1.\" $NetBSD: audio.9,v 1.43 2011/11/23 23:11:56 jmcneill Exp $ 2.\" 3.\" Copyright (c) 1999, 2000 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Lennart Augustsson. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd November 23, 2011 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 void (*get_locks)(void *, kmutex_t **, kmutex_t **); 91}; 92 93typedef struct audio_params { 94 u_int sample_rate; /* sample rate */ 95 u_int encoding; /* e.g. mu-law, linear, etc */ 96 u_int precision; /* bits/subframe */ 97 u_int validbits; /* valid bits in a subframe */ 98 u_int channels; /* mono(1), stereo(2) */ 99} audio_params_t; 100.Ed 101.Pp 102The high level audio driver attaches to the low level driver 103when the latter calls 104.Va audio_attach_mi . 105This call should be 106.Bd -literal 107 void 108 audio_attach_mi(ahwp, hdl, dev) 109 struct audio_hw_if *ahwp; 110 void *hdl; 111 struct device *dev; 112.Ed 113.Pp 114The 115.Va audio_hw_if 116struct is as shown above. 117The 118.Va hdl 119argument is a handle to some low level data structure. 120It is sent as the first argument to all the functions 121in 122.Va audio_hw_if 123when the high level driver calls them. 124.Va dev 125is the device struct for the hardware device. 126.Pp 127The upper layer of the audio driver allocates one buffer for playing 128and one for recording. 129It handles the buffering of data from the user processes in these. 130The data is presented to the lower level in smaller chunks, called blocks. 131If, during playback, there is no data available from the user process when 132the hardware request another block a block of silence will be used instead. 133Furthermore, if the user process does not read data quickly enough during 134recording data will be thrown away. 135.Pp 136The fields of 137.Va audio_hw_if 138are described in some more detail below. 139Some fields are optional and can be set to 0 if not needed. 140.Bl -tag -width indent 141.It Dv int open(void *hdl, int flags) 142optional, is called when the audio device is opened. 143It should initialize the hardware for I/O. 144Every successful call to 145.Va open 146is matched by a call to 147.Va close . 148Return 0 on success, otherwise an error code. 149.It Dv void close(void *hdl) 150optional, is called when the audio device is closed. 151.It Dv int drain(void *hdl) 152optional, is called before the device is closed or when 153.Dv AUDIO_DRAIN 154is called. 155It should make sure that no samples remain in to be played that could 156be lost when 157.Va close 158is called. 159Return 0 on success, otherwise an error code. 160.It Dv int query_encoding(void *hdl, struct audio_encoding *ae) 161is used when 162.Dv AUDIO_GETENC 163is called. 164It should fill the 165.Va audio_encoding 166structure and return 0 or, if there is no encoding with the 167given number, return EINVAL. 168.It Dv int set_params(void *hdl, int setmode, int usemode, 169.Dv "audio_params_t *play, audio_params_t *rec," 170.Pp 171.Dv "stream_filter_list_t *pfil, stream_filter_list_t *rfil)" 172.Pp 173Called to set the audio encoding mode. 174.Va setmode 175is a combination of the 176.Dv AUMODE_RECORD 177and 178.Dv AUMODE_PLAY 179flags to indicate which mode(s) are to be set. 180.Va usemode 181is also a combination of these flags, but indicates the current 182mode of the device (i.e., the value of 183.Va mode 184in the 185.Va audio_info 186struct). 187.Pp 188The 189.Va play 190and 191.Va rec 192structures contain the encoding parameters that should be set. 193The values of the structures may also be modified if the hardware 194cannot be set to exactly the requested mode (e.g., if the requested 195sampling rate is not supported, but one close enough is). 196.Pp 197If the hardware requires software assistance with some encoding 198(e.g., it might be lacking mu-law support) it should fill the 199.Va pfil 200for playing or 201.Va rfil 202for recording with conversion information. 203For example, if 204.Va play 205requests [8000Hz, mu-law, 8/8bit, 1ch] and the hardware does not 206support 8bit mu-law, but 16bit slinear_le, the driver should call 207.Dv pfil-\*[Gt]append() 208with 209.Va pfil , 210.Va mulaw_to_slinear16 , 211and audio_params_t representing [8000Hz, slinear_le, 16/16bit, 2ch]. 