561 lines
17 KiB
Groff
561 lines
17 KiB
Groff
.\" $NetBSD: audio.9,v 1.23 2002/10/14 13:43:14 wiz Exp $
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.\"
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.\" Copyright (c) 1999, 2000 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Lennart Augustsson.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd March 11, 2002
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.Dt AUDIO 9
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.Os
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.Sh NAME
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.Nm audio
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.Nd interface between low and high level audio drivers
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.Sh DESCRIPTION
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The audio device driver is divided into a high level,
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hardware independent layer, and a low level hardware
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dependent layer.
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The interface between these is the
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.Va audio_hw_if
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structure.
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.Bd -literal
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struct audio_hw_if {
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int (*open)(void *, int);
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void (*close)(void *);
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int (*drain)(void *);
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int (*query_encoding)(void *, struct audio_encoding *);
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int (*set_params)(void *, int, int,
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struct audio_params *, struct audio_params *);
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int (*round_blocksize)(void *, int);
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int (*commit_settings)(void *);
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int (*init_output)(void *, void *, int);
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int (*init_input)(void *, void *, int);
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int (*start_output)(void *, void *, int, void (*)(void *),
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void *);
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int (*start_input)(void *, void *, int, void (*)(void *),
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void *);
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int (*halt_output)(void *);
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int (*halt_input)(void *);
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int (*speaker_ctl)(void *, int);
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#define SPKR_ON 1
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#define SPKR_OFF 0
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int (*getdev)(void *, struct audio_device *);
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int (*setfd)(void *, int);
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int (*set_port)(void *, mixer_ctrl_t *);
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int (*get_port)(void *, mixer_ctrl_t *);
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int (*query_devinfo)(void *, mixer_devinfo_t *);
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void *(*allocm)(void *, int, size_t, int, int);
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void (*freem)(void *, void *, int);
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size_t (*round_buffersize)(void *, int, size_t);
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int (*mappage)(void *, void *, int, int);
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int (*get_props)(void *);
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int (*trigger_output)(void *, void *, void *, int,
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void (*)(void *), void *, struct audio_params *);
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int (*trigger_input)(void *, void *, void *, int,
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void (*)(void *), void *, struct audio_params *);
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int (*dev_ioctl)(void *, u_long, caddr_t, int, struct proc *);
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};
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struct audio_params {
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u_long sample_rate; /* sample rate */
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u_int encoding; /* ulaw, linear, etc */
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u_int precision; /* bits/sample */
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u_int channels; /* mono(1), stereo(2) */
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/* Software en/decode functions, set if SW coding required by HW */
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void (*sw_code)(void *, u_char *, int);
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int factor; /* coding space change */
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int factor_denom; /* denominator of factor */
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/*
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* The following four members represent what format is used in a
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* hardware. If hw_sample_rate != sample_rate || hw_channels !=
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* channels, the audio framework converts data. Encoding and
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* precision are converted in sw_code().
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* set_params() should set correct values to them if no conversion is
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* needed.
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*/
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u_long hw_sample_rate;
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u_int hw_encoding;
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u_int hw_precision;
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u_int hw_channels;
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};
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.Ed
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.Pp
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The high level audio driver attaches to the low level driver
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when the latter calls
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.Va audio_attach_mi .
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This call should be
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.Bd -literal
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void
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audio_attach_mi(ahwp, hdl, dev)
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struct audio_hw_if *ahwp;
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void *hdl;
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struct device *dev;
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.Ed
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.Pp
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The
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.Va audio_hw_if
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struct is as shown above.
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The
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.Va hdl
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argument is a handle to some low level data structure.
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It is sent as the first argument to all the functions
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in
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.Va audio_hw_if
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when the high level driver calls them.
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.Va dev
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is the device struct for the hardware device.
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.Pp
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The upper layer of the audio driver allocates one buffer for playing
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and one for recording.
