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Based on kernel version 4.3. Page generated on 2015-11-02 12:48 EST.

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	<!--
81	X!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
121	X!Edrivers/base/attribute_container.c
122	-->
123	!Edrivers/base/dd.c
124	<!--
125	X!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
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
151	-->
152	!Edrivers/acpi/scan.c
153	!Idrivers/acpi/scan.c
154	<!-- No correct structured comments
155	X!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
161	X!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
216	X!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>
305	X!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>
315	X!Idrivers/video/fbgen.c
316	     </sect1>
317	KAO -->
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
330	X!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>
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