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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" []>
4
5<book id="LinuxDriversAPI">
6 <bookinfo>
7 <title>Linux Device Drivers</title>
8
9 <legalnotice>
10 <para>
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
15 version.
16 </para>
17
18 <para>
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.
23 </para>
24
25 <para>
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,
29 MA 02111-1307 USA
30 </para>
31
32 <para>
33 For more details see the file COPYING in the source
34 distribution of Linux.
35 </para>
36 </legalnotice>
37 </bookinfo>
38
39<toc></toc>
40
41 <chapter id="Basics">
42 <title>Driver Basics</title>
43 <sect1><title>Driver Entry and Exit points</title>
44!Iinclude/linux/init.h
45 </sect1>
46
47 <sect1><title>Atomic and pointer manipulation</title>
48!Iarch/x86/include/asm/atomic.h
49 </sect1>
50
51 <sect1><title>Delaying, scheduling, and timer routines</title>
52!Iinclude/linux/sched.h
53!Ekernel/sched/core.c
54!Ikernel/sched/cpupri.c
55!Ikernel/sched/fair.c
56!Iinclude/linux/completion.h
57!Ekernel/time/timer.c
58 </sect1>
59 <sect1><title>Wait queues and Wake events</title>
60!Iinclude/linux/wait.h
61!Ekernel/sched/wait.c
62 </sect1>
63 <sect1><title>High-resolution timers</title>
64!Iinclude/linux/ktime.h
65!Iinclude/linux/hrtimer.h
66!Ekernel/time/hrtimer.c
67 </sect1>
68 <sect1><title>Workqueues and Kevents</title>
69!Iinclude/linux/workqueue.h
70!Ekernel/workqueue.c
71 </sect1>
72 <sect1><title>Internal Functions</title>
73!Ikernel/exit.c
74!Ikernel/signal.c
75!Iinclude/linux/kthread.h
76!Ekernel/kthread.c
77 </sect1>
78
79 <sect1><title>Kernel objects manipulation</title>
80<!--
81X!Iinclude/linux/kobject.h
82-->
83!Elib/kobject.c
84 </sect1>
85
86 <sect1><title>Kernel utility functions</title>
87!Iinclude/linux/kernel.h
88!Ekernel/printk/printk.c
89!Ekernel/panic.c
90!Ekernel/sys.c
91!Ekernel/rcu/srcu.c
92!Ekernel/rcu/tree.c
93!Ekernel/rcu/tree_plugin.h
94!Ekernel/rcu/update.c
95 </sect1>
96
97 <sect1><title>Device Resource Management</title>
98!Edrivers/base/devres.c
99 </sect1>
100
101 </chapter>
102
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
107 </sect1>
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
121X!Edrivers/base/attribute_container.c
122-->
123!Edrivers/base/dd.c
124<!--
125X!Edrivers/base/interface.c
126-->
127!Iinclude/linux/platform_device.h
128!Edrivers/base/platform.c
129!Edrivers/base/bus.c
130 </sect1>
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
141 </sect1>
142 <sect1><title>Device Drivers Power Management</title>
143!Edrivers/base/power/main.c
144 </sect1>
145 <sect1><title>Device Drivers ACPI Support</title>
146<!-- Internal functions only
147X!Edrivers/acpi/sleep/main.c
148X!Edrivers/acpi/sleep/wakeup.c
149X!Edrivers/acpi/motherboard.c
150X!Edrivers/acpi/bus.c
151-->
152!Edrivers/acpi/scan.c
153!Idrivers/acpi/scan.c
154<!-- No correct structured comments
155X!Edrivers/acpi/pci_bind.c
156-->
157 </sect1>
158 <sect1><title>Device drivers PnP support</title>
159!Idrivers/pnp/core.c
160<!-- No correct structured comments
161X!Edrivers/pnp/system.c
162 -->
163!Edrivers/pnp/card.c
164!Idrivers/pnp/driver.c
165!Edrivers/pnp/manager.c
166!Edrivers/pnp/support.c
167 </sect1>
168 <sect1><title>Userspace IO devices</title>
169!Edrivers/uio/uio.c
170!Iinclude/linux/uio_driver.h
171 </sect1>
172 </chapter>
173
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
180 </chapter>
181
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
193 </sect1>
194 </chapter>
195
196 <chapter id="snddev">
197 <title>Sound Devices</title>
198!Iinclude/sound/core.h
199!Esound/sound_core.c
200!Iinclude/sound/pcm.h
201!Esound/core/pcm.c
