xref: /netbsd/share/man/man9/audio.9 (revision 6550d01e)
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30.Dd November 10, 2007
31.Dt AUDIO 9
32.Os
33.Sh NAME
34.Nm audio
35.Nd interface between low and high level audio drivers
36.Sh DESCRIPTION
37The audio device driver is divided into a high level,
38hardware independent layer, and a low level hardware
39dependent layer.
40The interface between these is the
41.Va audio_hw_if
42structure.
43.Bd -literal
44struct audio_hw_if {
45	int	(*open)(void *, int);
46	void	(*close)(void *);
47	int	(*drain)(void *);
48
49	int	(*query_encoding)(void *, struct audio_encoding *);
50	int	(*set_params)(void *, int, int,
51		    audio_params_t *, audio_params_t *,
52		    stream_filter_list_t *, stream_filter_list_t *);
53	int	(*round_blocksize)(void *, int, int, const audio_params_t *);
54
55	int	(*commit_settings)(void *);
56
57	int	(*init_output)(void *, void *, int);
58	int	(*init_input)(void *, void *, int);
59	int	(*start_output)(void *, void *, int, void (*)(void *),
60	            void *);
61	int	(*start_input)(void *, void *, int, void (*)(void *),
62		    void *);
63	int	(*halt_output)(void *);
64	int	(*halt_input)(void *);
65
66	int	(*speaker_ctl)(void *, int);
67#define SPKR_ON  1
68#define SPKR_OFF 0
69
70	int	(*getdev)(void *, struct audio_device *);
71	int	(*setfd)(void *, int);
72
73	int	(*set_port)(void *, mixer_ctrl_t *);
74	int	(*get_port)(void *, mixer_ctrl_t *);
75
76	int	(*query_devinfo)(void *, mixer_devinfo_t *);
77
78	void	*(*allocm)(void *, int, size_t, struct malloc_type *, int);
79	void	(*freem)(void *, void *, struct malloc_type *);
80	size_t	(*round_buffersize)(void *, int, size_t);
81	paddr_t	(*mappage)(void *, void *, off_t, int);
82
83	int 	(*get_props)(void *);
84
85	int	(*trigger_output)(void *, void *, void *, int,
86		    void (*)(void *), void *, const audio_params_t *);
87	int	(*trigger_input)(void *, void *, void *, int,
88		    void (*)(void *), void *, const audio_params_t *);
89	int	(*dev_ioctl)(void *, u_long, void *, int, struct lwp *);
90	int	(*powerstate)(void *, int);
91#define	AUDIOPOWER_ON	1
92#define	AUDIOPOWER_OFF	0
93};
94
95typedef struct audio_params {
96	u_int	sample_rate;	/* sample rate */
97	u_int	encoding;	/* e.g. mu-law, linear, etc */
98	u_int	precision;	/* bits/subframe */
99	u_int	validbits;	/* valid bits in a subframe */
100	u_int	channels;	/* mono(1), stereo(2) */
101} audio_params_t;
102.Ed
103.Pp
104The high level audio driver attaches to the low level driver
105when the latter calls
106.Va audio_attach_mi .
107This call should be
108.Bd -literal
109    void
110    audio_attach_mi(ahwp, hdl, dev)
111	struct audio_hw_if *ahwp;
112	void *hdl;
113	struct device *dev;
114.Ed
115.Pp
116The
117.Va audio_hw_if
118struct is as shown above.
119The
120.Va hdl
121argument is a handle to some low level data structure.
122It is sent as the first argument to all the functions
123in
124.Va audio_hw_if
125when the high level driver calls them.
126.Va dev
127is the device struct for the hardware device.
128.Pp
129The upper layer of the audio driver allocates one buffer for playing
130and one for recording.
131It handles the buffering of data from the user processes in these.
132The data is presented to the lower level in smaller chunks, called blocks.
133If, during playback, there is no data available from the user process when
134the hardware request another block a block of silence will be used instead.
