summaryrefslogtreecommitdiff
path: root/Documentation/DocBook/kernel-api.tmpl
blob: fd2ef4d29b6d6e3f9061a452a089570d4ee654ba (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
	"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>

<book id="LinuxKernelAPI">
 <bookinfo>
  <title>The Linux Kernel API</title>
  
  <legalnotice>
   <para>
     This documentation is free software; you can redistribute
     it and/or modify it under the terms of the GNU General Public
     License as published by the Free Software Foundation; either
     version 2 of the License, or (at your option) any later
     version.
   </para>
      
   <para>
     This program is distributed in the hope that it will be
     useful, but WITHOUT ANY WARRANTY; without even the implied
     warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
     See the GNU General Public License for more details.
   </para>
      
   <para>
     You should have received a copy of the GNU General Public
     License along with this program; if not, write to the Free
     Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
     MA 02111-1307 USA
   </para>
      
   <para>
     For more details see the file COPYING in the source
     distribution of Linux.
   </para>
  </legalnotice>
 </bookinfo>

<toc></toc>

  <chapter id="Basics">
     <title>Driver Basics</title>
     <sect1><title>Driver Entry and Exit points</title>
!Iinclude/linux/init.h
     </sect1>

     <sect1><title>Atomic and pointer manipulation</title>
!Iinclude/asm-i386/atomic.h
!Iinclude/asm-i386/unaligned.h
     </sect1>

     <sect1><title>Delaying, scheduling, and timer routines</title>
!Iinclude/linux/sched.h
!Ekernel/sched.c
!Ekernel/timer.c
     </sect1>
     <sect1><title>High-resolution timers</title>
!Iinclude/linux/ktime.h
!Iinclude/linux/hrtimer.h
!Ekernel/hrtimer.c
     </sect1>
     <sect1><title>Workqueues and Kevents</title>
!Ekernel/workqueue.c
     </sect1>
     <sect1><title>Internal Functions</title>
!Ikernel/exit.c
!Ikernel/signal.c
!Iinclude/linux/kthread.h
!Ekernel/kthread.c
     </sect1>

     <sect1><title>Kernel objects manipulation</title>
<!--
X!Iinclude/linux/kobject.h
-->
!Elib/kobject.c
     </sect1>

     <sect1><title>Kernel utility functions</title>
!Iinclude/linux/kernel.h
!Ekernel/printk.c
!Ekernel/panic.c
!Ekernel/sys.c
!Ekernel/rcupdate.c
     </sect1>

     <sect1><title>Device Resource Management</title>
!Edrivers/base/devres.c
     </sect1>

  </chapter>

  <chapter id="adt">
     <title>Data Types</title>
     <sect1><title>Doubly Linked Lists</title>
!Iinclude/linux/list.h
     </sect1>
  </chapter>

  <chapter id="libc">
     <title>Basic C Library Functions</title>

     <para>
       When writing drivers, you cannot in general use routines which are
       from the C Library.  Some of the functions have been found generally
       useful and they are listed below.  The behaviour of these functions
       may vary slightly from those defined by ANSI, and these deviations
       are noted in the text.
     </para>

     <sect1><title>String Conversions</title>
!Ilib/vsprintf.c
!Elib/vsprintf.c
     </sect1>
     <sect1><title>String Manipulation</title>
<!-- All functions are exported at now
X!Ilib/string.c
 -->
!Elib/string.c
     </sect1>
     <sect1><title>Bit Operations</title>
!Iinclude/asm-i386/bitops.h
     </sect1>
  </chapter>

  <chapter id="kernel-lib">
     <title>Basic Kernel Library Functions</title>

     <para>
       The Linux kernel provides more basic utility functions.
     </para>

     <sect1><title>Bitmap Operations</title>
!Elib/bitmap.c
!Ilib/bitmap.c
     </sect1>

