[alsa-devel] Is there a function I can call from my ISR to tell ALSA to abort playback?

[Takashi Iwai]

At Fri, 16 Nov 2007 11:41:51 +0100 (CET),
Jaroslav Kysela wrote:
> 
> On Fri, 16 Nov 2007, Takashi Iwai wrote:
> 
> > At Thu, 15 Nov 2007 14:28:14 -0600,
> > Timur Tabi wrote:
> > > 
> > > Takashi Iwai wrote:
> > > > At Thu, 15 Nov 2007 09:00:54 -0600,
> > > > Timur Tabi wrote:
> > > >> Jaroslav Kysela wrote:
> > > >>
> > > >>> Yes, call snd_pcm_stop() function. The call must be protected with 
> > > >>> snd_pcm_stream_lock... See to i2c/other/ak4117.c for an example.
> > > >> That code calls snd_pcm_stop() from a timer, not an ISR.  Do I need the call to 
> > > >> wake_up() as well?
> > > > 
> > > > snd_pcm_stop() can be called from ISR, too (e.g.
> > > > snd_pcm_period_elapsed() may call snd_pcm_stop() when XRUN occurs).
> > > > You only need to protect it via snd_pcm_stream_lock*().
> > > 
> > > It doesn't seem to do much.  Here's the function I wrote:
> > > 
> > > static void fsl_dma_abort_stream(struct snd_pcm_substream *substream)
> > > {
> > > 	unsigned long flags;
> > > 
> > > 	snd_pcm_stream_lock_irqsave(substream, flags);
> > > 	if (snd_pcm_running(substream)) {
> > > 		snd_pcm_stop(substream, SNDRV_PCM_STATE_DRAINING);
> > 
> > You passed a wrong state.  Usually snd_pcm_stop() passes either
> > SNDRV_PCM_STATE_SETUP (for post-draining) or SNDRV_PCM_STATE_XRUN (for
> > errors).
> > 
> > > 		wake_up(&substream->runtime->sleep);
> > > 	}
> > > 	snd_pcm_stream_unlock_irqrestore(substream, flags);
> > > }
> > 
> > This wake_up is superfluous.  Now I understand your question in the
> > last mail...
> 
> I'm not sure if the wake call is superfluous, if driver ends to call 
> elapsed callbacks, there is no way to wakeup process when it sleeps 
> somewhere. I think that code might be covered with a nice macro with a 
> name like 'snd_pcm_hw_stopped()' or so.

But wake_up() is already in snd_pcm_post_stop().  How can this second
call help?


thanks,

Takashi