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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
<book id="ViaAudioGuide">
<bookinfo>
<title>Via 686 Audio Driver for Linux</title>
<authorgroup>
<author>
<firstname>Jeff</firstname>
<surname>Garzik</surname>
</author>
</authorgroup>
<copyright>
<year>1999-2001</year>
<holder>Jeff Garzik</holder>
</copyright>
<legalnotice>
<para>
This documentation is free software; you can redistribute
it and/or modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later
version.
</para>
<para>
This program is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU General Public License for more details.
</para>
<para>
You should have received a copy of the GNU General Public
License along with this program; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
MA 02111-1307 USA
</para>
<para>
For more details see the file COPYING in the source
distribution of Linux.
</para>
</legalnotice>
</bookinfo>
<toc></toc>
<chapter id="intro">
<title>Introduction</title>
<para>
The Via VT82C686A "super southbridge" chips contain
AC97-compatible audio logic which features dual 16-bit stereo
PCM sound channels (full duplex), plus a third PCM channel intended for use
in hardware-assisted FM synthesis.
</para>
<para>
The current Linux kernel audio driver for this family of chips
supports audio playback and recording, but hardware-assisted
FM features, and hardware buffer direct-access (mmap)
support are not yet available.
</para>
<para>
This driver supports any Linux kernel version after 2.4.10.
</para>
<para>
Please send bug reports to the mailing list <email>linux-via@gtf.org</email>.
To subscribe, e-mail <email>majordomo@gtf.org</email> with
</para>
<programlisting>
subscribe linux-via
</programlisting>
<para>
in the body of the message.
</para>
</chapter>
<chapter id="install">
<title>Driver Installation</title>
<para>
To use this audio driver, select the
CONFIG_SOUND_VIA82CXXX option in the section Sound during kernel configuration.
Follow the usual kernel procedures for rebuilding the kernel,
or building and installing driver modules.
</para>
<para>
To make this driver the default audio driver, you can add the
following to your /etc/conf.modules file:
</para>
<programlisting>
alias sound via82cxxx_audio
</programlisting>
<para>
Note that soundcore and ac97_codec support modules
are also required for working audio, in addition to
the via82cxxx_audio module itself.
</para>
</chapter>
<chapter id="reportbug">
<title>Submitting a bug report</title>
<sect1 id="bugrepdesc"><title>Description of problem</title>
<para>
Describe the application you were using to play/record sound, and how
to reproduce the problem.
</para>
</sect1>
<sect1 id="bugrepdiag"><title>Diagnostic output</title>
<para>
Obtain the via-audio-diag diagnostics program from
http://sf.net/projects/gkernel/ and provide a dump of the
audio chip's registers while the problem is occurring. Sample command line:
</para>
<programlisting>
./via-audio-diag -aps > diag-output.txt
</programlisting>
</sect1>
<sect1 id="bugrepdebug"><title>Driver debug output</title>
<para>
Define <constant>VIA_DEBUG</constant> at the beginning of the driver, then capture and email
the kernel log output. This can be viewed in the system kernel log (if
enabled), or via the dmesg program. Sample command line:
</para>
<programlisting>
dmesg > /tmp/dmesg-output.txt
</programlisting>
</sect1>
<sect1 id="bugrepprintk"><title>Bigger kernel message buffer</title>
<para>
If you wish to increase the size of the buffer displayed by dmesg, then
change the <constant>LOG_BUF_LEN</constant> macro at the top of linux/kernel/printk.c, recompile
your kernel, and pass the <constant>LOG_BUF_LEN</constant> value to dmesg. Sample command line with
<constant>LOG_BUF_LEN</constant> == 32768:
</para>
<programlisting>
dmesg -s 32768 > /tmp/dmesg-output.txt
</programlisting>
</sect1>
</chapter>
<chapter id="bugs">
<title>Known Bugs And Assumptions</title>
<para>
<variablelist>
<varlistentry><term>Low volume</term>
<listitem>
<para>
Volume too low on many systems. Workaround: use mixer program
such as xmixer to increase volume.
