Re: [PATCH v3 19/35] audio: register and unregister vmstate with AudioState

[Peter Xu <peterx@redhat.com>]

On Wed, Oct 29, 2025 at 10:42:00PM +0100, Philippe Mathieu-Daudé wrote:
> On 29/10/25 20:00, Marc-André Lureau wrote:
> > Hi
> > 
> > On Wed, Oct 29, 2025 at 5:51 PM Philippe Mathieu-Daudé
> > <philmd@linaro.org> wrote:
> > > 
> > > On 27/10/25 16:10, marcandre.lureau@redhat.com wrote:
> > > > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> > > > 
> > > > Proper lifecycle management with QOM state.
> > > > 
> > > > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > > > ---
> > > >    audio/audio.c | 7 ++++++-
> > > >    1 file changed, 6 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/audio/audio.c b/audio/audio.c
> > > > index 4c3c3fd52f..853930bb48 100644
> > > > --- a/audio/audio.c
> > > > +++ b/audio/audio.c
> > > > @@ -1614,6 +1614,8 @@ static void audio_vm_change_state_handler (void *opaque, bool running,
> > > >        audio_reset_timer (s);
> > > >    }
> > > > 
> > > > +static const VMStateDescription vmstate_audio;
> > > > +
> > > >    static void audio_state_init(Object *obj)
> > > >    {
> > > >        AudioState *s = AUDIO_STATE(obj);
> > > > @@ -1625,6 +1627,8 @@ static void audio_state_init(Object *obj)
> > > > 
> > > >        s->vmse = qemu_add_vm_change_state_handler(audio_vm_change_state_handler, s);
> > > >        assert(s->vmse != NULL);
> > > > +
> > > > +    vmstate_register_any(NULL, &vmstate_audio, s);
> > > 
> > > Please avoid legacy APIs:
> > > 
> > > /**
> > >    * vmstate_register_any() - legacy function to register state
> > >    * serialisation description and let the function choose the id
> > >    *
> > >    * New code shouldn't be using this function as QOM-ified devices have
> > >    * dc->vmsd to store the serialisation description.
> > >    *
> > >    * Returns: 0 on success, -1 on failure
> > >    */
> > > 
> > 
> > qdev/Device have vmsd, but not plain Object (or legacy code without object).
> 
> Hmm right. Cc'ing Peter & Fabiano.

Thanks, yeah this looks fine when it was already there.

When looking at it, what's interesting is vmstate_audio is actually empty..

Explanation in da77adbaf61, since 2021.  Maybe we could drop it completely
at some point as I know we start to deprecate machines over 6(?)  years.
But I don't know when is proper.

We also hit similar issue with TAP device where there was a demand to add
compat properties to TAP however it was not a qdev, hence it cannot use
compat properties mechanism..  I wonder if these devices will be (at some
point) be converted to be type device.

-- 
Peter Xu