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Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input
[linux-2.6-block.git] / Documentation / DocBook / dvb / demux.xml
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MCC		 1<title>DVB Demux Device</title>
2
3<para>The DVB demux device controls the filters of the DVB hardware/software. It can be
4accessed through <emphasis role="tt">/dev/adapter0/demux0</emphasis>. Data types and and ioctl definitions can be
5accessed by including <emphasis role="tt">linux/dvb/dmx.h</emphasis> in your application.
6</para>
7<section id="dmx_types">
8<title>Demux Data Types</title>
9
10<section id="dmx_output_t">
11<title>dmx_output_t</title>
12 <programlisting>
13 typedef enum
14 {
15 DMX_OUT_DECODER,
16 DMX_OUT_TAP,
17 DMX_OUT_TS_TAP
18 } dmx_output_t;
19</programlisting>
20<para><emphasis role="tt">DMX_OUT_TAP</emphasis> delivers the stream output to the demux device on which the ioctl is
21called.
22</para>
23<para><emphasis role="tt">DMX_OUT_TS_TAP</emphasis> routes output to the logical DVR device <emphasis role="tt">/dev/dvb/adapter0/dvr0</emphasis>,
24which delivers a TS multiplexed from all filters for which <emphasis role="tt">DMX_OUT_TS_TAP</emphasis> was
25specified.
26</para>
27</section>
28
29<section id="dmx_input_t">
30<title>dmx_input_t</title>
31 <programlisting>
32 typedef enum
33 {
34 DMX_IN_FRONTEND,
35 DMX_IN_DVR
36 } dmx_input_t;
37</programlisting>
38</section>
39
40<section id="dmx_pes_type_t">
41<title>dmx_pes_type_t</title>
42 <programlisting>
43 typedef enum
44 {
45 DMX_PES_AUDIO,
46 DMX_PES_VIDEO,
47 DMX_PES_TELETEXT,
48 DMX_PES_SUBTITLE,
49 DMX_PES_PCR,
50 DMX_PES_OTHER
51 } dmx_pes_type_t;
52</programlisting>
53</section>
54
55<section id="dmx_event_t">
56<title>dmx_event_t</title>
57 <programlisting>
58 typedef enum
59 {
60 DMX_SCRAMBLING_EV,
61 DMX_FRONTEND_EV
62 } dmx_event_t;
63</programlisting>
64</section>
65
66<section id="dmx_scrambling_status_t">
67<title>dmx_scrambling_status_t</title>
68 <programlisting>
69 typedef enum
70 {
71 DMX_SCRAMBLING_OFF,
72 DMX_SCRAMBLING_ON
73 } dmx_scrambling_status_t;
74</programlisting>
75</section>
76
77<section id="dmx_filter">
78<title>struct dmx_filter</title>
79 <programlisting>
80 typedef struct dmx_filter
81 {
82 uint8_t filter[DMX_FILTER_SIZE];
83 uint8_t mask[DMX_FILTER_SIZE];
84 } dmx_filter_t;
85</programlisting>
86</section>
87
88<section id="dmx_sct_filter_params">
89<title>struct dmx_sct_filter_params</title>
90 <programlisting>
91 struct dmx_sct_filter_params
92 {
93 uint16_t pid;
94 dmx_filter_t filter;
95 uint32_t timeout;
96 uint32_t flags;
97 #define DMX_CHECK_CRC 1
98 #define DMX_ONESHOT 2
99 #define DMX_IMMEDIATE_START 4
100 };
101</programlisting>
102</section>
103
104<section id="dmx_pes_filter_params">
105<title>struct dmx_pes_filter_params</title>
106 <programlisting>
107 struct dmx_pes_filter_params
108 {
109 uint16_t pid;
110 dmx_input_t input;
111 dmx_output_t output;
112 dmx_pes_type_t pes_type;
113 uint32_t flags;
114 };
115</programlisting>
116</section>
117
118<section id="dmx_event">
119<title>struct dmx_event</title>
120 <programlisting>
121 struct dmx_event
122 {
123 dmx_event_t event;
124 time_t timeStamp;
125 union
126 {
127 dmx_scrambling_status_t scrambling;
128 } u;
129 };
130</programlisting>
131</section>
132
133<section id="dmx_stc">
134<title>struct dmx_stc</title>
135 <programlisting>
136 struct dmx_stc {
137 unsigned int num; /&#x22C6; input : which STC? 0..N &#x22C6;/
138 unsigned int base; /&#x22C6; output: divisor for stc to get 90 kHz clock &#x22C6;/
139 uint64_t stc; /&#x22C6; output: stc in 'base'&#x22C6;90 kHz units &#x22C6;/
140 };
141</programlisting>
142 </section>
143
144</section>
145
146<section id="dmx_fcalls">
