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/tveeprom.h
227 !Iinclude/media/v4l2-async.h
228 !Iinclude/media/v4l2-ctrls.h
229 !Iinclude/media/v4l2-dv-timings.h
230 !Iinclude/media/v4l2-event.h
231 !Iinclude/media/v4l2-flash-led-class.h
232 !Iinclude/media/v4l2-mediabus.h
233 !Iinclude/media/v4l2-mem2mem.h
234 !Iinclude/media/v4l2-of.h
235 !Iinclude/media/v4l2-subdev.h
236 !Iinclude/media/videobuf2-core.h
237 !Iinclude/media/videobuf2-v4l2.h
238 !Iinclude/media/videobuf2-memops.h
240 <sect1><title>Digital TV (DVB) devices</title>
241 !Idrivers/media/dvb-core/dvb_ca_en50221.h
242 !Idrivers/media/dvb-core/dvb_frontend.h
243 !Idrivers/media/dvb-core/dvb_math.h
244 !Idrivers/media/dvb-core/dvb_ringbuffer.h
245 !Idrivers/media/dvb-core/dvbdev.h
247 <sect1><title>Remote Controller devices</title>
248 !Iinclude/media/rc-core.h
249 !Iinclude/media/lirc_dev.h
251 <sect1><title>Media Controller devices</title>
252 !Iinclude/media/media-device.h
253 !Iinclude/media/media-devnode.h
254 !Iinclude/media/media-entity.h
259 <chapter id="uart16x50">
260 <title>16x50 UART Driver</title>
261 !Edrivers/tty/serial/serial_core.c
262 !Edrivers/tty/serial/8250/8250_core.c
266 <title>Frame Buffer Library</title>
269 The frame buffer drivers depend heavily on four data structures.
270 These structures are declared in include/linux/fb.h. They are
271 fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
272 The last three can be made available to and from userland.
276 fb_info defines the current state of a particular video card.
277 Inside fb_info, there exists a fb_ops structure which is a
278 collection of needed functions to make fbdev and fbcon work.
279 fb_info is only visible to the kernel.
283 fb_var_screeninfo is used to describe the features of a video card
284 that are user defined. With fb_var_screeninfo, things such as
285 depth and the resolution may be defined.
289 The next structure is fb_fix_screeninfo. This defines the
290 properties of a card that are created when a mode is set and can't
291 be changed otherwise. A good example of this is the start of the
292 frame buffer memory. This "locks" the address of the frame buffer
293 memory, so that it cannot be changed or moved.
297 The last structure is fb_monospecs. In the old API, there was
298 little importance for fb_monospecs. This allowed for forbidden things
299 such as setting a mode of 800x600 on a fix frequency monitor. With
300 the new API, fb_monospecs prevents such things, and if used
301 correctly, can prevent a monitor from being cooked. fb_monospecs
302 will not be useful until kernels 2.5.x.
305 <sect1><title>Frame Buffer Memory</title>
306 !Edrivers/video/fbdev/core/fbmem.c
309 <sect1><title>Frame Buffer Console</title>
310 X!Edrivers/video/console/fbcon.c
313 <sect1><title>Frame Buffer Colormap</title>
314 !Edrivers/video/fbdev/core/fbcmap.c
317 drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
318 out until somebody adds docs. KAO
319 <sect1><title>Frame Buffer Generic Functions</title>
320 X!Idrivers/video/fbgen.c
323 <sect1><title>Frame Buffer Video Mode Database</title>
324 !Idrivers/video/fbdev/core/modedb.c
325 !Edrivers/video/fbdev/core/modedb.c
327 <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
328 !Edrivers/video/fbdev/macmodes.c
330 <sect1><title>Frame Buffer Fonts</title>
332 Refer to the file lib/fonts/fonts.c for more information.
334 <!-- FIXME: Removed for now since no structured comments in source
340 <chapter id="input_subsystem">
341 <title>Input Subsystem</title>
342 <sect1><title>Input core</title>
343 !Iinclude/linux/input.h
344 !Edrivers/input/input.c
345 !Edrivers/input/ff-core.c
346 !Edrivers/input/ff-memless.c
348 <sect1><title>Multitouch Library</title>
349 !Iinclude/linux/input/mt.h
350 !Edrivers/input/input-mt.c
352 <sect1><title>Polled input devices</title>
353 !Iinclude/linux/input-polldev.h
354 !Edrivers/input/input-polldev.c
356 <sect1><title>Matrix keyboars/keypads</title>
357 !Iinclude/linux/input/matrix_keypad.h
359 <sect1><title>Sparse keymap support</title>
360 !Iinclude/linux/input/sparse-keymap.h
361 !Edrivers/input/sparse-keymap.c
366 <title>Serial Peripheral Interface (SPI)</title>
368 SPI is the "Serial Peripheral Interface", widely used with
369 embedded systems because it is a simple and efficient
370 interface: basically a multiplexed shift register.
371 Its three signal wires hold a clock (SCK, often in the range
372 of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
373 a "Master In, Slave Out" (MISO) data line.
374 SPI is a full duplex protocol; for each bit shifted out the
375 MOSI line (one per clock) another is shifted in on the MISO line.
376 Those bits are assembled into words of various sizes on the
377 way to and from system memory.
