.\" $NetBSD: audio.9,v 1.17 2001/06/21 11:59:00 wiz Exp $ .\" .\" Copyright (c) 1999, 2000 The NetBSD Foundation, Inc. .\" All rights reserved. .\" .\" This code is derived from software contributed to The NetBSD Foundation .\" by Lennart Augustsson. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the NetBSD .\" Foundation, Inc. and its contributors. .\" 4. Neither the name of The NetBSD Foundation nor the names of its .\" contributors may be used to endorse or promote products derived .\" from this software without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS .\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGE. .\" .Dd February 11, 2000 .Dt AUDIO 9 .Os .Sh NAME .Nm audio .Nd interface between low and high level audio drivers .Sh DESCRIPTION The audio device driver is divided into a high level, hardware independent layer, and a low level hardware dependent layer. The interface between these is the .Va audio_hw_if structure. .Bd -literal struct audio_hw_if { int (*open)__P((void *, int)); void (*close)__P((void *)); int (*drain)__P((void *)); int (*query_encoding)__P((void *, struct audio_encoding *)); int (*set_params)__P((void *, int, int, struct audio_params *, struct audio_params *)); int (*round_blocksize)__P((void *, int)); int (*commit_settings)__P((void *)); int (*init_output)__P((void *, void *, int)); int (*init_input)__P((void *, void *, int)); int (*start_output)__P((void *, void *, int, void (*)(void *), void *)); int (*start_input)__P((void *, void *, int, void (*)(void *), void *)); int (*halt_output)__P((void *)); int (*halt_input)__P((void *)); int (*speaker_ctl)__P((void *, int)); #define SPKR_ON 1 #define SPKR_OFF 0 int (*getdev)__P((void *, struct audio_device *)); int (*setfd)__P((void *, int)); int (*set_port)__P((void *, mixer_ctrl_t *)); int (*get_port)__P((void *, mixer_ctrl_t *)); int (*query_devinfo)__P((void *, mixer_devinfo_t *)); void *(*allocm)__P((void *, int, size_t, int, int)); void (*freem)__P((void *, void *, int)); size_t (*round_buffersize)__P((void *, int, size_t)); int (*mappage)__P((void *, void *, int, int)); int (*get_props)__P((void *)); int (*trigger_output)__P((void *, void *, void *, int, void (*)(void *), void *, struct audio_params *)); int (*trigger_input)__P((void *, void *, void *, int, void (*)(void *), void *, struct audio_params *)); }; struct audio_params { u_long sample_rate; /* sample rate */ u_int encoding; /* ulaw, linear, etc */ u_int precision; /* bits/sample */ u_int channels; /* mono(1), stereo(2) */ /* Software en/decode functions, set if SW coding required by HW */ void (*sw_code)__P((void *, u_char *, int)); int factor; /* coding space change */ }; .Ed .Pp The high level audio driver attaches to the low level driver when the latter calls .Va audio_attach_mi . This call should be .Bd -literal void audio_attach_mi(ahwp, hdl, dev) struct audio_hw_if *ahwp; void *hdl; struct device *dev; .Ed .Pp The .Va audio_hw_if struct is as shown above. The .Va hdl argument is a handle to some low level data structure. It is sent as the first argument to all the functions in .Va audio_hw_if when the high level driver calls them. .Va dev is the device struct for the hardware device. .Pp The upper layer of the audio driver allocates one buffer for playing and one for recording. It handles the buffering of data from the user processes in these. The data is presented to the lower level in smaller chunks, called blocks. If there, during playback, is no data available from the user process when the hardware request another block a block of silence will be used instead. Furthermore, if the user process does not read data quickly enough during recording data will be thrown away. .Pp The fields of .Va audio_hw_if are described in some more detail below. Some fields are optional and can be set to 0 if not needed. .Bl -tag -width indent .It Dv int open(void *hdl, int flags) is called when the audio device is opened. It should initialize the hardware for I/O. Every successful call to .Va open is matched by a call to .Va close . Return 0 on success, otherwise an error code. .It Dv void close(void *hdl) is called when the audio device is closed. .It Dv int drain(void *hdl) optional, is called before the device is closed or when .Dv AUDIO_DRAIN is called. It should make sure that no samples remain in to be played that could be lost when .Va close is called. Return 0 on success, otherwise an error code. .It Dv int query_encoding(void *hdl, struct audio_encoding *ae) is used when .Dv AUDIO_GETENC is called. It should fill the .Va audio_encoding structure and return 0 or, if there is no encoding with the given number, return EINVAL. .It Dv int set_params(void *hdl, int setmode, int usemode, .Dv "struct audio_params *play, struct audio_params *rec)" .br Called to set the audio encoding mode. .Va setmode is a combination of the .Dv AUMODE_RECORD and .Dv AUMODE_PLAY flags to indicate which mode(s) are to be set. .Va usemode is also a combination of these flags, but indicates the current mode of the device (i.e. the value of .Va mode in the .Va audio_info struct). The .Va play and .Va rec structures contain the encoding parameters that should be set. If the hardware requires software assistance with some encoding (e.g., it might be lacking mulaw support) it should fill the .Va sw_code and .Va factor fields of these structures. The values of the structures may also be modified if the hardware cannot be set to exactly the requested mode (e.g. if the requested sampling rate is not supported, but one close enough is). If the device does not have the .Dv AUDIO_PROP_INDEPENDENT property the same value is passed in both .Va play and .Va rec and the encoding parameters from .Va play is copied into .Va rec after the call to .Va set_params . Return 0 on success, otherwise an error code. .It Dv int round_blocksize(void *hdl, int bs) optional, is called with the block size, .Va bs , that has been computed by the upper layer. It should return a block size, possibly changed according to the needs of the hardware driver. .It Dv int commit_settings(void *hdl) optional, is called after all calls to .Va set_params , and .Va set_port , are done. A hardware driver that needs to get the hardware in and out of command mode for each change can save all the changes during previous calls and do them all here. Return 0 on success, otherwise an error code. .It Dv int init_output(void *hdl, void *buffer, int size) optional, is called before any output starts, but when the total .Va size of the output .Va buffer has been determined. It can be used to initialize looping DMA for hardware that needs that. Return 0 on success, otherwise an error code. .It Dv int init_input(void *hdl, void *buffer, int size) optional, is called before any input starts, but when the total .Va size of the input .Va buffer has been determined. It can be used to initialize looping DMA for hardware that needs that. Return 0 on success, otherwise an error code. .It Dv int start_output(void *hdl, void *block, int blksize, .Dv "void (*intr)(void*), void *intrarg)" .br is called to start the transfer of .Va blksize bytes from .Va block to the audio hardware. The call should return when the data transfer has been initiated (normally with DMA). When the hardware is ready to accept more samples the function .Va intr should be called with the argument .Va intrarg . Calling .Va intr will normally initiate another call to .Va start_output . Return 0 on success, otherwise an error code. .It Dv int start_input(void *hdl, void *block, int blksize, .Dv "void (*intr)(void*), void *intrarg)" .br is called to start the transfer of .Va blksize bytes to .Va block from the audio hardware. The call should return when the data transfer has been initiated (normally with DMA). When the hardware is ready to deliver more samples the function .Va intr should be called with the argument .Va intrarg . Calling .Va intr will normally initiate another call to .Va start_input . Return 0 on success, otherwise an error code. .It Dv int halt_output(void *hdl) is called to abort the output transfer (started by .Va start_output ) in progress. Return 0 on success, otherwise an error code. .It Dv int halt_input(void *hdl) is called to abort the input transfer (started by .Va start_input ) in progress. Return 0 on success, otherwise an error code. .It Dv int speaker_ctl(void *hdl, int on) optional, is called when a half duplex device changes between playing and recording. It can, e.g., be used to turn on and off the speaker. Return 0 on success, otherwise an error code. .It Dv int getdev(void *hdl, struct audio_device *ret) Should fill the .Va audio_device struct with relevant information about the driver. Return 0 on success, otherwise an error code. .It Dv int setfd(void *hdl, int fd) optional, is called when .Dv AUDIO_SETFD is used, but only if the device has AUDIO_PROP_FULLDUPLEX set. Return 0 on success, otherwise an error code. .It Dv int set_port(void *hdl, mixer_ctl_t *mc) is called in when .Dv AUDIO_MIXER_WRITE is used. It should take data from the .Va mixer_ctl_t struct at set the corresponding