Re: [PATCH 3/3] hw/acpi/cpu_hotplug: Convert 'Object *device' -> 'DeviceState *parent'

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 28/2/23 23:09, Michael S. Tsirkin wrote:
> On Tue, Feb 28, 2023 at 11:05:24PM +0100, Philippe Mathieu-Daudé wrote:
>> On 28/2/23 22:41, Michael S. Tsirkin wrote:
>>> On Fri, Feb 03, 2023 at 05:30:21PM +0100, Philippe Mathieu-Daudé wrote:
>>>> ACPI CPU hotplug parent can't be any QOM object, it must be a QDev.
>>>> Convert AcpiCpuHotplug::device field as QDev to enforce this.
>>>> Rename 'owner' and 'device' variables as 'parent'.
>>>>
>>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>>>
>>>
>>> So instead of plain gpe->device we now have OBJECT all over
>>> the place. Why is this an improvement?
>>
>>  From QOM PoV, in this prototype change:
>>
>>    void legacy_acpi_cpu_hotplug_init(MemoryRegion *container,
>> - Object *owner,
>> + DeviceState *parent,
>>
>> we promote the parent/owner argument from generic Object to
>> Device, which is more restrictive.
>>
>> Thus now you can not pass any QOM object, it has to be a QDev.
> 
> None of the functions really seem to care what kind of object
> they get. Anything that results in less casting is a win
> in my book. More casting - a loss.

OK we are discussing QOM design then. I'll go back to this
in a future RFC. Sorry for having wasted your time meanwhile.