follow the standard Linux driver model. |
| (At this writing, a legacy model is more widely used.) |
| There are functions to perform various I2C protocol operations; at |
| this writing all such functions are usable only from task context. |
| </para> |
| |
| <para> |
| The System Management Bus (SMBus) is a sibling protocol. Most SMBus |
| systems are also I2C conformant. The electrical constraints are |
| tighter for SMBus, and it standardizes particular protocol messages |
| and idioms. Controllers that support I2C can also support most |
| SMBus operations, but SMBus controllers don't support all the protocol |
| options that an I2C controller will. |
| There are functions to perform various SMBus protocol operations, |
| either using I2C primitives or by issuing SMBus commands to |
| i2c_adapter devices which don't support those I2C operations. |
| </para> |
| |
| !Iinclude/linux/i2c.h |
| !Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info |
| !Edrivers/i2c/i2c-core.c |
| </chapter> |
| |
| <chapter id="hsi"> |
| <title>High Speed Synchronous Serial Interface (HSI)</title> |
| |
| <para> |
| High Speed Synchronous Serial Interface (HSI) is a |
| serial interface mainly used for connecting application |
| engines (APE) with cellular modem engines (CMT) in cellular |
| handsets. |
| |
| HSI provides multiplexing for up to 16 logical channels, |
| low-latency and full duplex communication. |
| </para> |
| |
| !Iinclude/linux/hsi/hsi.h |
| !Edrivers/hsi/hsi.c |
| </chapter> |
| |
| <chapter id="pwm"> |
| <title>Pulse-Width Modulation (PWM)</title> |
| <para> |
| Pulse-width modulation is a modulation technique primarily used to |
| control power supplied to electrical devices. |
| </para> |
| <para> |
| The PWM framework provides an abstraction for providers and consumers |
| of PWM signals. A controller that provides one or more PWM signals is |
| registered as <structname>struct pwm_chip</structname>. Providers are |
| expected to embed this structure in a driver-specific structure. This |
| structure contains fields that describe a particular chip. |
| </para> |
| <para> |
| A chip exposes one or more PWM signal sources, each of which exposed |
| as a <structname>struct pwm_device</structname>. Operations can be |
| performed on PWM devices to control the period, duty cycle, polarity |
| and active state of the signal. |
| </para> |
| <para> |
| Note that PWM devices are exclusive resources: they can always only be |
| used by one consumer at a time. |
| </para> |
| !Iinclude/linux/pwm.h |
| !Edrivers/pwm/core.c |
| </chapter> |
| |
| </book> |