diff options
author | Jonathan Corbet <corbet@lwn.net> | 2016-08-20 15:02:50 -0400 |
---|---|---|
committer | Jonathan Corbet <corbet@lwn.net> | 2016-08-22 16:11:22 -0400 |
commit | 47cb398dd75a9faa89d0617b55d4cf537935b731 (patch) | |
tree | 12ff5f67133219fcf86b6e1166a14e25838346da /Documentation/driver-api | |
parent | 5512128f027aec63a9a2ca792858801554a57baf (diff) |
Docs: sphinxify device-drivers.tmpl
Perform a basic sphinx conversion of the device-drivers docbook and move it
to its own directory.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/driver-api')
-rw-r--r-- | Documentation/driver-api/drivers.rst | 654 |
1 files changed, 654 insertions, 0 deletions
diff --git a/Documentation/driver-api/drivers.rst b/Documentation/driver-api/drivers.rst new file mode 100644 index 000000000000..17f99d441b52 --- /dev/null +++ b/Documentation/driver-api/drivers.rst | |||
@@ -0,0 +1,654 @@ | |||
1 | ==================== | ||
2 | Linux Device Drivers | ||
3 | ==================== | ||
4 | |||
5 | Driver Basics | ||
6 | ============= | ||
7 | |||
8 | Driver Entry and Exit points | ||
9 | ---------------------------- | ||
10 | |||
11 | .. kernel-doc:: include/linux/init.h | ||
12 | :internal: | ||
13 | |||
14 | Atomic and pointer manipulation | ||
15 | ------------------------------- | ||
16 | |||
17 | .. kernel-doc:: arch/x86/include/asm/atomic.h | ||
18 | :internal: | ||
19 | |||
20 | Delaying, scheduling, and timer routines | ||
21 | ---------------------------------------- | ||
22 | |||
23 | .. kernel-doc:: include/linux/sched.h | ||
24 | :internal: | ||
25 | |||
26 | .. kernel-doc:: kernel/sched/core.c | ||
27 | :export: | ||
28 | |||
29 | .. kernel-doc:: kernel/sched/cpupri.c | ||
30 | :internal: | ||
31 | |||
32 | .. kernel-doc:: kernel/sched/fair.c | ||
33 | :internal: | ||
34 | |||
35 | .. kernel-doc:: include/linux/completion.h | ||
36 | :internal: | ||
37 | |||
38 | .. kernel-doc:: kernel/time/timer.c | ||
39 | :export: | ||
40 | |||
41 | Wait queues and Wake events | ||
42 | --------------------------- | ||
43 | |||
44 | .. kernel-doc:: include/linux/wait.h | ||
45 | :internal: | ||
46 | |||
47 | .. kernel-doc:: kernel/sched/wait.c | ||
48 | :export: | ||
49 | |||
50 | High-resolution timers | ||
51 | ---------------------- | ||
52 | |||
53 | .. kernel-doc:: include/linux/ktime.h | ||
54 | :internal: | ||
55 | |||
56 | .. kernel-doc:: include/linux/hrtimer.h | ||
57 | :internal: | ||
58 | |||
59 | .. kernel-doc:: kernel/time/hrtimer.c | ||
60 | :export: | ||
61 | |||
62 | Workqueues and Kevents | ||
63 | ---------------------- | ||
64 | |||
65 | .. kernel-doc:: include/linux/workqueue.h | ||
66 | :internal: | ||
67 | |||
68 | .. kernel-doc:: kernel/workqueue.c | ||
69 | :export: | ||
70 | |||
71 | Internal Functions | ||
72 | ------------------ | ||
73 | |||
74 | .. kernel-doc:: kernel/exit.c | ||
75 | :internal: | ||
76 | |||
77 | .. kernel-doc:: kernel/signal.c | ||
78 | :internal: | ||
79 | |||
80 | .. kernel-doc:: include/linux/kthread.h | ||
81 | :internal: | ||
82 | |||
83 | .. kernel-doc:: kernel/kthread.c | ||
84 | :export: | ||
85 | |||
86 | Kernel objects manipulation | ||
87 | --------------------------- | ||
88 | |||
89 | .. kernel-doc:: lib/kobject.c | ||
90 | :export: | ||
91 | |||
92 | Kernel utility functions | ||
93 | ------------------------ | ||
94 | |||
95 | .. kernel-doc:: include/linux/kernel.h | ||
96 | :internal: | ||
97 | |||
98 | .. kernel-doc:: kernel/printk/printk.c | ||
