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17 .Dd February 1, 2019
18 .Dt MIXER 7I
19 .Os
20 .Sh NAME
21 .Nm mixer
22 .Nd generic mixer device interface
23 .Sh SYNOPSIS
24 .In sys/soundcard.h
25 .Sh DESCRIPTION
26 .Ss "Mixer Pseudo-Device"
27 The
28 .Pa /dev/mixer
29 pseudo-device is provided for two purposes:
30 .Bl -bullet -offset indent
31 .It
32 The first purpose is for applications that wish to learn about the list of
33 audio devices on the system, so that they can select (or provide for users to
34 select) an appropriate audio device.
35 The
36 .Pa /dev/mixer
37 pseudo-device
38 provides interfaces to enumerate all of the audio devices on the system.
39 .It
40 The second purpose is for mixer panel type applications which need to control
41 master settings for the audio hardware in the system, such as gain levels,
42 balance, port functionality, and other device features.
43 .El
44 .Pp
45 Ordinary audio applications should
46 .Em not
47 attempt to adjust their playback
48 or record volumes or other device settings using this device.
49 Instead, they
50 should use the
51 .Dv SNDCTL_DSP_SETPLAYVOL
52 and
53 .Dv SNDCTL_DSP_SETRECVOL
54 ioctls that are documented in
55 .Xr dsp 7I .
56 .Ss "Sndstat Device"
57 The
58 .Pa /dev/sndstat
59 device supports
60 .Xr read 2 ,
61 and can be read to
62 retrieve human-readable information about the audio devices on the system.
63 Software should not attempt to interpret the contents of this device.
64 .Sh IOCTLS
65 .Ss "Information IOCTLs"
66 The following ioctls are intended to aid applications in identifying the audio
67 devices available on the system.
68 These ioctls can be issued against either the
69 pseudo-device
70 .Pa /dev/mixer ,
71 or a against a file descriptor open to any
72 other audio device in the system.
73 .Pp
74 Applications should issue
75 .Dv SNDCTL_SYSINFO
76 first to learn what audio
77 devices and mixers are available on the system, and then use
78 .Dv SNDCTL_AUDIOINFO
79 or
80 .Dv SNDCTL_MIXERINFO
81 to obtain more information
82 about the audio devices or mixers, respectively.
83 .Bl -tag -width SNDCTL_AUDIOINFO
84 .It Dv OSS_GETVERSION
85 The argument is a pointer to an integer, which retrieves the version of the
86 .Sy OSS API
87 used.
88 The value is encoded with the major version (currently 4)
89 encoded in the most significant 16 bits, and a minor version encoded in the
90 lower 16 bits.
91 .It Dv SNDCTL_SYSINFO
92 The argument is a pointer to an
93 .Vt oss_sysinfo
94 structure, which has the following definition:
95 .Bd -literal -offset 2n
96 typedef struct oss_sysinfo {
97 char product[32]; /* E.g. SunOS Audio */
98 char version[32]; /* E.g. 4.0a */
99 int versionnum; /* See OSS_GETVERSION */
100 char options[128]; /* NOT SUPPORTED */
101
102 int numaudios; /* # of audio/dsp devices */
103 int openedaudio[8]; /* Reserved, always 0 */
104
105 int numsynths; /* NOT SUPPORTED, always 0 */
106 int nummidis; /* NOT SUPPORTED, always 0 */
107 int numtimers; /* NOT SUPPORTED, always 0 */
108 int nummixers; /* # of mixer devices */
109
110 /* Mask of midi devices are busy */
111 int openedmidi[8];
112
113 /* Number of sound cards in the system */
114 int numcards;
115
116 /* Number of audio engines in the system */
117 int numaudioengines;
118 char license[16]; /* E.g. "GPL" or "CDDL" */
119 char revision_info[256]; /* Reserved */
120 int filler[172]; /* Reserved */
121 } oss_sysinfo;
122 .Ed
123 .Pp
124 The important fields here are
125 .Fa numaudios ,
126 which is used to determine the
127 number of audio devices that can be queried with
128 .Dv SNDCTL_AUDIOINFO ,
129 .Fa nummixers
130 which provides a count of mixers on the system, and
131 .Fa numcards
132 which counts to total number of aggregate devices.
133 A
134 .Sy card
135 can consist of one or more audio devices and one or more mixers, although more
136 typically there is exactly one audio device and one mixer for each card.
