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Re: [libvirt] [PATCH] qemu: sound: Support intel 'hda' model



On Tue, Jan 11, 2011 at 09:58:42AM -0500, Cole Robinson wrote:
> On 01/11/2011 06:10 AM, Daniel P. Berrange wrote:
> > On Tue, Jan 11, 2011 at 11:46:14AM +0100, Gerd Hoffmann wrote:
> >> On 01/10/11 18:19, Cole Robinson wrote:
> >>> In QEMU, the card itself is a PCI device, but it requires
> >>> -device hda-output in order to actually get sound to the host. AIUI this
> >>> is just HDA configuration and does not require stable addressing, so
> >>> is not presently represented in the XML.
> >>
> >> It isn't that simple.  There are actually multiple devices involved.
> >> Each audio codec (yes, there can be multiple of these, up to 15) is
> >> connected via HDA Link to the pci controller.  Each audio codec has
> >> a codec address (HDA bus property: cad=[0..14]).
> >>
> >> So you can specify "-device intel-hda -device hda-duplex -device
> >> hda-output" and the guest has multiple audio devices.  Win7 even
> >> handles this correctly, whereas alsa uses only the first codec it
> >> finds (lowest codec address).  Not that this buys you much today,
> >> qemu mixes all channels together before sending them off to the
> >> hosts sound system, i.e. you don't see a stream per sound card in
> >> pulseaudio.  That might change in the future though.
> >>
> > 
> > So 'intel-hda' should really be considered as a controller,
> > and hda-output' & 'hda-duplex' are the things to be treated
> > as devices in the guest config.
> > 
> > This suggests a setup more like the one we did for virtio-serial
> > where we'd invent a new address type for codecs, and have XML
> > looking something like
> > 
> >     <controller type='hda' model='ich6'>
> >       <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>
> >     </controller>
> >     <sound model='hda-output'>
> >       <address type='hda' codec='0'/>
> >     </sound>
> >     <sound model='hda-duplex'>
> >       <address type='hda' codec='1'/>
> >     </sound>
> > 
> 
> Sounds good, though I think doing
> 
> <sound model='hda' mic="on|off"/>
> 
> would be preferable from a UI perspective, since it sounds like that's
> the only differentiating factor (or maybe use 'duplex' or 'input' etc.).
> Does that sound okay?

The problem with mic=on|off is that it only works for the
current case of choosing hda-output vs hda-duplex. It can't
cope with the scenario where QEMU adds more codecs, which
are unrelated to the microphone state, Gerd mentioned might
well happen

Regards,
Daniel


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