1 <?xml version="1.0" encoding="UTF-8"?>
2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
5 <book id="LinuxDriversAPI">
7 <title>Linux Device Drivers</title>
11 This documentation is free software; you can redistribute
12 it and/or modify it under the terms of the GNU General Public
13 License as published by the Free Software Foundation; either
14 version 2 of the License, or (at your option) any later
19 This program is distributed in the hope that it will be
20 useful, but WITHOUT ANY WARRANTY; without even the implied
21 warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
22 See the GNU General Public License for more details.
26 You should have received a copy of the GNU General Public
27 License along with this program; if not, write to the Free
28 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
33 For more details see the file COPYING in the source
34 distribution of Linux.
42 <title>Driver Basics</title>
43 <sect1><title>Driver Entry and Exit points</title>
44 !Iinclude/linux/init.h
47 <sect1><title>Atomic and pointer manipulation</title>
48 !Iarch/x86/include/asm/atomic.h
51 <sect1><title>Delaying, scheduling, and timer routines</title>
52 !Iinclude/linux/sched.h
54 !Ikernel/sched/cpupri.c
56 !Iinclude/linux/completion.h
59 <sect1><title>Wait queues and Wake events</title>
60 !Iinclude/linux/wait.h
63 <sect1><title>High-resolution timers</title>
64 !Iinclude/linux/ktime.h
65 !Iinclude/linux/hrtimer.h
66 !Ekernel/time/hrtimer.c
68 <sect1><title>Workqueues and Kevents</title>
69 !Iinclude/linux/workqueue.h
72 <sect1><title>Internal Functions</title>
75 !Iinclude/linux/kthread.h
79 <sect1><title>Kernel objects manipulation</title>
81 X!Iinclude/linux/kobject.h
86 <sect1><title>Kernel utility functions</title>
87 !Iinclude/linux/kernel.h
88 !Ekernel/printk/printk.c
93 !Ekernel/rcu/tree_plugin.h
97 <sect1><title>Device Resource Management</title>
98 !Edrivers/base/devres.c
103 <chapter id="devdrivers">
104 <title>Device drivers infrastructure</title>
105 <sect1><title>The Basic Device Driver-Model Structures </title>
106 !Iinclude/linux/device.h
108 <sect1><title>Device Drivers Base</title>
109 !Idrivers/base/init.c
110 !Edrivers/base/driver.c
111 !Edrivers/base/core.c
112 !Edrivers/base/syscore.c
113 !Edrivers/base/class.c
114 !Idrivers/base/node.c
115 !Edrivers/base/firmware_class.c
116 !Edrivers/base/transport_class.c
117 <!-- Cannot be included, because
118 attribute_container_add_class_device_adapter
119 and attribute_container_classdev_to_container
120 exceed allowed 44 characters maximum
121 X!Edrivers/base/attribute_container.c
125 X!Edrivers/base/interface.c
127 !Iinclude/linux/platform_device.h
128 !Edrivers/base/platform.c
131 <sect1><title>Device Drivers DMA Management</title>
132 !Edrivers/dma-buf/dma-buf.c
133 !Edrivers/dma-buf/fence.c
134 !Edrivers/dma-buf/seqno-fence.c
135 !Iinclude/linux/fence.h
136 !Iinclude/linux/seqno-fence.h
137 !Edrivers/dma-buf/reservation.c
138 !Iinclude/linux/reservation.h
139 !Edrivers/base/dma-coherent.c
140 !Edrivers/base/dma-mapping.c
142 <sect1><title>Device Drivers Power Management</title>
143 !Edrivers/base/power/main.c
145 <sect1><title>Device Drivers ACPI Support</title>
146 <!-- Internal functions only
147 X!Edrivers/acpi/sleep/main.c
148 X!Edrivers/acpi/sleep/wakeup.c
149 X!Edrivers/acpi/motherboard.c
150 X!Edrivers/acpi/bus.c
152 !Edrivers/acpi/scan.c
153 !Idrivers/acpi/scan.c
