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

[Takashi Iwai]

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...

> When I play a file, my DMA controller is incorrectly programmed (test case) and 
> this function gets triggered.  The application (aplay) does not terminate.

The app is *not* terminated, of course, but it must get an error when
it accesses to the PCM (-EPIPE in the case XRUN).


Takashi