[alsa-devel] [PATCH 0/3] Fallback mechanism for pulse plugin

David Henningsson david.henningsson at canonical.com
Wed Sep 14 11:51:26 CEST 2011

On 09/13/2011 10:47 AM, Colin Guthrie wrote:
> 'Twas brillig, and Takashi Iwai at 13/09/11 08:55 did gyre and gimble:
>>> Yup I think so. I'll put this on my list (I did try and suggest
>>> something like this a while back, but got little in the way of responses
>>> - I wanted to standardise things rather than have distro hacks
>>> everywhere - can't seem to find the email now, so I'll just resend it
>>> when I have some time to think straight)
>> Yeah, we want to have some really easy way to check whether PA is
>> enabled or not.  For example, in the case of X11, you can check
>> $DISPLAY (or options are given explicitly) as a primary check.
> Yeah, but sadly I don't think this is possible. The Ubuntu solution for
> example works differently to yours. (Disclaimer, I've already said I
> think this is ugly). It works by altering the config file dynamically
> such that the default is either dmix or pulse depending on whether PA is
> running. Of course "PA is running" is a broken check in the first place
> (see the "ugly" word in my disclaimer!) as we could be dealing with thin
> clients and remote PA daemons only, in which case there is no running
> PA.

I think adding a function in libpulse named is_PA_enabled() makes sense, 
as discussed somewhere else in this thread. Once we have that, we should 
change "PA is running" to "file_exists(libpulse.so.x) && 
dlopen(libpulse.so.x) && is_PA_enabled()". Does that seem to be a 
reasonable solution?

Then the PulseAudio side of things can decide how to determine the 
result value of is_PA_enabled() - environment variables, client.conf and 
all that.

Other than that I haven't studied the current sysdefault proposal in 
detail, but the general comment is that the sound system configuration 
in Linux is complex enough :-)

David Henningsson, Canonical Ltd.

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