Re: snd_pcm_drain() always fails

[Takashi Iwai <tiwai@suse.de>]

At Mon, 1 Aug 2005 20:10:15 +0200,
Hynek Hanke wrote:
> 
> > Nothing. If drain() is supposed to wait until all data are played and 
> > you're using the non-blocking mode, then it's definitely an error (thus 
> > -EAGAIN is returned - and it means from the driver perspective - I must 
> > wait and the application does not want this from me).
> 
> The documentation is very unclear about this. My guess was that it should bring
> me to the state DRAINING which should remain until all frames are played.

Patches are always welcome :)

> > Set the blocking mode before drain() is called (and return the mode back 
> > after it, if you want).
> 
> This is not possible. I'm using the non-blocking mode and poll() specifically
> because I need to receive external events (not comming from ALSA) too.
> 
> > The better way might be setting sw_params to wakeup app after all frames are
> > played and use the standard poll() call to wait in app.  
> 
> How can I do this or where can I read about it? I still need to receive those
> external events on other file descriptors. Is it possible with this approach?

Set avail_min swparams to the buffer size so that poll() won't return
unless the full buffer size becomes free (i.e. all samples are
played).  If stop_threshold is set to buffer size, the pcm stream will
be stopped automatically and set to XRUN state.


Takashi


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