Re: [edk2-devel] VirtIO sound device in qemu?

["Leif Lindholm" <leif@nuviainc.com>]

Hi Ethin,

Adapting and overcoming is very much the point of GSoC.
The purpose of this project was always to bring portable audio support
to EDK2, and longer-term the UEFI specification. Virtio was just the
ideal means to that end.

If it turns out not being the ideal way, that's just the way it is.
*But*, I want to point out that there is no reason why we couldn't
build this on top of a not-yet-upstream QEMU patchset - and help out
by providing an eager real consumer for it.
The virtio-snd RFC has been sent out, and it is very unlikely that it
will not end up being merged, if in a modified form from what the
first proof-of-concept looked like. Working with it would give you the
opportunity to influence that implementation, as well as the
virtio-snd standard.

*However*, if the state of the QEMU virtio-snd RFC is not one that
lends itself to basing other work on, then QEMU's usb-audio support is
a close second - that should also be portable to other
If we pick that route, you can always come back to virtio a bit later
if you make good progress on USB Audio Device Class 1.0.

/
    Leif

On Tue, Jun 08, 2021 at 13:52:14 -0500, Ethin Probst wrote:
> So I just might have to go with USB audio (the basic audio device
> class) since no code in QEMU for VirtIO audio has actually been
> committed upstream. Perusing the qemu code (specifically this:
> https://github.com/qemu/qemu/blob/master/hw/usb/dev-audio.c) it
> appears that Qemu implements v. 1.0 of the ADC specification. Section
> 5.3.3.1.2 of the USB basic audio device specification (v. 1.0)
> confirms that the bcdADC field should be set to 0100h. Will doing this
> violate any rules of GSoC or anything like that?
> I can implement VirtIO, but I will have no way of testing it until
> Qemu actually adds it in (unless there's another emulator that
> implements it). :-(
> 
> On 6/7/21, Leif Lindholm <leif@nuviainc.com> wrote:
> > On Mon, Jun 07, 2021 at 17:16:00 +0200, Laszlo Ersek wrote:
> >> On 06/07/21 13:40, Michael Brown wrote:
> >> > On 07/06/2021 05:41, Ethin Probst wrote:
> >> >> For my audio output protocol (I wonder if we should abbreviate it as
> >> >> AOP?) I need to get access to VirtIO devices in PCIe configuration
> >> >> space. However, I can't seem to find a way of telling QEMU to use this
> >> >> device for audio output. Is there something I missed, or something
> >> >> that does support this?
> >> >
> >> > Do you mean that you can't find a way to get QEMU to create a Virtio
> >> > audio device visible to the guest, or that you can't find a way to get
> >> > QEMU to connect this Virtio device to the host-side audio output?
> >>
> >> My latest (admittedly, quite old) information has been that QEMU does
> >> not implement a virtio-audio device yet. It's been work in progress.
> >> Best inquire on qemu-devel, CC'ing the audio subsys maintainers.
> >
> > An RFC sent out end of April has not yet seen a PATCH, but some
> > feedback:
> > https://lists.gnu.org/archive/html/qemu-devel/2021-04/msg06089.html
> >
> > /
> >     Leif
> >
> 
> 
> -- 
> Signed,
> Ethin D. Probst