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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/v4l2-async.h
225!Iinclude/media/v4l2-ctrls.h
226!Iinclude/media/v4l2-dv-timings.h
227!Iinclude/media/v4l2-event.h
228!Iinclude/media/v4l2-flash-led-class.h
229!Iinclude/media/v4l2-mediabus.h
230!Iinclude/media/v4l2-mem2mem.h
231!Iinclude/media/v4l2-of.h
232!Iinclude/media/v4l2-subdev.h
233!Iinclude/media/videobuf2-core.h
234!Iinclude/media/videobuf2-memops.h
235 </sect1>
236 <sect1><title>Digital TV (DVB) devices</title>
237!Idrivers/media/dvb-core/dvb_ca_en50221.h
238!Idrivers/media/dvb-core/dvb_frontend.h
239!Idrivers/media/dvb-core/dvb_math.h
240!Idrivers/media/dvb-core/dvb_ringbuffer.h
241!Idrivers/media/dvb-core/dvbdev.h
242 </sect1>
243 <sect1><title>Remote Controller devices</title>
244!Iinclude/media/rc-core.h
245 </sect1>
246 <sect1><title>Media Controller devices</title>
247!Iinclude/media/media-device.h
248!Iinclude/media/media-devnode.h
249!Iinclude/media/media-entity.h
250 </sect1>
251
252 </chapter>
253
254 <chapter id="uart16x50">
255 <title>16x50 UART Driver</title>
256!Edrivers/tty/serial/serial_core.c
257!Edrivers/tty/serial/8250/8250_core.c
258 </chapter>
259
260 <chapter id="fbdev">
261 <title>Frame Buffer Library</title>
262
263 <para>
264 The frame buffer drivers depend heavily on four data structures.
265 These structures are declared in include/linux/fb.h. They are
266 fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
267 The last three can be made available to and from userland.
268 </para>
269
270 <para>
271 fb_info defines the current state of a particular video card.
272 Inside fb_info, there exists a fb_ops structure which is a
273 collection of needed functions to make fbdev and fbcon work.
274 fb_info is only visible to the kernel.
275 </para>
276
277 <para>
278 fb_var_screeninfo is used to describe the features of a video card
279 that are user defined. With fb_var_screeninfo, things such as
280 depth and the resolution may be defined.
281 </para>
282
283 <para>
284 The next structure is fb_fix_screeninfo. This defines the
285 properties of a card that are created when a mode is set and can't
286 be changed otherwise. A good example of this is the start of the
287 frame buffer memory. This "locks" the address of the frame buffer
288 memory, so that it cannot be changed or moved.
289 </para>
290
291 <para>
292 The last structure is fb_monospecs. In the old API, there was
293 little importance for fb_monospecs. This allowed for forbidden things
294 such as setting a mode of 800x600 on a fix frequency monitor. With
295 the new API, fb_monospecs prevents such things, and if used
296 correctly, can prevent a monitor from being cooked. fb_monospecs
297 will not be useful until kernels 2.5.x.
298 </para>
299
300 <sect1><title>Frame Buffer Memory</title>
301!Edrivers/video/fbdev/core/fbmem.c
302 </sect1>
303<!--
304 <sect1><title>Frame Buffer Console</title>
305X!Edrivers/video/console/fbcon.c
306 </sect1>
307-->
308 <sect1><title>Frame Buffer Colormap</title>
309!Edrivers/video/fbdev/core/fbcmap.c
310 </sect1>
311<!-- FIXME:
