Is there a function I can call from my ISR to tell ALSA to abort playback?

Is there a function I can call from my ISR to tell ALSA to abort playback?

[Timur Tabi]

In my ISR, I call snd_pcm_period_elapsed() to tell it that a period has elapsed. 
  I can also detect if playback has aborted for some reason (e.g. DMA controller 
has died).  Is there a function I can call in my ISR to tell ALSA to abort 
playback or capture?

-- 
Timur Tabi
Linux kernel developer at Freescale

Re: Is there a function I can call from my ISR to tell ALSA to abort playback?

[Jaroslav Kysela]

On Wed, 14 Nov 2007, Timur Tabi wrote:

> In my ISR, I call snd_pcm_period_elapsed() to tell it that a period has 
> elapsed.
>   I can also detect if playback has aborted for some reason (e.g. DMA 
> controller has died).  Is there a function I can call in my ISR to tell 
> ALSA to abort playback or capture?

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.

						Jaroslav

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

Re: Is there a function I can call from my ISR to tell ALSA to abort playback?

[Takashi Iwai]

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*().


Takashi

Re: Is there a function I can call from my ISR to tell ALSA to abort playback?

[Timur Tabi]

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?

-- 
Timur Tabi
Linux kernel developer at Freescale

Re: Is there a function I can call from my ISR to tell ALSA to abort playback?

[Timur Tabi]

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);
		wake_up(&substream->runtime->sleep);
	}
	snd_pcm_stream_unlock_irqrestore(substream, flags);
}

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

I tried it with the wake_up() call, but it didn't make a difference.

-- 
Timur Tabi
Linux kernel developer at Freescale

Re: 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

Re: 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@perex.cz>
Linux Kernel Sound Maintainer
ALSA Project

Re: 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

Re: 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 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?

Overlooked. Thanks.

					Jaroslav

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