147<title>Demux Function Calls</title>
148
149<section id="dmx_fopen">
150<title>open()</title>
151<para>DESCRIPTION
152</para>
153<informaltable><tgroup cols="1"><tbody><row><entry
154 align="char">
155<para>This system call, used with a device name of /dev/dvb/adapter0/demux0,
156 allocates a new filter and returns a handle which can be used for subsequent
157 control of that filter. This call has to be made for each filter to be used, i.e. every
158 returned file descriptor is a reference to a single filter. /dev/dvb/adapter0/dvr0
159 is a logical device to be used for retrieving Transport Streams for digital
160 video recording. When reading from this device a transport stream containing
161 the packets from all PES filters set in the corresponding demux device
162 (/dev/dvb/adapter0/demux0) having the output set to DMX_OUT_TS_TAP. A
163 recorded Transport Stream is replayed by writing to this device. </para>
164<para>The significance of blocking or non-blocking mode is described in the
165 documentation for functions where there is a difference. It does not affect the
166 semantics of the open() call itself. A device opened in blocking mode can later
167 be put into non-blocking mode (and vice versa) using the F_SETFL command
168 of the fcntl system call.</para>
169</entry>
170 </row></tbody></tgroup></informaltable>
171<para>SYNOPSIS
172</para>
173<informaltable><tgroup cols="1"><tbody><row><entry
174 align="char">
175<para>int open(const char &#x22C6;deviceName, int flags);</para>
176</entry>
177 </row></tbody></tgroup></informaltable>
178<para>PARAMETERS
179</para>
180<informaltable><tgroup cols="2"><tbody><row><entry
181 align="char">
182<para>const char
183 *deviceName</para>
184</entry><entry
185 align="char">
186<para>Name of demux device.</para>
187</entry>
188 </row><row><entry
189 align="char">
190<para>int flags</para>
191</entry><entry
192 align="char">
193<para>A bit-wise OR of the following flags:</para>
194</entry>
195 </row><row><entry
196 align="char">
197</entry><entry
198 align="char">
199<para>O_RDWR read/write access</para>
200</entry>
201 </row><row><entry
202 align="char">
203</entry><entry
204 align="char">
205<para>O_NONBLOCK open in non-blocking mode</para>
206</entry>
207 </row><row><entry
208 align="char">
209</entry><entry
210 align="char">
211<para>(blocking mode is the default)</para>
212</entry>
213 </row></tbody></tgroup></informaltable>
214<para>ERRORS
215</para>
216<informaltable><tgroup cols="2"><tbody><row><entry
217 align="char">
218<para>ENODEV</para>
219</entry><entry
220 align="char">
221<para>Device driver not loaded/available.</para>
222</entry>
223 </row><row><entry
224 align="char">
225<para>EINVAL</para>
226</entry><entry
227 align="char">
228<para>Invalid argument.</para>
229</entry>
230 </row><row><entry
231 align="char">
232<para>EMFILE</para>
233</entry><entry
234 align="char">
235<para>&#8220;Too many open files&#8221;, i.e. no more filters available.</para>
236</entry>
237 </row><row><entry
238 align="char">
239<para>ENOMEM</para>
240</entry><entry
241 align="char">
242<para>The driver failed to allocate enough memory.</para>
243</entry>
244 </row></tbody></tgroup></informaltable>
245</section>
246
247<section id="dmx_fclose">
248<title>close()</title>
249<para>DESCRIPTION
250</para>
251<informaltable><tgroup cols="1"><tbody><row><entry
252 align="char">
253<para>This system call deactivates and deallocates a filter that was previously
254 allocated via the open() call.</para>
255</entry>
256 </row></tbody></tgroup></informaltable>
257<para>SYNOPSIS
258</para>
259<informaltable><tgroup cols="1"><tbody><row><entry
260 align="char">
261<para>int close(int fd);</para>
262</entry>
263 </row></tbody></tgroup></informaltable>