</para>
</listitem></varlistentry>
</variablelist>
</para>
</chapter>
<chapter id="thanks">
<title>Thanks</title>
<para>
Via for providing e-mail support, specs, and NDA'd source code.
</para>
<para>
MandrakeSoft for providing hacking time.
</para>
<para>
AC97 mixer interface fixes and debugging by Ron Cemer <email>roncemer@gte.net</email>.
</para>
<para>
Rui Sousa <email>rui.sousa@conexant.com</email>, for bugfixing
MMAP support, and several other notable fixes that resulted from
his hard work and testing.
</para>
<para>
Adrian Cox <email>adrian@humboldt.co.uk</email>, for bugfixing
MMAP support, and several other notable fixes that resulted from
his hard work and testing.
</para>
<para>
Thomas Sailer for further bugfixes.
</para>
</chapter>
<chapter id="notes">
<title>Random Notes</title>
<para>
Two /proc pseudo-files provide diagnostic information. This is generally
not useful to most users. Power users can disable CONFIG_SOUND_VIA82CXXX_PROCFS,
and remove the /proc support code. Once
version 2.0.0 is released, the /proc support code will be disabled by
default. Available /proc pseudo-files:
</para>
<programlisting>
/proc/driver/via/0/info
/proc/driver/via/0/ac97
</programlisting>
<para>
This driver by default supports all PCI audio devices which report
a vendor id of 0x1106, and a device id of 0x3058. Subsystem vendor
and device ids are not examined.
</para>
<para>
GNU indent formatting options:
<programlisting>
-kr -i8 -ts8 -br -ce -bap -sob -l80 -pcs -cs -ss -bs -di1 -nbc -lp -psl
</programlisting>
</para>
<para>
Via has graciously donated e-mail support and source code to help further
the development of this driver. Their assistance has been invaluable
in the design and coding of the next major version of this driver.
</para>
<para>
The Via audio chip apparently provides a second PCM scatter-gather
DMA channel just for FM data, but does not have a full hardware MIDI
processor. I haven't put much thought towards a solution here, but it
might involve using SoftOSS midi wave table, or simply disabling MIDI
support altogether and using the FM PCM channel as a second (input? output?)
</para>
</chapter>
<chapter id="changelog">
<title>Driver ChangeLog</title>
<sect1 id="version191"><title>
Version 1.9.1
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
DSP read/write bugfixes from Thomas Sailer.
</para>
</listitem>
<listitem>
<para>
Add new PCI id for single-channel use of Via 8233.
</para>
</listitem>
<listitem>
<para>
Other bug fixes, tweaks, new ioctls.
</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="version1115"><title>
Version 1.1.15
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
Support for variable fragment size and variable fragment number (Rui
Sousa)
</para>
</listitem>
<listitem>
<para>
Fixes for the SPEED, STEREO, CHANNELS, FMT ioctls when in read &
write mode (Rui Sousa)
</para>
</listitem>
<listitem>
<para>
Mmaped sound is now fully functional. (Rui Sousa)
</para>
</listitem>
<listitem>
<para>
Make sure to enable PCI device before reading any of its PCI
config information. (fixes potential hotplug problems)
</para>
</listitem>
<listitem>
<para>
Clean up code a bit and add more internal function documentation.
</para>
</listitem>
<listitem>
<para>
AC97 codec access fixes (Adrian Cox)
</para>
</listitem>
<listitem>
<para>
Big endian fixes (Adrian Cox)
</para>
</listitem>
<listitem>
<para>
MIDI support (Adrian Cox)
</para>
</listitem>
<listitem>
<para>
Detect and report locked-rate AC97 codecs. If your hardware only
supports 48Khz (locked rate), then your recording/playback software
must upsample or downsample accordingly. The hardware cannot do it.
</para>
</listitem>
<listitem>
<para>
Use new pci_request_regions and pci_disable_device functions in
kernel 2.4.6.
</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="version1114"><title>
Version 1.1.14
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
Use VM_RESERVE when available, to eliminate unnecessary page faults.
</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="version1112"><title>
Version 1.1.12
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
mmap bug fixes from Linus.
</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="version1111"><title>
Version 1.1.11
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
Many more bug fixes. mmap enabled by default, but may still be buggy.
