[alsa-devel] [PATCH] ASoC: OMAP: Add checking to detect bufferless pcms

Peter Ujfalusi peter.ujfalusi at nokia.com
Wed Apr 22 11:42:46 CEST 2009

On Wednesday 22 April 2009 11:30:32 ext Jarkko Nikula wrote:
> On Wed, Apr 22, 2009 at 4:56 AM, Joonyoung Shim
> <jy0922.shim at samsung.com<mailto:jy0922.shim at samsung.com>> wrote: Add
> checking in hw_params and prepare to detect bufferless pcms(i.e. BT <-->
> codec).
> I see exactly similar lines in s3c24xx-pcm.c but don't point now the use
> case where this is used and I don't have idea what is this all about.
> Is this something where DAI driver or another end of connection is used to
> provide clocking and the whole setup is then controlled with ALSA PCM API?
> Somehow I have the feeling that would there be a better way to achieve it
> than with dummy bufferless transfer?

In the twl codec, the BT interface does not have dedicated clock line, but it 
is (re)using the clock lines for the voice PCM interface. So in order to get 
BT data going between the BT and the codec, the voice PCM interface has to 
generate the clocks.

But I think this could be done even without the need for the alsa PCM 
interface, probably well placed DAPM switches would also can take care of 

> --
> Jarkko


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