212If the driver needs multiple conversions, a conversion nearest to the 213hardware should be set to the head of 214.Va pfil 215or 216.Va rfil . 217The definition of 218.Dv stream_filter_list_t 219follows: 220.Bd -literal 221typedef struct stream_filter_list { 222 void (*append)(struct stream_filter_list *, 223 stream_filter_factory_t, 224 const audio_params_t *); 225 void (*prepend)(struct stream_filter_list *, 226 stream_filter_factory_t, 227 const audio_params_t *); 228 void (*set)(struct stream_filter_list *, int, 229 stream_filter_factory_t, 230 const audio_params_t *); 231 int req_size; 232 struct stream_filter_req { 233 stream_filter_factory_t *factory; 234 audio_params_t param; /* from-param for recording, 235 to-param for playing */ 236 } filters[AUDIO_MAX_FILTERS]; 237} stream_filter_list_t; 238.Ed 239.Pp 240For playing, 241.Va pfil 242constructs conversions as follows: 243.Bd -literal 244 (play) == write(2) input 245 | pfil-\*[Gt]filters[pfil-\*[Gt]req_size-1].factory 246 (pfil-\*[Gt]filters[pfil-\*[Gt]req_size-1].param) 247 | pfil-\*[Gt]filters[pfil-\*[Gt]req_size-2].factory 248 : 249 | pfil-\*[Gt]filters[1].factory 250 (pfil-\*[Gt]filters[1].param) 251 | pfil-\*[Gt]filters[0].factory 252 (pfil-\*[Gt]filters[0].param) == hardware input 253.Ed 254.Pp 255For recording, 256.Va rfil 257constructs conversions as follows: 258.Bd -literal 259 (rfil-\*[Gt]filters[0].param) == hardware output 260 | rfil-\*[Gt]filters[0].factory 261 (rfil-\*[Gt]filters[1].param) 262 | rfil-\*[Gt]filters[1].factory 263 : 264 | rfil-\*[Gt]filters[rfil-\*[Gt]req_size-2].factory 265 (rfil-\*[Gt]filters[rfil-\*[Gt]req_size-1].param) 266 | rfil-\*[Gt]filters[rfil-\*[Gt]req_size-1].factory 267 (rec) == read(2) output 268.Ed 269.Pp 270If the device does not have the 271.Dv AUDIO_PROP_INDEPENDENT 272property the same value is passed in both 273.Va play 274and 275.Va rec 276and the encoding parameters from 277.Va play 278is copied into 279.Va rec 280after the call to 281.Va set_params . 282Return 0 on success, otherwise an error code. 283.It Dv int round_blocksize(void *hdl, int bs, int mode, 284.Dv "const audio_params_t *param)" 285.Pp 286optional, is called with the block size, 287.Va bs , 288that has been computed by the upper layer, 289.Va mode , 290.Dv AUMODE_PLAY 291or 292.Dv AUMODE_RECORD , 293and 294.Va param , 295encoding parameters for the hardware. 296It should return a block size, possibly changed according to the needs 297of the hardware driver. 298.It Dv int commit_settings(void *hdl) 299optional, is called after all calls to 300.Va set_params , 301and 302.Va set_port , 303are done. 304A hardware driver that needs to get the hardware in and out of command 305mode for each change can save all the changes during previous calls and 306do them all here. 307Return 0 on success, otherwise an error code. 308.It Dv int init_output(void *hdl, void *buffer, int size) 309optional, is called before any output starts, but when the total 310.Va size 311of the output 312.Va buffer 313has been determined. 314It can be used to initialize looping DMA for hardware that needs that. 315Return 0 on success, otherwise an error code. 316.It Dv int init_input(void *hdl, void *buffer, int size) 317optional, is called before any input starts, but when the total 318.Va size 319of the input 320.Va buffer 321has been determined. 322It can be used to initialize looping DMA for hardware that needs that. 323Return 0 on success, otherwise an error code. 324.It Dv int start_output(void *hdl, void *block, int blksize, 325.Dv "void (*intr)(void*), void *intrarg)" 326.Pp 327is called to start the transfer of 328.Va blksize 329bytes from 330.Va block 331to the audio hardware. 332The call should return when the data transfer has been initiated 333(normally with DMA). 334When the hardware is ready to accept more samples the function 335.Va intr 336should be called with the argument 337.Va intrarg . 338Calling 339.Va intr 340will normally initiate another call to 341.Va start_output . 