     <sect1><title>Command-line Parsing</title>
!Elib/cmdline.c
     </sect1>

     <sect1 id="crc"><title>CRC Functions</title>
!Elib/crc7.c
!Elib/crc16.c
!Elib/crc-itu-t.c
!Elib/crc32.c
!Elib/crc-ccitt.c
     </sect1>
  </chapter>

  <chapter id="mm">
     <title>Memory Management in Linux</title>
     <sect1><title>The Slab Cache</title>
!Iinclude/linux/slab.h
!Emm/slab.c
     </sect1>
     <sect1><title>User Space Memory Access</title>
!Iinclude/asm-i386/uaccess.h
!Earch/i386/lib/usercopy.c
     </sect1>
     <sect1><title>More Memory Management Functions</title>
!Iinclude/linux/rmap.h
!Emm/readahead.c
!Emm/filemap.c
!Emm/memory.c
!Emm/vmalloc.c
!Imm/page_alloc.c
!Emm/mempool.c
!Emm/page-writeback.c
!Emm/truncate.c
     </sect1>
  </chapter>


  <chapter id="ipc">
     <title>Kernel IPC facilities</title>

     <sect1><title>IPC utilities</title>
!Iipc/util.c
     </sect1>
  </chapter>

  <chapter id="kfifo">
     <title>FIFO Buffer</title>
     <sect1><title>kfifo interface</title>
!Iinclude/linux/kfifo.h
!Ekernel/kfifo.c
     </sect1>
  </chapter>

  <chapter id="relayfs">
     <title>relay interface support</title>

     <para>
	Relay interface support
	is designed to provide an efficient mechanism for tools and
	facilities to relay large amounts of data from kernel space to
	user space.
     </para>

     <sect1><title>relay interface</title>
!Ekernel/relay.c
!Ikernel/relay.c
     </sect1>
  </chapter>

  <chapter id="netcore">
     <title>Linux Networking</title>
     <sect1><title>Networking Base Types</title>
!Iinclude/linux/net.h
     </sect1>
     <sect1><title>Socket Buffer Functions</title>
!Iinclude/linux/skbuff.h
!Iinclude/net/sock.h
!Enet/socket.c
!Enet/core/skbuff.c
!Enet/core/sock.c
!Enet/core/datagram.c
!Enet/core/stream.c
     </sect1>
     <sect1><title>Socket Filter</title>
!Enet/core/filter.c
     </sect1>
     <sect1><title>Generic Network Statistics</title>
!Iinclude/linux/gen_stats.h
!Enet/core/gen_stats.c
!Enet/core/gen_estimator.c
     </sect1>
     <sect1><title>SUN RPC subsystem</title>
<!-- The !D functionality is not perfect, garbage has to be protected by comments
!Dnet/sunrpc/sunrpc_syms.c
-->
!Enet/sunrpc/xdr.c
!Enet/sunrpc/svcsock.c
!Enet/sunrpc/sched.c
     </sect1>
  </chapter>

  <chapter id="netdev">
     <title>Network device support</title>
     <sect1><title>Driver Support</title>
!Enet/core/dev.c
!Enet/ethernet/eth.c
!Iinclude/linux/etherdevice.h
!Edrivers/net/phy/phy.c
!Idrivers/net/phy/phy.c
!Edrivers/net/phy/phy_device.c
!Idrivers/net/phy/phy_device.c
!Edrivers/net/phy/mdio_bus.c
!Idrivers/net/phy/mdio_bus.c
<!-- FIXME: Removed for now since no structured comments in source
X!Enet/core/wireless.c
-->
     </sect1>
     <sect1><title>Synchronous PPP</title>
!Edrivers/net/wan/syncppp.c
     </sect1>
  </chapter>

  <chapter id="modload">
     <title>Module Support</title>
     <sect1><title>Module Loading</title>
!Ekernel/kmod.c
     </sect1>
     <sect1><title>Inter Module support</title>
        <para>
           Refer to the file kernel/module.c for more information.
        </para>
<!-- FIXME: Removed for now since no structured comments in source
X!Ekernel/module.c
-->
     </sect1>
  </chapter>