154 <!-- No correct structured comments
155 X!Edrivers/acpi/pci_bind.c
158 <sect1><title>Device drivers PnP support</title>
160 <!-- No correct structured comments
161 X!Edrivers/pnp/system.c
164 !Idrivers/pnp/driver.c
165 !Edrivers/pnp/manager.c
166 !Edrivers/pnp/support.c
168 <sect1><title>Userspace IO devices</title>
170 !Iinclude/linux/uio_driver.h
174 <chapter id="parportdev">
175 <title>Parallel Port Devices</title>
176 !Iinclude/linux/parport.h
177 !Edrivers/parport/ieee1284.c
178 !Edrivers/parport/share.c
179 !Idrivers/parport/daisy.c
182 <chapter id="message_devices">
183 <title>Message-based devices</title>
184 <sect1><title>Fusion message devices</title>
185 !Edrivers/message/fusion/mptbase.c
186 !Idrivers/message/fusion/mptbase.c
187 !Edrivers/message/fusion/mptscsih.c
188 !Idrivers/message/fusion/mptscsih.c
189 !Idrivers/message/fusion/mptctl.c
190 !Idrivers/message/fusion/mptspi.c
191 !Idrivers/message/fusion/mptfc.c
192 !Idrivers/message/fusion/mptlan.c
196 <chapter id="snddev">
197 <title>Sound Devices</title>
198 !Iinclude/sound/core.h
200 !Iinclude/sound/pcm.h
202 !Esound/core/device.c
204 !Esound/core/rawmidi.c
206 !Esound/core/memory.c
207 !Esound/core/pcm_memory.c
209 !Esound/core/isadma.c
210 !Esound/core/control.c
211 !Esound/core/pcm_lib.c
213 !Esound/core/pcm_native.c
214 !Esound/core/memalloc.c
215 <!-- FIXME: Removed for now since no structured comments in source
216 X!Isound/sound_firmware.c
220 <chapter id="mediadev">
221 <title>Media Devices</title>
223 <sect1><title>Video2Linux devices</title>
224 !Iinclude/media/tuner.h
225 !Iinclude/media/tuner-types.h
226 !Iinclude/media/v4l2-async.h
227 !Iinclude/media/v4l2-ctrls.h
228 !Iinclude/media/v4l2-dv-timings.h
229 !Iinclude/media/v4l2-event.h
230 !Iinclude/media/v4l2-flash-led-class.h
231 !Iinclude/media/v4l2-mediabus.h
232 !Iinclude/media/v4l2-mem2mem.h
233 !Iinclude/media/v4l2-of.h
234 !Iinclude/media/v4l2-subdev.h
235 !Iinclude/media/videobuf2-core.h
236 !Iinclude/media/videobuf2-v4l2.h
237 !Iinclude/media/videobuf2-memops.h
239 <sect1><title>Digital TV (DVB) devices</title>
240 !Idrivers/media/dvb-core/dvb_ca_en50221.h
241 !Idrivers/media/dvb-core/dvb_frontend.h
242 !Idrivers/media/dvb-core/dvb_math.h
243 !Idrivers/media/dvb-core/dvb_ringbuffer.h
244 !Idrivers/media/dvb-core/dvbdev.h
246 <sect1><title>Remote Controller devices</title>
247 !Iinclude/media/rc-core.h
249 <sect1><title>Media Controller devices</title>
250 !Iinclude/media/media-device.h
251 !Iinclude/media/media-devnode.h
252 !Iinclude/media/media-entity.h
257 <chapter id="uart16x50">
258 <title>16x50 UART Driver</title>
259 !Edrivers/tty/serial/serial_core.c
260 !Edrivers/tty/serial/8250/8250_core.c
264 <title>Frame Buffer Library</title>
267 The frame buffer drivers depend heavily on four data structures.
268 These structures are declared in include/linux/fb.h. They are
269 fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
270 The last three can be made available to and from userland.
274 fb_info defines the current state of a particular video card.
275 Inside fb_info, there exists a fb_ops structure which is a
276 collection of needed functions to make fbdev and fbcon work.
277 fb_info is only visible to the kernel.
281 fb_var_screeninfo is used to describe the features of a video card
282 that are user defined. With fb_var_screeninfo, things such as
283 depth and the resolution may be defined.