202!Esound/core/device.c
203!Esound/core/info.c
204!Esound/core/rawmidi.c
205!Esound/core/sound.c
206!Esound/core/memory.c
207!Esound/core/pcm_memory.c
208!Esound/core/init.c
209!Esound/core/isadma.c
210!Esound/core/control.c
211!Esound/core/pcm_lib.c
212!Esound/core/hwdep.c
213!Esound/core/pcm_native.c
214!Esound/core/memalloc.c
215<!-- FIXME: Removed for now since no structured comments in source
216X!Isound/sound_firmware.c
217-->
218 </chapter>
219
220 <chapter id="mediadev">
221 <title>Media Devices</title>
222
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-mc.h
233!Iinclude/media/v4l2-mediabus.h
234!Iinclude/media/v4l2-mem2mem.h
235!Iinclude/media/v4l2-of.h
236!Iinclude/media/v4l2-subdev.h
237!Iinclude/media/videobuf2-core.h
238!Iinclude/media/videobuf2-v4l2.h
239!Iinclude/media/videobuf2-memops.h
240 </sect1>
241 <sect1><title>Digital TV (DVB) devices</title>
242 <sect1><title>Digital TV Common functions</title>
243!Idrivers/media/dvb-core/dvb_math.h
244!Idrivers/media/dvb-core/dvb_ringbuffer.h
245!Idrivers/media/dvb-core/dvbdev.h
246 </sect1>
247 <sect1><title>Digital TV Frontend kABI</title>
248!Pdrivers/media/dvb-core/dvb_frontend.h Digital TV Frontend
249!Idrivers/media/dvb-core/dvb_frontend.h
250 </sect1>
251 <sect1><title>Digital TV Demux kABI</title>
252!Pdrivers/media/dvb-core/demux.h Digital TV Demux
253 <sect1><title>Demux Callback API</title>
254!Pdrivers/media/dvb-core/demux.h Demux Callback
255 </sect1>
256!Idrivers/media/dvb-core/demux.h
257 </sect1>
258 <sect1><title>Digital TV Conditional Access kABI</title>
259!Idrivers/media/dvb-core/dvb_ca_en50221.h
260 </sect1>
261 </sect1>
262 <sect1><title>Remote Controller devices</title>
263!Iinclude/media/rc-core.h
264!Iinclude/media/lirc_dev.h
265 </sect1>
266 <sect1><title>Media Controller devices</title>
267!Pinclude/media/media-device.h Media Controller
268!Iinclude/media/media-device.h
269!Iinclude/media/media-devnode.h
270!Iinclude/media/media-entity.h
271 </sect1>
272
273 </chapter>
274
275 <chapter id="uart16x50">
276 <title>16x50 UART Driver</title>
277!Edrivers/tty/serial/serial_core.c
278!Edrivers/tty/serial/8250/8250_core.c
279 </chapter>
280
281 <chapter id="fbdev">
282 <title>Frame Buffer Library</title>
283
284 <para>
285 The frame buffer drivers depend heavily on four data structures.
286 These structures are declared in include/linux/fb.h. They are
287 fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
288 The last three can be made available to and from userland.
289 </para>
290
291 <para>
292 fb_info defines the current state of a particular video card.
293 Inside fb_info, there exists a fb_ops structure which is a
294 collection of needed functions to make fbdev and fbcon work.
295 fb_info is only visible to the kernel.
296 </para>
297
298 <para>
299 fb_var_screeninfo is used to describe the features of a video card
300 that are user defined. With fb_var_screeninfo, things such as
301 depth and the resolution may be defined.
302 </para>
303
304 <para>
305 The next structure is fb_fix_screeninfo. This defines the
306 properties of a card that are created when a mode is set and can't
307 be changed otherwise. A good example of this is the start of the
308 frame buffer memory. This "locks" the address of the frame buffer
309 memory, so that it cannot be changed or moved.
310 </para>
311
312 <para>
313 The last structure is fb_monospecs. In the old API, there was
314 little importance for fb_monospecs. This allowed for forbidden things
315 such as setting a mode of 800x600 on a fix frequency monitor. With
316 the new API, fb_monospecs prevents such things, and if used
317 correctly, can prevent a monitor from being cooked. fb_monospecs
318 will not be useful until kernels 2.5.x.