342Return 0 on success, otherwise an error code. 343.It Dv int start_input(void *hdl, void *block, int blksize, 344.Dv "void (*intr)(void*), void *intrarg)" 345.Pp 346is called to start the transfer of 347.Va blksize 348bytes to 349.Va block 350from the audio hardware. 351The call should return when the data transfer has been initiated 352(normally with DMA). 353When the hardware is ready to deliver more samples the function 354.Va intr 355should be called with the argument 356.Va intrarg . 357Calling 358.Va intr 359will normally initiate another call to 360.Va start_input . 361Return 0 on success, otherwise an error code. 362.It Dv int halt_output(void *hdl) 363is called to abort the output transfer (started by 364.Va start_output ) 365in progress. 366Return 0 on success, otherwise an error code. 367.It Dv int halt_input(void *hdl) 368is called to abort the input transfer (started by 369.Va start_input ) 370in progress. 371Return 0 on success, otherwise an error code. 372.It Dv int speaker_ctl(void *hdl, int on) 373optional, is called when a half duplex device changes between 374playing and recording. 375It can, e.g., be used to turn on 376and off the speaker. 377Return 0 on success, otherwise an error code. 378.It Dv int getdev(void *hdl, struct audio_device *ret) 379Should fill the 380.Va audio_device 381struct with relevant information about the driver. 382Return 0 on success, otherwise an error code. 383.It Dv int setfd(void *hdl, int fd) 384optional, is called when 385.Dv AUDIO_SETFD 386is used, but only if the device has AUDIO_PROP_FULLDUPLEX set. 387Return 0 on success, otherwise an error code. 388.It Dv int set_port(void *hdl, mixer_ctrl_t *mc) 389is called in when 390.Dv AUDIO_MIXER_WRITE 391is used. 392It should take data from the 393.Va mixer_ctrl_t 394struct at set the corresponding mixer values. 395Return 0 on success, otherwise an error code. 396.It Dv int get_port(void *hdl, mixer_ctrl_t *mc) 397is called in when 398.Dv AUDIO_MIXER_READ 399is used. 400It should fill the 401.Va mixer_ctrl_t 402struct. 403Return 0 on success, otherwise an error code. 404.It Dv int query_devinfo(void *hdl, mixer_devinfo_t *di) 405is called in when 406.Dv AUDIO_MIXER_DEVINFO 407is used. 408It should fill the 409.Va mixer_devinfo_t 410struct. 411Return 0 on success, otherwise an error code. 412.It Dv "void *allocm(void *hdl, int direction, size_t size, struct malloc_type *type, int flags)" 413.Pp 414optional, is called to allocate the device buffers. 415If not present 416.Xr malloc 9 417is used instead (with the same arguments but the first two). 418The reason for using a device dependent routine instead of 419.Xr malloc 9 420is that some buses need special allocation to do DMA. 421Returns the address of the buffer, or 0 on failure. 422.It Dv void freem(void *hdl, void *addr, struct malloc_type *type) 423optional, is called to free memory allocated by 424.Va alloc . 425If not supplied 426.Xr free 9 427is used. 428.It Dv size_t round_buffersize(void *hdl, int direction, size_t bufsize) 429optional, is called at startup to determine the audio 430buffer size. 431The upper layer supplies the suggested size in 432.Va bufsize , 433which the hardware driver can then change if needed. 434E.g., DMA on the ISA bus cannot exceed 65536 bytes. 435.It Dv "paddr_t mappage(void *hdl, void *addr, off_t offs, int prot)" 436.Pp 437optional, is called for 438.Xr mmap 2 . 439Should return the map value for the page at offset 440.Va offs 441from address 442.Va addr 443mapped with protection 444.Va prot . 445Returns -1 on failure, or a machine dependent opaque value 446on success. 447.It Dv int get_props(void *hdl) 448Should return the device properties; i.e., a combination of 449AUDIO_PROP_xxx. 450.It Dv int trigger_output(void *hdl, void *start, void *end, 451.Dv "int blksize, void (*intr)(void*), void *intrarg," 452.Pp 453.Dv "const audio_params_t *param)" 454.Pp 455optional, is called to start the transfer of data from the circular buffer 456delimited by 457.Va start 458and 459.Va end 460to the audio hardware, parameterized as in 461.Va param . 