287 The next structure is fb_fix_screeninfo. This defines the
288 properties of a card that are created when a mode is set and can't
289 be changed otherwise. A good example of this is the start of the
290 frame buffer memory. This "locks" the address of the frame buffer
291 memory, so that it cannot be changed or moved.
295 The last structure is fb_monospecs. In the old API, there was
296 little importance for fb_monospecs. This allowed for forbidden things
297 such as setting a mode of 800x600 on a fix frequency monitor. With
298 the new API, fb_monospecs prevents such things, and if used
299 correctly, can prevent a monitor from being cooked. fb_monospecs
300 will not be useful until kernels 2.5.x.
303 <sect1><title>Frame Buffer Memory</title>
304 !Edrivers/video/fbdev/core/fbmem.c
307 <sect1><title>Frame Buffer Console</title>
308 X!Edrivers/video/console/fbcon.c
311 <sect1><title>Frame Buffer Colormap</title>
312 !Edrivers/video/fbdev/core/fbcmap.c
315 drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
316 out until somebody adds docs. KAO
317 <sect1><title>Frame Buffer Generic Functions</title>
318 X!Idrivers/video/fbgen.c
321 <sect1><title>Frame Buffer Video Mode Database</title>
322 !Idrivers/video/fbdev/core/modedb.c
323 !Edrivers/video/fbdev/core/modedb.c
325 <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
326 !Edrivers/video/fbdev/macmodes.c
328 <sect1><title>Frame Buffer Fonts</title>
330 Refer to the file lib/fonts/fonts.c for more information.
332 <!-- FIXME: Removed for now since no structured comments in source
338 <chapter id="input_subsystem">
339 <title>Input Subsystem</title>
340 <sect1><title>Input core</title>
341 !Iinclude/linux/input.h
342 !Edrivers/input/input.c
343 !Edrivers/input/ff-core.c
344 !Edrivers/input/ff-memless.c
346 <sect1><title>Multitouch Library</title>
347 !Iinclude/linux/input/mt.h
348 !Edrivers/input/input-mt.c
350 <sect1><title>Polled input devices</title>
351 !Iinclude/linux/input-polldev.h
352 !Edrivers/input/input-polldev.c
354 <sect1><title>Matrix keyboars/keypads</title>
355 !Iinclude/linux/input/matrix_keypad.h
357 <sect1><title>Sparse keymap support</title>
358 !Iinclude/linux/input/sparse-keymap.h
359 !Edrivers/input/sparse-keymap.c
364 <title>Serial Peripheral Interface (SPI)</title>
366 SPI is the "Serial Peripheral Interface", widely used with
367 embedded systems because it is a simple and efficient
368 interface: basically a multiplexed shift register.
369 Its three signal wires hold a clock (SCK, often in the range
370 of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
371 a "Master In, Slave Out" (MISO) data line.
372 SPI is a full duplex protocol; for each bit shifted out the
373 MOSI line (one per clock) another is shifted in on the MISO line.
374 Those bits are assembled into words of various sizes on the
375 way to and from system memory.
376 An additional chipselect line is usually active-low (nCS);
377 four signals are normally used for each peripheral, plus
378 sometimes an interrupt.
381 The SPI bus facilities listed here provide a generalized
382 interface to declare SPI busses and devices, manage them
383 according to the standard Linux driver model, and perform
384 input/output operations.
385 At this time, only "master" side interfaces are supported,
386 where Linux talks to SPI peripherals and does not implement
387 such a peripheral itself.
388 (Interfaces to support implementing SPI slaves would
389 necessarily look different.)
392 The programming interface is structured around two kinds of driver,
393 and two kinds of device.
394 A "Controller Driver" abstracts the controller hardware, which may
395 be as simple as a set of GPIO pins or as complex as a pair of FIFOs
396 connected to dual DMA engines on the other side of the SPI shift
397 register (maximizing throughput). Such drivers bridge between
398 whatever bus they sit on (often the platform bus) and SPI, and
399 expose the SPI side of their device as a
400 <structname>struct spi_master</structname>.