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It handles the buffering of data from the user processes in these.
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The data is presented to the lower level in smaller chunks, called blocks.
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If there, during playback, is no data available from the user process when
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the hardware request another block a block of silence will be used instead.
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Furthermore, if the user process does not read data quickly enough during
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recording data will be thrown away.
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.Pp
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The fields of
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.Va audio_hw_if
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are described in some more detail below.
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Some fields are optional and can be set to 0 if not needed.
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.Bl -tag -width indent
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.It Dv int open(void *hdl, int flags)
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is called when the audio device is opened.
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It should initialize the hardware for I/O.
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Every successful call to
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.Va open
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is matched by a call to
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.Va close .
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Return 0 on success, otherwise an error code.
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.It Dv void close(void *hdl)
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is called when the audio device is closed.
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.It Dv int drain(void *hdl)
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optional, is called before the device is closed or when
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.Dv AUDIO_DRAIN
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is called.
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It should make sure that no samples remain in to be played that could
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be lost when
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.Va close
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is called.
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Return 0 on success, otherwise an error code.
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.It Dv int query_encoding(void *hdl, struct audio_encoding *ae)
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is used when
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.Dv AUDIO_GETENC
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is called.
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It should fill the
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.Va audio_encoding
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structure and return 0 or, if there is no encoding with the
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given number, return EINVAL.
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.It Dv int set_params(void *hdl, int setmode, int usemode,
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.Dv "struct audio_params *play, struct audio_params *rec)"
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.br
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Called to set the audio encoding mode.
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.Va setmode
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is a combination of the
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.Dv AUMODE_RECORD
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and
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.Dv AUMODE_PLAY
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flags to indicate which mode(s) are to be set.
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.Va usemode
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is also a combination of these flags, but indicates the current
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mode of the device (i.e., the value of
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.Va mode
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in the
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.Va audio_info
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struct).
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The
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.Va play
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and
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.Va rec
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structures contain the encoding parameters that should be set.
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.Pp
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If the hardware requires software assistance with some encoding
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(e.g., it might be lacking mulaw support) it should fill the
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.Va sw_code ,
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.Va factor
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and
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.Va factor_denom
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fields of these structures with translation information, and
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set to hw_* fields what format the hardware actually uses.
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For example, if
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.Va play
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requests [8000Hz, mulaw, 8bit, 1ch] and the hardware supports
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not 8bit mulaw but 16bit slinear_le, the driver should set
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.Va mulaw_to_slinear16_le
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to
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.Va sw_code ,
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2 to
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.Va factor ,
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1 to
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.Va factor_denom ,
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.Dv AUDIO_ENCODING_SLINEAR_LE
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to
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.Va hw_encoding
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and 16 to
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.Va hw_precision .
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The values of the structures may also be modified if the hardware
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cannot be set to exactly the requested mode (e.g., if the requested
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sampling rate is not supported, but one close enough is).
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.Pp
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The hardware driver can also request sampling rate conversion
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and mono-stereo conversion.
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If
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.Va set_params
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sets to
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.Va hw_sampling_rate
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a value which is different than
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.Va sampling_rate
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or sets to
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.Va hw_channels
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a value which is different than
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.Va channels ,
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and set
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.Dv AUDIO_ENCODING_SLINEAR_LE
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to
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.Va hw_encoding ,
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the hardware independent driver performs sampling rate and/or mono-stereo
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conversion.
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If such conversion is not needed,
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.Va set_params
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must keep
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.Va sampling_rate
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and
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.Va channels
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are the same as
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.Va hw_sampling_rate
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and
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.Va hw_channels
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respectively.
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.Pp
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Note: The order of conversion is
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.Va sw_code
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followed by sampling rate and mono-stereo in playing,
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and sampling rate and mono-stereo followed by
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.Va sw_code
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in recording.