135Furthermore, if the user process does not read data quickly enough during
136recording data will be thrown away.
137.Pp
138The fields of
139.Va audio_hw_if
140are described in some more detail below.
141Some fields are optional and can be set to 0 if not needed.
142.Bl -tag -width indent
143.It Dv int open(void *hdl, int flags)
144optional, is called when the audio device is opened.
145It should initialize the hardware for I/O.
146Every successful call to
147.Va open
148is matched by a call to
149.Va close .
150Return 0 on success, otherwise an error code.
151.It Dv void close(void *hdl)
152optional, is called when the audio device is closed.
153.It Dv int drain(void *hdl)
154optional, is called before the device is closed or when
155.Dv AUDIO_DRAIN
156is called.
157It should make sure that no samples remain in to be played that could
158be lost when
159.Va close
160is called.
161Return 0 on success, otherwise an error code.
162.It Dv int query_encoding(void *hdl, struct audio_encoding *ae)
163is used when
164.Dv AUDIO_GETENC
165is called.
166It should fill the
167.Va audio_encoding
168structure and return 0 or, if there is no encoding with the
169given number, return EINVAL.
170.It Dv int set_params(void *hdl, int setmode, int usemode,
171.Dv "audio_params_t *play, audio_params_t *rec,"
172.Pp
173.Dv "stream_filter_list_t *pfil, stream_filter_list_t *rfil)"
174.Pp
175Called to set the audio encoding mode.
176.Va setmode
177is a combination of the
178.Dv AUMODE_RECORD
179and
180.Dv AUMODE_PLAY
181flags to indicate which mode(s) are to be set.
182.Va usemode
183is also a combination of these flags, but indicates the current
184mode of the device (i.e., the value of
185.Va mode
186in the
187.Va audio_info
188struct).
189.Pp
190The
191.Va play
192and
193.Va rec
194structures contain the encoding parameters that should be set.
195The values of the structures may also be modified if the hardware
196cannot be set to exactly the requested mode (e.g., if the requested
197sampling rate is not supported, but one close enough is).
198.Pp
199If the hardware requires software assistance with some encoding
200(e.g., it might be lacking mu-law support) it should fill the
201.Va pfil
202for playing or
203.Va rfil
204for recording with conversion information.
205For example, if
206.Va play
207requests [8000Hz, mu-law, 8/8bit, 1ch] and the hardware does not
208support 8bit mu-law, but 16bit slinear_le, the driver should call
209.Dv pfil-\*[Gt]append()
210with
211.Va pfil ,
212.Va mulaw_to_slinear16 ,
213and audio_params_t representing [8000Hz, slinear_le, 16/16bit, 2ch].
214If the driver needs multiple conversions, a conversion nearest to the
215hardware should be set to the head of
216.Va pfil
217or
218.Va rfil .
