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

[Jaroslav Kysela]

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
> -EAGAIN
> -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 :)

0.

-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

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