99 | :export: | ||
100 | |||
101 | .. kernel-doc:: kernel/panic.c | ||
102 | :export: | ||
103 | |||
104 | .. kernel-doc:: kernel/sys.c | ||
105 | :export: | ||
106 | |||
107 | .. kernel-doc:: kernel/rcu/srcu.c | ||
108 | :export: | ||
109 | |||
110 | .. kernel-doc:: kernel/rcu/tree.c | ||
111 | :export: | ||
112 | |||
113 | .. kernel-doc:: kernel/rcu/tree_plugin.h | ||
114 | :export: | ||
115 | |||
116 | .. kernel-doc:: kernel/rcu/update.c | ||
117 | :export: | ||
118 | |||
119 | Device Resource Management | ||
120 | -------------------------- | ||
121 | |||
122 | .. kernel-doc:: drivers/base/devres.c | ||
123 | :export: | ||
124 | |||
125 | Device drivers infrastructure | ||
126 | ============================= | ||
127 | |||
128 | The Basic Device Driver-Model Structures | ||
129 | ---------------------------------------- | ||
130 | |||
131 | .. kernel-doc:: include/linux/device.h | ||
132 | :internal: | ||
133 | |||
134 | Device Drivers Base | ||
135 | ------------------- | ||
136 | |||
137 | .. kernel-doc:: drivers/base/init.c | ||
138 | :internal: | ||
139 | |||
140 | .. kernel-doc:: drivers/base/driver.c | ||
141 | :export: | ||
142 | |||
143 | .. kernel-doc:: drivers/base/core.c | ||
144 | :export: | ||
145 | |||
146 | .. kernel-doc:: drivers/base/syscore.c | ||
147 | :export: | ||
148 | |||
149 | .. kernel-doc:: drivers/base/class.c | ||
150 | :export: | ||
151 | |||
152 | .. kernel-doc:: drivers/base/node.c | ||
153 | :internal: | ||
154 | |||
155 | .. kernel-doc:: drivers/base/firmware_class.c | ||
156 | :export: | ||
157 | |||
158 | .. kernel-doc:: drivers/base/transport_class.c | ||
159 | :export: | ||
160 | |||
161 | .. kernel-doc:: drivers/base/dd.c | ||
162 | :export: | ||
163 | |||
164 | .. kernel-doc:: include/linux/platform_device.h | ||
165 | :internal: | ||
166 | |||
167 | .. kernel-doc:: drivers/base/platform.c | ||
168 | :export: | ||
169 | |||
170 | .. kernel-doc:: drivers/base/bus.c | ||
171 | :export: | ||
172 | |||
173 | Buffer Sharing and Synchronization | ||
174 | ---------------------------------- | ||
175 | |||
176 | The dma-buf subsystem provides the framework for sharing buffers for | ||
177 | hardware (DMA) access across multiple device drivers and subsystems, and | ||
178 | for synchronizing asynchronous hardware access. | ||
179 | |||
180 | This is used, for example, by drm "prime" multi-GPU support, but is of | ||
181 | course not limited to GPU use cases. | ||
182 | |||
183 | The three main components of this are: (1) dma-buf, representing a | ||
184 | sg_table and exposed to userspace as a file descriptor to allow passing | ||
185 | between devices, (2) fence, which provides a mechanism to signal when | ||
186 | one device as finished access, and (3) reservation, which manages the | ||
187 | shared or exclusive fence(s) associated with the buffer. | ||
188 | |||
189 | dma-buf | ||
190 | ~~~~~~~ | ||
191 | |||
192 | .. kernel-doc:: drivers/dma-buf/dma-buf.c | ||
193 | :export: | ||
194 | |||
195 | .. kernel-doc:: include/linux/dma-buf.h | ||
196 | :internal: | ||
197 | |||
198 | reservation | ||
199 | ~~~~~~~~~~~ | ||
200 | |||
201 | .. kernel-doc:: drivers/dma-buf/reservation.c | ||
202 | :doc: Reservation Object Overview | ||
203 | |||
204 | .. kernel-doc:: drivers/dma-buf/reservation.c | ||
205 | :export: | ||
206 | |||
207 | .. kernel-doc:: include/linux/reservation.h | ||
208 | :internal: | ||
209 | |||
210 | fence | ||