219The definition of
220.Dv stream_filter_list_t
221follows:
222.Bd -literal
223typedef struct stream_filter_list {
224	void (*append)(struct stream_filter_list *,
225		       stream_filter_factory_t,
226		       const audio_params_t *);
227	void (*prepend)(struct stream_filter_list *,
228			stream_filter_factory_t,
229			const audio_params_t *);
230	void (*set)(struct stream_filter_list *, int,
231		    stream_filter_factory_t,
232		    const audio_params_t *);
233	int req_size;
234	struct stream_filter_req {
235		stream_filter_factory_t *factory;
236		audio_params_t param; /* from-param for recording,
237					 to-param for playing */
238	} filters[AUDIO_MAX_FILTERS];
239} stream_filter_list_t;
240.Ed
241.Pp
242For playing,
243.Va pfil
244constructs conversions as follows:
245.Bd -literal
246	(play) == write(2) input
247	  |	pfil-\*[Gt]filters[pfil-\*[Gt]req_size-1].factory
248	(pfil-\*[Gt]filters[pfil-\*[Gt]req_size-1].param)
249	  |	pfil-\*[Gt]filters[pfil-\*[Gt]req_size-2].factory
250	  :
251	  |	pfil-\*[Gt]filters[1].factory
252	(pfil-\*[Gt]filters[1].param)
253	  |	pfil-\*[Gt]filters[0].factory
254	(pfil-\*[Gt]filters[0].param)  == hardware input
255.Ed
256.Pp
257For recording,
258.Va rfil
259constructs conversions as follows:
260.Bd -literal
261	(rfil-\*[Gt]filters[0].param) == hardware output
262	  |	rfil-\*[Gt]filters[0].factory
263	(rfil-\*[Gt]filters[1].param)
264	  |	rfil-\*[Gt]filters[1].factory
265	  :
266	  |	rfil-\*[Gt]filters[rfil-\*[Gt]req_size-2].factory
267	(rfil-\*[Gt]filters[rfil-\*[Gt]req_size-1].param)
268	  |	rfil-\*[Gt]filters[rfil-\*[Gt]req_size-1].factory
269	(rec)  == read(2) output
270.Ed
271.Pp
272If the device does not have the
273.Dv AUDIO_PROP_INDEPENDENT
274property the same value is passed in both
275.Va play
276and
277.Va rec
278and the encoding parameters from
279.Va play
280is copied into
281.Va rec
282after the call to
283.Va set_params .
284Return 0 on success, otherwise an error code.
285.It Dv int round_blocksize(void *hdl, int bs, int mode,
286.Dv "const audio_params_t *param)"
287.Pp
288optional, is called with the block size,
289.Va bs ,
290that has been computed by the upper layer,
291.Va mode ,
292.Dv AUMODE_PLAY
293or
294.Dv AUMODE_RECORD ,
295and
296.Va param ,
297encoding parameters for the hardware.
298It should return a block size, possibly changed according to the needs
299of the hardware driver.
300.It Dv int commit_settings(void *hdl)
301optional, is called after all calls to
302.Va set_params ,
303and
304.Va set_port ,
305are done.
306A hardware driver that needs to get the hardware in and out of command
307mode for each change can save all the changes during previous calls and
308do them all here.
309Return 0 on success, otherwise an error code.
310.It Dv int init_output(void *hdl, void *buffer, int size)
311optional, is called before any output starts, but when the total
312.Va size
313of the output
314.Va buffer
315has been determined.
316It can be used to initialize looping DMA for hardware that needs that.
317Return 0 on success, otherwise an error code.
318.It Dv int init_input(void *hdl, void *buffer, int size)
319optional, is called before any input starts, but when the total
320.Va size
321of the input
322.Va buffer
323has been determined.
324It can be used to initialize looping DMA for hardware that needs that.
325Return 0 on success, otherwise an error code.
326.It Dv int start_output(void *hdl, void *block, int blksize,
327.Dv "void (*intr)(void*), void *intrarg)"
328.Pp
329is called to start the transfer of
330.Va blksize
331bytes from
332.Va block
333to the audio hardware.
334The call should return when the data transfer has been initiated
335(normally with DMA).
336When the hardware is ready to accept more samples the function
337.Va intr
338should be called with the argument
339.Va intrarg .
340Calling
341.Va intr
342will normally initiate another call to
343.Va start_output .
344Return 0 on success, otherwise an error code.
345.It Dv int start_input(void *hdl, void *block, int blksize,
346.Dv "void (*intr)(void*), void *intrarg)"
347.Pp
348is called to start the transfer of
349.Va blksize
350bytes to
351.Va block
352from the audio hardware.
353The call should return when the data transfer has been initiated
354(normally with DMA).
355When the hardware is ready to deliver more samples the function
356.Va intr
357should be called with the argument
358.Va intrarg .
359Calling
360.Va intr
361will normally initiate another call to
362.Va start_input .
363Return 0 on success, otherwise an error code.
364.It Dv int halt_output(void *hdl)
365is called to abort the output transfer (started by
366.Va start_output )
367in progress.