</para>
</listitem>
<listitem>
<para>
Uses new and spiffy method of mmap'ing the DMA buffer, based
on a suggestion from Linus.
</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="version1110"><title>
Version 1.1.10
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
Many bug fixes. mmap enabled by default, but may still be buggy.
</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="version119"><title>
Version 1.1.9
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
Redesign and rewrite audio playback implementation. (faster and smaller, hopefully)
</para>
</listitem>
<listitem>
<para>
Implement recording and full duplex (DSP_CAP_DUPLEX) support.
</para>
</listitem>
<listitem>
<para>
Make procfs support optional.
</para>
</listitem>
<listitem>
<para>
Quick interrupt status check, to lessen overhead in interrupt
sharing situations.
</para>
</listitem>
<listitem>
<para>
Add mmap(2) support. Disabled for now, it is still buggy and experimental.
</para>
</listitem>
<listitem>
<para>
Surround all syscalls with a semaphore for cheap and easy SMP protection.
</para>
</listitem>
<listitem>
<para>
Fix bug in channel shutdown (hardware channel reset) code.
</para>
</listitem>
<listitem>
<para>
Remove unnecessary spinlocks (better performance).
</para>
</listitem>
<listitem>
<para>
Eliminate "unknown AFMT" message by using a different method
of selecting the best AFMT_xxx sound sample format for use.
</para>
</listitem>
<listitem>
<para>
Support for realtime hardware pointer position reporting
(DSP_CAP_REALTIME, SNDCTL_DSP_GETxPTR ioctls)
</para>
</listitem>
<listitem>
<para>
Support for capture/playback triggering
(DSP_CAP_TRIGGER, SNDCTL_DSP_SETTRIGGER ioctls)
</para>
</listitem>
<listitem>
<para>
SNDCTL_DSP_SETDUPLEX and SNDCTL_DSP_POST ioctls now handled.
</para>
</listitem>
<listitem>
<para>
Rewrite open(2) and close(2) logic to allow only one user at
a time. All other open(2) attempts will sleep until they succeed.
FIXME: open(O_RDONLY) and open(O_WRONLY) should be allowed to succeed.
</para>
</listitem>
<listitem>
<para>
Reviewed code to ensure that SMP and multiple audio devices
are fully supported.
</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="version118"><title>
Version 1.1.8
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
Clean up interrupt handler output. Fixes the following kernel error message:
</para>
<programlisting>
unhandled interrupt ...
</programlisting>
</listitem>
<listitem>
<para>
Convert documentation to DocBook, so that PDF, HTML and PostScript (.ps) output is readily
available.
</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="version117"><title>
Version 1.1.7
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
Fix module unload bug where mixer device left registered
after driver exit
</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="version116"><title>
Version 1.1.6
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
Rewrite via_set_rate to mimic ALSA basic AC97 rate setting
</para>
</listitem>
<listitem>
<para>
Remove much dead code
</para>
</listitem>
<listitem>
<para>
Complete spin_lock_irqsave -> spin_lock_irq conversion in via_dsp_ioctl
</para>
</listitem>
<listitem>
<para>
Fix build problem in via_dsp_ioctl
</para>
</listitem>
<listitem>
<para>
Optimize included headers to eliminate headers found in linux/sound
</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="version115"><title>
Version 1.1.5
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
Disable some overly-verbose debugging code
</para>
</listitem>
<listitem>
<para>
Remove unnecessary sound locks
</para>
</listitem>
<listitem>
<para>
Fix some ioctls for better time resolution
</para>
</listitem>
<listitem>
<para>
Begin spin_lock_irqsave -> spin_lock_irq conversion in via_dsp_ioctl
</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="version114"><title>
Version 1.1.4
</title>
<itemizedlist spacing="compact">
<listitem>
<para>
Completed rewrite of driver. Eliminated SoundBlaster compatibility
completely, and now uses the much-faster scatter-gather DMA engine.
</para>
</listitem>
</itemizedlist>
</sect1>
</chapter>
<chapter id="intfunctions">
<title>Internal Functions</title>
!Isound/oss/via82cxxx_audio.c
</chapter>
</book>
