alsa drivers; was Re: kernels for Lenny.

[peasthope@shaw.ca]

Nigel and anyone interested in alsa and USB development,

nh> ... both snd-intel8x0, and snd-hda-intel are 
being loaded, and it seems like they are both trying to grab card0, which is 
resulting in neither getting card0, and snd-usb-audio is getting card0, 
because the other 2 are having a non resolvable argument as to who gets 
card0.

There are two sound devices.  Intel 82801BA/BAM 
AC'97 on the system board and C-media USB plugged in.

>From my previous investigation.
  
dalton:~# cat /proc/asound/cards
 0 [default        ]: USB-Audio - C-Media USB Headphone Set  
                      C-Media USB Headphone Set   at usb-0000:00:1f.2-2, full speed

If the C-Media is card 0, then the Intel device 
should be card 1.  The Intel drivers should not 
involve a USB device ... unless it contains 
an Intel or Intel-like chip.

nh> Try adding the 3 lines below to the bottom of 
the alsa-base file.

There is a simple test before editing alsa-base.  
Unplug the C-Media device before starting the 
system and plug it after the on-board Intel chip 
is initialized.  This is from my first trial.

dalton:~# cat /proc/asound/cards
 0 [I82801BAICH2   ]: ICH - Intel 82801BA-ICH2
                      Intel 82801BA-ICH2 with AD1885 at irq 17
 1 [default        ]: USB-Audio - C-Media USB Headphone Set
                      C-Media USB Headphone Set   at usb-0000:00:1f.2-2, full speed

Which seems consistent with my hypothesis.

Further hypothesizing: the Intel 82801 invokes 
snd_intel8x0 while the C-Media USB invokes snd_hda_intel.

I'll try this unplug/replug procedure a few more times 
and report next week.

USB and udev are appealing concepts but implementation 
is certainly non-trivial.

Thanks for the help.  Progress would be difficult 
without it.

Regards,         ... Peter E.











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