  <chapter id="hardware">
     <title>Hardware Interfaces</title>
     <sect1><title>Interrupt Handling</title>
!Ekernel/irq/manage.c
     </sect1>

     <sect1><title>DMA Channels</title>
!Ekernel/dma.c
     </sect1>

     <sect1><title>Resources Management</title>
!Ikernel/resource.c
!Ekernel/resource.c
     </sect1>

     <sect1><title>MTRR Handling</title>
!Earch/i386/kernel/cpu/mtrr/main.c
     </sect1>

     <sect1><title>PCI Support Library</title>
!Edrivers/pci/pci.c
!Edrivers/pci/pci-driver.c
!Edrivers/pci/remove.c
!Edrivers/pci/pci-acpi.c
!Edrivers/pci/search.c
!Edrivers/pci/msi.c
!Edrivers/pci/bus.c
<!-- FIXME: Removed for now since no structured comments in source
X!Edrivers/pci/hotplug.c
-->
!Edrivers/pci/probe.c
!Edrivers/pci/rom.c
     </sect1>
     <sect1><title>PCI Hotplug Support Library</title>
!Edrivers/pci/hotplug/pci_hotplug_core.c
     </sect1>
     <sect1><title>MCA Architecture</title>
	<sect2><title>MCA Device Functions</title>
           <para>
              Refer to the file arch/i386/kernel/mca.c for more information.
           </para>
<!-- FIXME: Removed for now since no structured comments in source
X!Earch/i386/kernel/mca.c
-->
	</sect2>
	<sect2><title>MCA Bus DMA</title>
!Iinclude/asm-i386/mca_dma.h
	</sect2>
     </sect1>
  </chapter>

  <chapter id="firmware">
     <title>Firmware Interfaces</title>
     <sect1><title>DMI Interfaces</title>
!Edrivers/firmware/dmi_scan.c
     </sect1>
     <sect1><title>EDD Interfaces</title>
!Idrivers/firmware/edd.c
     </sect1>
  </chapter>

  <chapter id="security">
     <title>Security Framework</title>
!Esecurity/security.c
  </chapter>

  <chapter id="audit">
     <title>Audit Interfaces</title>
!Ekernel/audit.c
!Ikernel/auditsc.c
!Ikernel/auditfilter.c
  </chapter>

  <chapter id="accounting">
     <title>Accounting Framework</title>
!Ikernel/acct.c
  </chapter>

  <chapter id="pmfuncs">
     <title>Power Management</title>
!Ekernel/power/pm.c
  </chapter>

  <chapter id="devdrivers">
     <title>Device drivers infrastructure</title>
     <sect1><title>Device Drivers Base</title>
<!--
X!Iinclude/linux/device.h
-->
!Edrivers/base/driver.c
!Edrivers/base/core.c
!Edrivers/base/class.c
!Edrivers/base/firmware_class.c
!Edrivers/base/transport_class.c
!Edrivers/base/dmapool.c
<!-- Cannot be included, because
     attribute_container_add_class_device_adapter
 and attribute_container_classdev_to_container
     exceed allowed 44 characters maximum
X!Edrivers/base/attribute_container.c
-->
!Edrivers/base/sys.c
<!--
X!Edrivers/base/interface.c
-->
!Edrivers/base/platform.c
!Edrivers/base/bus.c
     </sect1>
     <sect1><title>Device Drivers Power Management</title>
!Edrivers/base/power/main.c
!Edrivers/base/power/resume.c
!Edrivers/base/power/suspend.c
     </sect1>
     <sect1><title>Device Drivers ACPI Support</title>
<!-- Internal functions only
X!Edrivers/acpi/sleep/main.c
X!Edrivers/acpi/sleep/wakeup.c
X!Edrivers/acpi/motherboard.c
X!Edrivers/acpi/bus.c
-->
!Edrivers/acpi/scan.c
!Idrivers/acpi/scan.c
<!-- No correct structured comments
X!Edrivers/acpi/pci_bind.c
-->
     </sect1>
     <sect1><title>Device drivers PnP support</title>
!Edrivers/pnp/core.c
<!-- No correct structured comments
X!Edrivers/pnp/system.c
 -->
!Edrivers/pnp/card.c
!Edrivers/pnp/driver.c
!Edrivers/pnp/manager.c
!Edrivers/pnp/support.c
     </sect1>
  </chapter>