312 drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
313 out until somebody adds docs. KAO
314 <sect1><title>Frame Buffer Generic Functions</title>
315X!Idrivers/video/fbgen.c
316 </sect1>
317KAO -->
318 <sect1><title>Frame Buffer Video Mode Database</title>
319!Idrivers/video/fbdev/core/modedb.c
320!Edrivers/video/fbdev/core/modedb.c
321 </sect1>
322 <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
323!Edrivers/video/fbdev/macmodes.c
324 </sect1>
325 <sect1><title>Frame Buffer Fonts</title>
326 <para>
327 Refer to the file lib/fonts/fonts.c for more information.
328 </para>
329<!-- FIXME: Removed for now since no structured comments in source
330X!Ilib/fonts/fonts.c
331-->
332 </sect1>
333 </chapter>
334
335 <chapter id="input_subsystem">
336 <title>Input Subsystem</title>
337 <sect1><title>Input core</title>
338!Iinclude/linux/input.h
339!Edrivers/input/input.c
340!Edrivers/input/ff-core.c
341!Edrivers/input/ff-memless.c
342 </sect1>
343 <sect1><title>Multitouch Library</title>
344!Iinclude/linux/input/mt.h
345!Edrivers/input/input-mt.c
346 </sect1>
347 <sect1><title>Polled input devices</title>
348!Iinclude/linux/input-polldev.h
349!Edrivers/input/input-polldev.c
350 </sect1>
351 <sect1><title>Matrix keyboars/keypads</title>
352!Iinclude/linux/input/matrix_keypad.h
353 </sect1>
354 <sect1><title>Sparse keymap support</title>
355!Iinclude/linux/input/sparse-keymap.h
356!Edrivers/input/sparse-keymap.c
357 </sect1>
358 </chapter>
359
360 <chapter id="spi">
361 <title>Serial Peripheral Interface (SPI)</title>
362 <para>
363 SPI is the "Serial Peripheral Interface", widely used with
364 embedded systems because it is a simple and efficient
365 interface: basically a multiplexed shift register.
366 Its three signal wires hold a clock (SCK, often in the range
367 of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
368 a "Master In, Slave Out" (MISO) data line.
369 SPI is a full duplex protocol; for each bit shifted out the
370 MOSI line (one per clock) another is shifted in on the MISO line.
371 Those bits are assembled into words of various sizes on the
372 way to and from system memory.
373 An additional chipselect line is usually active-low (nCS);
374 four signals are normally used for each peripheral, plus
375 sometimes an interrupt.
376 </para>
377 <para>
378 The SPI bus facilities listed here provide a generalized
379 interface to declare SPI busses and devices, manage them
380 according to the standard Linux driver model, and perform
381 input/output operations.
382 At this time, only "master" side interfaces are supported,
383 where Linux talks to SPI peripherals and does not implement
384 such a peripheral itself.
385 (Interfaces to support implementing SPI slaves would
386 necessarily look different.)
387 </para>
388 <para>
389 The programming interface is structured around two kinds of driver,
390 and two kinds of device.
391 A "Controller Driver" abstracts the controller hardware, which may
392 be as simple as a set of GPIO pins or as complex as a pair of FIFOs
393 connected to dual DMA engines on the other side of the SPI shift
394 register (maximizing throughput). Such drivers bridge between
395 whatever bus they sit on (often the platform bus) and SPI, and
396 expose the SPI side of their device as a
397 <structname>struct spi_master</structname>.
398 SPI devices are children of that master, represented as a
399 <structname>struct spi_device</structname> and manufactured from
400 <structname>struct spi_board_info</structname> descriptors which
401 are usually provided by board-specific initialization code.
402 A <structname>struct spi_driver</structname> is called a
403 "Protocol Driver", and is bound to a spi_device using normal
404 driver model calls.
405 </para>
406 <para>
407 The I/O model is a set of queued messages. Protocol drivers
408 submit one or more <structname>struct spi_message</structname>
409 objects, which are processed and completed asynchronously.
410 (There are synchronous wrappers, however.) Messages are
411 built from one or more <structname>struct spi_transfer</structname>
412 objects, each of which wraps a full duplex SPI transfer.
413 A variety of protocol tweaking options are needed, because
414 different chips adopt very different policies for how they
415 use the bits transferred with SPI.
