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

[Jaroslav Kysela]

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.

						Jaroslav

-----
Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project