Daniel P. Berrangé wrote:
> On Sat, Jul 18, 2020 at 04:31:16PM +0400, Roman Bogorodskiy wrote:
> > Extend <sound> device element to accept "soundDevice"
> > sub-element which allows to map guest sound device to host
> > sound device.
> >
> > Example
> >
> > <sound model='ich6'>
> > <soundDevice playback='/dev/dsp0' recording='/dev/dsp0'/>
> > </sound>
>
> IIUC, FreeBSD's audio subsystem is the classic OSS API ?
The sound(4) manpage[1] claims it supports most of the OSS ioctls().
>
> >
> > The "playback" attribute points to the playback device,
> > and "recording" attribute points to the recording device.
>
> I'm thinking about how we'll have to deal with QEMU's sound backend
> options, and alignment with BHyve / FreeBSD.
>
> In QEMU there are multiple backends, OSS, ALSA, PulseAudio, SPICE,
> VNC, and many more. The backends have many properties, and many
> of the properties can be set separately for input and output.
>
> IIUC, QEMU can expose multiple sound devices to the guest too.
>
> I think this means that we can have a M:N relationship between
> a sound device, and an audio backend, not just 1:1.
>
> Assuming I'm right about the M:N relationship, I assume that
> of multiple cards all do playback concurrently, something
> will have todo mixing of the streams ? How will that work
> with audio capture, is only one card allowed to capture at
> any time ?
In case of FreeBSD, the sound driver does mixing on its own, i.e.
you can boot multiple guests pointed to /dev/dsp0 and audio streams from
these guests will be played properly.
I didn't test capturing though.
> I'm copying Gerd to confirm the above...
>
> Anyway, if we have M:N relation, then we'll need separate
> configuration elements.
>
> So I think we'd need to allow something like this:
>
> <sound model='ich6'>
> <audio id="audio0"/>
> </sound>
>
> <sound model='ich6'>
> <audio id="audio1"/>
> </sound>
>
> <sound model='ich6'>
> <audio id="audio1"/>
> </sound>
>
> <audio type="oss" id="audio0">
> <input dev='/dev/dsp0'/>
> <output dev='/dev/dsp0'/>
> </audio>
>
> <audio type="spice" id="audio1"/>
>
>
> Here we have one sound device connected to OSS, and two sound
> devices connected to SPICE.
>
> >
> > Signed-off-by: Roman Bogorodskiy <bogorodskiy@xxxxxxxxx>
> > ---
> > docs/schemas/domaincommon.rng | 15 +++++++++++++++
> > src/conf/domain_conf.c | 24 ++++++++++++++++++++++++
> > src/conf/domain_conf.h | 3 +++
> > 3 files changed, 42 insertions(+)
> >
> > diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
> > index a810f569c6..b11b3f2af6 100644
> > --- a/docs/schemas/domaincommon.rng
> > +++ b/docs/schemas/domaincommon.rng
> > @@ -4346,6 +4346,18 @@
> > </attribute>
> > </element>
> > </define>
> > + <define name="soundDevice">
> > + <element name="soundDevice">
> > + <attribute name="playback">
> > + <text/>
> > + </attribute>
> > + <optional>
> > + <attribute name="recording">
> > + <text/>
> > + </attribute>
> > + </optional>
> > + </element>
> > + </define>
> > <define name="sound">
> > <element name="sound">
> > <attribute name="model">
> > @@ -4366,6 +4378,9 @@
> > <optional>
> > <ref name="address"/>
> > </optional>
> > + <optional>
> > + <ref name="soundDevice"/>
> > + </optional>
> > <zeroOrMore>
> > <ref name="codec"/>
> > </zeroOrMore>
> > diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> > index 7ecd2818b9..b678a2319d 100644
> > --- a/src/conf/domain_conf.c
> > +++ b/src/conf/domain_conf.c
> > @@ -2850,6 +2850,9 @@ void virDomainSoundDefFree(virDomainSoundDefPtr def)
> > virDomainSoundCodecDefFree(def->codecs[i]);
> > VIR_FREE(def->codecs);
> >
> > + VIR_FREE(def->playback);
> > + VIR_FREE(def->recording);
> > +
> > VIR_FREE(def);
> > }
> >
> > @@ -14984,6 +14987,8 @@ virDomainSoundDefParseXML(virDomainXMLOptionPtr xmlopt,
> > virDomainSoundDefPtr def;
> > VIR_XPATH_NODE_AUTORESTORE(ctxt);
> > g_autofree char *model = NULL;
> > + char *recording = NULL;
> > + xmlNodePtr soundDeviceNode;
> >
> > if (VIR_ALLOC(def) < 0)
> > return NULL;
> > @@ -15024,6 +15029,14 @@ virDomainSoundDefParseXML(virDomainXMLOptionPtr xmlopt,
> > }
> > }
> >
> > + soundDeviceNode = virXPathNode("./soundDevice", ctxt);
> > + if (soundDeviceNode) {
> > + def->playback = virXMLPropString(soundDeviceNode, "playback");
> > + recording = virXMLPropString(soundDeviceNode, "recording");
> > + if (recording)
> > + def->recording = recording;
> > + }
> > +
> > if (virDomainDeviceInfoParseXML(xmlopt, node, &def->info, flags) < 0)
> > goto error;
> >
> > @@ -15056,6 +15069,9 @@ virDomainSoundDefEquals(const virDomainSoundDef *a,
> > !virDomainDeviceInfoAddressIsEqual(&a->info, &b->info))
> > return false;
> >
> > + if ((a->playback != b->playback) || (a->recording != b->recording))
> > + return false;
> > +
> > return true;
> > }
> >
> > @@ -27284,6 +27300,14 @@ virDomainSoundDefFormat(virBufferPtr buf,
> > for (i = 0; i < def->ncodecs; i++)
> > virDomainSoundCodecDefFormat(&childBuf, def->codecs[i]);
> >
> > + if (def->playback) {
> > + virBufferAsprintf(&childBuf, "<soundDevice playback='%s'", def->playback);
> > + if (def->recording)
> > + virBufferAsprintf(&childBuf, " recording='%s'/>\n", def->recording);
> > + else
> > + virBufferAddLit(&childBuf, "/>\n");
> > + }
> > +
> > if (virDomainDeviceInfoFormat(&childBuf, &def->info, flags) < 0)
> > return -1;
> >
> > diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
> > index 241149af24..b501f48442 100644
> > --- a/src/conf/domain_conf.h
> > +++ b/src/conf/domain_conf.h
> > @@ -1415,6 +1415,9 @@ struct _virDomainSoundDef {
> >
> > size_t ncodecs;
> > virDomainSoundCodecDefPtr *codecs;
> > +
> > + char *playback;
> > + char *recording;
> > };
> >
> > typedef enum {
> > --
> > 2.27.0
> >
>
> Regards,
> Daniel
> --
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>
Roman Bogorodskiy
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