[libvirt] [PATCH 3/6] qemu: explicitly disable audio if there is no sound device

[Peter Krempa]

On Tue, Nov 21, 2017 at 11:48:20 +0000, Daniel Berrange wrote:
> On Tue, Nov 21, 2017 at 12:44:44PM +0100, Peter Krempa wrote:
> > On Tue, Nov 21, 2017 at 11:24:06 +0000, Daniel Berrange wrote:
> > > IOW, I don't think this patch is desirable.
> > 
> > We could allow hotplug only if qemu will allow to specify the sound
> > output per-soundcard which would avoid this problem.
> 
> I agree that having ability to configure distinct outputs per sound card
> might be useful, I don't think it is a blocking feature for hotplugging
> sound cards. ie, there's no reason why a user should not be able to
> unplug their current sound card, and plug in a new sound card for a
> running guests - they would only ever have 1 sound card present at
> a time in that scenario, so distinct outputs is not a requirement
> for that usecase.

While not a requirement, mandating that new features are available only
with new software sometimes saves a lot of headaches. I would not
mind if sound device hotplug will be supported only when specific
outputs can be selected when adding the sound card and would not work
without that.

Unfortunately qemu does not yet support this and I don't think that they
will any soon.

Also code for outputting to pulseaudio does not get much love. I had to
fix it so that the virtual sound mixer does not mess with physical
michrophone volume setting in the host. And it was broken for years.

I agree that this patch could bite us though, given that I don't see
qemu fixing the sound backends soon as they did not do it until now.
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