137 .It Dv SNDCTL_AUDIOINFO
138 The argument is a pointer to an
139 .Vt oss_audioinfo
140 structure, which has the following structure:
141 .Bd -literal -offset 2n
142 typedef struct oss_audioinfo {
143 int dev; /* Device to query */
144 char name[64]; /* Human readable name */
145 int busy; /* reserved */
146 int pid; /* reserved */
147
148 /* PCM_CAP_INPUT, PCM_CAP_OUTPUT */
149 int caps;
150 int iformats; /* Supported input formats */
151 int oformats; /* Supported output formats */
152 int magic; /* reserved */
153 char cmd[64]; /* reserved */
154 int card_number;
155 int port_number; /* reserved */
156 int mixer_dev;
157
158 /* Obsolete field. Replaced by devnode */
159 int legacy_device;
160 int enabled; /* reserved */
161 int flags; /* reserved */
162 int min_rate; /* Minimum sample rate */
163 int max_rate; /* Maximum sample rate */
164 int min_channels; /* Minimum number of channels */
165 int max_channels; /* Maximum number of channels */
166 int binding; /* reserved */
167 int rate_source; /* reserved */
168 char handle[32]; /* reserved */
169 unsigned int nrates; /* reserved */
170 unsigned int rates[20]; /* reserved */
171 char song_name[64]; /* reserved */
172 char label[16]; /* reserved */
173 int latency; /* reserved */
174
175 /* Device special file name (absolute path) */
176 char devnode[32];
177 int next_play_engine; /* reserved */
178 int next_rec_engine; /* reserved */
179 int filler[184]; /* reserved */
180 } oss_audioinfo;
181 .Ed
182 .Pp
183 In the above structure, all of the fields are reserved except the following:
184 .Fa dev ,
185 .Fa name ,
186 .Fa card_number ,
187 .Fa mixer_dev ,
188 .Fa caps ,
189 .Fa min_rate ,
190 .Fa max_rate ,
191 .Fa min_channels ,
192 .Fa max_channels ,
193 and
194 .Fa devnode .
195 The reserved fields are provided for compatibility with other OSS
196 implementations, and available for legacy applications.
197 New applications should not attempt to use these fields.
198 .Pp
199 The
200 .Fa dev
201 field should be initialized by the application to the number of
202 the device to query.
203 This is a number between zero (inclusive) and value of
204 .Fa numaudios
205 (exclusive) returned by
206 .Dv SNDCTL_SYSINFO .
207 Alternatively,
208 when issuing the ioctl against a real mixer or
209 .Sy dsp
210 device, the special
211 value
212 .Sy -1
213 can be used to indicate that the query is being made against the device opened.
214 If
215 .Sy -1
216 is used, the field is overwritten with the device
217 number for the current device on successful return.
218 .Pp
219 No other fields are significant upon entry, but a successful return contains
220 details of the device.
221 .Pp
222 The
223 .Fa name
224 field is a human readable name representing the device.
225 Applications should not try to interpret it.
226 .Pp
227 The
228 .Fa card_number
229 field indicates the number assigned to the aggregate device.
230 This can be used with the
231 .Dv SNDCTL_CARDINFO
232 ioctl.
233 .Pp
234 The
235 .Fa mixer_dev
236 is the mixer device number for the mixing device associated
237 with the audio device.
238 This can be used with the
239 .Dv SNDCTL_MIXERINFO
240 ioctl.
241 .Pp
242 The
243 .Fa caps
244 field contains any of the bits
245 .Dv PCM_CAP_INPUT ,
246 .Dv PCM_CAP_OUTPUT ,
247 and
248 .Dv PCM_CAP_DUPLEX .
249 Indicating whether the device
250 support input, output, and whether input and output can be used simultaneously.
251 All other bits are reserved.
252 .Pp
253 The
254 .Fa min_rate
255 and
256 .Fa max_rate
257 fields indicate the minimum and maximum sample rates supported by the device.
258 Most applications should try to use the maximum supported rate for the best
259 audio quality and lowest system resource consumption.
260 .Pp
261 The
262 .Fa min_channels
263 and
264 .Fa max_channels
265 provide an indication of the number of channels (1 for mono, 2 for stereo,
266 6 for 5\&.1, etc\&.) supported by the device.
267 .Pp
268 The
269 .Fa devnode
270 field contains the actual full path to the device node for this device, such as
271 .Pa /dev/sound/audio810:0dsp .