211 | ~~~~~ | ||
212 | |||
213 | .. kernel-doc:: drivers/dma-buf/fence.c | ||
214 | :export: | ||
215 | |||
216 | .. kernel-doc:: include/linux/fence.h | ||
217 | :internal: | ||
218 | |||
219 | .. kernel-doc:: drivers/dma-buf/seqno-fence.c | ||
220 | :export: | ||
221 | |||
222 | .. kernel-doc:: include/linux/seqno-fence.h | ||
223 | :internal: | ||
224 | |||
225 | .. kernel-doc:: drivers/dma-buf/fence-array.c | ||
226 | :export: | ||
227 | |||
228 | .. kernel-doc:: include/linux/fence-array.h | ||
229 | :internal: | ||
230 | |||
231 | .. kernel-doc:: drivers/dma-buf/reservation.c | ||
232 | :export: | ||
233 | |||
234 | .. kernel-doc:: include/linux/reservation.h | ||
235 | :internal: | ||
236 | |||
237 | .. kernel-doc:: drivers/dma-buf/sync_file.c | ||
238 | :export: | ||
239 | |||
240 | .. kernel-doc:: include/linux/sync_file.h | ||
241 | :internal: | ||
242 | |||
243 | Device Drivers DMA Management | ||
244 | ----------------------------- | ||
245 | |||
246 | .. kernel-doc:: drivers/base/dma-coherent.c | ||
247 | :export: | ||
248 | |||
249 | .. kernel-doc:: drivers/base/dma-mapping.c | ||
250 | :export: | ||
251 | |||
252 | Device Drivers Power Management | ||
253 | ------------------------------- | ||
254 | |||
255 | .. kernel-doc:: drivers/base/power/main.c | ||
256 | :export: | ||
257 | |||
258 | Device Drivers ACPI Support | ||
259 | --------------------------- | ||
260 | |||
261 | .. kernel-doc:: drivers/acpi/scan.c | ||
262 | :export: | ||
263 | |||
264 | .. kernel-doc:: drivers/acpi/scan.c | ||
265 | :internal: | ||
266 | |||
267 | Device drivers PnP support | ||
268 | -------------------------- | ||
269 | |||
270 | .. kernel-doc:: drivers/pnp/core.c | ||
271 | :internal: | ||
272 | |||
273 | .. kernel-doc:: drivers/pnp/card.c | ||
274 | :export: | ||
275 | |||
276 | .. kernel-doc:: drivers/pnp/driver.c | ||
277 | :internal: | ||
278 | |||
279 | .. kernel-doc:: drivers/pnp/manager.c | ||
280 | :export: | ||
281 | |||
282 | .. kernel-doc:: drivers/pnp/support.c | ||
283 | :export: | ||
284 | |||
285 | Userspace IO devices | ||
286 | -------------------- | ||
287 | |||
288 | .. kernel-doc:: drivers/uio/uio.c | ||
289 | :export: | ||
290 | |||
291 | .. kernel-doc:: include/linux/uio_driver.h | ||
292 | :internal: | ||
293 | |||
294 | Parallel Port Devices | ||
295 | ===================== | ||
296 | |||
297 | .. kernel-doc:: include/linux/parport.h | ||
298 | :internal: | ||
299 | |||
300 | .. kernel-doc:: drivers/parport/ieee1284.c | ||
301 | :export: | ||
302 | |||
303 | .. kernel-doc:: drivers/parport/share.c | ||
304 | :export: | ||
305 | |||
306 | .. kernel-doc:: drivers/parport/daisy.c | ||
307 | :internal: | ||
308 | |||
309 | Message-based devices | ||
310 | ===================== | ||
311 | |||
312 | Fusion message devices | ||
313 | ---------------------- | ||
314 | |||
315 | .. kernel-doc:: drivers/message/fusion/mptbase.c | ||
316 | :export: | ||
317 | |||
318 | .. kernel-doc:: drivers/message/fusion/mptbase.c | ||
319 | :internal: | ||
320 | |||
321 | .. kernel-doc:: drivers/message/fusion/mptscsih.c | ||
322 | :export: | ||
323 | |||
324 | .. kernel-doc:: drivers/message/fusion/mptscsih.c | ||
325 | :internal: | ||
326 | |||
327 | .. kernel-doc:: drivers/message/fusion/mptctl.c | ||
328 | :internal: | ||
329 | |||
330 | .. kernel-doc:: drivers/message/fusion/mptspi.c | ||
331 | :internal: | ||
332 | |||
333 | .. kernel-doc:: drivers/message/fusion/mptfc.c | ||
