<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook V3.1//EN"[]>

<book id="ViaAudioGuide">
 <bookinfo>
  <title>Via 686 Audio Driver for Linux</title>
  
  <authorgroup>
   <author>
    <firstname>Jeff</firstname>
    <surname>Garzik</surname>
    <affiliation>
     <address>
      <email>jgarzik@mandrakesoft.com</email>
     </address>
    </affiliation>
   </author>
  </authorgroup>

  <copyright>
   <year>2000</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 2.3.50.
  </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://gtf.org/garzik/drivers/via82cxxx/ 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>MMAP support</term>
    <listitem>
    <para>
    	MMAP support is currently missing.  Make sure to
	test with Quake.
    </para>
    </listitem></varlistentry>

    <varlistentry><term>AC97 codec timeout during init</term>
    <listitem>
    <para>
    	A warning message "via82cxxx: timeout while reading AC97
	codec" is printed during driver initialization.  This
	message can safely be ignored.
    </para>
    </listitem></varlistentry>

    <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>

    <varlistentry><term>RealPlayer trouble</term>
    <listitem>
    <para>
	RealPlayer output very scratchy.  Workaround:  use esd, and
	configure RealPlayer to output to esd.
    </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>
  </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:  -kr -i8 -pcs
  </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="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/drivers/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>
!Idrivers/sound/via82cxxx_audio.c
  </chapter>

</book>
