[alsa-devel] How to support several cards using the same driver?

Cliff Cai xcahua at hotmail.com
Thu May 1 09:52:25 CEST 2008

Hi all,
   I have a sound card which has 8 DAC/ADC pairs,and each DAC/ADC pair can be seen as an independent sub-card.
An 8-slot buffer struct is introduced to feed/get data to/from the 8 sub-cards.For example, if an application wants to play music using
No.x(x,from 0 to 7) sub-card,the driver only need to copy the data from pcm layer to NO.x slot in the buffer struct and fill the other 7 slots with zero.
The driver has been implemented now.
   The problem is how to expose the 8 sub-cards to application,So the application developer can see 8 independant device nodes
under /dev.Those are /dev/dsp0,/dev/dsp1,...dev/dsp7(for oss emulation) or card0,card1...card7(for alsa).When one sub-card is opened 
the driver need to get the index of the sub-card,so it can feed/get data to/from the relevant slot.For example ,if an application opens /dev/dsp7,
then the index "7" can be seen by the driver,and the driver know that No.7 slot will be used.
   Have I made myself clear?Any suggestion is appreciated!
Best Regards
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