[alsa-devel] ALSA Mixer issue

Jaroslav Kysela perex at perex.cz
Fri Jul 30 15:30:01 CEST 2010

On Fri, 30 Jul 2010, sudarshan bisht wrote:

> Hi ,
> I wanted to know that can we use multiple handlers for the same ALSA mixer ?
> My use case is something like this .
> I have two modules and having two different handlers for ALSA mixer.  First
> module does some volume change , and I try to read the latest volume using
> my second handler ( of first second module) .
> But I am not getting the most recent value in second handler ( the volume
> set by the first module )  so I feel there is some inconsistency when I use
> two handlers from two different modules in order to fetch volume information
> from the ALSA mixer.

You must sync the cached information using poll() or select() on file 
descriptors returned by snd_mixer_poll_descriptors_*() functions and call 
snd_mixer_handle_events() if any events are waiting.


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

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