Re: [PATCH 34/36] machine: Use DEFINE_PROP_STRING for string properties

[Eduardo Habkost]

On Fri, Oct 30, 2020 at 09:41:46PM +0100, Paolo Bonzini wrote:
> Il ven 30 ott 2020, 21:03 Eduardo Habkost <ehabkost@redhat.com> ha scritto:
> 
> > >     OBJECT_CLASS_PROPERTY_ADD_STR(oc, MachineState, kernel_filename,
> > >                                   "kernel", prop_allow_set_always);
> >
> > I like the idea of having an interface like this, but I would
> > like to avoid having to write even more boilerplate for each
> > property type to make this work.
> >
> > What would you think of:
> >    OBJECT_CLASS_PROPERTY_ADD(oc,
> >        PROP_STRING("kernel", MachineState, kernel_filename),
> >        prop_allow_set_always);
> >
> > Then we could make the same PROP_STRING macro usable both as
> > object_class_property_add_static() argument and as initializer
> > for existing static Property arrays.
> >
> 
> The name should be an argument to OBJECT_CLASS_PROPERTY_ADD though (which
> could be a function and not  macro; perhaps
> object_class_property_add_field?). PROP_STRING would be
> DEFINE_PROP_STRING(NULL, etc.) and would not be entirely reusable in
> Property arrays.
> 
> But even with that snag I agree with your less-boilerplate argument against
> my proposal.
> 
> Since most if not all device properties would have to specify the same
> allow-set function, we would end up defining more macros
> DEVICE_CLASS_PROPERTY_ADD_STR, and so on. If the Property isbpassed a
> struct, instead, we can define just one wrapper
> device_class_property_add_field.
> 
> So what about:
> 
> 1) add new constructors without the DEFINE prefix and without the name
> argument
> 
> 2) add object_class_property_add_field
> 
> And later:
> 
> 3) add device_class_property_add_field and remove dc->props
> 
> 4) remove the name field from Property.

Sounds good, and I like the "field property" name.  It is more
descriptive than "static property".

-- 
Eduardo