264<para>PARAMETERS
265</para>
266<informaltable><tgroup cols="2"><tbody><row><entry
267 align="char">
268<para>int fd</para>
269</entry><entry
270 align="char">
271<para>File descriptor returned by a previous call to open().</para>
272</entry>
273 </row></tbody></tgroup></informaltable>
274<para>ERRORS
275</para>
276<informaltable><tgroup cols="2"><tbody><row><entry
277 align="char">
278<para>EBADF</para>
279</entry><entry
280 align="char">
281<para>fd is not a valid open file descriptor.</para>
282</entry>
283 </row></tbody></tgroup></informaltable>
284</section>
285
286<section id="dmx_fread">
287<title>read()</title>
288<para>DESCRIPTION
289</para>
290<informaltable><tgroup cols="1"><tbody><row><entry
291 align="char">
292<para>This system call returns filtered data, which might be section or PES data. The
293 filtered data is transferred from the driver&#8217;s internal circular buffer to buf. The
294 maximum amount of data to be transferred is implied by count.</para>
295</entry>
296 </row><row><entry
297 align="char">
298<para>When returning section data the driver always tries to return a complete single
299 section (even though buf would provide buffer space for more data). If the size
300 of the buffer is smaller than the section as much as possible will be returned,
301 and the remaining data will be provided in subsequent calls.</para>
302</entry>
303 </row><row><entry
304 align="char">
305<para>The size of the internal buffer is 2 * 4096 bytes (the size of two maximum
306 sized sections) by default. The size of this buffer may be changed by using the
307 DMX_SET_BUFFER_SIZE function. If the buffer is not large enough, or if
308 the read operations are not performed fast enough, this may result in a buffer
309 overflow error. In this case EOVERFLOW will be returned, and the circular
310 buffer will be emptied. This call is blocking if there is no data to return, i.e. the
311 process will be put to sleep waiting for data, unless the O_NONBLOCK flag
312 is specified.</para>
313</entry>
314 </row><row><entry
315 align="char">
316<para>Note that in order to be able to read, the filtering process has to be started
317 by defining either a section or a PES filter by means of the ioctl functions,
318 and then starting the filtering process via the DMX_START ioctl function
319 or by setting the DMX_IMMEDIATE_START flag. If the reading is done
320 from a logical DVR demux device, the data will constitute a Transport Stream
321 including the packets from all PES filters in the corresponding demux device
322 /dev/dvb/adapter0/demux0 having the output set to DMX_OUT_TS_TAP.</para>
323</entry>
324 </row></tbody></tgroup></informaltable>
325<para>SYNOPSIS
326</para>
327<informaltable><tgroup cols="1"><tbody><row><entry
328 align="char">
329<para>size_t read(int fd, void &#x22C6;buf, size_t count);</para>
330</entry>
331 </row></tbody></tgroup></informaltable>
332<para>PARAMETERS
333</para>
334<informaltable><tgroup cols="2"><tbody><row><entry
335 align="char">
336<para>int fd</para>
337</entry><entry
338 align="char">
339<para>File descriptor returned by a previous call to open().</para>
340</entry>
341 </row><row><entry
342 align="char">
343<para>void *buf</para>
344</entry><entry
345 align="char">
346<para>Pointer to the buffer to be used for returned filtered data.</para>
347</entry>
348 </row><row><entry
349 align="char">
350<para>size_t count</para>
351</entry><entry
352 align="char">
353<para>Size of buf.</para>
354</entry>
355 </row></tbody></tgroup></informaltable>
356<para>ERRORS
357</para>
358<informaltable><tgroup cols="2"><tbody><row><entry
359 align="char">
360<para>EWOULDBLOCK</para>
361</entry><entry
362 align="char">
363<para>No data to return and O_NONBLOCK was specified.</para>
