Re: [Qemu-devel] [PATCH 06/15] piix: create i8254 through composition

[Anthony Liguori]

On 01/31/2012 08:34 AM, Jan Kiszka wrote:
> On 2012-01-26 20:00, Anthony Liguori wrote:
> > @@ -548,6 +550,13 @@ static int piix3_realize(PCIDevice *dev)
> >       /* Setup the RTC IRQ */
> >       s->rtc.irq = rtc_irq;
> >
> > +    /* Realize the PIT */
> > +    qdev_set_parent_bus(DEVICE(&s->pit), BUS(s->bus));
> > +    qdev_init_nofail(DEVICE(&s->pit));
> > +
> > +    /* FIXME this should be refactored */
> > +    pcspk_init(ISA_DEVICE(&s->pit));
>
> Fixing ATM, ie. converting to qdev/QOM.
>
> Q: How do I use qdev_property_add_link&  Co. to establish the relation
> from the speaker port device to the PIT?

In the state structure, have:

struct PCSpkState {
    ...
    PITState *pit;
};

In the pcspk instance_init, do:

object_property_add_link(obj, "pit", TYPE_PIT, (Object **)&s->pit, NULL);

In the pcspk realize function (DeviceClass::init), do:

assert(s->pit != NULL); // make sure the pit link is set

And that's it.

You can set the s->pit field directly.  You are not required to use any special 
QOM function to interact with link properties.

BTW, this is yet another benefit of making structures public.  You can take the 
address of a child and set link fields directly without accessors.

Regards,

Anthony LIguori

> Jan