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

[Paolo Bonzini <pbonzini@redhat.com>]

Il 10/01/2014 15:44, Igor Mammedov ha scritto:
> 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,

You're right, I misremembered.

>> 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.

This is needed only because you allow creating objects that do not have
ObjectRealizeInterface.  With a UserCreatable interface, the dynamic
cast would be in vl.c and qmp.c (to check whether the user is actually
allowed to use -object on that device) and there's no duplication at the
call sites of the 2nd-stage init method.

> I'm fine with UserCreatable, lets wait couple days if there is no objection
> or another suggestions and I'll then respin series.

Thanks!

Paolo