.\"	$OpenBSD: ac97.4,v 1.18 2010/02/26 14:14:14 sobrado Exp $
.\"
.\" Copyright (c) 1999, 2000 Constantine Sapuntzakis
.\"
.\" Author:	Constantine Sapuntzakis <csapuntz@stanford.edu>
.\"
.\" 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. The name of the author may not be used to endorse or promote
.\"    products derived from this software without specific prior written
.\"    permission.
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``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 AUTHOR 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 $Mdocdate: February 26 2010 $
.Dt AC97 4
.Os
.Sh NAME
.Nm ac97
.Nd generic AC'97 codec driver
.Sh DESCRIPTION
AC'97 codecs contain the analog to digital (A/D), digital to analog
(D/A), and mixing circuitry of many modern sound cards.
AC'97 codecs, for the most part, do not talk to host buses like the PCI bus
directly.
Instead, they communicate through an interface chip, called
the host controller.
The Ensoniq AudioPCI 97 (see
.Xr eap 4 )
is an example of such a host controller.
.Pp
Unlike many drivers, the
.Nm
driver does not appear in the configuration file.
Instead, the driver is automatically attached by the drivers that require it.
.Sh SEE ALSO
.Xr auacer 4 ,
.Xr auich 4 ,
.Xr auixp 4 ,
.Xr autri 4 ,
.Xr auvia 4 ,
.Xr clcs 4 ,
.Xr clct 4 ,
.Xr eap 4 ,
.Xr emu 4 ,
.Xr esa 4 ,
.Xr fms 4 ,
.Xr maestro 4 ,
.Xr neo 4 ,
.Xr yds 4
.Sh BUGS
The
.Nm
driver does not keep track of the current user settings and instead
relies on the hardware to do this.
.Pp
The
.Nm
driver could do more to detect mixer channels that don't work and cull
them from the list.