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/timer.c
58     </sect1>
59     <sect1><title>Wait queues and Wake events</title>
60!Iinclude/linux/wait.h
61!Ekernel/wait.c
62     </sect1>
63     <sect1><title>High-resolution timers</title>
64!Iinclude/linux/ktime.h
65!Iinclude/linux/hrtimer.h
66!Ekernel/hrtimer.c
67     </sect1>
68     <sect1><title>Workqueues and Kevents</title>
69!Ekernel/workqueue.c
70     </sect1>
71     <sect1><title>Internal Functions</title>
72!Ikernel/exit.c
73!Ikernel/signal.c
74!Iinclude/linux/kthread.h
75!Ekernel/kthread.c
76     </sect1>
77
78     <sect1><title>Kernel objects manipulation</title>
79<!--
80X!Iinclude/linux/kobject.h
81-->
82!Elib/kobject.c
83     </sect1>
84
85     <sect1><title>Kernel utility functions</title>
86!Iinclude/linux/kernel.h
87!Ekernel/printk.c
88!Ekernel/panic.c
89!Ekernel/sys.c
90!Ekernel/rcupdate.c
91     </sect1>
92
93     <sect1><title>Device Resource Management</title>
94!Edrivers/base/devres.c
95     </sect1>
96
97  </chapter>
98
99  <chapter id="devdrivers">
100     <title>Device drivers infrastructure</title>
101     <sect1><title>The Basic Device Driver-Model Structures </title>
102!Iinclude/linux/device.h
103     </sect1>
104     <sect1><title>Device Drivers Base</title>
105!Idrivers/base/init.c
106!Edrivers/base/driver.c
107!Edrivers/base/core.c
108!Edrivers/base/syscore.c
109!Edrivers/base/class.c
110!Idrivers/base/node.c
111!Edrivers/base/firmware_class.c
112!Edrivers/base/transport_class.c
113<!-- Cannot be included, because
114     attribute_container_add_class_device_adapter
115 and attribute_container_classdev_to_container
116     exceed allowed 44 characters maximum
117X!Edrivers/base/attribute_container.c
118-->
119!Edrivers/base/dd.c
120<!--
121X!Edrivers/base/interface.c
122-->
123!Iinclude/linux/platform_device.h
124!Edrivers/base/platform.c
125!Edrivers/base/bus.c
126     </sect1>
127     <sect1><title>Device Drivers DMA Management</title>
128!Edrivers/base/dma-buf.c
129!Edrivers/base/dma-coherent.c
130!Edrivers/base/dma-mapping.c
131     </sect1>
132     <sect1><title>Device Drivers Power Management</title>
133!Edrivers/base/power/main.c
134     </sect1>
135     <sect1><title>Device Drivers ACPI Support</title>
136<!-- Internal functions only
137X!Edrivers/acpi/sleep/main.c
138X!Edrivers/acpi/sleep/wakeup.c
139X!Edrivers/acpi/motherboard.c
140X!Edrivers/acpi/bus.c
141-->
142!Edrivers/acpi/scan.c
143!Idrivers/acpi/scan.c
144<!-- No correct structured comments
145X!Edrivers/acpi/pci_bind.c
146-->
147     </sect1>
148     <sect1><title>Device drivers PnP support</title>
149!Idrivers/pnp/core.c
150<!-- No correct structured comments
151X!Edrivers/pnp/system.c
152 -->
153!Edrivers/pnp/card.c
154!Idrivers/pnp/driver.c
155!Edrivers/pnp/manager.c
156!Edrivers/pnp/support.c
157     </sect1>
158     <sect1><title>Userspace IO devices</title>
159!Edrivers/uio/uio.c
160!Iinclude/linux/uio_driver.h
161     </sect1>
162  </chapter>
163
164  <chapter id="parportdev">
165     <title>Parallel Port Devices</title>
166!Iinclude/linux/parport.h
167!Edrivers/parport/ieee1284.c
168!Edrivers/parport/share.c
169!Idrivers/parport/daisy.c
170  </chapter>
171
172  <chapter id="message_devices">
173	<title>Message-based devices</title>
174     <sect1><title>Fusion message devices</title>
175!Edrivers/message/fusion/mptbase.c
176!Idrivers/message/fusion/mptbase.c
177!Edrivers/message/fusion/mptscsih.c
178!Idrivers/message/fusion/mptscsih.c
179!Idrivers/message/fusion/mptctl.c
180!Idrivers/message/fusion/mptspi.c
181!Idrivers/message/fusion/mptfc.c
182!Idrivers/message/fusion/mptlan.c
183     </sect1>
184     <sect1><title>I2O message devices</title>
185!Iinclude/linux/i2o.h
186!Idrivers/message/i2o/core.h
187!Edrivers/message/i2o/iop.c
188!Idrivers/message/i2o/iop.c
189!Idrivers/message/i2o/config-osm.c
190!Edrivers/message/i2o/exec-osm.c
191!Idrivers/message/i2o/exec-osm.c
192!Idrivers/message/i2o/bus-osm.c
193!Edrivers/message/i2o/device.c
194!Idrivers/message/i2o/device.c
195!Idrivers/message/i2o/driver.c
196!Idrivers/message/i2o/pci.c
197!Idrivers/message/i2o/i2o_block.c
198!Idrivers/message/i2o/i2o_scsi.c
199!Idrivers/message/i2o/i2o_proc.c
200     </sect1>
201  </chapter>
202
203  <chapter id="snddev">
204     <title>Sound Devices</title>
205!Iinclude/sound/core.h
206!Esound/sound_core.c
207!Iinclude/sound/pcm.h
208!Esound/core/pcm.c
209!Esound/core/device.c
210!Esound/core/info.c
211!Esound/core/rawmidi.c
212!Esound/core/sound.c
