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Date: Tue, 31 Jan 2012 15:51:55 +0100
From: Jan Kiszka <jan.kiszka@siemens.com>
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	<4F27FBE6.7040800@siemens.com> <4F27FEFD.5070507@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH 06/15] piix: create i8254 through
	composition
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Peter Maydell <peter.maydell@linaro.org>, Anthony Liguori <aliguori@us.ibm.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Markus Armbruster <armbru@redhat.com>, Avi Kivity <avi@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>

On 2012-01-31 15:47, Anthony Liguori wrote:
> 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.

Well, that has two sides. We introduced properties to avoid this direct
messing.

Does linking also work without exposing internals?

Jan

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