Re: [Qemu-devel] [PATCH v4 4/8] bcm2835_peripherals: add rollup device for bcm2835 peripherals

[Andrew Baumann]

> From: Peter Crosthwaite [mailto:address@hidden
> Sent: Monday, 25 January 2016 22:14
> 
> On Fri, Jan 15, 2016 at 3:58 PM, Andrew Baumann
> <address@hidden> wrote:
[...]
> > +static void bcm2835_peripherals_init(Object *obj)
> > +{
> > +    BCM2835PeripheralState *s = BCM2835_PERIPHERALS(obj);
> > +
> > +    /* Memory region for peripheral devices, which we export to our
> parent */
> > +    memory_region_init_io(&s->peri_mr, obj, NULL, s, "bcm2835-
> peripherals",
> > +                          0x1000000);
> 
> Should this just be normal memory_region_init?

I think so -- it's just a container region, and I probably copy and pasted the 
API here. The two MR init APIs seem almost but not-quite identical when NULL 
callbacks are used. Can you briefly explain the difference?

> > +    object_property_add_child(obj, "peripheral-io", OBJECT(&s->peri_mr),
> NULL);
> 
> This seems like a weird parenting, to have the SoC as child to an
> object it just created. Is the problem you need a parent before others
> can parent to you?

I'm confused by this question: Unless I'm mistaken, the parent here is 
BCM2835PeripheralState, the child is the new memory region we just called init 
on.

Thanks,
Andrew