Re: [Qemu-devel] [RFC 0/5] -object/object-add support custom location and 2nd stage initialization

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 10 Jan 2014 12:38:57 +0100
Paolo Bonzini <pbonzini@redhat.com> wrote:

> Il 10/01/2014 12:28, Igor Mammedov ha scritto:
> >> > Regarding the "overloading" of the realize name, I was against it in
> >> > previous discussion and I still am (I was in favor of something like
> >> > UserCreatable and naming the method "complete" or "construct"), but I
> >> > didn't want to sound too negative. :)
> > issue with naming interface as CommandLine or UserCreatable is that, it could
> > be used not only by CLI/user but also it could be used internally. For example
> > see "[PATCH 3/5] virtio_rng: use object_realize interface instead of calling
> > backend API", where default backend is created by frontend.
> 
> I see.  Yes, with something like UserCreatable, you would not have that
I'm not sure why I wouldn't have that path. It does exactly what you've
just written vvv,

> patch.  Instead, UserCreatable's complete method would redirect to the
> backend-specific API.
i.e. it calls  cast<UserCreatable>(default_rng).complete() which
redirects to backend specific API, where UserCreatable.complete()
is rng_backend_realize()

> 
> BTW, note that UserCreatable's complete method should take a
> UserCreatable (or whatever the name is) as the first parameter, not an
> Object.  This would affect that patch, too.
It does, 'void (*realize)(ObjectRealizeInterface *obj, Error **errp);'

call_object_realize_interface(Object *obj,...) is a wrapper
that reduces casting code duplication at call sites since it's used
at more then 1 place.

> 
> > how about naming it for what it is: object-2nd-stage-init
> 
> That would also work for me (TwoStageConstructable or something like that).
> 
> One advantage of UserCreatable is that -object/object_add could check
> for it and reject creation of objects that are not meant for
> command-line instantiation.  You could do the same for
> TwoStageConstructable, but it would look weird to define an object as
> two-stage constructable with an empty complete method.
> 
> With a name like UserCreatable, instead, it would be quite natural to do
> this:
> 
> void user_creatable_complete(UserCreatable *uc, Error **errp)
> {
>     UserCreatableClass *ucc = USER_CREATABLE_GET_CLASS(uc);
>     if (ucc->complete) {
>         ucc->complete(uc, errp);
>     }
> }
> 
> > neutral object-complementary-interface that could be extended later with
> > another methods
> 
> No, we don't want a hodge-podge interface that's basically UserCreatable
> except in the name. :)
I'm fine with UserCreatable, lets wait couple days if there is no objection
or another suggestions and I'll then respin series.

> 
> Paolo