mixer values. Return 0 on success, otherwise an error code. .It Dv int get_port(void *hdl, mixer_ctl_t *mc) is called in when .Dv AUDIO_MIXER_READ is used. It should fill the .Va mixer_ctl_t struct. Return 0 on success, otherwise an error code. .It Dv int query_devinfo(void *hdl, mixer_devinfo_t *di) is called in when .Dv AUDIO_MIXER_DEVINFO is used. It should fill the .Va mixer_devinfo_t struct. Return 0 on success, otherwise an error code. .It Dv "void *allocm(void *hdl, int direction, size_t size, int type, int flags)" .br optional, is called to allocate the device buffers. If not present .Xr malloc 9 is used instead (with the same arguments but the first two). The reason for using a device dependent routine instead of .Xr malloc 9 is that some buses need special allocation to do DMA. Returns the address of the buffer, or 0 on failure. .It Dv void freem(void *hdl, void *addr, int type) optional, is called to free memory allocated by .Va alloc . If not supplied .Xr free 9 is used. .It Dv size_t round_buffersize(void *hdl, int direction, size_t bufsize) optional, is called at startup to determine the audio buffer size. The upper layer supplies the suggested size in .Va bufsize , which the hardware driver can then change if needed. E.g., DMA on the ISA bus cannot exceed 65536 bytes. .It Dv "int mappage(void *hdl, void *addr, int offs, int prot)" .br optional, is called for .Xr mmap 2 . Should return the map value for the page at offset .Va offs from address .Va addr mapped with protection .Va prot . Returns -1 on failure, or a machine dependent opaque value on success. .It Dv int get_props(void *hdl) Should return the device properties; i.e. a combination of AUDIO_PROP_xxx. .It Dv int trigger_output(void *hdl, void *start, void *end, .Dv "int blksize, void (*intr)(void*), void *intrarg," .br .Dv "struct audio_params *param)" .br optional, is called to start the transfer of data from the circular buffer delimited by .Va start and .Va end to the audio hardware, parameterized as in .Va param . The call should return when the data transfer has been initiated (normally with DMA). When the hardware is finished transferring each .Va blksize sized block, the function .Va intr should be called with the argument .Va intrarg (typically from the audio hardware interrupt service routine). Once started the transfer may be stopped using .Va halt_output . Return 0 on success, otherwise an error code. .It Dv int trigger_input(void *hdl, void *start, void *end, .Dv "int blksize, void (*intr)(void*), void *intrarg," .br .Dv "struct audio_params *param)" .br optional, is called to start the transfer of data from the audio hardware, parameterized as in .Va param , to the circular buffer delimited by .Va start and .Va end . The call should return when the data transfer has been initiated (normally with DMA). When the hardware is finished transferring each .Va blksize sized block, the function .Va intr should be called with the argument .Va intrarg (typically from the audio hardware interrupt service routine). Once started the transfer may be stopped using .Va halt_input . Return 0 on success, otherwise an error code. .El .Pp The .Va query_devinfo method should define certain mixer controls for .Dv AUDIO_SETINFO to be able to change the port and gain. .Pp If the audio hardware is capable of input from more than one source it should define .Dv AudioNsource in class .Dv AudioCrecord . This mixer control should be of type .Dv AUDIO_MIXER_ENUM or .Dv AUDIO_MIXER_SET and enumerate the possible input sources. For each of the named sources there should be a control in the .Dv AudioCinputs class of type .Dv AUDIO_MIXER_VALUE if recording level of the source can be set. If the overall recording level can be changed (i.e. regardless of the input source) then this control should be named .Dv AudioNrecord and be of class .Dv AudioCinputs . .Pp If the audio hardware is capable of output to more than one destination it should define .Dv AudioNoutput in class .Dv AudioCmonitor . This mixer control should be of type .Dv AUDIO_MIXER_ENUM or .Dv AUDIO_MIXER_SET and enumerate the possible destinations. For each of the named destinations there should be a control in the .Dv AudioCoutputs class of type .Dv AUDIO_MIXER_VALUE if output level of the destination can be set. If the overall output level can be changed (i.e. regardless of the destination) then this control should be named .Dv AudioNmaster and be of class .Dv AudioCoutputs . .Sh SEE ALSO .Xr audio 4 .Sh HISTORY This .Nm interface first appeared in .Nx 1.3 .