334 | :internal: | ||
335 | |||
336 | .. kernel-doc:: drivers/message/fusion/mptlan.c | ||
337 | :internal: | ||
338 | |||
339 | Sound Devices | ||
340 | ============= | ||
341 | |||
342 | .. kernel-doc:: include/sound/core.h | ||
343 | :internal: | ||
344 | |||
345 | .. kernel-doc:: sound/sound_core.c | ||
346 | :export: | ||
347 | |||
348 | .. kernel-doc:: include/sound/pcm.h | ||
349 | :internal: | ||
350 | |||
351 | .. kernel-doc:: sound/core/pcm.c | ||
352 | :export: | ||
353 | |||
354 | .. kernel-doc:: sound/core/device.c | ||
355 | :export: | ||
356 | |||
357 | .. kernel-doc:: sound/core/info.c | ||
358 | :export: | ||
359 | |||
360 | .. kernel-doc:: sound/core/rawmidi.c | ||
361 | :export: | ||
362 | |||
363 | .. kernel-doc:: sound/core/sound.c | ||
364 | :export: | ||
365 | |||
366 | .. kernel-doc:: sound/core/memory.c | ||
367 | :export: | ||
368 | |||
369 | .. kernel-doc:: sound/core/pcm_memory.c | ||
370 | :export: | ||
371 | |||
372 | .. kernel-doc:: sound/core/init.c | ||
373 | :export: | ||
374 | |||
375 | .. kernel-doc:: sound/core/isadma.c | ||
376 | :export: | ||
377 | |||
378 | .. kernel-doc:: sound/core/control.c | ||
379 | :export: | ||
380 | |||
381 | .. kernel-doc:: sound/core/pcm_lib.c | ||
382 | :export: | ||
383 | |||
384 | .. kernel-doc:: sound/core/hwdep.c | ||
385 | :export: | ||
386 | |||
387 | .. kernel-doc:: sound/core/pcm_native.c | ||
388 | :export: | ||
389 | |||
390 | .. kernel-doc:: sound/core/memalloc.c | ||
391 | :export: | ||
392 | |||
393 | 16x50 UART Driver | ||
394 | ================= | ||
395 | |||
396 | .. kernel-doc:: drivers/tty/serial/serial_core.c | ||
397 | :export: | ||
398 | |||
399 | .. kernel-doc:: drivers/tty/serial/8250/8250_core.c | ||
400 | :export: | ||
401 | |||
402 | Frame Buffer Library | ||
403 | ==================== | ||
404 | |||
405 | The frame buffer drivers depend heavily on four data structures. These | ||
406 | structures are declared in include/linux/fb.h. They are fb_info, | ||
407 | fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs. The last | ||
408 | three can be made available to and from userland. | ||
409 | |||
410 | fb_info defines the current state of a particular video card. Inside | ||
411 | fb_info, there exists a fb_ops structure which is a collection of | ||
412 | needed functions to make fbdev and fbcon work. fb_info is only visible | ||
413 | to the kernel. | ||
414 | |||
415 | fb_var_screeninfo is used to describe the features of a video card | ||
416 | that are user defined. With fb_var_screeninfo, things such as depth | ||
417 | and the resolution may be defined. | ||
418 | |||
419 | The next structure is fb_fix_screeninfo. This defines the properties | ||
420 | of a card that are created when a mode is set and can't be changed | ||
421 | otherwise. A good example of this is the start of the frame buffer | ||
422 | memory. This "locks" the address of the frame buffer memory, so that it | ||
423 | cannot be changed or moved. | ||
424 | |||
425 | The last structure is fb_monospecs. In the old API, there was little | ||
426 | importance for fb_monospecs. This allowed for forbidden things such as | ||
427 | setting a mode of 800x600 on a fix frequency monitor. With the new API, | ||
428 | fb_monospecs prevents such things, and if used correctly, can prevent a | ||
429 | monitor from being cooked. fb_monospecs will not be useful until | ||
430 | kernels 2.5.x. | ||
431 | |||
432 | Frame Buffer Memory | ||