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.Pp
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If the device does not have the
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.Dv AUDIO_PROP_INDEPENDENT
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property the same value is passed in both
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.Va play
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and
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.Va rec
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and the encoding parameters from
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.Va play
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is copied into
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.Va rec
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after the call to
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.Va set_params .
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Return 0 on success, otherwise an error code.
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.It Dv int round_blocksize(void *hdl, int bs)
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optional, is called with the block size,
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.Va bs ,
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that has been computed by the upper layer.
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It should return a block size, possibly changed according to the needs
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of the hardware driver.
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.It Dv int commit_settings(void *hdl)
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optional, is called after all calls to
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.Va set_params ,
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and
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.Va set_port ,
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are done.
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A hardware driver that needs to get the hardware in and out of command
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mode for each change can save all the changes during previous calls and
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do them all here.
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Return 0 on success, otherwise an error code.
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.It Dv int init_output(void *hdl, void *buffer, int size)
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optional, is called before any output starts, but when the total
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.Va size
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of the output
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.Va buffer
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has been determined.
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It can be used to initialize looping DMA for hardware that needs that.
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Return 0 on success, otherwise an error code.
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.It Dv int init_input(void *hdl, void *buffer, int size)
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optional, is called before any input starts, but when the total
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.Va size
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of the input
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.Va buffer
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has been determined.
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It can be used to initialize looping DMA for hardware that needs that.
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Return 0 on success, otherwise an error code.
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.It Dv int start_output(void *hdl, void *block, int blksize,
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.Dv "void (*intr)(void*), void *intrarg)"
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.br
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is called to start the transfer of
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.Va blksize
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bytes from
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.Va block
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to the audio hardware.
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The call should return when the data transfer has been initiated
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(normally with DMA).
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When the hardware is ready to accept more samples the function
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.Va intr
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should be called with the argument
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.Va intrarg .
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Calling
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.Va intr
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will normally initiate another call to
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.Va start_output .
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Return 0 on success, otherwise an error code.
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.It Dv int start_input(void *hdl, void *block, int blksize,
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.Dv "void (*intr)(void*), void *intrarg)"
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.br
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is called to start the transfer of
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.Va blksize
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bytes to
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.Va block
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from the audio hardware.
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The call should return when the data transfer has been initiated
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(normally with DMA).
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When the hardware is ready to deliver more samples the function
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.Va intr
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should be called with the argument
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.Va intrarg .
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Calling
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.Va intr
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will normally initiate another call to
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.Va start_input .
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Return 0 on success, otherwise an error code.
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.It Dv int halt_output(void *hdl)
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is called to abort the output transfer (started by
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.Va start_output )
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in progress.
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Return 0 on success, otherwise an error code.
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.It Dv int halt_input(void *hdl)
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is called to abort the input transfer (started by
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.Va start_input )
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in progress.
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Return 0 on success, otherwise an error code.
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.It Dv int speaker_ctl(void *hdl, int on)
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optional, is called when a half duplex device changes between
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playing and recording.
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It can, e.g., be used to turn on
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and off the speaker.
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Return 0 on success, otherwise an error code.
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.It Dv int getdev(void *hdl, struct audio_device *ret)
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Should fill the
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.Va audio_device
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struct with relevant information about the driver.
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Return 0 on success, otherwise an error code.
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.It Dv int setfd(void *hdl, int fd)
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optional, is called when
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.Dv AUDIO_SETFD
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is used, but only if the device has AUDIO_PROP_FULLDUPLEX set.
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Return 0 on success, otherwise an error code.
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.It Dv int set_port(void *hdl, mixer_ctl_t *mc)
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is called in when
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.Dv AUDIO_MIXER_WRITE
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is used.
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It should take data from the
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.Va mixer_ctl_t
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struct at set the corresponding mixer values.
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Return 0 on success, otherwise an error code.
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.It Dv int get_port(void *hdl, mixer_ctl_t *mc)
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is called in when
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.Dv AUDIO_MIXER_READ
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is used.
