[alsa-devel] How to define card specific pcm devices?

[Liam Girdwood]

On Wed, 2012-09-05 at 12:24 +0100, Girdwood, Liam wrote:
> On 5 September 2012 06:41, Tanu Kaskinen <tanuk at iki.fi> wrote:
>         On Wed, 2012-08-29 at 09:44 +0800, Raymond Yau wrote:
>         > strictly speaking your mic is not a true stereo mic and the
>         channel
>         > map is [left, null] instead of the normal map [left,right]
>         of line-in
>         > or stereo mic
>         
>         
>         I think specifying the channel map like you suggest would be a
>         good
>         solution. Supporting it would require some extra work in
>         PulseAudio, but
>         I think PulseAudio will anyway have to be extended to query
>         the channel
>         map information from UCM.
>         
>         Now the problem is that UCM doesn't provide the channel map
>         information
>         at all. Should the channel map be provided in the device
>         "Value"
>         section? Like this:
>         
>         SectionDevice."my-mono-mic" {
>         
>                 ...
>         
>                 Value {
>                         # Does this value become redundant if
>                         # the "CaptureChannelMap" value is added?
>                         CaptureChannels "2"
>         

I would expect to see a "1" here unless we cannot open the pcm in mono
mode.

>                         # Channel names match the constants in
>                         # Takashi's proposed channel map API
>                         CaptureChannelMap "FL, NA"
>                 }
>         
>         }

This seems fine and should be a simple patch for UCM too. Pulsaudio
could use the map information/preference from UCM (like above) to
configure the driver using Takashi's new channel map API.

>         
>         Opinions? (Liam added to CC - am I right in that you should be
>         CC'd in
>         all UCM related discussions?)

Yes, please and Mark too (now on CC).

Thanks

Liam

>