433 | ------------------- | ||
434 | |||
435 | .. kernel-doc:: drivers/video/fbdev/core/fbmem.c | ||
436 | :export: | ||
437 | |||
438 | Frame Buffer Colormap | ||
439 | --------------------- | ||
440 | |||
441 | .. kernel-doc:: drivers/video/fbdev/core/fbcmap.c | ||
442 | :export: | ||
443 | |||
444 | Frame Buffer Video Mode Database | ||
445 | -------------------------------- | ||
446 | |||
447 | .. kernel-doc:: drivers/video/fbdev/core/modedb.c | ||
448 | :internal: | ||
449 | |||
450 | .. kernel-doc:: drivers/video/fbdev/core/modedb.c | ||
451 | :export: | ||
452 | |||
453 | Frame Buffer Macintosh Video Mode Database | ||
454 | ------------------------------------------ | ||
455 | |||
456 | .. kernel-doc:: drivers/video/fbdev/macmodes.c | ||
457 | :export: | ||
458 | |||
459 | Frame Buffer Fonts | ||
460 | ------------------ | ||
461 | |||
462 | Refer to the file lib/fonts/fonts.c for more information. | ||
463 | |||
464 | Input Subsystem | ||
465 | =============== | ||
466 | |||
467 | Input core | ||
468 | ---------- | ||
469 | |||
470 | .. kernel-doc:: include/linux/input.h | ||
471 | :internal: | ||
472 | |||
473 | .. kernel-doc:: drivers/input/input.c | ||
474 | :export: | ||
475 | |||
476 | .. kernel-doc:: drivers/input/ff-core.c | ||
477 | :export: | ||
478 | |||
479 | .. kernel-doc:: drivers/input/ff-memless.c | ||
480 | :export: | ||
481 | |||
482 | Multitouch Library | ||
483 | ------------------ | ||
484 | |||
485 | .. kernel-doc:: include/linux/input/mt.h | ||
486 | :internal: | ||
487 | |||
488 | .. kernel-doc:: drivers/input/input-mt.c | ||
489 | :export: | ||
490 | |||
491 | Polled input devices | ||
492 | -------------------- | ||
493 | |||
494 | .. kernel-doc:: include/linux/input-polldev.h | ||
495 | :internal: | ||
496 | |||
497 | .. kernel-doc:: drivers/input/input-polldev.c | ||
498 | :export: | ||
499 | |||
500 | Matrix keyboards/keypads | ||
501 | ------------------------ | ||
502 | |||
503 | .. kernel-doc:: include/linux/input/matrix_keypad.h | ||
504 | :internal: | ||
505 | |||
506 | Sparse keymap support | ||
507 | --------------------- | ||
508 | |||
509 | .. kernel-doc:: include/linux/input/sparse-keymap.h | ||
510 | :internal: | ||
511 | |||
512 | .. kernel-doc:: drivers/input/sparse-keymap.c | ||
513 | :export: | ||
514 | |||
515 | Serial Peripheral Interface (SPI) | ||
516 | ================================= | ||
517 | |||
518 | SPI is the "Serial Peripheral Interface", widely used with embedded | ||
519 | systems because it is a simple and efficient interface: basically a | ||
520 | multiplexed shift register. Its three signal wires hold a clock (SCK, | ||
521 | often in the range of 1-20 MHz), a "Master Out, Slave In" (MOSI) data | ||
522 | line, and a "Master In, Slave Out" (MISO) data line. SPI is a full | ||
523 | duplex protocol; for each bit shifted out the MOSI line (one per clock) | ||
524 | another is shifted in on the MISO line. Those bits are assembled into | ||
525 | words of various sizes on the way to and from system memory. An | ||
526 | additional chipselect line is usually active-low (nCS); four signals are | ||
527 | normally used for each peripheral, plus sometimes an interrupt. | ||
528 | |||
529 | The SPI bus facilities listed here provide a generalized interface to | ||
530 | declare SPI busses and devices, manage them according to the standard | ||
531 | Linux driver model, and perform input/output operations. At this time, | ||
