[Alsa-user] CMI9739 sound volume

[Alexei D. <de...@se...>]

Hi!

I, like a MANY other people, have a mother board with a built-in C-Media 
Electronics CMI9739 sound chip (also some other CMedia chips are affected). 
It seems to be a very popular solution currently among hardware 
manufacturers. Unfortunately, under ALSA this "sound card" has one _VERY_ 
serious issue - it has no PCM volume control. Master volume doesn't work 
either (though it is present). Only PCM volume switch is available - it is 
possible to turn it on (full volume) or off (no sound). ALSA driver 
(snd-intel8x0, snd-ac97-codec) is in general better than the OSS driver from 
C-Media - it has more controls, allows microphone "boost", has no problems 
with arts sound daemon etc. But it has absolutely no volume control...

AFAIK, the problem is that chip doesn't have hardware PCM volume control - 
this should be done in software. There is also the patch (by Chen Li Tien) 
available for alsa-1.0.0.rc2: 
http://www.mail-archive.com/alsa-devel%40lists.sourceforge.net/msg10804.html
It is supposed to fix the problem. I've applied it to the alsa-1.0.4 - PCM 
volume control slider appears in the mixers but does _nothing_, volume 
doesn't change. I've also found this page: 
http://edseek.com/index.php/archives/2004/03/03/c-media-electronics-cmi9739-mixer-pcm-no-volume/
It states that the patch doesn't work on alsa-1.0.3rc2.

So, can somebody help with this? There is an open-source OSS driver from 
manufacturer, the specs for the chip are open and even the patch (I've looked 
inside - it seems to have the needed code) is available!!! Can the patch be 
fixed and applied to the mainstream alsa? Or may be somebody can help with 
fixing it? I'm a professional programmer myself, I can try to do this but I 
need a help - I know NOTHING about ALSA architecture and writing of the 
kernel modules in general :-(((

Also I have one question about ALSA in general - is it possible to have 
simultaneos playback from the different applications in ALSA? Lots of modern 
OSS drivers allow this - but this seem to not work with ALSA :-( Sound server 
is neccessary for the thing the sound card can do itself without bugs & 
processor load... :-(

	Alexei