213!Esound/core/memory.c
214!Esound/core/pcm_memory.c
215!Esound/core/init.c
216!Esound/core/isadma.c
217!Esound/core/control.c
218!Esound/core/pcm_lib.c
219!Esound/core/hwdep.c
220!Esound/core/pcm_native.c
221!Esound/core/memalloc.c
222<!-- FIXME: Removed for now since no structured comments in source
223X!Isound/sound_firmware.c
224-->
225  </chapter>
226
227  <chapter id="uart16x50">
228     <title>16x50 UART Driver</title>
229!Edrivers/tty/serial/serial_core.c
230!Edrivers/tty/serial/8250/8250.c
231  </chapter>
232
233  <chapter id="fbdev">
234     <title>Frame Buffer Library</title>
235
236     <para>
237       The frame buffer drivers depend heavily on four data structures.
238       These structures are declared in include/linux/fb.h.  They are
239       fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
240       The last three can be made available to and from userland.
241     </para>
242
243     <para>
244       fb_info defines the current state of a particular video card.
245       Inside fb_info, there exists a fb_ops structure which is a
246       collection of needed functions to make fbdev and fbcon work.
247       fb_info is only visible to the kernel.
248     </para>
249
250     <para>
251       fb_var_screeninfo is used to describe the features of a video card
252       that are user defined.  With fb_var_screeninfo, things such as
253       depth and the resolution may be defined.
254     </para>
255
256     <para>
257       The next structure is fb_fix_screeninfo. This defines the
258       properties of a card that are created when a mode is set and can't
259       be changed otherwise.  A good example of this is the start of the
260       frame buffer memory.  This "locks" the address of the frame buffer
261       memory, so that it cannot be changed or moved.
262     </para>
263
264     <para>
265       The last structure is fb_monospecs. In the old API, there was
266       little importance for fb_monospecs. This allowed for forbidden things
267       such as setting a mode of 800x600 on a fix frequency monitor. With
268       the new API, fb_monospecs prevents such things, and if used
269       correctly, can prevent a monitor from being cooked.  fb_monospecs
270       will not be useful until kernels 2.5.x.
271     </para>
272
273     <sect1><title>Frame Buffer Memory</title>
274!Edrivers/video/fbmem.c
275     </sect1>
276<!--
277     <sect1><title>Frame Buffer Console</title>
278X!Edrivers/video/console/fbcon.c
279     </sect1>
280-->
281     <sect1><title>Frame Buffer Colormap</title>
282!Edrivers/video/fbcmap.c
283     </sect1>
284<!-- FIXME:
285  drivers/video/fbgen.c has no docs, which stuffs up the sgml.  Comment
286  out until somebody adds docs.  KAO
287     <sect1><title>Frame Buffer Generic Functions</title>
288X!Idrivers/video/fbgen.c
289     </sect1>
290KAO -->
291     <sect1><title>Frame Buffer Video Mode Database</title>
292!Idrivers/video/modedb.c
293!Edrivers/video/modedb.c
294     </sect1>
295     <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
296!Edrivers/video/macmodes.c
297     </sect1>
298     <sect1><title>Frame Buffer Fonts</title>
299        <para>
300           Refer to the file drivers/video/console/fonts.c for more information.
301        </para>
302<!-- FIXME: Removed for now since no structured comments in source
303X!Idrivers/video/console/fonts.c
304-->
305     </sect1>
306  </chapter>
307
308  <chapter id="input_subsystem">
309     <title>Input Subsystem</title>
310     <sect1><title>Input core</title>
311!Iinclude/linux/input.h
312!Edrivers/input/input.c
313!Edrivers/input/ff-core.c
314!Edrivers/input/ff-memless.c
315     </sect1>
316     <sect1><title>Multitouch Library</title>
317!Iinclude/linux/input/mt.h
318!Edrivers/input/input-mt.c
319     </sect1>
320     <sect1><title>Polled input devices</title>
321!Iinclude/linux/input-polldev.h
322!Edrivers/input/input-polldev.c
323     </sect1>
324     <sect1><title>Matrix keyboars/keypads</title>
325!Iinclude/linux/input/matrix_keypad.h
326     </sect1>
327     <sect1><title>Sparse keymap support</title>
328!Iinclude/linux/input/sparse-keymap.h
329!Edrivers/input/sparse-keymap.c
330     </sect1>
331  </chapter>
332
333  <chapter id="spi">
334      <title>Serial Peripheral Interface (SPI)</title>
335  <para>
336	SPI is the "Serial Peripheral Interface", widely used with
337	embedded systems because it is a simple and efficient
338	interface:  basically a multiplexed shift register.
