snd_amd5536.ko is a FreeBSD 7.0 and 6.x audio (sound) driver for the 
AMD 5536 companion chip sound system.  This driver was developed on 
an ALIX 1C low power computer board from PC Engines, with a 500 Mhz 
AMD Geode LX CPU and an AMD cs5536 companion chip. The Alix 1D is 
now the current board:

http://www.mini-box.com/Alix-1C-Board-1-LAN-1-MINI-PCI_2?sc=8&category=754

This driver was developed for FreeBSD 7.0 and FreeBSD 6.2.
The driver has 2 play channels and 1 record channel. However, since
the Alix 1C has only a single codec, the two play channels must use
the same dma busmaster, and hence they must have the same rate (speed)
and the same block size.  Currently, channel 0 takes precedence.



I. To load this driver: 

1) Make a /usr/src/modules/sound/driver/amd5536 directory.
   (you MUST be root to load this driver).
2) Download snd_amd5536.tar.gz into this directory.  At this time it is at:
   www.modelofreality.org/snd_amd5536
3) "Unzip" and "Untar" the file:
   gzip -d snd_amd5536.tar.gz
   tar xvf snd_amd5536.tar
4) Move snd_amd5536.ko to the /boot/kernel directory:
   mv ./snd_amd5536.ko /boot/kernel
5) load the driver with the kernel dynamic loader:
   kldload snd_amd5536.ko
6) To allow the mic to work, run:
   mixer rec 75
   Run   mixer  again to check.  The "rec" level should be 75.
   (If you want to use the "line" interface instead of the mic:
   mixer +rec line    )
7) Turn OFF the vchan interface for FreeBSD 7.0.  (This is mandatory
   since the vchan interface wants to run the two play channels
   at different rates):
   sysctl dev.pcm.0.play.vchans=0
   sysctl dev.pcm.0.rec.vchans=0
   run     cat /dev/sndstat     to verify.  It should say
   2p:0v/1r:0v channels duplex default



II. The driver should now be loaded and ready.  To test the device:

1) cat count.raw > /dev/dsp
   You should hear me counting out of the speakers.
2) While this is playing, switch to another terminal by pressing ALT-F2.
   cat count.raw > /dev/dsp
   You should hear both left and right channels simultaneously counting.
   You can also    cat 1khz.raw > /dev/dsp    to hear a 1 khz sine wave.
3) Switch back to the primary terminal by pressing ALT-F1.
   Put a mic into the mic jack.
   cat /dev/dsp > test.raw   
   Speak into the microphone and when finished, press CTRL-c. 
4) To hear what you recorded:
   cat test.raw > /dev/dsp   
5) You can also run ./loopback to hear the mono mic input from the speakers.
   Press CTRL-c to exit.

   

III. Settings for automatic boot.

1) Put   
   snd_amd5536_load="YES"
   into  /boot/loader.conf   to automatically load on bootup.
   (snd_amd5536.ko must be in the /boot/kernel directory).
2) Rather than running  mixer rec 75  everytime to enable record, 
   one can put  hint.pcm.0.rec="75" into the /boot/device.hints file.
3) Put dev.pcm.0.play.vchans=0                    (use no spaces)
       dev.pcm.0.rec.vchans=0
   into the /etc/sysctl.conf file, to automatically turn off the vchan
   interface (mandatory).



IV. Compiling this driver on FreeBSD 7.0:

1) You must have "source files" installed for this to work.
   If you do not have source files installed, find out how to install
   them from the freebsd.org site.
2) Move the amd5536.c and amd5536.h files to the
   /usr/src/sys/dev/sound/pci directory
   While in the /usr/src/sys/modules/sound/driver/amd5536 directory:
   mv ./amd5536.c /usr/src/sys/dev/sound/pci
   mv ./amd5536.h /usr/src/sys/dev/sound/pci
3) You should be root to compile this driver.  Type
   make
   The sound driver should compile.
4) Don't forget that the snd_amd5536.ko must be placed into the 
   /boot/kernel directory for automatic boot.  If you want to 
   run the new driver temporarily, then first unload the current one:
   kldunload -n snd_amd5536
5) Then load the new one:
   kldload ./snd_amd5536.ko
6) Check by running:
   kldstat    or    cat /dev/sndstat



V.  Other notes.
   
1) This drivers supports 2 mono channels simultaneously: Channel 0 and 
   Channel 1.  However, if Channel 0 is programmed as stereo, it takes
   precedence and uses both left and right channels. Channel 1 will not
   be heard out of the right channel in if Channel 0 is running in stereo. 
   
2) The 1 record channel is independent and runs in either stereo or mono.  
   However, if record is run mono, then only the left channel is recorded!  
   The right channel is ignored in this case.

3) The vchan interface should not be used.  

4) Channel 0 takes precedence over Channel 1.  Change the blocksize for
   channel 0 to change the blocksize for both.  Change the rate for
   channel 0 to change the rate for both.  For programmers:  open
   /dev/dsp to get play channel 0, then open /dev/dsp0.1 to get
   play channel 1.  Set the rate and blocksize for channel 0.


Andrew Gray


ancelgray?yahoo.com