272 Applications should open this file to access the device.
273 .It Dv SNDCTL_CARDINFO
274 The argument is a pointer to a
275 .Vt struct oss_card_info ,
276 which has the following definition:
277 .Bd -literal -offset 2n
278 typedef struct oss_card_info {
279 int card;
280 char shortname[16];
281 char longname[128];
282 int flags; /* reserved */
283 char hw_info[400];
284 int intr_count; /* reserved */
285 int ack_count; /* reserved */
286 int filler[154];
287 } oss_card_info;
288 .Ed
289 .Pp
290 This ioctl is used to query for information about the aggregate audio device.
291 .Pp
292 The
293 .Fa card
294 field should be initialized by the application to the number of
295 the card to query.
296 This is a number between zero
297 .Pq inclusive
298 and value of
299 .Fa numcards
300 .Pq exclusive
301 returned by
302 .Dv SNDCTL_SYSINFO .
303 Alternatively,
304 when issuing the ioctl against a real mixer or
305 .Sy dsp
306 device, the special value
307 .Sy -1
308 can be used to indicate that the query is being made against the device opened.
309 If
310 .Sy -1
311 is used, the field is overwritten with the number
312 for the current hardware device on successful return.
313 .Pp
314 The
315 .Fa shortname ,
316 .Fa longname ,
317 and
318 .Fa hw_info
319 contain
320 .Sy ASCIIZ
321 strings describing the device in more detail.
322 The
323 .Fa hw_info
324 member can contain multiple lines of detail, each line ending in a NEWLINE.
325 .Pp
326 The
327 .Fa flag ,
328 .Fa intr_count ,
329 and
330 .Fa ack_count
331 fields are not used by this implementation.
332 .It Dv SNDCTL_MIXERINFO
333 The argument is a pointer to a
334 .Vt struct oss_mixer_info ,
335 which has the following definition:
336 .Bd -literal -offset 2n
337 typedef struct oss_mixerinfo {
338 int dev;
339 char id[16]; /* Reserved */
340 char name[32];
341 int modify_counter;
342 int card_number;
343 int port_number; /* Reserved */
344 char handle[32]; /* Reserved */
345 int magic; /* Reserved */
346 int enabled; /* Reserved */
347 int caps; /* Reserved */
348 int flags; /* Reserved */
349 int nrext;
350 int priority;
351
352 /* Deice special file name (absolute path) */
353 char devnode[32];
354 int legacy_device; /* Reserved */
355 int filler[245]; /* Reserved */
356 } oss_mixerinfo;
357 .Ed
358 .Pp
359 In the above structure, all of the fields are reserved except the following:
360 .Fa dev ,
361 .Fa name ,
362 .Fa modify_counter ,
363 .Fa card_number ,
364 .Fa nrext ,
365 .Fa priority ,
366 and
367 .Fa devnode .
368 The reserved fields are provided for compatibility with other
369 OSS implementations, and available for legacy applications.
370 New applications should not attempt to use these fields.
371 .Pp
372 The
373 .Fa dev
374 field should be initialized by the application to the number of
375 the device to query.
376 This is a number between zero inclusive and value of
377 .Fa nummixers
378 (exclusive) returned by
379 .Dv SNDCTL_SYSINFO ,
380 or by
381 .Dv SNDCTL_MIX_NRMIX .
382 Alternatively, when issuing the ioctl against a real mixer or
383 .Sy dsp
384 device, the special value
385 .Sy -1
386 can be used to indicate
387 that the query is being made against the device opened.
388 If
389 .Sy -1
390 is used,
391 the field is overwritten with the mixer number for the current open file on
392 successful return.
393 .Pp
394 No other fields are significant upon entry, but on successful return contains
395 details of the device.
396 .Pp
397 The
398 .Fa name
399 field is a human readable name representing the device.
400 Applications should not try to interpret it.
401 .Pp
402 The
403 .Fa modify_counter
404 is changed by the mixer framework each time the
405 settings for the various controls or extensions of the device are changed.
406 Applications can poll this value to learn if any other changes need to be
407 searched for.
408 .Pp
409 The
410 .Fa card_number
411 field is the number of the aggregate audio device this
412 mixer is located on.
413 It can be used with the
414 .Dv SNDCTL_CARDINFO
415 ioctl.
416 .Pp
417 The
418 .Fa nrext
419 field is the number of mixer extensions available on this mixer.