368Return 0 on success, otherwise an error code.
369.It Dv int halt_input(void *hdl)
370is called to abort the input transfer (started by
371.Va start_input )
372in progress.
373Return 0 on success, otherwise an error code.
374.It Dv int speaker_ctl(void *hdl, int on)
375optional, is called when a half duplex device changes between
376playing and recording.
377It can, e.g., be used to turn on
378and off the speaker.
379Return 0 on success, otherwise an error code.
380.It Dv int getdev(void *hdl, struct audio_device *ret)
381Should fill the
382.Va audio_device
383struct with relevant information about the driver.
384Return 0 on success, otherwise an error code.
385.It Dv int setfd(void *hdl, int fd)
386optional, is called when
387.Dv AUDIO_SETFD
388is used, but only if the device has AUDIO_PROP_FULLDUPLEX set.
389Return 0 on success, otherwise an error code.
390.It Dv int set_port(void *hdl, mixer_ctrl_t *mc)
391is called in when
392.Dv AUDIO_MIXER_WRITE
393is used.
394It should take data from the
395.Va mixer_ctrl_t
396struct at set the corresponding mixer values.
397Return 0 on success, otherwise an error code.
398.It Dv int get_port(void *hdl, mixer_ctrl_t *mc)
399is called in when
400.Dv AUDIO_MIXER_READ
401is used.
402It should fill the
403.Va mixer_ctrl_t
404struct.
405Return 0 on success, otherwise an error code.
406.It Dv int query_devinfo(void *hdl, mixer_devinfo_t *di)
407is called in when
408.Dv AUDIO_MIXER_DEVINFO
409is used.
410It should fill the
411.Va mixer_devinfo_t
412struct.
413Return 0 on success, otherwise an error code.
414.It Dv "void *allocm(void *hdl, int direction, size_t size, struct malloc_type *type, int flags)"
415.Pp
416optional, is called to allocate the device buffers.
417If not present
418.Xr malloc 9
419is used instead (with the same arguments but the first two).
420The reason for using a device dependent routine instead of
421.Xr malloc 9
422is that some buses need special allocation to do DMA.
423Returns the address of the buffer, or 0 on failure.
424.It Dv void freem(void *hdl, void *addr, struct malloc_type *type)
425optional, is called to free memory allocated by
426.Va alloc .
427If not supplied
428.Xr free 9
429is used.
430.It Dv size_t round_buffersize(void *hdl, int direction, size_t bufsize)
431optional, is called at startup to determine the audio
432buffer size.
433The upper layer supplies the suggested size in
434.Va bufsize ,
435which the hardware driver can then change if needed.
436E.g., DMA on the ISA bus cannot exceed 65536 bytes.
437.It Dv "paddr_t mappage(void *hdl, void *addr, off_t offs, int prot)"
438.Pp
439optional, is called for
440.Xr mmap 2 .
441Should return the map value for the page at offset
442.Va offs
443from address
444.Va addr
445mapped with protection
446.Va prot .
447Returns -1 on failure, or a machine dependent opaque value
448on success.
449.It Dv int get_props(void *hdl)
450Should return the device properties; i.e., a combination of
451AUDIO_PROP_xxx.
452.It Dv int trigger_output(void *hdl, void *start, void *end,
453.Dv "int blksize, void (*intr)(void*), void *intrarg,"
454.Pp
455.Dv "const audio_params_t *param)"
456.Pp
457optional, is called to start the transfer of data from the circular buffer
458delimited by
459.Va start
460and
461.Va end
462to the audio hardware, parameterized as in
463.Va param .
464The call should return when the data transfer has been initiated
465(normally with DMA).
466When the hardware is finished transferring each
467.Va blksize
468sized block, the function
469.Va intr
470should be called with the argument
471.Va intrarg
472(typically from the audio hardware interrupt service routine).
473Once started the transfer may be stopped using
474.Va halt_output .
