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

[Takashi Iwai]

On Fri, 11 Mar 2016 11:37:47 +0100,
Vinod Koul wrote:
> 
> On Fri, Mar 11, 2016 at 10:04:25AM +0000, Charles Keepax wrote:
> > On Fri, Mar 11, 2016 at 01:18:43PM +0530, Vinod Koul wrote:
> > > On Thu, Mar 10, 2016 at 10:44:51AM +0000, Charles Keepax wrote:
> > > > The soc_compr_pointer does not correctly pass any errors returned by the
> > > > driver callback back up the stack. This patch corrects this issue.
> > > 
> > > Should we do that :) I am not too sure. Pointer query is supposed to read
> > > the current value and return. You are trying to indicate that stream has
> > > gone bad which is not the same as read faced an error...
> > > 
> > > Also please use cover letter for these things to describe problem you are
> > > trying to solve.
> > 
> > Apologies for not doing so, I had been viewing this as more of a
> > simple oversight in the framework rather than a design choice.
> > 
> > The problem I am looking at is the DSP suffers an unrecoverable
> > error. We can find out about this error in our driver because the
> > DSP returns some error status to us.  This is fine if user-space
> > is doing a read as reads return error status back to user-space
> > so the user can find out that things have gone bad. However, if
> > user-space is doing an avail request there is no path for the
> > error to come back up to user-space. The pointer request returns
> > zero available data, so a read never happens and we basically
> > just end up sitting waiting for data on a stream that we know
> > full well has died.
> 
> So this confirms my hunch and we should then notify core of error by stopping
> the stream properly and then return error on poll/pointer query.
> 
> So cna try this untested patch, whcih includes a hack for stopped state. We
> don't seem to have a stopped state in ALSA, that bit would need refinement

In PCM, the stopped state is either SETUP/PREPARE or XRUN.


Takashi