420 See the
421 .Dv SNDCTL_MIX_NREXT
422 description.
423 .Pp
424 The priority is used by the framework to assign a preference that applications
425 can use in choosing a device.
426 Higher values are preferable.
427 Mixers with priorities less than -1 should never be selected by default.
428 .Pp
429 The
430 .Fa devnode
431 field contains the actual full path to the device node for
432 the physical mixer, such as
433 .Pa /dev/sound/audio810:0mixer .
434 Applications
435 should open this file to access the mixer settings.
436 .El
437 .Ss "Mixer Extension IOCTLs"
438 The pseudo
439 .Pa /dev/mixer
440 device supports ioctls that can change the
441 oarious settings for the audio hardware in the system.
442 .Pp
443 Those ioctls should only be used by dedicated mixer applications or desktop
444 olumme controls, and not by typical ordinary audio applications such as media
445 players.
446 Ordinary applications that wish to adjust their own volume settings
447 should use the
448 .Dv SNDCTL_DSP_SETPLAYVOL
449 or
450 .Dv SNDCTL_DSP_SETRECVOL
451 ioctls for that purpose.
452 See
453 .Xr dsp 7I
454 for more information.
455 Ordinary
456 applications should never attempt to change master port selection or hardware
457 settings such as monitor gain settings.
458 .Pp
459 The ioctls in this section can only be used to access the mixer device that is
460 associated with the current file descriptor.
461 .Pp
462 Applications should not assume that a single
463 .Pa /dev/mixer
464 node is able to access any physical settings.
465 Instead, they should use the ioctl
466 .Dv SNDCTL_MIXERINFO
467 to determine the device path for the real mixer device,
468 and issue ioctls on a file descriptor opened against the corresponding
469 .Fa devnode
470 field.
471 .Pp
472 When a
473 .Fa dev
474 member is specified in each of the following ioctls, the
475 application should specify
476 .Sy -1 ,
477 although for compatibility the mixer
478 allows the application to specify the mixer device number.
479 .Pp
480 .Bl -tag -width SNDCTL_MIX_ENUMINFO -compact
481 .It Dv SNDCTL_MIX_NRMIX
482 The argument is a pointer to an integer, which receives the number of mixer
483 devices in the system.
484 Each can be queried by using its number with the
485 .Dv SNDCTL_MIXERINFO
486 ioctl.
487 The same information is available using the
488 .Fa SNDCTL_SYSINFO
489 ioctl.
490 .Pp
491 .It Dv SNDCTL_MIX_NREXT
492 The argument is a pointer to an integer.
493 On entry, the integer should contain
494 the special value
495 .Sy -1 .
496 On return the argument receives the number of mixer
497 extensions (or mixer controls) supported by the mixer device.
498 More details
499 about each extension can be obtained by
500 .Fa SNDCTL_MIX_EXTINFO
501 ioctl.
502 .Pp
503 .It Dv SNDCTL_MIX_EXTINFO
504 The argument is a pointer to an
505 .Vt oss_mixext
506 structure which is defined as follows:
507 .Bd -literal -offset 2n
508 typedef struct oss_mixext {
509 int dev; /* Mixer device number */
510 int ctrl; /* Extension number */
511 int type; /* Entry type */
512 int maxvalue;
513 int minvalue;
514 int flags;
515 char id[16]; /* Mnemonic ID (internal use) */
516 int parent; /* Entry# of parent (-1 if root) */
517 int dummy; /* NOT SUPPORTED */
518 int timestamp;
519 char data[64]; /* Reserved */
520
521 /* Mask of allowed enum values */
522 unsigned char enum_present[32];
523 int control_no; /* Reserved */
524 unsigned int desc; /* NOT SUPPORTED */
525 char extname[32];
526 int update_counter;
527 int filler[7]; /* Reserved */
528 } oss_mixext;
529 .Ed
530 .Pp
531 On entry, the
532 .Fa dev
533 field should be initialized to the value
534 .Sy -1 ,
535 and
536 the
537 .Fa ctrl
538 field should be initialized with the number of the extension
539 being accessed.
540 Between 0, inclusive, and the value returned by
541 .Dv SNDCTL_MIX_NREXT ,
542 exclusive.
543 .Pp
544 Mixer extensions are organized as a logical tree, starting with a root node.
545 The root node always has a
546 .Fa ctrl
547 value of zero.