416 </para>
417!Iinclude/linux/spi/spi.h
418!Fdrivers/spi/spi.c spi_register_board_info
419!Edrivers/spi/spi.c
420 </chapter>
421
422 <chapter id="i2c">
423 <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
424
425 <para>
426 I<superscript>2</superscript>C (or without fancy typography, "I2C")
427 is an acronym for the "Inter-IC" bus, a simple bus protocol which is
428 widely used where low data rate communications suffice.
429 Since it's also a licensed trademark, some vendors use another
430 name (such as "Two-Wire Interface", TWI) for the same bus.
431 I2C only needs two signals (SCL for clock, SDA for data), conserving
432 board real estate and minimizing signal quality issues.
433 Most I2C devices use seven bit addresses, and bus speeds of up
434 to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
435 found wide use.
436 I2C is a multi-master bus; open drain signaling is used to
437 arbitrate between masters, as well as to handshake and to
438 synchronize clocks from slower clients.
439 </para>
440
441 <para>
442 The Linux I2C programming interfaces support only the master
443 side of bus interactions, not the slave side.
444 The programming interface is structured around two kinds of driver,
445 and two kinds of device.
446 An I2C "Adapter Driver" abstracts the controller hardware; it binds
447 to a physical device (perhaps a PCI device or platform_device) and
448 exposes a <structname>struct i2c_adapter</structname> representing
449 each I2C bus segment it manages.
450 On each I2C bus segment will be I2C devices represented by a
451 <structname>struct i2c_client</structname>. Those devices will
452 be bound to a <structname>struct i2c_driver</structname>,
453 which should follow the standard Linux driver model.
454 (At this writing, a legacy model is more widely used.)
455 There are functions to perform various I2C protocol operations; at
456 this writing all such functions are usable only from task context.
457 </para>
458
459 <para>
460 The System Management Bus (SMBus) is a sibling protocol. Most SMBus
461 systems are also I2C conformant. The electrical constraints are
462 tighter for SMBus, and it standardizes particular protocol messages
463 and idioms. Controllers that support I2C can also support most
464 SMBus operations, but SMBus controllers don't support all the protocol
465 options that an I2C controller will.
466 There are functions to perform various SMBus protocol operations,
467 either using I2C primitives or by issuing SMBus commands to
468 i2c_adapter devices which don't support those I2C operations.
469 </para>
470
471!Iinclude/linux/i2c.h
472!Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
473!Edrivers/i2c/i2c-core.c
474 </chapter>
475
476 <chapter id="hsi">
477 <title>High Speed Synchronous Serial Interface (HSI)</title>
478
479 <para>
480 High Speed Synchronous Serial Interface (HSI) is a
481 serial interface mainly used for connecting application
482 engines (APE) with cellular modem engines (CMT) in cellular
483 handsets.
484
485 HSI provides multiplexing for up to 16 logical channels,
486 low-latency and full duplex communication.
487 </para>
488
489!Iinclude/linux/hsi/hsi.h
490!Edrivers/hsi/hsi.c
491 </chapter>
492
493 <chapter id="pwm">
494 <title>Pulse-Width Modulation (PWM)</title>
495 <para>
496 Pulse-width modulation is a modulation technique primarily used to
497 control power supplied to electrical devices.
498 </para>
499 <para>
500 The PWM framework provides an abstraction for providers and consumers
501 of PWM signals. A controller that provides one or more PWM signals is
502 registered as <structname>struct pwm_chip</structname>. Providers are
503 expected to embed this structure in a driver-specific structure. This
504 structure contains fields that describe a particular chip.
505 </para>
506 <para>
507 A chip exposes one or more PWM signal sources, each of which exposed
508 as a <structname>struct pwm_device</structname>. Operations can be
509 performed on PWM devices to control the period, duty cycle, polarity
510 and active state of the signal.
511 </para>
512 <para>
513 Note that PWM devices are exclusive resources: they can always only be
514 used by one consumer at a time.
515 </para>
516!Iinclude/linux/pwm.h
517!Edrivers/pwm/core.c
518 </chapter>
519
520</book>