Re: [PATCH v3 12/14] audio: forbid mixing default audiodev backend and -audiodev

[Paolo Bonzini]

On Fri, Sep 29, 2023 at 1:55 PM BALATON Zoltan <balaton@eik.bme.hu> wrote:
>
> On Fri, 29 Sep 2023, Paolo Bonzini wrote:
> > Now that all callers support setting an audiodev, forbid using the default
> > audiodev if any audiodev is defined on the command line.  To make the
> > detection easier make AUD_register_card() return false on error.
>
> So this means that now qemu-system-ppc -M pegasos2 -audiodev sdl,id=au
> will give an error saying that audiodev must be specified but does not say
> it should be set on the machine so users will not know, as oppsed to now
> just getting a warning but things still working

The plan is to extend -audio with -M audiodev= support, so you can use
"-M pegasos2" for the default backend or "-M pegasos2 -audio sdl" for a
specific one. I didn't include it yet because I also want to add support for
something like "-audio none", removing the current QEMU_AUDIO_DRV
special case that is needed by libqtest.

> This is not helpful. Why
> is this feature deprecated and what does removing bring that justifies
> this? Could we keep the more intuitive current behaviour and drop the
> deprecation instead unless removing this is needed for later patches as
> the current default handling is more convenient for command line users.

There's intuitivity, and there's behavior that is only intuitive if you are
used to it. For example, -audiodev is the only backend that does
something even if its id is never referenced. In that it's completely
different from -blockdev/-chardev and from -object backends.

The idea of this patch is that "-audiodev" means "opt out of all magic",
but I'll drop it for now and wait until I figure out how to handle "-audio"
without a model.

Paolo