364</entry>
365 </row><row><entry
366 align="char">
367<para>EBADF</para>
368</entry><entry
369 align="char">
370<para>fd is not a valid open file descriptor.</para>
371</entry>
372 </row><row><entry
373 align="char">
374<para>ECRC</para>
375</entry><entry
376 align="char">
377<para>Last section had a CRC error - no data returned. The
378 buffer is flushed.</para>
379</entry>
380 </row><row><entry
381 align="char">
382<para>EOVERFLOW</para>
383</entry><entry
384 align="char">
385</entry>
386 </row><row><entry
387 align="char">
388</entry><entry
389 align="char">
390<para>The filtered data was not read from the buffer in due
391 time, resulting in non-read data being lost. The buffer is
392 flushed.</para>
393</entry>
394 </row><row><entry
395 align="char">
396<para>ETIMEDOUT</para>
397</entry><entry
398 align="char">
399<para>The section was not loaded within the stated timeout
400 period. See ioctl DMX_SET_FILTER for how to set a
401 timeout.</para>
402</entry>
403 </row><row><entry
404 align="char">
405<para>EFAULT</para>
406</entry><entry
407 align="char">
408<para>The driver failed to write to the callers buffer due to an
409 invalid *buf pointer.</para>
410</entry>
411 </row></tbody></tgroup></informaltable>
412</section>
413
414<section id="dmx_fwrite">
415<title>write()</title>
416<para>DESCRIPTION
417</para>
418<informaltable><tgroup cols="1"><tbody><row><entry
419 align="char">
420<para>This system call is only provided by the logical device /dev/dvb/adapter0/dvr0,
421 associated with the physical demux device that provides the actual DVR
422 functionality. It is used for replay of a digitally recorded Transport Stream.
423 Matching filters have to be defined in the corresponding physical demux
424 device, /dev/dvb/adapter0/demux0. The amount of data to be transferred is
425 implied by count.</para>
426</entry>
427 </row></tbody></tgroup></informaltable>
428<para>SYNOPSIS
429</para>
430<informaltable><tgroup cols="1"><tbody><row><entry
431 align="char">
432<para>ssize_t write(int fd, const void &#x22C6;buf, size_t
433 count);</para>
434</entry>
435 </row></tbody></tgroup></informaltable>
436<para>PARAMETERS
437</para>
438<informaltable><tgroup cols="2"><tbody><row><entry
439 align="char">
440<para>int fd</para>
441</entry><entry
442 align="char">
443<para>File descriptor returned by a previous call to open().</para>
444</entry>
445 </row><row><entry
446 align="char">
447<para>void *buf</para>
448</entry><entry
449 align="char">
450<para>Pointer to the buffer containing the Transport Stream.</para>
451</entry>
452 </row><row><entry
453 align="char">
454<para>size_t count</para>
455</entry><entry
456 align="char">
457<para>Size of buf.</para>
458</entry>
459 </row></tbody></tgroup></informaltable>
460<para>ERRORS
461</para>
462<informaltable><tgroup cols="2"><tbody><row><entry
463 align="char">
464<para>EWOULDBLOCK</para>
465</entry><entry
466 align="char">
467<para>No data was written. This
468 might happen if O_NONBLOCK was specified and there
469 is no more buffer space available (if O_NONBLOCK is
470 not specified the function will block until buffer space is
471 available).</para>
472</entry>
473 </row><row><entry
474 align="char">
475<para>EBUSY</para>
476</entry><entry
477 align="char">
478<para>This error code indicates that there are conflicting
479 requests. The corresponding demux device is setup to
480 receive data from the front- end. Make sure that these
481 filters are stopped and that the filters with input set to
482 DMX_IN_DVR are started.</para>
483</entry>
484 </row><row><entry
485 align="char">
486<para>EBADF</para>
487</entry><entry
488 align="char">
489<para>fd is not a valid open file descriptor.</para>
490</entry>