319 </para>
320
321 <sect1><title>Frame Buffer Memory</title>
322!Edrivers/video/fbdev/core/fbmem.c
323 </sect1>
324<!--
325 <sect1><title>Frame Buffer Console</title>
326X!Edrivers/video/console/fbcon.c
327 </sect1>
328-->
329 <sect1><title>Frame Buffer Colormap</title>
330!Edrivers/video/fbdev/core/fbcmap.c
331 </sect1>
332<!-- FIXME:
333 drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
334 out until somebody adds docs. KAO
335 <sect1><title>Frame Buffer Generic Functions</title>
336X!Idrivers/video/fbgen.c
337 </sect1>
338KAO -->
339 <sect1><title>Frame Buffer Video Mode Database</title>
340!Idrivers/video/fbdev/core/modedb.c
341!Edrivers/video/fbdev/core/modedb.c
342 </sect1>
343 <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
344!Edrivers/video/fbdev/macmodes.c
345 </sect1>
346 <sect1><title>Frame Buffer Fonts</title>
347 <para>
348 Refer to the file lib/fonts/fonts.c for more information.
349 </para>
350<!-- FIXME: Removed for now since no structured comments in source
351X!Ilib/fonts/fonts.c
352-->
353 </sect1>
354 </chapter>
355
356 <chapter id="input_subsystem">
357 <title>Input Subsystem</title>
358 <sect1><title>Input core</title>
359!Iinclude/linux/input.h
360!Edrivers/input/input.c
361!Edrivers/input/ff-core.c
362!Edrivers/input/ff-memless.c
363 </sect1>
364 <sect1><title>Multitouch Library</title>
365!Iinclude/linux/input/mt.h
366!Edrivers/input/input-mt.c
367 </sect1>
368 <sect1><title>Polled input devices</title>
369!Iinclude/linux/input-polldev.h
370!Edrivers/input/input-polldev.c
371 </sect1>
372 <sect1><title>Matrix keyboards/keypads</title>
373!Iinclude/linux/input/matrix_keypad.h
374 </sect1>
375 <sect1><title>Sparse keymap support</title>
376!Iinclude/linux/input/sparse-keymap.h
377!Edrivers/input/sparse-keymap.c
378 </sect1>
379 </chapter>
380
381 <chapter id="spi">
382 <title>Serial Peripheral Interface (SPI)</title>
383 <para>
384 SPI is the "Serial Peripheral Interface", widely used with
385 embedded systems because it is a simple and efficient
386 interface: basically a multiplexed shift register.
387 Its three signal wires hold a clock (SCK, often in the range
388 of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
389 a "Master In, Slave Out" (MISO) data line.
390 SPI is a full duplex protocol; for each bit shifted out the
391 MOSI line (one per clock) another is shifted in on the MISO line.
392 Those bits are assembled into words of various sizes on the
393 way to and from system memory.
394 An additional chipselect line is usually active-low (nCS);
395 four signals are normally used for each peripheral, plus
396 sometimes an interrupt.
397 </para>
398 <para>
399 The SPI bus facilities listed here provide a generalized
400 interface to declare SPI busses and devices, manage them
401 according to the standard Linux driver model, and perform
402 input/output operations.
403 At this time, only "master" side interfaces are supported,
404 where Linux talks to SPI peripherals and does not implement
405 such a peripheral itself.
406 (Interfaces to support implementing SPI slaves would
407 necessarily look different.)
408 </para>
409 <para>
410 The programming interface is structured around two kinds of driver,
411 and two kinds of device.
412 A "Controller Driver" abstracts the controller hardware, which may
413 be as simple as a set of GPIO pins or as complex as a pair of FIFOs
414 connected to dual DMA engines on the other side of the SPI shift
415 register (maximizing throughput). Such drivers bridge between
416 whatever bus they sit on (often the platform bus) and SPI, and
417 expose the SPI side of their device as a
418 <structname>struct spi_master</structname>.
419 SPI devices are children of that master, represented as a
420 <structname>struct spi_device</structname> and manufactured from
421 <structname>struct spi_board_info</structname> descriptors which
422 are usually provided by board-specific initialization code.
423 A <structname>struct spi_driver</structname> is called a
424 "Protocol Driver", and is bound to a spi_device using normal
425 driver model calls.
426 </para>
427 <para>
428 The I/O model is a set of queued messages. Protocol drivers
429 submit one or more <structname>struct spi_message</structname>
430 objects, which are processed and completed asynchronously.
