[alsa-devel] [PATCH 1/4] ASoC: compress: Pass error out of soc_compr_pointer

[Vinod Koul]

On Fri, Mar 11, 2016 at 11:25:22AM +0100, Takashi Iwai wrote:
> > I guess my return question would be I can imagine many reasons
> > why a pointer query might fail, especially for off chip DSPs.
> > What is the reasoning for wanting to hide those errors from the
> > rest of the system? It seems to me it would be best to handle an
> > error as soon as it is noticed, and if a particular system has a
> > pointer request that never fails then it can just not return an
> > error.
> 
> IMO, propagating the error immediately is a good thing.  I guess it
> wasn't checked in the pointer callback just because the pointer
> callback was supposed to be a simple state copy without involving the
> state change.
> 
> OTOH, another question is whether it's enough just to tell the error
> there as is.  When such an error is detected, it essentially means
> that the whole DSP got wrong.  What we can do at best is to prepare
> for recovery.  And this requires the state change.

Yes, for recovery on our DSP we do inoke snd_pcm_stop() for all the open
streams and then get these restarted. I think we need to do same for
compress too..

> Actually, PCM pointer callback may return a special value indicating
> an XRUN error.  The PCM core reacts for it, stops the stream and
> changes the stream state, so that further accesses get the error
> consistently.  Similar mechanism would be needed for compress API, I
> suppose.

I didnt know that :)

-- 
~Vinod