548 The structure of the tree can be determined by looking at the parent field,
549 which contains the extension number of the parent extension, or
550 .Sy -1
551 if the extension is the root extension.
552 .Pp
553 The type indicates the type of extension used.
554 This implementation supports the following values:
555 .Bl -column -offset 2n "MIXT_STEREOSLIDER" "Enumerated value, 0 to maxvalue"
556 .It Dv MIXT_DEVROOT Ta Root node for extension tree
557 .It Dv MIXT_GROUP Ta Logical grouping of controls
558 .It Dv MXIT_ONOFF Ta Boolean value, 0 = off, 1 = on.
559 .It Dv MIXT_ENUM Ta Enumerated value, 0 to maxvalue.
560 .It Dv MIXT_MONOSLIDER Ta Monophonic slider, 0 to 255.
561 .It Dv MIXT_STEREOSLIDER Ta Stereophonic slider, 0 to 255 (encoded as lower two bytes in value.)
562 .It Dv MIXT_MARKER Ta Place holder, can ignore.
563 .El
564 .Pp
565 The flags field is a bit array.
566 This implementation makes use of the following
567 possible bits:
568 .Bl -column -offset 2n "MIXF_WRITEABLE" "Extensions value is modifiable"
569 .It Dv MIXF_READABLE Ta Extension's value is readable.
570 .It Dv MIXF_WRITEABLE Ta Extension's value is modifiable.
571 .It Dv MIXF_POLL Ta Extension can self-update.
572 .It Dv MIXF_PCMVOL Ta Extension is for master PCM playback volume.
573 .It Dv MIXF_MAINVOL Ta Extension is for a typical analog volume
574 .It Dv MIXF_RECVOL Ta Extension is for master record gain.
575 .It Dv MIXF_MONVOL Ta Extension is for a monitor source's gain.
576 .El
577 .Pp
578 The
579 .Fa id
580 field contains an
581 .Sy ASCIIZ
582 identifier for the extension.
583 .Pp
584 The timestamp field is set when the extension tree is first initialized.
585 Applications must use the same timestamp value when attempting to change the
586 values.
587 A change in the timestamp indicates a change a in the structure of the
588 extension tree.
589 .Pp
590 The
591 .Fa enum_present
592 field is a bit mask of possible enumeration values.
593 If a
594 bit is present in the
595 .Fa enum_present
596 mask, then the corresponding enumeration value is legal.
597 The mask is in little endian order.
598 .Pp
599 The
600 .Fa desc
601 field provides information about scoping, which can be useful as
602 layout hints to applications.
603 The following hints are available:
604 .Bl -column -offset 2n "MIXEXT_SCOPE_MONITOR" "No scoping hint provided."
605 .It Dv MIXEXT_SCOPE_MASK Ta Mask of possible scope values.
606 .It Dv MIXEXT_SCOPE_INPUT Ta Extension is an input control.
607 .It Dv MIXEXT_SCOPE_OUTPUT Ta Extension is an output control.
608 .It Dv MIXEXT_SCOPE_MONITOR Ta Extension relates to input monitoring.
609 .It Dv MIXEXT_SCOPE_OTHER Ta No scoping hint provided.
610 .El
611 .Pp
612 The
613 .Fa extname
614 is the full name of the extension.
615 .Pp
616 The
617 .Fa update_counter
618 is incremented each time the control's value is changed.
619 .Pp
620 .It Dv SNDCTL_MIX_ENUMINFO
621 The argument is a pointer to an
622 .Vt oss_mixer_enuminfo
623 structure, which is defined as follows:
624 .Bd -literal -offset 2n
625 typedef struct oss_mixer_enuminfo {
626 int dev;
627 int ctrl;
628 int nvalues;
629 int version;
630 short strindex[255];
631 char strings[3000];
632 } oss_mixer_enuminfo;
633 .Ed
634 .Pp
635 On entry, the
636 .Fa dev
637 field should be initialized to the value
638 .Sy -1 ,
639 and
640 the
641 .Fa ctrl
642 field should be initialized with the number of the extension being accessed.
643 Between 0, inclusive, and the value returned by
644 .Dv SNDCTL_MIX_NREXT ,
645 exclusive.
646 .Pp
647 On return the
648 .Fa nvalues
649 field contains the number of values, and
650 .Fa strindex
651 contains an array of indices into the strings member, each index
652 pointing to an
653 .Sy ASCIIZ
654 describing the enumeration value.
