[alsa-devel] How to report error in _pointer function?
tiwai at suse.de
Mon Aug 11 09:19:20 CEST 2008
At Fri, 08 Aug 2008 17:26:11 -0500,
Timur Tabi wrote:
> Takashi Iwai wrote:
> > So, the PCM status is properly changed to XRUN as expected. From the
> > driver perspective, everything must be fine.
> I've been debugging aplay. The main loop is function pcm_write(). It calls
> writei_func() which returns -EPIPE. This causes aplay to jump to xrun(), which
> attempts to recover.
> This is not what I want. I don't want to return overrun/underrun. I want to
> return failure. Returning XRUN is wrong.
> Instead, I need to take a look at this code I have:
> snd_pcm_stream_lock_irqsave(substream, flags);
> if (snd_pcm_running(substream))
> snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
> snd_pcm_stream_unlock_irqrestore(substream, flags);
> It's the call to snd_pcm_stop() that I don't like. There doesn't appear to be a
> SNDRV_PCM_STATE_xxx state that makes sense. This function should eventually
> bring me to snd_pcm_pre_stop(). But this function returns -EBADFD because the
> current state is RUNNING and not OPEN. Because it returns an error,
> snd_pcm_do_stop() is never called.
Hm? snd_pcm_pre_stop() returns -EBADFD if the stream *IS* OPEN.
If it's RUNNING, it will stop the stream and change the state.
> This doesn't make any sense to me. Why should I be able to stop a stream only
> if it's open but not running? If it's open, but not running, then there's
> nothing to stop! Can you explain the restriction in snd_pcm_pre_stop()?
If the state is OPEN, it means that the stream is already stopped.
Not sure which version you are referring, but I see no problem in the current code, at least...
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