  <chapter id="blkdev">
     <title>Block Devices</title>
!Eblock/ll_rw_blk.c
  </chapter>

  <chapter id="chrdev">
	<title>Char devices</title>
!Efs/char_dev.c
  </chapter>

  <chapter id="miscdev">
     <title>Miscellaneous Devices</title>
!Edrivers/char/misc.c
  </chapter>

  <chapter id="parportdev">
     <title>Parallel Port Devices</title>
!Iinclude/linux/parport.h
!Edrivers/parport/ieee1284.c
!Edrivers/parport/share.c
!Idrivers/parport/daisy.c
  </chapter>

  <chapter id="message_devices">
	<title>Message-based devices</title>
     <sect1><title>Fusion message devices</title>
!Edrivers/message/fusion/mptbase.c
!Idrivers/message/fusion/mptbase.c
!Edrivers/message/fusion/mptscsih.c
!Idrivers/message/fusion/mptscsih.c
!Idrivers/message/fusion/mptctl.c
!Idrivers/message/fusion/mptspi.c
!Idrivers/message/fusion/mptfc.c
!Idrivers/message/fusion/mptlan.c
     </sect1>
     <sect1><title>I2O message devices</title>
!Iinclude/linux/i2o.h
!Idrivers/message/i2o/core.h
!Edrivers/message/i2o/iop.c
!Idrivers/message/i2o/iop.c
!Idrivers/message/i2o/config-osm.c
!Edrivers/message/i2o/exec-osm.c
!Idrivers/message/i2o/exec-osm.c
!Idrivers/message/i2o/bus-osm.c
!Edrivers/message/i2o/device.c
!Idrivers/message/i2o/device.c
!Idrivers/message/i2o/driver.c
!Idrivers/message/i2o/pci.c
!Idrivers/message/i2o/i2o_block.c
!Idrivers/message/i2o/i2o_scsi.c
!Idrivers/message/i2o/i2o_proc.c
     </sect1>
  </chapter>

  <chapter id="snddev">
     <title>Sound Devices</title>
!Iinclude/sound/core.h
!Esound/sound_core.c
!Iinclude/sound/pcm.h
!Esound/core/pcm.c
!Esound/core/device.c
!Esound/core/info.c
!Esound/core/rawmidi.c
!Esound/core/sound.c
!Esound/core/memory.c
!Esound/core/pcm_memory.c
!Esound/core/init.c
!Esound/core/isadma.c
!Esound/core/control.c
!Esound/core/pcm_lib.c
!Esound/core/hwdep.c
!Esound/core/pcm_native.c
!Esound/core/memalloc.c
<!-- FIXME: Removed for now since no structured comments in source
X!Isound/sound_firmware.c
-->
  </chapter>

  <chapter id="uart16x50">
     <title>16x50 UART Driver</title>
!Iinclude/linux/serial_core.h
!Edrivers/serial/serial_core.c
!Edrivers/serial/8250.c
  </chapter>

  <chapter id="z85230">
     <title>Z85230 Support Library</title>
!Edrivers/net/wan/z85230.c
  </chapter>