655 .Pp
656 .It Dv SNDCTL_MIX_READ
657 .It Dv SNDCTL_MIX_WRITE
658 The argument is a pointer to an
659 .Vt oss_mixer_value
660 structure, defined as follows:
661 .Bd -literal -offset 2n
662 typedef struct oss_mixer_value {
663 int dev;
664 int ctrl;
665 int value;
666
667 /* Reserved for future use. Initialize to 0 */
668 int flags;
669
670 /* Must be set to oss_mixext.timestamp */
671 int timestamp;
672
673 /* Reserved for future use. Initialize to 0 */
674 int filler[8];
675 } oss_mixer_value;
676 .Pp
677 .Ed
678 On entry, the
679 .Fa dev
680 field should be initialized to the value
681 .Sy -1 ,
682 and the
683 .Fa ctrl
684 field should be initialized with the number of the extension
685 being accessed.
686 Between 0, inclusive, and the value returned by
687 .Dv SNDCTL_MIX_NREXT ,
688 exclusive.
689 Additionally, the timestamp member must be
690 initialized to the same value as was supplied in the
691 .Vt oss_mixext
692 structure
693 used with
694 .Dv SNDCTL_MIX_EXTINFO .
695 .Pp
696 For
697 .Dv SNDCTL_MIX_WRITE ,
698 the application should supply the new value for the extension.
699 For
700 .Dv SNDCTL_MIX_READ ,
701 the mixer returns the extensions current value in value.
702 .El
703 .Ss "Compatibility IOCTLs"
704 The following ioctls are for compatibility use only:
705 .Pp
706 .Bl -tag -offset 2n -width SNDCTL_MIX_ENUMINFO -compact
707 .It Dv SOUND_MIXER_READ_VOLUME
708 .It Dv SOUND_MIXER_READ_PCM
709 .It Dv SOUND_MIXER_READ_OGAIN
710 .It Dv SOUND_MIXER_READ_RECGAIN
711 .It Dv SOUND_MIXER_READ_RECLEV
712 .It Dv SOUND_MIXER_READ_IGAIN
713 .It Dv SOUND_MIXER_READ_RECSRC
714 .It Dv SOUND_MIXER_READ_RECMASK
715 .It Dv SOUND_MIXER_READ_DEVMASK
716 .It Dv SOUND_MIXER_READ_STEREODEVS
717 .It Dv SOUND_MIXER_WRITE_VOLUME
718 .It Dv SOUND_MIXER_WRITE_PCM
719 .It Dv SOUND_MIXER_WRITE_OGAIN
720 .It Dv SOUND_MIXER_WRITE_RECGAIN
721 .It Dv SOUND_MIXER_WRITE_RECLEV
722 .It Dv SOUND_MIXER_WRITE_IGAIN
723 .It Dv SOUND_MIXER_WRITE_RECSRC
724 .It Dv SOUND_MIXER_WRITE_RECMASK
725 .It Dv SOUND_MIXER_INFO
726 .It Dv SNDCTL_AUDIOINFO_EX
727 .It Dv SNDCTL_ENGINEINFO
728 .El
729 .Pp
730 These ioctls can affect the software volume levels associated with the calling
731 process.
732 They have no effect on the physical hardware levels or settings.
733 They should not be used in new applications.
734 .Sh FILES
735 .Bl -tag -width /dev/sndstat
736 .It Pa /dev/mixer
737 Symbolic link to the pseudo mixer device for the system
738 .It Pa /dev/sndstat
739 Sound status device
740 .El
741 .Sh ERRORS
742 An
743 .Xr ioctl 2
744 fails if:
745 .Bl -tag -width EINVAL
746 .It Er EINVAL
747 The parameter changes requested in the ioctl are invalid or are not supported
748 by the device.
749 .It Er ENXIO
750 The device or extension referenced does not exist.
751 .El
752 .Sh ARCHITECTURE
753 SPARC
754 x86
755 .Sh INTERFACE STABILITY
756 The information and mixer extension IOCTLs are Uncommitted.
757 The Compatibility IOCTLs are Obsolete Uncommitted.
758 The extension names are Uncommitted.
759 .Sh SEE ALSO
760 .Xr close 2 ,
761 .Xr ioctl 2 ,
762 .Xr open 2 ,
763 .Xr read 2 ,
764 .Xr attributes 5 ,
765 .Xr dsp 7I
766 .Sh BUGS
767 The names of mixer extensions are not guaranteed to be predictable.