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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="LinuxKernelAPI">
6 <bookinfo>
7 <title>The Linux Kernel API</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!Iinclude/asm-x86/atomic_32.h
49!Iinclude/asm-x86/unaligned.h
50 </sect1>
51
52 <sect1><title>Delaying, scheduling, and timer routines</title>
53!Iinclude/linux/sched.h
54!Ekernel/sched.c
55!Ekernel/timer.c
56 </sect1>
57 <sect1><title>High-resolution timers</title>
58!Iinclude/linux/ktime.h
59!Iinclude/linux/hrtimer.h
60!Ekernel/hrtimer.c
61 </sect1>
62 <sect1><title>Workqueues and Kevents</title>
63!Ekernel/workqueue.c
64 </sect1>
65 <sect1><title>Internal Functions</title>
66!Ikernel/exit.c
67!Ikernel/signal.c
68!Iinclude/linux/kthread.h
69!Ekernel/kthread.c
70 </sect1>
71
72 <sect1><title>Kernel objects manipulation</title>
73<!--
74X!Iinclude/linux/kobject.h
75-->
76!Elib/kobject.c
77 </sect1>
78
79 <sect1><title>Kernel utility functions</title>
80!Iinclude/linux/kernel.h
81!Ekernel/printk.c
82!Ekernel/panic.c
83!Ekernel/sys.c
84!Ekernel/rcupdate.c
85 </sect1>
86
87 <sect1><title>Device Resource Management</title>
88!Edrivers/base/devres.c
89 </sect1>
90
91 </chapter>
92
93 <chapter id="adt">
94 <title>Data Types</title>
95 <sect1><title>Doubly Linked Lists</title>
96!Iinclude/linux/list.h
97 </sect1>
98 </chapter>
99
100 <chapter id="libc">
101 <title>Basic C Library Functions</title>
102
103 <para>
104 When writing drivers, you cannot in general use routines which are
105 from the C Library. Some of the functions have been found generally
106 useful and they are listed below. The behaviour of these functions
107 may vary slightly from those defined by ANSI, and these deviations
108 are noted in the text.
109 </para>
110
111 <sect1><title>String Conversions</title>
112!Ilib/vsprintf.c
113!Elib/vsprintf.c
114 </sect1>
115 <sect1><title>String Manipulation</title>
116<!-- All functions are exported at now
117X!Ilib/string.c
118 -->
119!Elib/string.c
120 </sect1>
121 <sect1><title>Bit Operations</title>
122!Iinclude/asm-x86/bitops_32.h
123 </sect1>
124 </chapter>
125
126 <chapter id="kernel-lib">
127 <title>Basic Kernel Library Functions</title>
128
129 <para>
130 The Linux kernel provides more basic utility functions.
131 </para>
132
133 <sect1><title>Bitmap Operations</title>
134!Elib/bitmap.c
135!Ilib/bitmap.c
136 </sect1>
137
138 <sect1><title>Command-line Parsing</title>
139!Elib/cmdline.c
140 </sect1>
141
142 <sect1 id="crc"><title>CRC Functions</title>
143!Elib/crc7.c
144!Elib/crc16.c
145!Elib/crc-itu-t.c
146!Elib/crc32.c
147!Elib/crc-ccitt.c
148 </sect1>
149 </chapter>
150
151 <chapter id="mm">
152 <title>Memory Management in Linux</title>
153 <sect1><title>The Slab Cache</title>
154!Iinclude/linux/slab.h
155!Emm/slab.c
156 </sect1>
157 <sect1><title>User Space Memory Access</title>
158!Iinclude/asm-x86/uaccess_32.h
159!Earch/x86/lib/usercopy_32.c
160 </sect1>
161 <sect1><title>More Memory Management Functions</title>
162!Emm/readahead.c
163!Emm/filemap.c
164!Emm/memory.c
165!Emm/vmalloc.c
166!Imm/page_alloc.c
167!Emm/mempool.c
168!Emm/dmapool.c
169!Emm/page-writeback.c
170!Emm/truncate.c
171 </sect1>
172 </chapter>
173
174
175 <chapter id="ipc">
176 <title>Kernel IPC facilities</title>
177
178 <sect1><title>IPC utilities</title>
179!Iipc/util.c
180 </sect1>
181 </chapter>
182
183 <chapter id="kfifo">
184 <title>FIFO Buffer</title>
185 <sect1><title>kfifo interface</title>
186!Iinclude/linux/kfifo.h
187!Ekernel/kfifo.c
188 </sect1>
189 </chapter>
190
191 <chapter id="relayfs">
192 <title>relay interface support</title>
193
194 <para>
195 Relay interface support
196 is designed to provide an efficient mechanism for tools and
197 facilities to relay large amounts of data from kernel space to
198 user space.
