Re: [Qemu-devel] [PATCH for-next v2 01/22] object: Add OBJECT_GET_PARENT_CLASS() macro

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 08/06/2013 06:33 PM, Andreas Färber wrote:
> Am 06.08.2013 07:54, schrieb Alexey Kardashevskiy:
>> On 08/01/2013 12:17 PM, Andreas Färber wrote:
>>> The object argument is currently unused and may be used to optimize the
>>> class lookup when needed.
>>>
>>> Inspired-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
>>> Signed-off-by: Andreas Färber <afaerber@suse.de>
>>> ---
>>>  include/qom/object.h | 10 ++++++++++
>>>  1 file changed, 10 insertions(+)
>>>
>>> diff --git a/include/qom/object.h b/include/qom/object.h
>>> index 23fc048..a8e71dc 100644
>>> --- a/include/qom/object.h
>>> +++ b/include/qom/object.h
>>> @@ -511,6 +511,16 @@ struct TypeInfo
>>>      OBJECT_CLASS_CHECK(class, object_get_class(OBJECT(obj)), name)
>>>  
>>>  /**
>>> + * OBJECT_GET_PARENT_CLASS:
>>> + * @obj: The object to obtain the parent class for.
>>> + * @name: The QOM typename of @obj.
>>> + *
>>> + * Returns the parent class for a given object of a specific class.
>>> + */
>>> +#define OBJECT_GET_PARENT_CLASS(obj, name) \
>>> +    object_class_get_parent(object_class_by_name(name))
>>> +
>>> +/**
>>>   * InterfaceInfo:
>>>   * @type: The name of the interface.
>>>   *
>>>
>>
>> Has anyone ever tried to use this macro?
> 
> Since you're asking me, obviously later in this virtio series it's used
> and in the IndustryPack series as well.
> 
> I'm not aware of anyone else having used it yet - I'm still waiting for
> review feedback from Peter Cr. and/or Anthony (or you!) before I put it
> on qom-next.


Still do not understand what "obj" is doing here.
This what I would suggest:

#define OBJECT_GET_PARENT_CLASS(obj, name) \
    object_class_get_parent(OBJECT_GET_CLASS(ObjectClass, (obj), (name)))

@name here is just to make sure we are at the right level of the class
hierarchy.

And use it like this:

static void xics_kvm_cpu_setup(XICSState *icp, PowerPCCPU *cpu)
{
    XICSStateClass *xsc = XICS_COMMON_CLASS(
		OBJECT_GET_PARENT_CLASS(OBJECT(icp), TYPE_KVM_XICS));
...

Here both source and destination classes are checked, everyone must be happy :)


-- 
Alexey