491 </row></tbody></tgroup></informaltable>
492</section>
493
494<section id="dmx_start">
495<title>DMX_START</title>
496<para>DESCRIPTION
497</para>
498<informaltable><tgroup cols="1"><tbody><row><entry
499 align="char">
500<para>This ioctl call is used to start the actual filtering operation defined via the ioctl
501 calls DMX_SET_FILTER or DMX_SET_PES_FILTER.</para>
502</entry>
503 </row></tbody></tgroup></informaltable>
504<para>SYNOPSIS
505</para>
506<informaltable><tgroup cols="1"><tbody><row><entry
507 align="char">
508<para>int ioctl( int fd, int request = DMX_START);</para>
509</entry>
510 </row></tbody></tgroup></informaltable>
511<para>PARAMETERS
512</para>
513<informaltable><tgroup cols="2"><tbody><row><entry
514 align="char">
515<para>int fd</para>
516</entry><entry
517 align="char">
518<para>File descriptor returned by a previous call to open().</para>
519</entry>
520 </row><row><entry
521 align="char">
522<para>int request</para>
523</entry><entry
524 align="char">
525<para>Equals DMX_START for this command.</para>
526</entry>
527 </row></tbody></tgroup></informaltable>
528<para>ERRORS
529</para>
530<informaltable><tgroup cols="2"><tbody><row><entry
531 align="char">
532<para>EBADF</para>
533</entry><entry
534 align="char">
535<para>fd is not a valid file descriptor.</para>
536</entry>
537 </row><row><entry
538 align="char">
539<para>EINVAL</para>
540</entry><entry
541 align="char">
542<para>Invalid argument, i.e. no filtering parameters provided via
543 the DMX_SET_FILTER or DMX_SET_PES_FILTER
544 functions.</para>
545</entry>
546 </row><row><entry
547 align="char">
548<para>EBUSY</para>
549</entry><entry
550 align="char">
551<para>This error code indicates that there are conflicting
552 requests. There are active filters filtering data from
553 another input source. Make sure that these filters are
554 stopped before starting this filter.</para>
555</entry>
556 </row></tbody></tgroup></informaltable>
557</section>
558
559<section id="dmx_stop">
560<title>DMX_STOP</title>
561<para>DESCRIPTION
562</para>
563<informaltable><tgroup cols="1"><tbody><row><entry
564 align="char">
565<para>This ioctl call is used to stop the actual filtering operation defined via the
566 ioctl calls DMX_SET_FILTER or DMX_SET_PES_FILTER and started via
567 the DMX_START command.</para>
568</entry>
569 </row></tbody></tgroup></informaltable>
570<para>SYNOPSIS
571</para>
572<informaltable><tgroup cols="1"><tbody><row><entry
573 align="char">
574<para>int ioctl( int fd, int request = DMX_STOP);</para>
575</entry>
576 </row></tbody></tgroup></informaltable>
577<para>PARAMETERS
578</para>
579<informaltable><tgroup cols="2"><tbody><row><entry
580 align="char">
581<para>int fd</para>
582</entry><entry
583 align="char">
584<para>File descriptor returned by a previous call to open().</para>
585</entry>
586 </row><row><entry
587 align="char">
588<para>int request</para>
589</entry><entry
590 align="char">
591<para>Equals DMX_STOP for this command.</para>
592</entry>
593 </row></tbody></tgroup></informaltable>
594<para>ERRORS
595</para>
596<informaltable><tgroup cols="2"><tbody><row><entry
597 align="char">
598<para>EBADF</para>
599</entry><entry
600 align="char">
601<para>fd is not a valid file descriptor.</para>
602</entry>
603 </row></tbody></tgroup></informaltable>
604</section>
605
606<section id="dmx_set_filter">
607<title>DMX_SET_FILTER</title>
608<para>DESCRIPTION
609</para>
610<informaltable><tgroup cols="1"><tbody><row><entry
611 align="char">
612<para>This ioctl call sets up a filter according to the filter and mask parameters
613 provided. A timeout may be defined stating number of seconds to wait for a
614 section to be loaded. A value of 0 means that no timeout should be applied.