378 An additional chipselect line is usually active-low (nCS);
379 four signals are normally used for each peripheral, plus
380 sometimes an interrupt.
383 The SPI bus facilities listed here provide a generalized
384 interface to declare SPI busses and devices, manage them
385 according to the standard Linux driver model, and perform
386 input/output operations.
387 At this time, only "master" side interfaces are supported,
388 where Linux talks to SPI peripherals and does not implement
389 such a peripheral itself.
390 (Interfaces to support implementing SPI slaves would
391 necessarily look different.)
394 The programming interface is structured around two kinds of driver,
395 and two kinds of device.
396 A "Controller Driver" abstracts the controller hardware, which may
397 be as simple as a set of GPIO pins or as complex as a pair of FIFOs
398 connected to dual DMA engines on the other side of the SPI shift
399 register (maximizing throughput). Such drivers bridge between
400 whatever bus they sit on (often the platform bus) and SPI, and
401 expose the SPI side of their device as a
402 <structname>struct spi_master</structname>.
403 SPI devices are children of that master, represented as a
404 <structname>struct spi_device</structname> and manufactured from
405 <structname>struct spi_board_info</structname> descriptors which
406 are usually provided by board-specific initialization code.
407 A <structname>struct spi_driver</structname> is called a
408 "Protocol Driver", and is bound to a spi_device using normal
412 The I/O model is a set of queued messages. Protocol drivers
413 submit one or more <structname>struct spi_message</structname>
414 objects, which are processed and completed asynchronously.
415 (There are synchronous wrappers, however.) Messages are
416 built from one or more <structname>struct spi_transfer</structname>
417 objects, each of which wraps a full duplex SPI transfer.
418 A variety of protocol tweaking options are needed, because
419 different chips adopt very different policies for how they
420 use the bits transferred with SPI.
422 !Iinclude/linux/spi/spi.h
423 !Fdrivers/spi/spi.c spi_register_board_info
428 <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
431 I<superscript>2</superscript>C (or without fancy typography, "I2C")
432 is an acronym for the "Inter-IC" bus, a simple bus protocol which is
433 widely used where low data rate communications suffice.
434 Since it's also a licensed trademark, some vendors use another
435 name (such as "Two-Wire Interface", TWI) for the same bus.
436 I2C only needs two signals (SCL for clock, SDA for data), conserving
437 board real estate and minimizing signal quality issues.
438 Most I2C devices use seven bit addresses, and bus speeds of up
439 to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
441 I2C is a multi-master bus; open drain signaling is used to
442 arbitrate between masters, as well as to handshake and to
443 synchronize clocks from slower clients.
447 The Linux I2C programming interfaces support only the master
448 side of bus interactions, not the slave side.
449 The programming interface is structured around two kinds of driver,
450 and two kinds of device.
451 An I2C "Adapter Driver" abstracts the controller hardware; it binds
452 to a physical device (perhaps a PCI device or platform_device) and
453 exposes a <structname>struct i2c_adapter</structname> representing
454 each I2C bus segment it manages.
455 On each I2C bus segment will be I2C devices represented by a
456 <structname>struct i2c_client</structname>. Those devices will
457 be bound to a <structname>struct i2c_driver</structname>,
458 which should follow the standard Linux driver model.
459 (At this writing, a legacy model is more widely used.)
460 There are functions to perform various I2C protocol operations; at
461 this writing all such functions are usable only from task context.
465 The System Management Bus (SMBus) is a sibling protocol. Most SMBus
466 systems are also I2C conformant. The electrical constraints are
467 tighter for SMBus, and it standardizes particular protocol messages
468 and idioms. Controllers that support I2C can also support most
469 SMBus operations, but SMBus controllers don't support all the protocol
470 options that an I2C controller will.
471 There are functions to perform various SMBus protocol operations,
472 either using I2C primitives or by issuing SMBus commands to
473 i2c_adapter devices which don't support those I2C operations.
476 !Iinclude/linux/i2c.h
477 !Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
478 !Edrivers/i2c/i2c-core.c
482 <title>High Speed Synchronous Serial Interface (HSI)</title>
485 High Speed Synchronous Serial Interface (HSI) is a
486 serial interface mainly used for connecting application
487 engines (APE) with cellular modem engines (CMT) in cellular
490 HSI provides multiplexing for up to 16 logical channels,
491 low-latency and full duplex communication.
494 !Iinclude/linux/hsi/hsi.h
499 <title>Pulse-Width Modulation (PWM)</title>
501 Pulse-width modulation is a modulation technique primarily used to
502 control power supplied to electrical devices.
505 The PWM framework provides an abstraction for providers and consumers
506 of PWM signals. A controller that provides one or more PWM signals is
507 registered as <structname>struct pwm_chip</structname>. Providers are
508 expected to embed this structure in a driver-specific structure. This
509 structure contains fields that describe a particular chip.
512 A chip exposes one or more PWM signal sources, each of which exposed
513 as a <structname>struct pwm_device</structname>. Operations can be
514 performed on PWM devices to control the period, duty cycle, polarity
515 and active state of the signal.
518 Note that PWM devices are exclusive resources: they can always only be
519 used by one consumer at a time.
521 !Iinclude/linux/pwm.h