199 </para>
200
201 <sect1><title>relay interface</title>
202!Ekernel/relay.c
203!Ikernel/relay.c
204 </sect1>
205 </chapter>
206
207 <chapter id="modload">
208 <title>Module Support</title>
209 <sect1><title>Module Loading</title>
210!Ekernel/kmod.c
211 </sect1>
212 <sect1><title>Inter Module support</title>
213 <para>
214 Refer to the file kernel/module.c for more information.
215 </para>
216<!-- FIXME: Removed for now since no structured comments in source
217X!Ekernel/module.c
218-->
219 </sect1>
220 </chapter>
221
222 <chapter id="hardware">
223 <title>Hardware Interfaces</title>
224 <sect1><title>Interrupt Handling</title>
225!Ekernel/irq/manage.c
226 </sect1>
227
228 <sect1><title>DMA Channels</title>
229!Ekernel/dma.c
230 </sect1>
231
232 <sect1><title>Resources Management</title>
233!Ikernel/resource.c
234!Ekernel/resource.c
235 </sect1>
236
237 <sect1><title>MTRR Handling</title>
238!Earch/x86/kernel/cpu/mtrr/main.c
239 </sect1>
240
241 <sect1><title>PCI Support Library</title>
242!Edrivers/pci/pci.c
243!Edrivers/pci/pci-driver.c
244!Edrivers/pci/remove.c
245!Edrivers/pci/pci-acpi.c
246!Edrivers/pci/search.c
247!Edrivers/pci/msi.c
248!Edrivers/pci/bus.c
249<!-- FIXME: Removed for now since no structured comments in source
250X!Edrivers/pci/hotplug.c
251-->
252!Edrivers/pci/probe.c
253!Edrivers/pci/rom.c
254 </sect1>
255 <sect1><title>PCI Hotplug Support Library</title>
256!Edrivers/pci/hotplug/pci_hotplug_core.c
257 </sect1>
258 <sect1><title>MCA Architecture</title>
259 <sect2><title>MCA Device Functions</title>
260 <para>
261 Refer to the file arch/x86/kernel/mca_32.c for more information.
262 </para>
263<!-- FIXME: Removed for now since no structured comments in source
264X!Earch/x86/kernel/mca_32.c
265-->
266 </sect2>
267 <sect2><title>MCA Bus DMA</title>
268!Iinclude/asm-x86/mca_dma.h
269 </sect2>
270 </sect1>
271 </chapter>
272
273 <chapter id="firmware">
274 <title>Firmware Interfaces</title>
275 <sect1><title>DMI Interfaces</title>
276!Edrivers/firmware/dmi_scan.c
277 </sect1>
278 <sect1><title>EDD Interfaces</title>
279!Idrivers/firmware/edd.c
280 </sect1>
281 </chapter>
282
283 <chapter id="security">
284 <title>Security Framework</title>
285!Isecurity/security.c
286 </chapter>
287
288 <chapter id="audit">
289 <title>Audit Interfaces</title>
290!Ekernel/audit.c
291!Ikernel/auditsc.c
292!Ikernel/auditfilter.c
293 </chapter>
294
295 <chapter id="accounting">
296 <title>Accounting Framework</title>
297!Ikernel/acct.c
298 </chapter>
299
300 <chapter id="pmfuncs">
301 <title>Power Management</title>
302!Ekernel/power/pm.c
303 </chapter>
304
305 <chapter id="devdrivers">
306 <title>Device drivers infrastructure</title>
307 <sect1><title>Device Drivers Base</title>
308<!--
309X!Iinclude/linux/device.h
310-->
311!Edrivers/base/driver.c
312!Edrivers/base/core.c
313!Edrivers/base/class.c
314!Edrivers/base/firmware_class.c
315!Edrivers/base/transport_class.c
316<!-- Cannot be included, because
317 attribute_container_add_class_device_adapter
318 and attribute_container_classdev_to_container
319 exceed allowed 44 characters maximum
320X!Edrivers/base/attribute_container.c
321-->
322!Edrivers/base/sys.c
323<!--
324X!Edrivers/base/interface.c
325-->
326!Edrivers/base/platform.c
327!Edrivers/base/bus.c
328 </sect1>
329 <sect1><title>Device Drivers Power Management</title>
330!Edrivers/base/power/main.c
331 </sect1>
332 <sect1><title>Device Drivers ACPI Support</title>