532 | only "master" side interfaces are supported, where Linux talks to SPI | ||
533 | peripherals and does not implement such a peripheral itself. (Interfaces | ||
534 | to support implementing SPI slaves would necessarily look different.) | ||
535 | |||
536 | The programming interface is structured around two kinds of driver, and | ||
537 | two kinds of device. A "Controller Driver" abstracts the controller | ||
538 | hardware, which may be as simple as a set of GPIO pins or as complex as | ||
539 | a pair of FIFOs connected to dual DMA engines on the other side of the | ||
540 | SPI shift register (maximizing throughput). Such drivers bridge between | ||
541 | whatever bus they sit on (often the platform bus) and SPI, and expose | ||
542 | the SPI side of their device as a :c:type:`struct spi_master | ||
543 | <spi_master>`. SPI devices are children of that master, | ||
544 | represented as a :c:type:`struct spi_device <spi_device>` and | ||
545 | manufactured from :c:type:`struct spi_board_info | ||
546 | <spi_board_info>` descriptors which are usually provided by | ||
547 | board-specific initialization code. A :c:type:`struct spi_driver | ||
548 | <spi_driver>` is called a "Protocol Driver", and is bound to a | ||
549 | spi_device using normal driver model calls. | ||
550 | |||
551 | The I/O model is a set of queued messages. Protocol drivers submit one | ||
552 | or more :c:type:`struct spi_message <spi_message>` objects, | ||
553 | which are processed and completed asynchronously. (There are synchronous | ||
554 | wrappers, however.) Messages are built from one or more | ||
555 | :c:type:`struct spi_transfer <spi_transfer>` objects, each of | ||
556 | which wraps a full duplex SPI transfer. A variety of protocol tweaking | ||
557 | options are needed, because different chips adopt very different | ||
558 | policies for how they use the bits transferred with SPI. | ||
559 | |||
560 | .. kernel-doc:: include/linux/spi/spi.h | ||
561 | :internal: | ||
562 | |||
563 | .. kernel-doc:: drivers/spi/spi.c | ||
564 | :functions: spi_register_board_info | ||
565 | |||
566 | .. kernel-doc:: drivers/spi/spi.c | ||
567 | :export: | ||
568 | |||
569 | I\ :sup:`2`\ C and SMBus Subsystem | ||
570 | ================================== | ||
571 | |||
572 | I\ :sup:`2`\ C (or without fancy typography, "I2C") is an acronym for | ||
573 | the "Inter-IC" bus, a simple bus protocol which is widely used where low | ||
574 | data rate communications suffice. Since it's also a licensed trademark, | ||
575 | some vendors use another name (such as "Two-Wire Interface", TWI) for | ||
576 | the same bus. I2C only needs two signals (SCL for clock, SDA for data), | ||
577 | conserving board real estate and minimizing signal quality issues. Most | ||
578 | I2C devices use seven bit addresses, and bus speeds of up to 400 kHz; | ||
579 | there's a high speed extension (3.4 MHz) that's not yet found wide use. | ||
580 | I2C is a multi-master bus; open drain signaling is used to arbitrate | ||
581 | between masters, as well as to handshake and to synchronize clocks from | ||
582 | slower clients. | ||
583 | |||
584 | The Linux I2C programming interfaces support only the master side of bus | ||
585 | interactions, not the slave side. The programming interface is | ||
586 | structured around two kinds of driver, and two kinds of device. An I2C | ||
587 | "Adapter Driver" abstracts the controller hardware; it binds to a | ||