462The call should return when the data transfer has been initiated 463(normally with DMA). 464When the hardware is finished transferring each 465.Va blksize 466sized block, the function 467.Va intr 468should be called with the argument 469.Va intrarg 470(typically from the audio hardware interrupt service routine). 471Once started the transfer may be stopped using 472.Va halt_output . 473Return 0 on success, otherwise an error code. 474.It Dv int trigger_input(void *hdl, void *start, void *end, 475.Dv "int blksize, void (*intr)(void*), void *intrarg," 476.Pp 477.Dv "const audio_params_t *param)" 478.Pp 479optional, is called to start the transfer of data from the audio hardware, 480parameterized as in 481.Va param , 482to the circular buffer delimited by 483.Va start 484and 485.Va end . 486The call should return when the data transfer has been initiated 487(normally with DMA). 488When the hardware is finished transferring each 489.Va blksize 490sized block, the function 491.Va intr 492should be called with the argument 493.Va intrarg 494(typically from the audio hardware interrupt service routine). 495Once started the transfer may be stopped using 496.Va halt_input . 497Return 0 on success, otherwise an error code. 498.It Dv int dev_ioctl(void *hdl, u_long cmd, void *addr, 499.Pp 500.Dv "int flag, struct lwp *l)" 501.Pp 502optional, is called when an 503.Xr ioctl 2 504is not recognized by the generic audio driver. 505Return 0 on success, otherwise an error code. 506.It Dv void get_locks(void *hdl, kmutex_t **intr, kmutex_t **thread) 507Returns the interrupt and thread locks to the common audio layer. 508.El 509.Pp 510The 511.Va query_devinfo 512method should define certain mixer controls for 513.Dv AUDIO_SETINFO 514to be able to change the port and gain, 515and 516.Dv AUDIO_GETINFO 517to read them, as follows. 518.Pp 519If the record mixer is capable of input from more than one source, 520it should define 521.Dv AudioNsource 522in class 523.Dv AudioCrecord . 524This mixer control should be of type 525.Dv AUDIO_MIXER_ENUM 526or 527.Dv AUDIO_MIXER_SET 528and enumerate the possible input sources. 529Each of the named sources for which the recording level can be set 530should have a control in the 531.Dv AudioCrecord 532class of type 533.Dv AUDIO_MIXER_VALUE , 534except the 535.Qq mixerout 536source is special, 537and will never have its own control. 538Its selection signifies, 539rather, 540that various sources in class 541.Dv AudioCrecord 542will be combined and presented to the single recording output 543in the same fashion that the sources of class 544.Dv AudioCinputs 545are combined and presented to the playback output(s). 546If the overall recording level can be changed, 547regardless of the input source, 548then this control should be named 549.Dv AudioNmaster 550and be of class 551.Dv AudioCrecord . 552.Pp 553Controls for various sources that affect only the playback output, 554as opposed to recording, 555should be in the 556.Dv AudioCinputs 557class, 558as of course should any controls that affect both playback and recording. 559.Pp 560If the play 561mixer is capable of output to more than one destination, 562it should define 563.Dv AudioNselect 564in class 565.Dv AudioCoutputs . 566This mixer control should be of type 567.Dv AUDIO_MIXER_ENUM 568or 569.Dv AUDIO_MIXER_SET 570and enumerate the possible destinations. 571For each of the named destinations for which the output level can be set, 572there should be 573a control in the 574.Dv AudioCoutputs 575class of type 576.Dv AUDIO_MIXER_VALUE . 577If the overall output level can be changed, 578which is invariably the case, 579then this control should be named 580.Dv AudioNmaster 581and be of class 582.Dv AudioCoutputs . 583.Pp 584There's one additional source recognized specially by 585.Dv AUDIO_SETINFO 586and 587.Dv AUDIO_GETINFO , 588to be presented as monitor_gain, 589and that is a control named 590.Dv AudioNmonitor , 591of class 592.Dv AudioCmonitor . 593.Sh SEE ALSO 594.Xr audio 4 595.Sh HISTORY 596This 597.Nm 598interface first appeared in 599.Nx 1.3 . 600