333<!-- Internal functions only
334X!Edrivers/acpi/sleep/main.c
335X!Edrivers/acpi/sleep/wakeup.c
336X!Edrivers/acpi/motherboard.c
337X!Edrivers/acpi/bus.c
338-->
339!Edrivers/acpi/scan.c
340!Idrivers/acpi/scan.c
341<!-- No correct structured comments
342X!Edrivers/acpi/pci_bind.c
343-->
344 </sect1>
345 <sect1><title>Device drivers PnP support</title>
346!Idrivers/pnp/core.c
347<!-- No correct structured comments
348X!Edrivers/pnp/system.c
349 -->
350!Edrivers/pnp/card.c
351!Idrivers/pnp/driver.c
352!Edrivers/pnp/manager.c
353!Edrivers/pnp/support.c
354 </sect1>
355 <sect1><title>Userspace IO devices</title>
356!Edrivers/uio/uio.c
357!Iinclude/linux/uio_driver.h
358 </sect1>
359 </chapter>
360
361 <chapter id="blkdev">
362 <title>Block Devices</title>
363!Eblock/blk-core.c
364!Eblock/blk-map.c
365!Iblock/blk-sysfs.c
366!Eblock/blk-settings.c
367!Eblock/blk-exec.c
368!Eblock/blk-barrier.c
369!Eblock/blk-tag.c
370 </chapter>
371
372 <chapter id="chrdev">
373 <title>Char devices</title>
374!Efs/char_dev.c
375 </chapter>
376
377 <chapter id="miscdev">
378 <title>Miscellaneous Devices</title>
379!Edrivers/char/misc.c
380 </chapter>
381
382 <chapter id="parportdev">
383 <title>Parallel Port Devices</title>
384!Iinclude/linux/parport.h
385!Edrivers/parport/ieee1284.c
386!Edrivers/parport/share.c
387!Idrivers/parport/daisy.c
388 </chapter>
389
390 <chapter id="message_devices">
391 <title>Message-based devices</title>
392 <sect1><title>Fusion message devices</title>
393!Edrivers/message/fusion/mptbase.c
394!Idrivers/message/fusion/mptbase.c
395!Edrivers/message/fusion/mptscsih.c
396!Idrivers/message/fusion/mptscsih.c
397!Idrivers/message/fusion/mptctl.c
398!Idrivers/message/fusion/mptspi.c
399!Idrivers/message/fusion/mptfc.c
400!Idrivers/message/fusion/mptlan.c
401 </sect1>
402 <sect1><title>I2O message devices</title>
403!Iinclude/linux/i2o.h
404!Idrivers/message/i2o/core.h
405!Edrivers/message/i2o/iop.c
406!Idrivers/message/i2o/iop.c
407!Idrivers/message/i2o/config-osm.c
408!Edrivers/message/i2o/exec-osm.c
409!Idrivers/message/i2o/exec-osm.c
410!Idrivers/message/i2o/bus-osm.c
411!Edrivers/message/i2o/device.c
412!Idrivers/message/i2o/device.c
413!Idrivers/message/i2o/driver.c
414!Idrivers/message/i2o/pci.c
415!Idrivers/message/i2o/i2o_block.c
416!Idrivers/message/i2o/i2o_scsi.c
417!Idrivers/message/i2o/i2o_proc.c
418 </sect1>
419 </chapter>
420
421 <chapter id="snddev">
422 <title>Sound Devices</title>
423!Iinclude/sound/core.h
424!Esound/sound_core.c
425!Iinclude/sound/pcm.h
426!Esound/core/pcm.c
427!Esound/core/device.c
428!Esound/core/info.c
429!Esound/core/rawmidi.c
430!Esound/core/sound.c
431!Esound/core/memory.c
432!Esound/core/pcm_memory.c
433!Esound/core/init.c
434!Esound/core/isadma.c
435!Esound/core/control.c
436!Esound/core/pcm_lib.c
437!Esound/core/hwdep.c
438!Esound/core/pcm_native.c
439!Esound/core/memalloc.c
440<!-- FIXME: Removed for now since no structured comments in source
441X!Isound/sound_firmware.c
442-->
443 </chapter>
444
445 <chapter id="uart16x50">
446 <title>16x50 UART Driver</title>
447!Iinclude/linux/serial_core.h
448!Edrivers/serial/serial_core.c
449!Edrivers/serial/8250.c
450 </chapter>
451
452 <chapter id="fbdev">
453 <title>Frame Buffer Library</title>
454
455 <para>
456 The frame buffer drivers depend heavily on four data structures.
457 These structures are declared in include/linux/fb.h. They are
