[alsa-devel] 0 or EAGAIN from snd_pcm_update_avail()?

Jaroslav Kysela perex at perex.cz
Fri Apr 3 09:04:08 CEST 2009

On Thu, 2 Apr 2009, Ludovico Cavedon wrote:

> Hi all,
> if snd_pcm_update_avail() gets called on a PCM device in non-blocking
> mode when no data is availabe jet, what is the expected return value?
> -0
> -either is valid
> I am asking this question because pulseaudio expect to receive 0, but
> the the bluetooth headset pcm transfer callback returns EAGAIN, so I
> want to find out against whoms I should open a bug :)


-EAGAIN should be returned only for R/W operations but not for buffer 
position routines. They should return always immediatelly with 
useable value (thus EAGAIN does not make sense).


Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

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