[alsa-devel] [PATCH] ALSA: compress: Make sure we trigger STOP before closing the stream.

[Vinod Koul]

On Mon, Sep 23, 2013 at 11:19:39AM +0100, Liam Girdwood wrote:
> On Thu, 2013-09-19 at 18:43 +0200, Takashi Iwai wrote:
> > At Mon, 16 Sep 2013 12:01:23 +0100,
> > Liam Girdwood wrote:
> > > 
> > > On Mon, 2013-09-16 at 09:27 +0530, Vinod Koul wrote:
> > > > On Fri, Sep 13, 2013 at 05:43:16PM +0100, Liam Girdwood wrote:
> > > > > Currently we assume that userspace will shut down the compressed stream
> > > > > correctly. However, if userspcae dies (e.g. cplay & ctrl-C) we dont
> > > > > stop the stream before freeing it.
> > > > > 
> > > > > This now checks that the stream is stopped before freeing.
> > > > > 
> > > > > Signed-off-by: Liam Girdwood <liam.r.girdwood at linux.intel.com>
> > > > > ---
> > > > >  sound/core/compress_offload.c | 12 ++++++++++++
> > > > >  1 file changed, 12 insertions(+)
> > > > > 
> > > > > diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
> > > > > index 99db892..a9ae4f3 100644
> > > > > --- a/sound/core/compress_offload.c
> > > > > +++ b/sound/core/compress_offload.c
> > > > > @@ -139,6 +139,18 @@ static int snd_compr_open(struct inode *inode, struct file *f)
> > > > >  static int snd_compr_free(struct inode *inode, struct file *f)
> > > > >  {
> > > > >  	struct snd_compr_file *data = f->private_data;
> > > > > +	struct snd_compr_runtime *runtime = data->stream.runtime;
> > > > > +
> > > > > +	switch (runtime->state) {
> > > > > +	case SNDRV_PCM_STATE_RUNNING:
> > > > > +	case SNDRV_PCM_STATE_DRAINING:
> > > > > +	case SNDRV_PCM_STATE_PAUSED:
> > > > > +		data->stream.ops->trigger(&data->stream, SNDRV_PCM_TRIGGER_STOP);
> > > > when usermode dies the free will get invoked as we have below. The free is a
> > > > valid trigger from any state. So shouldnt the DSP then STOP the DMAs and free
> > > > the streams.
> > > 
> > > This means that the compressed stream ops don't follow the PCM ops wrt
> > > trigger() sequencing (i.e. we have to add extra logic in free to deal
> > > with this difference).
> > > 
> > > I think it would be better to follow the PCM operations use case here as
> > > it simplifies the driver code and stops people making the false
> > > assumption that trigger() works the same way throughout ALSA ?   
> > 
> > Well, the trigger of compress API has a few more jobs than PCM,
> > and it's exactly what should be fixed (e.g. the proper handling of
> > drain).  We need a bit more consensus over that.
Drain handling would be different, I am working on taht way, havent been able to
get the time it needs...

> > So, I didn't apply this patch yet.  If Vinod is happy with this (even
> > as a temporary solution), let me know.
Sorry my bad, your and Liam mail went to some other folder due to my bad rules
set. Sorry for not reverting earlier..
> 
> Without this patch we have the two different sequences for shutdown
> depending on whether userspace dies or not. i.e.
> 
> 1) Normal: trigger(start) -> play -> trigger(stop) -> close()
> 
> 2) ctrl-C: trigger(start) -> play -> ctrl-C -> close() 
> 
> So we miss out the trigger(STOP) and close the device with the stream
> still in a trigger running state.
my point was since we have DSPs we can let DSP internally treat free in not
stopped cases as goto stop and then free. We do this way in our DSPs and save us
a cmd to be sent. Above way though fine will just add that cmd.

The patch is okay but only argument i had was that we can save one cmd since we
have a DSP. Am okay if we have this too..

~Vinod

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