588 | physical device (perhaps a PCI device or platform_device) and exposes a | ||
589 | :c:type:`struct i2c_adapter <i2c_adapter>` representing each | ||
590 | I2C bus segment it manages. On each I2C bus segment will be I2C devices | ||
591 | represented by a :c:type:`struct i2c_client <i2c_client>`. | ||
592 | Those devices will be bound to a :c:type:`struct i2c_driver | ||
593 | <i2c_driver>`, which should follow the standard Linux driver | ||
594 | model. (At this writing, a legacy model is more widely used.) There are | ||
595 | functions to perform various I2C protocol operations; at this writing | ||
596 | all such functions are usable only from task context. | ||
597 | |||
598 | The System Management Bus (SMBus) is a sibling protocol. Most SMBus | ||
599 | systems are also I2C conformant. The electrical constraints are tighter | ||
600 | for SMBus, and it standardizes particular protocol messages and idioms. | ||
601 | Controllers that support I2C can also support most SMBus operations, but | ||
602 | SMBus controllers don't support all the protocol options that an I2C | ||
603 | controller will. There are functions to perform various SMBus protocol | ||
604 | operations, either using I2C primitives or by issuing SMBus commands to | ||
605 | i2c_adapter devices which don't support those I2C operations. | ||
606 | |||
607 | .. kernel-doc:: include/linux/i2c.h | ||
608 | :internal: | ||
609 | |||
610 | .. kernel-doc:: drivers/i2c/i2c-boardinfo.c | ||
611 | :functions: i2c_register_board_info | ||
612 | |||
613 | .. kernel-doc:: drivers/i2c/i2c-core.c | ||
614 | :export: | ||
615 | |||
616 | High Speed Synchronous Serial Interface (HSI) | ||
617 | ============================================= | ||
618 | |||
619 | High Speed Synchronous Serial Interface (HSI) is a serial interface | ||
620 | mainly used for connecting application engines (APE) with cellular modem | ||
621 | engines (CMT) in cellular handsets. HSI provides multiplexing for up to | ||
622 | 16 logical channels, low-latency and full duplex communication. | ||
623 | |||
624 | .. kernel-doc:: include/linux/hsi/hsi.h | ||
625 | :internal: | ||
626 | |||
627 | .. kernel-doc:: drivers/hsi/hsi_core.c | ||
628 | :export: | ||
629 | |||
630 | Pulse-Width Modulation (PWM) | ||
631 | ============================ | ||
632 | |||
633 | Pulse-width modulation is a modulation technique primarily used to | ||
634 | control power supplied to electrical devices. | ||
635 | |||
636 | The PWM framework provides an abstraction for providers and consumers of | ||
637 | PWM signals. A controller that provides one or more PWM signals is | ||
638 | registered as :c:type:`struct pwm_chip <pwm_chip>`. Providers | ||
639 | are expected to embed this structure in a driver-specific structure. | ||
640 | This structure contains fields that describe a particular chip. | ||
641 | |||
642 | A chip exposes one or more PWM signal sources, each of which exposed as | ||
643 | a :c:type:`struct pwm_device <pwm_device>`. Operations can be | ||
644 | performed on PWM devices to control the period, duty cycle, polarity and | ||
645 | active state of the signal. | ||
646 | |||
647 | Note that PWM devices are exclusive resources: they can always only be | ||
648 | used by one consumer at a time. | ||
649 | |||
650 | .. kernel-doc:: include/linux/pwm.h | ||
651 | :internal: | ||
652 | |||
653 | .. kernel-doc:: drivers/pwm/core.c | ||
654 | :export: | ||