339	Its three signal wires hold a clock (SCK, often in the range
340	of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
341	a "Master In, Slave Out" (MISO) data line.
342	SPI is a full duplex protocol; for each bit shifted out the
343	MOSI line (one per clock) another is shifted in on the MISO line.
344	Those bits are assembled into words of various sizes on the
345	way to and from system memory.
346	An additional chipselect line is usually active-low (nCS);
347	four signals are normally used for each peripheral, plus
348	sometimes an interrupt.
349  </para>
350  <para>
351	The SPI bus facilities listed here provide a generalized
352	interface to declare SPI busses and devices, manage them
353	according to the standard Linux driver model, and perform
354	input/output operations.
355	At this time, only "master" side interfaces are supported,
356	where Linux talks to SPI peripherals and does not implement
357	such a peripheral itself.
358	(Interfaces to support implementing SPI slaves would
359	necessarily look different.)
360  </para>
361  <para>
362	The programming interface is structured around two kinds of driver,
363	and two kinds of device.
364	A "Controller Driver" abstracts the controller hardware, which may
365	be as simple as a set of GPIO pins or as complex as a pair of FIFOs
366	connected to dual DMA engines on the other side of the SPI shift
367	register (maximizing throughput).  Such drivers bridge between
368	whatever bus they sit on (often the platform bus) and SPI, and
369	expose the SPI side of their device as a
370	<structname>struct spi_master</structname>.
371	SPI devices are children of that master, represented as a
372	<structname>struct spi_device</structname> and manufactured from
373	<structname>struct spi_board_info</structname> descriptors which
374	are usually provided by board-specific initialization code.
375	A <structname>struct spi_driver</structname> is called a
376	"Protocol Driver", and is bound to a spi_device using normal
377	driver model calls.
378  </para>
379  <para>
380	The I/O model is a set of queued messages.  Protocol drivers
381	submit one or more <structname>struct spi_message</structname>
382	objects, which are processed and completed asynchronously.
383	(There are synchronous wrappers, however.)  Messages are
384	built from one or more <structname>struct spi_transfer</structname>
385	objects, each of which wraps a full duplex SPI transfer.
386	A variety of protocol tweaking options are needed, because
387	different chips adopt very different policies for how they
388	use the bits transferred with SPI.
389  </para>
390!Iinclude/linux/spi/spi.h
391!Fdrivers/spi/spi.c spi_register_board_info
392!Edrivers/spi/spi.c
393  </chapter>
394
395  <chapter id="i2c">
396     <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
397
398     <para>
399	I<superscript>2</superscript>C (or without fancy typography, "I2C")
400	is an acronym for the "Inter-IC" bus, a simple bus protocol which is
401	widely used where low data rate communications suffice.
402	Since it's also a licensed trademark, some vendors use another
403	name (such as "Two-Wire Interface", TWI) for the same bus.
404	I2C only needs two signals (SCL for clock, SDA for data), conserving
405	board real estate and minimizing signal quality issues.
406	Most I2C devices use seven bit addresses, and bus speeds of up
407	to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
408	found wide use.
409	I2C is a multi-master bus; open drain signaling is used to
410	arbitrate between masters, as well as to handshake and to
411	synchronize clocks from slower clients.
412     </para>
413
414     <para>
415	The Linux I2C programming interfaces support only the master
416	side of bus interactions, not the slave side.
417	The programming interface is structured around two kinds of driver,
418	and two kinds of device.
419	An I2C "Adapter Driver" abstracts the controller hardware; it binds
420	to a physical device (perhaps a PCI device or platform_device) and
421	exposes a <structname>struct i2c_adapter</structname> representing
422	each I2C bus segment it manages.
423	On each I2C bus segment will be I2C devices represented by a
424	<structname>struct i2c_client</structname>.  Those devices will
425	be bound to a <structname>struct i2c_driver</structname>,
426	which should follow the standard Linux driver model.
427	(At this writing, a legacy model is more widely used.)
428	There are functions to perform various I2C protocol operations; at
429	this writing all such functions are usable only from task context.
430     </para>
431
432     <para>
433	The System Management Bus (SMBus) is a sibling protocol.  Most SMBus
434	systems are also I2C conformant.  The electrical constraints are
435	tighter for SMBus, and it standardizes particular protocol messages
436	and idioms.  Controllers that support I2C can also support most
437	SMBus operations, but SMBus controllers don't support all the protocol
438	options that an I2C controller will.
439	There are functions to perform various SMBus protocol operations,
440	either using I2C primitives or by issuing SMBus commands to
441	i2c_adapter devices which don't support those I2C operations.
442     </para>
443
444!Iinclude/linux/i2c.h
445!Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
446!Edrivers/i2c/i2c-core.c
447  </chapter>
448
449</book>
450