401 SPI devices are children of that master, represented as a
402 <structname>struct spi_device</structname> and manufactured from
403 <structname>struct spi_board_info</structname> descriptors which
404 are usually provided by board-specific initialization code.
405 A <structname>struct spi_driver</structname> is called a
406 "Protocol Driver", and is bound to a spi_device using normal
410 The I/O model is a set of queued messages. Protocol drivers
411 submit one or more <structname>struct spi_message</structname>
412 objects, which are processed and completed asynchronously.
413 (There are synchronous wrappers, however.) Messages are
414 built from one or more <structname>struct spi_transfer</structname>
415 objects, each of which wraps a full duplex SPI transfer.
416 A variety of protocol tweaking options are needed, because
417 different chips adopt very different policies for how they
418 use the bits transferred with SPI.
420 !Iinclude/linux/spi/spi.h
421 !Fdrivers/spi/spi.c spi_register_board_info
426 <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
429 I<superscript>2</superscript>C (or without fancy typography, "I2C")
430 is an acronym for the "Inter-IC" bus, a simple bus protocol which is
431 widely used where low data rate communications suffice.
432 Since it's also a licensed trademark, some vendors use another
433 name (such as "Two-Wire Interface", TWI) for the same bus.
434 I2C only needs two signals (SCL for clock, SDA for data), conserving
435 board real estate and minimizing signal quality issues.
436 Most I2C devices use seven bit addresses, and bus speeds of up
437 to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
439 I2C is a multi-master bus; open drain signaling is used to
440 arbitrate between masters, as well as to handshake and to
441 synchronize clocks from slower clients.
445 The Linux I2C programming interfaces support only the master
446 side of bus interactions, not the slave side.
447 The programming interface is structured around two kinds of driver,
448 and two kinds of device.
449 An I2C "Adapter Driver" abstracts the controller hardware; it binds
450 to a physical device (perhaps a PCI device or platform_device) and
451 exposes a <structname>struct i2c_adapter</structname> representing
452 each I2C bus segment it manages.
453 On each I2C bus segment will be I2C devices represented by a
454 <structname>struct i2c_client</structname>. Those devices will
455 be bound to a <structname>struct i2c_driver</structname>,
456 which should follow the standard Linux driver model.
457 (At this writing, a legacy model is more widely used.)
458 There are functions to perform various I2C protocol operations; at
459 this writing all such functions are usable only from task context.
463 The System Management Bus (SMBus) is a sibling protocol. Most SMBus
464 systems are also I2C conformant. The electrical constraints are
465 tighter for SMBus, and it standardizes particular protocol messages
466 and idioms. Controllers that support I2C can also support most
467 SMBus operations, but SMBus controllers don't support all the protocol
468 options that an I2C controller will.
469 There are functions to perform various SMBus protocol operations,
470 either using I2C primitives or by issuing SMBus commands to
471 i2c_adapter devices which don't support those I2C operations.
474 !Iinclude/linux/i2c.h
475 !Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
476 !Edrivers/i2c/i2c-core.c
480 <title>High Speed Synchronous Serial Interface (HSI)</title>
483 High Speed Synchronous Serial Interface (HSI) is a
484 serial interface mainly used for connecting application
485 engines (APE) with cellular modem engines (CMT) in cellular
488 HSI provides multiplexing for up to 16 logical channels,
489 low-latency and full duplex communication.
492 !Iinclude/linux/hsi/hsi.h
497 <title>Pulse-Width Modulation (PWM)</title>
499 Pulse-width modulation is a modulation technique primarily used to
500 control power supplied to electrical devices.
503 The PWM framework provides an abstraction for providers and consumers
504 of PWM signals. A controller that provides one or more PWM signals is
505 registered as <structname>struct pwm_chip</structname>. Providers are
506 expected to embed this structure in a driver-specific structure. This
507 structure contains fields that describe a particular chip.
510 A chip exposes one or more PWM signal sources, each of which exposed
511 as a <structname>struct pwm_device</structname>. Operations can be
512 performed on PWM devices to control the period, duty cycle, polarity
513 and active state of the signal.
516 Note that PWM devices are exclusive resources: they can always only be
517 used by one consumer at a time.
519 !Iinclude/linux/pwm.h