[alsa-devel] [PATCH v2] davinci-mcasp: Add support for multichannel playback

[Bedia, Vaibhav]

Hi Daniel,

On Tue, Mar 05, 2013 at 21:31:59, Daniel Mack wrote:
[...]
> 
> As Michal described, we used a board with a multichannel Codec on it,
> which connects 3 of its I2S inputs to the AM33xx's AXR data lines.
> 
> Software wise, we tested with 'aplay -cX', and that seems to work just fine.
> 

Since you are using a multichannel codec things are a lot simplified for you :)
Someone might want to hook up multiple codecs to get multi-channel behavior.
There will be only 1 CPU DAI but there can be upto 16 CODEC DAIs operating in
sync. I haven't really followed the recent ASoC changes so I don't know whether
something like this can be handled right now.

Mark, Liam,

Any suggestions?

[...]
> >>  	return 0;
> >> @@ -936,13 +978,13 @@ static struct snd_soc_dai_driver davinci_mcasp_dai[] = {
> >>  		.name		= "davinci-mcasp.0",
> >>  		.playback	= {
> >>  			.channels_min	= 2,
> >> -			.channels_max 	= 2,
> >> +			.channels_max	= 8,
> > 
> > Why are you setting this to 8?
> 
> Well, the ASoC core will look at this field when parsing the dai links,
> and will build a sound card that has min(codec_dai->channels_max,
> cpu_dai->channels_max) channels. Hence, this number has to reflect the
> maximum possible output channels for this DAI. In v3, it's actually set
> to 512. Or was that not your question?

32 slots on a max of 16 serializers gives the max as 512 and hence I wanted
to know why 8 was selected.

Regards,
Vaibhav