615 Finally there is a flag field where it is possible to state whether a section should
616 be CRC-checked, whether the filter should be a &#8221;one-shot&#8221; filter, i.e. if the
617 filtering operation should be stopped after the first section is received, and
618 whether the filtering operation should be started immediately (without waiting
619 for a DMX_START ioctl call). If a filter was previously set-up, this filter will
620 be canceled, and the receive buffer will be flushed.</para>
621</entry>
622 </row></tbody></tgroup></informaltable>
623<para>SYNOPSIS
624</para>
625<informaltable><tgroup cols="1"><tbody><row><entry
626 align="char">
627<para>int ioctl( int fd, int request = DMX_SET_FILTER,
628 struct dmx_sct_filter_params &#x22C6;params);</para>
629</entry>
630 </row></tbody></tgroup></informaltable>
631<para>PARAMETERS
632</para>
633<informaltable><tgroup cols="2"><tbody><row><entry
634 align="char">
635<para>int fd</para>
636</entry><entry
637 align="char">
638<para>File descriptor returned by a previous call to open().</para>
639</entry>
640 </row><row><entry
641 align="char">
642<para>int request</para>
643</entry><entry
644 align="char">
645<para>Equals DMX_SET_FILTER for this command.</para>
646</entry>
647 </row><row><entry
648 align="char">
649<para>struct
650 dmx_sct_filter_params
651 *params</para>
652</entry><entry
653 align="char">
654<para>Pointer to structure containing filter parameters.</para>
655</entry>
656 </row></tbody></tgroup></informaltable>
657<para>ERRORS
658</para>
659<informaltable><tgroup cols="2"><tbody><row><entry
660 align="char">
661<para>EBADF</para>
662</entry><entry
663 align="char">
664<para>fd is not a valid file descriptor.</para>
665</entry>
666 </row><row><entry
667 align="char">
668<para>EINVAL</para>
669</entry><entry
670 align="char">
671<para>Invalid argument.</para>
672</entry>
673 </row></tbody></tgroup></informaltable>
674</section>
675
676<section id="dmx_set_pes_filter">
677<title>DMX_SET_PES_FILTER</title>
678<para>DESCRIPTION
679</para>
680<informaltable><tgroup cols="1"><tbody><row><entry
681 align="char">
682<para>This ioctl call sets up a PES filter according to the parameters provided. By a
683 PES filter is meant a filter that is based just on the packet identifier (PID), i.e.
684 no PES header or payload filtering capability is supported.</para>
685</entry>
686 </row><row><entry
687 align="char">
688<para>The transport stream destination for the filtered output may be set. Also the
689 PES type may be stated in order to be able to e.g. direct a video stream directly
690 to the video decoder. Finally there is a flag field where it is possible to state
691 whether the filtering operation should be started immediately (without waiting
692 for a DMX_START ioctl call). If a filter was previously set-up, this filter will
693 be cancelled, and the receive buffer will be flushed.</para>
694</entry>
695 </row></tbody></tgroup></informaltable>
696<para>SYNOPSIS
697</para>
698<informaltable><tgroup cols="1"><tbody><row><entry
699 align="char">
700<para>int ioctl( int fd, int request = DMX_SET_PES_FILTER,
701 struct dmx_pes_filter_params &#x22C6;params);</para>
702</entry>
703 </row></tbody></tgroup></informaltable>
704<para>PARAMETERS
705</para>
706<informaltable><tgroup cols="2"><tbody><row><entry
707 align="char">
708<para>int fd</para>
709</entry><entry
710 align="char">
711<para>File descriptor returned by a previous call to open().</para>
712</entry>
713 </row><row><entry
714 align="char">
715<para>int request</para>
716</entry><entry
717 align="char">
718<para>Equals DMX_SET_PES_FILTER for this command.</para>
719</entry>
720 </row><row><entry
721 align="char">
722<para>struct
723 dmx_pes_filter_params
724 *params</para>