458 fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
459 The last three can be made available to and from userland.
460 </para>
461
462 <para>
463 fb_info defines the current state of a particular video card.
464 Inside fb_info, there exists a fb_ops structure which is a
465 collection of needed functions to make fbdev and fbcon work.
466 fb_info is only visible to the kernel.
467 </para>
468
469 <para>
470 fb_var_screeninfo is used to describe the features of a video card
471 that are user defined. With fb_var_screeninfo, things such as
472 depth and the resolution may be defined.
473 </para>
474
475 <para>
476 The next structure is fb_fix_screeninfo. This defines the
477 properties of a card that are created when a mode is set and can't
478 be changed otherwise. A good example of this is the start of the
479 frame buffer memory. This "locks" the address of the frame buffer
480 memory, so that it cannot be changed or moved.
481 </para>
482
483 <para>
484 The last structure is fb_monospecs. In the old API, there was
485 little importance for fb_monospecs. This allowed for forbidden things
486 such as setting a mode of 800x600 on a fix frequency monitor. With
487 the new API, fb_monospecs prevents such things, and if used
488 correctly, can prevent a monitor from being cooked. fb_monospecs
489 will not be useful until kernels 2.5.x.
490 </para>
491
492 <sect1><title>Frame Buffer Memory</title>
493!Edrivers/video/fbmem.c
494 </sect1>
495<!--
496 <sect1><title>Frame Buffer Console</title>
497X!Edrivers/video/console/fbcon.c
498 </sect1>
499-->
500 <sect1><title>Frame Buffer Colormap</title>
501!Edrivers/video/fbcmap.c
502 </sect1>
503<!-- FIXME:
504 drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
505 out until somebody adds docs. KAO
506 <sect1><title>Frame Buffer Generic Functions</title>
507X!Idrivers/video/fbgen.c
508 </sect1>
509KAO -->
510 <sect1><title>Frame Buffer Video Mode Database</title>
511!Idrivers/video/modedb.c
512!Edrivers/video/modedb.c
513 </sect1>
514 <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
515!Edrivers/video/macmodes.c
516 </sect1>
517 <sect1><title>Frame Buffer Fonts</title>
518 <para>
519 Refer to the file drivers/video/console/fonts.c for more information.
520 </para>
521<!-- FIXME: Removed for now since no structured comments in source
522X!Idrivers/video/console/fonts.c
523-->
524 </sect1>
525 </chapter>
526
527 <chapter id="input_subsystem">
528 <title>Input Subsystem</title>
529!Iinclude/linux/input.h
530!Edrivers/input/input.c
531!Edrivers/input/ff-core.c
532!Edrivers/input/ff-memless.c
533 </chapter>
534
535 <chapter id="spi">
536 <title>Serial Peripheral Interface (SPI)</title>
537 <para>
538 SPI is the "Serial Peripheral Interface", widely used with
539 embedded systems because it is a simple and efficient
540 interface: basically a multiplexed shift register.
541 Its three signal wires hold a clock (SCK, often in the range
542 of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
543 a "Master In, Slave Out" (MISO) data line.
544 SPI is a full duplex protocol; for each bit shifted out the
545 MOSI line (one per clock) another is shifted in on the MISO line.
546 Those bits are assembled into words of various sizes on the
547 way to and from system memory.
548 An additional chipselect line is usually active-low (nCS);
549 four signals are normally used for each peripheral, plus
550 sometimes an interrupt.
