Jeff Garzik

jgarzik@mandrakesoft.com

2000 Jeff Garzik 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. 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. 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 For more details see the file COPYING in the source distribution of Linux. 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. 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. This driver supports any Linux kernel version after 2.3.50. Please send bug reports to the mailing list linux-via@gtf.org. To subscribe, e-mail majordomo@gtf.org with subscribe linux-via in the body of the message. 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. To make this driver the default audio driver, you can add the following to your /etc/conf.modules file: alias sound via82cxxx_audio Note that soundcore and ac97_codec support modules are also required for working audio, in addition to the via82cxxx_audio module itself. Describe the application you were using to play/record sound, and how to reproduce the problem. 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: ./via-audio-diag -aps > diag-output.txt Define VIA_DEBUG 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: dmesg > /tmp/dmesg-output.txt If you wish to increase the size of the buffer displayed by dmesg, then change the LOG_BUF_LEN macro at the top of linux/kernel/printk.c, recompile your kernel, and pass the LOG_BUF_LEN value to dmesg. Sample command line with LOG_BUF_LEN == 32768: dmesg -s 32768 > /tmp/dmesg-output.txt MMAP support MMAP support is currently missing. Make sure to test with Quake. AC97 codec timeout during init A warning message "via82cxxx: timeout while reading AC97 codec" is printed during driver initialization. This message can safely be ignored. Low volume Volume too low on many systems. Workaround: use mixer program such as xmixer to increase volume. RealPlayer trouble RealPlayer output very scratchy. Workaround: use esd, and configure RealPlayer to output to esd. Via for providing e-mail support, specs, and NDA'd source code. MandrakeSoft for providing hacking time. AC97 mixer interface fixes and debugging by Ron Cemer roncemer@gte.net. 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: /proc/driver/via/0/info /proc/driver/via/0/ac97 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. GNU indent formatting options: -kr -i8 -pcs 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. 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?) Use VM_RESERVE when available, to eliminate unnecessary page faults. mmap bug fixes from Linus. Many more bug fixes. mmap enabled by default, but may still be buggy. Uses new and spiffy method of mmap'ing the DMA buffer, based on a suggestion from Linus. Many bug fixes. mmap enabled by default, but may still be buggy. Redesign and rewrite audio playback implementation. (faster and smaller, hopefully) Implement recording and full duplex (DSP_CAP_DUPLEX) support. Make procfs support optional. Quick interrupt status check, to lessen overhead in interrupt sharing situations. Add mmap(2) support. Disabled for now, it is still buggy and experimental. Surround all syscalls with a semaphore for cheap and easy SMP protection. Fix bug in channel shutdown (hardware channel reset) code. Remove unnecessary spinlocks (better performance). Eliminate "unknown AFMT" message by using a different method of selecting the best AFMT_xxx sound sample format for use. Support for realtime hardware pointer position reporting (DSP_CAP_REALTIME, SNDCTL_DSP_GETxPTR ioctls) Support for capture/playback triggering (DSP_CAP_TRIGGER, SNDCTL_DSP_SETTRIGGER ioctls) SNDCTL_DSP_SETDUPLEX and SNDCTL_DSP_POST ioctls now handled. 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. Reviewed code to ensure that SMP and multiple audio devices are fully supported. Clean up interrupt handler output. Fixes the following kernel error message: unhandled interrupt ... Convert documentation to DocBook, so that PDF, HTML and PostScript (.ps) output is readily available. Fix module unload bug where mixer device left registered after driver exit Rewrite via_set_rate to mimic ALSA basic AC97 rate setting Remove much dead code Complete spin_lock_irqsave -> spin_lock_irq conversion in via_dsp_ioctl Fix build problem in via_dsp_ioctl Optimize included headers to eliminate headers found in linux/drivers/sound Disable some overly-verbose debugging code Remove unnecessary sound locks Fix some ioctls for better time resolution Begin spin_lock_irqsave -> spin_lock_irq conversion in via_dsp_ioctl Completed rewrite of driver. Eliminated SoundBlaster compatibility completely, and now uses the much-faster scatter-gather DMA engine. !Idrivers/sound/via82cxxx_audio.c