725</entry><entry
726 align="char">
727<para>Pointer to structure containing filter parameters.</para>
728</entry>
729 </row></tbody></tgroup></informaltable>
730<para>ERRORS
731</para>
732<informaltable><tgroup cols="2"><tbody><row><entry
733 align="char">
734<para>EBADF</para>
735</entry><entry
736 align="char">
737<para>fd is not a valid file descriptor.</para>
738</entry>
739 </row><row><entry
740 align="char">
741<para>EINVAL</para>
742</entry><entry
743 align="char">
744<para>Invalid argument.</para>
745</entry>
746 </row><row><entry
747 align="char">
748<para>EBUSY</para>
749</entry><entry
750 align="char">
751<para>This error code indicates that there are conflicting
752 requests. There are active filters filtering data from
753 another input source. Make sure that these filters are
754 stopped before starting this filter.</para>
755</entry>
756 </row></tbody></tgroup></informaltable>
757</section>
758
759<section id="dms_set_buffer_size">
760<title>DMX_SET_BUFFER_SIZE</title>
761<para>DESCRIPTION
762</para>
763<informaltable><tgroup cols="1"><tbody><row><entry
764 align="char">
765<para>This ioctl call is used to set the size of the circular buffer used for filtered data.
766 The default size is two maximum sized sections, i.e. if this function is not called
767 a buffer size of 2 * 4096 bytes will be used.</para>
768</entry>
769 </row></tbody></tgroup></informaltable>
770<para>SYNOPSIS
771</para>
772<informaltable><tgroup cols="1"><tbody><row><entry
773 align="char">
774<para>int ioctl( int fd, int request =
775 DMX_SET_BUFFER_SIZE, unsigned long size);</para>
776</entry>
777 </row></tbody></tgroup></informaltable>
778<para>PARAMETERS
779</para>
780<informaltable><tgroup cols="2"><tbody><row><entry
781 align="char">
782<para>int fd</para>
783</entry><entry
784 align="char">
785<para>File descriptor returned by a previous call to open().</para>
786</entry>
787 </row><row><entry
788 align="char">
789<para>int request</para>
790</entry><entry
791 align="char">
792<para>Equals DMX_SET_BUFFER_SIZE for this command.</para>
793</entry>
794 </row><row><entry
795 align="char">
796<para>unsigned long size</para>
797</entry><entry
798 align="char">
799<para>Size of circular buffer.</para>
800</entry>
801 </row></tbody></tgroup></informaltable>
802<para>ERRORS
803</para>
804<informaltable><tgroup cols="2"><tbody><row><entry
805 align="char">
806<para>EBADF</para>
807</entry><entry
808 align="char">
809<para>fd is not a valid file descriptor.</para>
810</entry>
811 </row><row><entry
812 align="char">
813<para>ENOMEM</para>
814</entry><entry
815 align="char">
816<para>The driver was not able to allocate a buffer of the
817 requested size.</para>
818</entry>
819 </row></tbody></tgroup></informaltable>
820</section>
821
822<section id="dmx_get_event">
823<title>DMX_GET_EVENT</title>
824<para>DESCRIPTION
825</para>
826<informaltable><tgroup cols="1"><tbody><row><entry
827 align="char">
828<para>This ioctl call returns an event if available. If an event is not available,
829 the behavior depends on whether the device is in blocking or non-blocking
830 mode. In the latter case, the call fails immediately with errno set to
831 EWOULDBLOCK. In the former case, the call blocks until an event becomes
832 available.</para>
833</entry>
834 </row><row><entry
835 align="char">
836<para>The standard Linux poll() and/or select() system calls can be used with the
837 device file descriptor to watch for new events. For select(), the file descriptor
838 should be included in the exceptfds argument, and for poll(), POLLPRI should
839 be specified as the wake-up condition. Only the latest event for each filter is
840 saved.</para>
841</entry>
842 </row></tbody></tgroup></informaltable>
843<para>SYNOPSIS
844</para>
