Re: [PATCH] qom: deprecate use of instance level properties

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Oct 14, 2026 at 10:05:01AM +0100, Mark Cave-Ayland wrote:
> On 13/10/2026 13:06, Daniel P. Berrangé wrote:
> 
> > Add API docs to object_property_(add/try_add/del) to recommend
> > use of class properties instead.
> > 
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > ---
> >   include/qom/object.h | 25 ++++++++++++++++++++++---
> >   1 file changed, 22 insertions(+), 3 deletions(-)
> > 
> > diff --git a/include/qom/object.h b/include/qom/object.h
> > index 4c0645817a5..d3fddb449f5 100644
> > --- a/include/qom/object.h
> > +++ b/include/qom/object.h
> > @@ -1171,6 +1171,16 @@ void object_unref(void *obj);
> >    * @opaque: an opaque pointer to pass to the callbacks for the property
> >    * @errp: pointer to error object
> >    *
> > + * Further use of this method is deprecated. Properties for an
> > + * object should be statically declared against the class, and
> > + * not be permitted to vary at runtime. Use the
> > + * object_class_property_add() method (and its variants) instead.
> > + *
> > + * If usage scenarios require differing subsets of properties
> > + * to be present, this should be handled by creating further
> > + * specialized subclasses instead of dynamically registering
> > + * properties against instances.
> > + *
> >    * Returns: The #ObjectProperty; this can be used to set the @resolve
> >    * callback for child and link properties.
> >    */
> > @@ -1183,9 +1193,6 @@ ObjectProperty *object_property_try_add(Object *obj, const char *name,
> >   /**
> >    * object_property_add:
> > - * Same as object_property_try_add() with @errp hardcoded to
> > - * &error_abort.
> > - *
> >    * @obj: the object to add a property to
> >    * @name: the name of the property.  This can contain any character except for
> >    *  a forward slash.  In general, you should use hyphens '-' instead of
> > @@ -1202,6 +1209,12 @@ ObjectProperty *object_property_try_add(Object *obj, const char *name,
> >    *   meant to allow a property to free its opaque upon object
> >    *   destruction.  This may be NULL.
> >    * @opaque: an opaque pointer to pass to the callbacks for the property
> > + *
> > + * Same as object_property_try_add() with @errp hardcoded to
> > + * &error_abort.
> > + *
> > + * Further use of this method is deprecated, see
> > + * object_property_try_add() for details.
> >    */
> >   ObjectProperty *object_property_add(Object *obj, const char *name,
> >                                       const char *type,
> > @@ -1210,6 +1223,12 @@ ObjectProperty *object_property_add(Object *obj, const char *name,
> >                                       ObjectPropertyRelease *release,
> >                                       void *opaque);
> > +/**
> > + * object_property_del:
> > + *
> > + * Further use of this method is deprecated, see
> > + * object_property_try_add() for details.
> > + */
> >   void object_property_del(Object *obj, const char *name);
> >   ObjectProperty *object_class_property_add(ObjectClass *klass, const char *name,
> 
> Looks good to me, and at least it means LLMs should pick up the recommended
> usage going forward. Do we also want to update checkpatch.pl to emit a
> warning if someone uses these legacy functions so that it gets flagged
> during local testing/CI too?

As long as we have piles of code still using the old instance level
APIs remaining to be converted, I think a checkpatch test will be
too annoying.

> Anyhow:
> Reviewed-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>

With regards,
Daniel
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