551 </para>
552 <para>
553 The SPI bus facilities listed here provide a generalized
554 interface to declare SPI busses and devices, manage them
555 according to the standard Linux driver model, and perform
556 input/output operations.
557 At this time, only "master" side interfaces are supported,
558 where Linux talks to SPI peripherals and does not implement
559 such a peripheral itself.
560 (Interfaces to support implementing SPI slaves would
561 necessarily look different.)
562 </para>
563 <para>
564 The programming interface is structured around two kinds of driver,
565 and two kinds of device.
566 A "Controller Driver" abstracts the controller hardware, which may
567 be as simple as a set of GPIO pins or as complex as a pair of FIFOs
568 connected to dual DMA engines on the other side of the SPI shift
569 register (maximizing throughput). Such drivers bridge between
570 whatever bus they sit on (often the platform bus) and SPI, and
571 expose the SPI side of their device as a
572 <structname>struct spi_master</structname>.
573 SPI devices are children of that master, represented as a
574 <structname>struct spi_device</structname> and manufactured from
575 <structname>struct spi_board_info</structname> descriptors which
576 are usually provided by board-specific initialization code.
577 A <structname>struct spi_driver</structname> is called a
578 "Protocol Driver", and is bound to a spi_device using normal
579 driver model calls.
580 </para>
581 <para>
582 The I/O model is a set of queued messages. Protocol drivers
583 submit one or more <structname>struct spi_message</structname>
584 objects, which are processed and completed asynchronously.
585 (There are synchronous wrappers, however.) Messages are
586 built from one or more <structname>struct spi_transfer</structname>
587 objects, each of which wraps a full duplex SPI transfer.
588 A variety of protocol tweaking options are needed, because
589 different chips adopt very different policies for how they
590 use the bits transferred with SPI.
591 </para>
592!Iinclude/linux/spi/spi.h
593!Fdrivers/spi/spi.c spi_register_board_info
594!Edrivers/spi/spi.c
595 </chapter>
596
597 <chapter id="i2c">
598 <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
599
600 <para>
601 I<superscript>2</superscript>C (or without fancy typography, "I2C")
602 is an acronym for the "Inter-IC" bus, a simple bus protocol which is
603 widely used where low data rate communications suffice.
604 Since it's also a licensed trademark, some vendors use another
605 name (such as "Two-Wire Interface", TWI) for the same bus.
606 I2C only needs two signals (SCL for clock, SDA for data), conserving
607 board real estate and minimizing signal quality issues.
608 Most I2C devices use seven bit addresses, and bus speeds of up
609 to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
610 found wide use.
611 I2C is a multi-master bus; open drain signaling is used to
612 arbitrate between masters, as well as to handshake and to
613 synchronize clocks from slower clients.
614 </para>
615
616 <para>
617 The Linux I2C programming interfaces support only the master
618 side of bus interactions, not the slave side.
619 The programming interface is structured around two kinds of driver,
620 and two kinds of device.
621 An I2C "Adapter Driver" abstracts the controller hardware; it binds
622 to a physical device (perhaps a PCI device or platform_device) and
623 exposes a <structname>struct i2c_adapter</structname> representing
624 each I2C bus segment it manages.
625 On each I2C bus segment will be I2C devices represented by a
626 <structname>struct i2c_client</structname>. Those devices will
627 be bound to a <structname>struct i2c_driver</structname>,
628 which should follow the standard Linux driver model.
629 (At this writing, a legacy model is more widely used.)
630 There are functions to perform various I2C protocol operations; at
631 this writing all such functions are usable only from task context.
632 </para>
633
634 <para>
635 The System Management Bus (SMBus) is a sibling protocol. Most SMBus
636 systems are also I2C conformant. The electrical constraints are
637 tighter for SMBus, and it standardizes particular protocol messages
638 and idioms. Controllers that support I2C can also support most
639 SMBus operations, but SMBus controllers don't support all the protocol
640 options that an I2C controller will.
641 There are functions to perform various SMBus protocol operations,
642 either using I2C primitives or by issuing SMBus commands to
643 i2c_adapter devices which don't support those I2C operations.
644 </para>
645
646!Iinclude/linux/i2c.h
647!Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
648!Edrivers/i2c/i2c-core.c
649 </chapter>
650
651</book>