845<informaltable><tgroup cols="1"><tbody><row><entry
846 align="char">
847<para>int ioctl( int fd, int request = DMX_GET_EVENT,
848 struct dmx_event &#x22C6;ev);</para>
849</entry>
850 </row></tbody></tgroup></informaltable>
851<para>PARAMETERS
852</para>
853<informaltable><tgroup cols="2"><tbody><row><entry
854 align="char">
855<para>int fd</para>
856</entry><entry
857 align="char">
858<para>File descriptor returned by a previous call to open().</para>
859</entry>
860 </row><row><entry
861 align="char">
862<para>int request</para>
863</entry><entry
864 align="char">
865<para>Equals DMX_GET_EVENT for this command.</para>
866</entry>
867 </row><row><entry
868 align="char">
869<para>struct dmx_event *ev</para>
870</entry><entry
871 align="char">
872<para>Pointer to the location where the event is to be stored.</para>
873</entry>
874 </row></tbody></tgroup></informaltable>
875<para>ERRORS
876</para>
877<informaltable><tgroup cols="2"><tbody><row><entry
878 align="char">
879<para>EBADF</para>
880</entry><entry
881 align="char">
882<para>fd is not a valid file descriptor.</para>
883</entry>
884 </row><row><entry
885 align="char">
886<para>EFAULT</para>
887</entry><entry
888 align="char">
889<para>ev points to an invalid address.</para>
890</entry>
891 </row><row><entry
892 align="char">
893<para>EWOULDBLOCK</para>
894</entry><entry
895 align="char">
896<para>There is no event pending, and the device is in
897 non-blocking mode.</para>
898</entry>
899 </row></tbody></tgroup></informaltable>
900</section>
901
902<section id="dmx_get_stc">
903<title>DMX_GET_STC</title>
904<para>DESCRIPTION
905</para>
906<informaltable><tgroup cols="1"><tbody><row><entry
907 align="char">
908<para>This ioctl call returns the current value of the system time counter (which is driven
909 by a PES filter of type DMX_PES_PCR). Some hardware supports more than one
910 STC, so you must specify which one by setting the num field of stc before the ioctl
911 (range 0...n). The result is returned in form of a ratio with a 64 bit numerator
912 and a 32 bit denominator, so the real 90kHz STC value is stc-&#x003E;stc /
913 stc-&#x003E;base
914 .</para>
915</entry>
916 </row></tbody></tgroup></informaltable>
917<para>SYNOPSIS
918</para>
919<informaltable><tgroup cols="1"><tbody><row><entry
920 align="char">
921<para>int ioctl( int fd, int request = DMX_GET_STC, struct
922 dmx_stc &#x22C6;stc);</para>
923</entry>
924 </row></tbody></tgroup></informaltable>
925<para>PARAMETERS
926</para>
927<informaltable><tgroup cols="2"><tbody><row><entry
928 align="char">
929<para>int fd</para>
930</entry><entry
931 align="char">
932<para>File descriptor returned by a previous call to open().</para>
933</entry>
934 </row><row><entry
935 align="char">
936<para>int request</para>
937</entry><entry
938 align="char">
939<para>Equals DMX_GET_STC for this command.</para>
940</entry>
941 </row><row><entry
942 align="char">
943<para>struct dmx_stc *stc</para>
944</entry><entry
945 align="char">
946<para>Pointer to the location where the stc is to be stored.</para>
947</entry>
948 </row></tbody></tgroup></informaltable>
949<para>ERRORS
950</para>
951<informaltable><tgroup cols="2"><tbody><row><entry
952 align="char">
953<para>EBADF</para>
954</entry><entry
955 align="char">
956<para>fd is not a valid file descriptor.</para>
957</entry>
958 </row><row><entry
959 align="char">
960<para>EFAULT</para>
961</entry><entry
962 align="char">
963<para>stc points to an invalid address.</para>
964</entry>
965 </row><row><entry
966 align="char">
967<para>EINVAL</para>
968</entry><entry
969 align="char">
970<para>Invalid stc number.</para>
971</entry>
972 </row></tbody></tgroup></informaltable>
973 </section></section>
Linux 6.x block layer and io_uring tree(s)