475Return 0 on success, otherwise an error code.
476.It Dv int trigger_input(void *hdl, void *start, void *end,
477.Dv "int blksize, void (*intr)(void*), void *intrarg,"
478.Pp
479.Dv "const audio_params_t *param)"
480.Pp
481optional, is called to start the transfer of data from the audio hardware,
482parameterized as in
483.Va param ,
484to the circular buffer delimited by
485.Va start
486and
487.Va end .
488The call should return when the data transfer has been initiated
489(normally with DMA).
490When the hardware is finished transferring each
491.Va blksize
492sized block, the function
493.Va intr
494should be called with the argument
495.Va intrarg
496(typically from the audio hardware interrupt service routine).
497Once started the transfer may be stopped using
498.Va halt_input .
499Return 0 on success, otherwise an error code.
500.It Dv int dev_ioctl(void *hdl, u_long cmd, void *addr,
501.Pp
502.Dv "int flag, struct lwp *l)"
503.Pp
504optional, is called when an
505.Xr ioctl 2
506is not recognized by the generic audio driver.
507Return 0 on success, otherwise an error code.
508.It Dv int powerstate(void *hdl, int state)
509.Pp
510optional, is called on the first open and last close of the audio
511device.
512.Va state
513may be one of
514.Dv AUDIOPOWER_ON
515or
516.Dv AUDIOPOWER_OFF .
517Returns 0 on success, otherwise an error code.
518.El
519.Pp
520The
521.Va query_devinfo
522method should define certain mixer controls for
523.Dv AUDIO_SETINFO
524to be able to change the port and gain,
525and
526.Dv AUDIO_GETINFO
527to read them, as follows.
528.Pp
529If the record mixer is capable of input from more than one source,
530it should define
531.Dv AudioNsource
532in class
533.Dv AudioCrecord .
534This mixer control should be of type
535.Dv AUDIO_MIXER_ENUM
536or
537.Dv AUDIO_MIXER_SET
538and enumerate the possible input sources.
539Each of the named sources for which the recording level can be set
540should have a control in the
541.Dv AudioCrecord
542class of type
543.Dv AUDIO_MIXER_VALUE ,
544except the
545.Qq mixerout
546source is special,
547and will never have its own control.
548Its selection signifies,
549rather,
550that various sources in class
551.Dv AudioCrecord
552will be combined and presented to the single recording output
553in the same fashion that the sources of class
554.Dv AudioCinputs
555are combined and presented to the playback output(s).
556If the overall recording level can be changed,
557regardless of the input source,
558then this control should be named
559.Dv AudioNmaster
560and be of class
561.Dv AudioCrecord .
562.Pp
563Controls for various sources that affect only the playback output,
564as opposed to recording,
565should be in the
566.Dv AudioCinputs
567class,
568as of course should any controls that affect both playback and recording.
569.Pp
570If the play
571mixer is capable of output to more than one destination,
572it should define
573.Dv AudioNselect
574in class
575.Dv AudioCoutputs .
576This mixer control should be of type
577.Dv AUDIO_MIXER_ENUM
578or
579.Dv AUDIO_MIXER_SET
580and enumerate the possible destinations.
581For each of the named destinations for which the output level can be set,
582there should be
583a control in the
584.Dv AudioCoutputs
585class of type
586.Dv AUDIO_MIXER_VALUE .
587If the overall output level can be changed,
588which is invariably the case,
589then this control should be named
590.Dv AudioNmaster
591and be of class
592.Dv AudioCoutputs .
593.Pp
594There's one additional source recognized specially by
595.Dv AUDIO_SETINFO
596and
597.Dv AUDIO_GETINFO ,
598to be presented as monitor_gain,
599and that is a control named
600.Dv AudioNmonitor ,
601of class
602.Dv AudioCmonitor .
603.Sh SEE ALSO
604.Xr audio 4
605.Sh HISTORY
606This
607.Nm
608interface first appeared in
609.Nx 1.3 .
610