Bug in ALSA OSS mixer emulation. Volume++ does not work.

[James Courtier-Dutton <James@superbug.demon.co.uk>]

Hi,

  The alsa keeps state of all mixer levels in alsa's internal format 
which has min,max info. So, for example if alsa has 0-31 levels, 
converting that to the OSS 0-100 range is easy with a simple 
calculation, but if an OSS app just does Volume++, the change will be 
lost in the conversion from OSS to ALSA to actually set the state. So, 
to work the way it should, OSS will have to cache all mixer state in OSS 
format, thus requiring 2 state tables.

E.g.
OSS Volume(0-100)   ALSA Volume(0-31)
OSS = ALSA * 100/31;

0		    0
1                   0
2                   0
3                   1
4                   1
etc.

So, if OSS Volume is 2, and the OSS application does Volume++, the OSS 
volume will be set to 3. but if OSS Volume is 3, and the OSS application 
does Volume++, the OSS volume will stay at 3!

Cheers
James



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