Re: [PATCH 00/18] RFC: Remove deprecated audio features

[Martin Kletzander]

On Mon, Apr 25, 2022 at 06:05:56PM +0100, Mark Cave-Ayland wrote:
> On 25/04/2022 09:21, Martin Kletzander wrote:
>
> > I wanted to deal with https://bugzilla.redhat.com/2043498 and I got a
> > suggesstion that removing deprecated features could actually make it
> > easier to propagate the error.  In the end (last patch) it turns out the
> > error is still just reported with error_fatal, so it probably is not
> > really needed, but I really wanted to dig into QEMU more and learn some
> > of the internals for quite some time now.  So I used the opportunity.
> > The one-liner ended up being an 18 patch series which was, for someone
> > who has just one commit in QEMU codebase, a pretty challenging task.
> > Although I tried my best to do things properly, I am not sure whether I
> > handled everything correctly, hence the RFC.
> >
> > Any comments are very much appreciated.  Thanks and have a nice day ;)
> >
> > Martin Kletzander (18):
> >    hw/audio: Remove -soundhw support
> >    hw/input/tsc210x: Extract common init code into new function
> >    hw/audio: Simplify hda audio init
> >    hw/audio/lm4549: Add errp error reporting to init function
> >    tests/qtest: Specify audiodev= and -audiodev
> >    ui/vnc: Require audiodev=
> >    Introduce machine's default-audiodev property
> >    audio: Add easy dummy audio initialiser
> >    hw/display/xlnx_dp.c: Add audiodev property
> >    hw/input/tsc210x.c: Support machine-default audiodev with fallback
> >    hw/arm: Support machine-default audiodev with fallback
> >    hw/ppc: Support machine-default audiodev with fallback
> >    audio: Make AUD_register_card fallible and require audiodev=
> >    audio: Require AudioState in AUD_add_capture
> >    audio: Be more strict during audio backend initialisation
> >    audio: Remove legacy audio environment variables and options
> >    audio: Remove unused can_be_default
> >    audio/spiceaudio: Fail initialisation when not using spice

[...]

> Thanks for the tidy-up! I'm not too familiar with the audio code, however one 
> thing I
> noticed is that in patch 11 you are using qdev_prop_set_string() to set the 
> audiodev
> for the machines.
>
> For CharDevs there already exists a qdev_prop_set_chr() function which is used 
> to
> assign the chardev backend to the device, so I'm wondering if it makes sense to 
> add a
> similar qdev_prop_set_audiodev() function in the same way? Then if the method of
> referencing the audiodev from the device ever changes from being a string 
> containing
> the name, it won't require updating all of the callers.

I guess that could be possible, but I'm not familiar with QEMU code much
and to be honest have no idea how I would go about doing that right now.

> Finally a quick glance at the tsc210x and lm4549 devices indicates that they are
> using global device _init() functions which shouldn't really be used in modern
> implementations. If you are interested in QOMify-ing these devices as part of 
> this
> work, then I can certainly help provide some pointers for getting started.

I thought about it for some devices.  Not all the devices I touched
here, because I feel like that would lead to a rabbit hole.  And 18
patches just because I wanted to error out in one condition was already
too much =)  But I'll be glad for any pointers on where to start and how
should I get to it.  Thanks.

> ATB,
>
> Mark.

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