  <chapter id="fbdev">
     <title>Frame Buffer Library</title>

     <para>
       The frame buffer drivers depend heavily on four data structures.  
       These structures are declared in include/linux/fb.h.  They are 
       fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs. 
       The last three can be made available to and from userland. 
     </para>

     <para>
       fb_info defines the current state of a particular video card. 
       Inside fb_info, there exists a fb_ops structure which is a 
       collection of needed functions to make fbdev and fbcon work.
       fb_info is only visible to the kernel.
     </para>

     <para>
       fb_var_screeninfo is used to describe the features of a video card 
       that are user defined.  With fb_var_screeninfo, things such as
       depth and the resolution may be defined.
     </para>

     <para>
       The next structure is fb_fix_screeninfo. This defines the 
       properties of a card that are created when a mode is set and can't 
       be changed otherwise.  A good example of this is the start of the 
       frame buffer memory.  This "locks" the address of the frame buffer
       memory, so that it cannot be changed or moved.
     </para>

     <para>
       The last structure is fb_monospecs. In the old API, there was 
       little importance for fb_monospecs. This allowed for forbidden things 
       such as setting a mode of 800x600 on a fix frequency monitor. With 
       the new API, fb_monospecs prevents such things, and if used 
       correctly, can prevent a monitor from being cooked.  fb_monospecs
       will not be useful until kernels 2.5.x.
     </para>

     <sect1><title>Frame Buffer Memory</title>
!Edrivers/video/fbmem.c
     </sect1>
<!--
     <sect1><title>Frame Buffer Console</title>
X!Edrivers/video/console/fbcon.c
     </sect1>
-->
     <sect1><title>Frame Buffer Colormap</title>
!Edrivers/video/fbcmap.c
     </sect1>
<!-- FIXME:
  drivers/video/fbgen.c has no docs, which stuffs up the sgml.  Comment
  out until somebody adds docs.  KAO
     <sect1><title>Frame Buffer Generic Functions</title>
X!Idrivers/video/fbgen.c
     </sect1>
KAO -->
     <sect1><title>Frame Buffer Video Mode Database</title>
!Idrivers/video/modedb.c
!Edrivers/video/modedb.c
     </sect1>
     <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
!Edrivers/video/macmodes.c
     </sect1>
     <sect1><title>Frame Buffer Fonts</title>
        <para>
           Refer to the file drivers/video/console/fonts.c for more information.
        </para>
<!-- FIXME: Removed for now since no structured comments in source
X!Idrivers/video/console/fonts.c
-->
     </sect1>
  </chapter>

  <chapter id="input_subsystem">
     <title>Input Subsystem</title>
!Iinclude/linux/input.h
!Edrivers/input/input.c
!Edrivers/input/ff-core.c
!Edrivers/input/ff-memless.c
  </chapter>

