[alsa-devel] [PATCH 2/3] ASoC: Blackfin: add multi-channel supporting in Blackfin ASoC driver and AD1980 codec driver

[Takashi Iwai]

At Tue, 21 Oct 2008 10:49:16 +0100,
Mark Brown wrote:
> 
> On Tue, Oct 21, 2008 at 05:48:56PM +0800, Cai, Cliff wrote:
> > >From: Takashi Iwai [mailto:tiwai at suse.de] 
> 
> > >But, CONFIG_SND_MULTICHAN_SUPPORT would change any buffer 
> > >allocation behavior?  I don't find it...
> 
> > It will change the ac97 frame size defined in bf5xx-ac97.h,the frame
> > size the basic unit of the DMA buffer 
> 
> So this is purely a restriction in the driver, rather than a property of
> the hardware - is there any reason why you can't change the size of
> buffer that you allocate at runtime?

It'd be possible, as far as I understand.  It's rather a design
issue.

bf5xx driver preallocates the max size buffer.  Otherwise you may get
no large buffer at later fragmentation.  And that size is different
between with and without multi-channel support.


Takashi