F11: OSS and pulseaudio conflict

[Warren Togami]

I ran into an application yesterday that seemed to make pulseaudio
daemon fail.  After a lot of digging, someone else realized that this
application was actually using OSS output.  OSS currently grabs /dev/dsp
(provided by snd-pcm-oss), making it appear that pulseaudio has "failed".

OSS applications are so rare these days, I did not even consider that it
was using OSS.  This is likely to be a rare but repetitive source of
confusion in the future.

Removing snd-pcm-oss makes /dev/dsp disappear (which is a good thing).
Even with /dev/dsp gone, padsp wrapper allows an OSS app to output to
pulseaudio.  Only this isn't a good permanent solution because we do not
want LD_PRELOAD wrapping everything.

I think perhaps during F11 we should do the following:

1) alsa-plugins-pulseaudio seems to be the key package someone must
remove if they really want to disable pulseaudio on their system.  This
package could ship a /etc/modprobe.d/blacklist-oss file listing
snd-*-oss modules.  This way OSS comes back if pulseaudio is disabled.

2) If someone REALLY wants OSS mixed in their pulseaudio desktop, they
can use padsp.  This should be documented loudly in release notes.  This
is no different from F9 and F10.

3) Later make /dev/dsp redirection to pulseaudio permanent without LD
hacks with the proposed FUSD?  What is the status of this?

Warren Togami
wtogami at redhat.com