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

[Anthony Liguori <anthony@codemonkey.ws>]

On 01/31/2012 08:58 AM, Paolo Bonzini wrote:
> On 01/31/2012 03:51 PM, Jan Kiszka wrote:
>>> >
>>> > 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.
>> Well, that has two sides. We introduced properties to avoid this direct
>> messing.
>>
>> Does linking also work without exposing internals?
>
> Perhaps it doesn't need to expose internals. Just like we create interfaces
> automatically when creating a parent object, perhaps we can create children as
> well, like
>
> TypeInfo type_piix3 = {
> ...
> .children = {
> { "pic[0]", TYPE_I8259, offsetof(PIIX3, pic[0]) },
> { "pic[1]", TYPE_I8259, offsetof(PIIX3, pic[1]) },
> { "pit, TYPE_I8254, offsetof(PIIX3, pit) },
> { "rtc", TYPE_RTC, offsetof(PIIX3, rtc) },


Eeek.  I absolutely want to avoid any offset based interfaces.

You can just as well do:

void object_property_add_child(Object *obj, const char *name,
                                const char *type, Object **child);

It could then do:

*child = object_new(type);

Regards,

Anthony Liguori


> { }
> }
> }
>
> QOM's object_init would allocate a single malloced block for all of them, carve
> out space for the parent and all children, and add the properties.
>
> Paolo
>