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

Cai, Cliff Cliff.Cai at analog.com
Tue Oct 21 12:33:27 CEST 2008


>-----Original Message-----
>From: Mark Brown [mailto:broonie at sirena.org.uk] 
>Sent: Tuesday, October 21, 2008 6:15 PM
>To: Bryan Wu
>Cc: Takashi Iwai; Cai, Cliff; alsa-devel at alsa-project.org
>Subject: Re: [alsa-devel] [PATCH 2/3] ASoC: Blackfin: add 
>multi-channel supporting in Blackfin ASoC driver and AD1980 
>codec driver
>On Tue, Oct 21, 2008 at 05:55:23PM +0800, Bryan Wu wrote:
>> But you know, it is very difficult for us to allocate big 
>buffer in an 
>> NOMMU machine (such as Blackfin) on the fly, So we prefer to 
>> them at the beginning. And in the embedded world, when the user want 
>> to use multi-channel function, they will enable this option. If they 
>> don't, they won't do that. It is very simple for both us and our 
>> users, although it is less elegant than Mark's idea.
>So the issue is that you want to force a static allocation at 
>startup due to hardware limitations?  That makes a bit more 
>sense.  I guess that's OK but I'd suggest changing the code to 
>also allow the user to select four channels - not all 
>multi-channel systems use six channels.

The buffer struct of ac97 frame for 4/6 channels only has one slot
difference -- LFE slot,
6-channel mode does support 4-channel mode.

>Another option would be to select it at driver startup time.
>I'm still not sure that this is something that should be 
>selected via the kernel configuration rather than by the 
>machine driver - I would expect the use of six channels to be 
>a property of the system rather than of the particular kernel build.

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