431 (There are synchronous wrappers, however.) Messages are
432 built from one or more <structname>struct spi_transfer</structname>
433 objects, each of which wraps a full duplex SPI transfer.
434 A variety of protocol tweaking options are needed, because
435 different chips adopt very different policies for how they
436 use the bits transferred with SPI.
437 </para>
438!Iinclude/linux/spi/spi.h
439!Fdrivers/spi/spi.c spi_register_board_info
440!Edrivers/spi/spi.c
441 </chapter>
442
443 <chapter id="i2c">
444 <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
445
446 <para>
447 I<superscript>2</superscript>C (or without fancy typography, "I2C")
448 is an acronym for the "Inter-IC" bus, a simple bus protocol which is
449 widely used where low data rate communications suffice.
450 Since it's also a licensed trademark, some vendors use another
451 name (such as "Two-Wire Interface", TWI) for the same bus.
452 I2C only needs two signals (SCL for clock, SDA for data), conserving
453 board real estate and minimizing signal quality issues.
454 Most I2C devices use seven bit addresses, and bus speeds of up
455 to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
456 found wide use.
457 I2C is a multi-master bus; open drain signaling is used to
458 arbitrate between masters, as well as to handshake and to
459 synchronize clocks from slower clients.
460 </para>
461
462 <para>
463 The Linux I2C programming interfaces support only the master
464 side of bus interactions, not the slave side.
465 The programming interface is structured around two kinds of driver,
466 and two kinds of device.
467 An I2C "Adapter Driver" abstracts the controller hardware; it binds
468 to a physical device (perhaps a PCI device or platform_device) and
469 exposes a <structname>struct i2c_adapter</structname> representing
470 each I2C bus segment it manages.
471 On each I2C bus segment will be I2C devices represented by a
472 <structname>struct i2c_client</structname>. Those devices will
473 be bound to a <structname>struct i2c_driver</structname>,
474 which should follow the standard Linux driver model.
475 (At this writing, a legacy model is more widely used.)
476 There are functions to perform various I2C protocol operations; at
477 this writing all such functions are usable only from task context.
478 </para>
479
480 <para>
481 The System Management Bus (SMBus) is a sibling protocol. Most SMBus
482 systems are also I2C conformant. The electrical constraints are
483 tighter for SMBus, and it standardizes particular protocol messages
484 and idioms. Controllers that support I2C can also support most
485 SMBus operations, but SMBus controllers don't support all the protocol
486 options that an I2C controller will.
487 There are functions to perform various SMBus protocol operations,
488 either using I2C primitives or by issuing SMBus commands to
489 i2c_adapter devices which don't support those I2C operations.
490 </para>
491
492!Iinclude/linux/i2c.h
493!Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
494!Edrivers/i2c/i2c-core.c
495 </chapter>
496
497 <chapter id="hsi">
498 <title>High Speed Synchronous Serial Interface (HSI)</title>
499
500 <para>
501 High Speed Synchronous Serial Interface (HSI) is a
502 serial interface mainly used for connecting application
503 engines (APE) with cellular modem engines (CMT) in cellular
504 handsets.
505
506 HSI provides multiplexing for up to 16 logical channels,
507 low-latency and full duplex communication.
508 </para>
509
510!Iinclude/linux/hsi/hsi.h
511!Edrivers/hsi/hsi.c
512 </chapter>
513
514 <chapter id="pwm">
515 <title>Pulse-Width Modulation (PWM)</title>
516 <para>
517 Pulse-width modulation is a modulation technique primarily used to
518 control power supplied to electrical devices.
519 </para>
520 <para>
521 The PWM framework provides an abstraction for providers and consumers
522 of PWM signals. A controller that provides one or more PWM signals is
523 registered as <structname>struct pwm_chip</structname>. Providers are
524 expected to embed this structure in a driver-specific structure. This
525 structure contains fields that describe a particular chip.
526 </para>
527 <para>
528 A chip exposes one or more PWM signal sources, each of which exposed
529 as a <structname>struct pwm_device</structname>. Operations can be
530 performed on PWM devices to control the period, duty cycle, polarity
531 and active state of the signal.
532 </para>
533 <para>
534 Note that PWM devices are exclusive resources: they can always only be
535 used by one consumer at a time.
536 </para>
537!Iinclude/linux/pwm.h
538!Edrivers/pwm/core.c
539 </chapter>
540
541</book>