  <chapter id="spi">
      <title>Serial Peripheral Interface (SPI)</title>
  <para>
	SPI is the "Serial Peripheral Interface", widely used with
	embedded systems because it is a simple and efficient
	interface:  basically a multiplexed shift register.
	Its three signal wires hold a clock (SCK, often in the range
	of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
	a "Master In, Slave Out" (MISO) data line.
	SPI is a full duplex protocol; for each bit shifted out the
	MOSI line (one per clock) another is shifted in on the MISO line.
	Those bits are assembled into words of various sizes on the
	way to and from system memory.
	An additional chipselect line is usually active-low (nCS);
	four signals are normally used for each peripheral, plus
	sometimes an interrupt.
  </para>
  <para>
	The SPI bus facilities listed here provide a generalized
	interface to declare SPI busses and devices, manage them
	according to the standard Linux driver model, and perform
	input/output operations.
	At this time, only "master" side interfaces are supported,
	where Linux talks to SPI peripherals and does not implement
	such a peripheral itself.
	(Interfaces to support implementing SPI slaves would
	necessarily look different.)
  </para>
  <para>
	The programming interface is structured around two kinds of driver,
	and two kinds of device.
	A "Controller Driver" abstracts the controller hardware, which may
	be as simple as a set of GPIO pins or as complex as a pair of FIFOs
	connected to dual DMA engines on the other side of the SPI shift
	register (maximizing throughput).  Such drivers bridge between
	whatever bus they sit on (often the platform bus) and SPI, and
	expose the SPI side of their device as a
	<structname>struct spi_master</structname>.
	SPI devices are children of that master, represented as a
	<structname>struct spi_device</structname> and manufactured from
	<structname>struct spi_board_info</structname> descriptors which
	are usually provided by board-specific initialization code.
	A <structname>struct spi_driver</structname> is called a
	"Protocol Driver", and is bound to a spi_device using normal
	driver model calls.
  </para>
  <para>
	The I/O model is a set of queued messages.  Protocol drivers
	submit one or more <structname>struct spi_message</structname>
	objects, which are processed and completed asynchronously.
	(There are synchronous wrappers, however.)  Messages are
	built from one or more <structname>struct spi_transfer</structname>
	objects, each of which wraps a full duplex SPI transfer.
	A variety of protocol tweaking options are needed, because
	different chips adopt very different policies for how they
	use the bits transferred with SPI.
  </para>
!Iinclude/linux/spi/spi.h
!Fdrivers/spi/spi.c spi_register_board_info
!Edrivers/spi/spi.c
  </chapter>

  <chapter id="i2c">
     <title>I<superscript>2</superscript>C and SMBus Subsystem</title>

     <para>
	I<superscript>2</superscript>C (or without fancy typography, "I2C")
	is an acronym for the "Inter-IC" bus, a simple bus protocol which is
	widely used where low data rate communications suffice.
	Since it's also a licensed trademark, some vendors use another
	name (such as "Two-Wire Interface", TWI) for the same bus.
	I2C only needs two signals (SCL for clock, SDA for data), conserving
	board real estate and minimizing signal quality issues.
	Most I2C devices use seven bit addresses, and bus speeds of up
	to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
	found wide use.
	I2C is a multi-master bus; open drain signaling is used to
	arbitrate between masters, as well as to handshake and to
	synchronize clocks from slower clients.
     </para>

     <para>
	The Linux I2C programming interfaces support only the master
	side of bus interactions, not the slave side.
	The programming interface is structured around two kinds of driver,
	and two kinds of device.
	An I2C "Adapter Driver" abstracts the controller hardware; it binds
	to a physical device (perhaps a PCI device or platform_device) and
	exposes a <structname>struct i2c_adapter</structname> representing
	each I2C bus segment it manages.
	On each I2C bus segment will be I2C devices represented by a
	<structname>struct i2c_client</structname>.  Those devices will
	be bound to a <structname>struct i2c_driver</structname>,
	which should follow the standard Linux driver model.
	(At this writing, a legacy model is more widely used.)
	There are functions to perform various I2C protocol operations; at
	this writing all such functions are usable only from task context.
     </para>

     <para>
	The System Management Bus (SMBus) is a sibling protocol.  Most SMBus
	systems are also I2C conformant.  The electrical constraints are
	tighter for SMBus, and it standardizes particular protocol messages
	and idioms.  Controllers that support I2C can also support most
	SMBus operations, but SMBus controllers don't support all the protocol
	options that an I2C controller will.
	There are functions to perform various SMBus protocol operations,
	either using I2C primitives or by issuing SMBus commands to
	i2c_adapter devices which don't support those I2C operations.
     </para>

!Iinclude/linux/i2c.h
!Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
!Edrivers/i2c/i2c-core.c
  </chapter>

  <chapter id="splice">
      <title>splice API</title>
  <para>)
	splice is a method for moving blocks of data around inside the
	kernel, without continually transferring it between the kernel
	and user space.
  </para>
!Iinclude/linux/splice.h
!Ffs/splice.c
  </chapter>


</book>