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It should fill the
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.Va mixer_ctl_t
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struct.
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Return 0 on success, otherwise an error code.
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.It Dv int query_devinfo(void *hdl, mixer_devinfo_t *di)
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is called in when
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.Dv AUDIO_MIXER_DEVINFO
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is used.
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It should fill the
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.Va mixer_devinfo_t
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struct.
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Return 0 on success, otherwise an error code.
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.It Dv "void *allocm(void *hdl, int direction, size_t size, int type, int flags)"
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.br
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optional, is called to allocate the device buffers.
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If not present
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.Xr malloc 9
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is used instead (with the same arguments but the first two).
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The reason for using a device dependent routine instead of
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.Xr malloc 9
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is that some buses need special allocation to do DMA.
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Returns the address of the buffer, or 0 on failure.
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.It Dv void freem(void *hdl, void *addr, int type)
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optional, is called to free memory allocated by
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.Va alloc .
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If not supplied
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.Xr free 9
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is used.
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.It Dv size_t round_buffersize(void *hdl, int direction, size_t bufsize)
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optional, is called at startup to determine the audio
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buffer size.
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The upper layer supplies the suggested size in
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.Va bufsize ,
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which the hardware driver can then change if needed.
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E.g., DMA on the ISA bus cannot exceed 65536 bytes.
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.It Dv "int mappage(void *hdl, void *addr, int offs, int prot)"
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.br
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optional, is called for
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.Xr mmap 2 .
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Should return the map value for the page at offset
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.Va offs
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from address
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.Va addr
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mapped with protection
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.Va prot .
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Returns -1 on failure, or a machine dependent opaque value
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on success.
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.It Dv int get_props(void *hdl)
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Should return the device properties; i.e., a combination of
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AUDIO_PROP_xxx.
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.It Dv int trigger_output(void *hdl, void *start, void *end,
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.Dv "int blksize, void (*intr)(void*), void *intrarg,"
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.br
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.Dv "struct audio_params *param)"
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.br
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optional, is called to start the transfer of data from the circular buffer
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delimited by
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.Va start
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and
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.Va end
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to the audio hardware, parameterized as in
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.Va param .
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The call should return when the data transfer has been initiated
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(normally with DMA).
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When the hardware is finished transferring each
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.Va blksize
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sized block, the function
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.Va intr
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should be called with the argument
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.Va intrarg
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(typically from the audio hardware interrupt service routine).
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Once started the transfer may be stopped using
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.Va halt_output .
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Return 0 on success, otherwise an error code.
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.It Dv int trigger_input(void *hdl, void *start, void *end,
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.Dv "int blksize, void (*intr)(void*), void *intrarg,"
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.br
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.Dv "struct audio_params *param)"
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.br
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optional, is called to start the transfer of data from the audio hardware,
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parameterized as in
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.Va param ,
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to the circular buffer delimited by
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.Va start
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and
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.Va end .
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The call should return when the data transfer has been initiated
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(normally with DMA).
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When the hardware is finished transferring each
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.Va blksize
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sized block, the function
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.Va intr
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should be called with the argument
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.Va intrarg
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(typically from the audio hardware interrupt service routine).
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Once started the transfer may be stopped using
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.Va halt_input .
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Return 0 on success, otherwise an error code.
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.It Dv int dev_ioctl(void *hdl, u_long cmd, caddr_t addr,
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.br
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.Dv "int flag, struct proc *p)"
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.br
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optional, is called when an
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.Xr ioctl 2
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is not recognized by the generic audio driver.
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Return 0 on success, otherwise an error code.
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.El
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.Pp
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The
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.Va query_devinfo
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method should define certain mixer controls for
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.Dv AUDIO_SETINFO
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to be able to change the port and gain.
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.Pp
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If the audio hardware is capable of input from more
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than one source it should define
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.Dv AudioNsource
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in class
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.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 .
|