Re: [Qemu-devel] [PATCH v7 08/25] x86-iommu: introduce parent class

[Jan Kiszka <jan.kiszka@web.de>]

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On 2016-05-23 23:48, Marcel Apfelbaum wrote:
> On 05/23/2016 08:06 PM, David Kiarie wrote:
>> On Tue, May 17, 2016 at 10:15 AM, Peter Xu <peterx@redhat.com> wrote:
>>> Introducing parent class for intel-iommu devices named "x86-iommu". This
>>> is preparation work to abstract shared functionalities out from Intel
>>> and AMD IOMMUs. Currently, only the parent class is introduced. It does
>>> nothing yet.
>>>
>>> Signed-off-by: Peter Xu <peterx@redhat.com>
>>> ---
>>>   hw/i386/Makefile.objs         |  2 +-
> 
> [...]
> 
>>> +
>>> +static const TypeInfo x86_iommu_info = {
>>> +    .name          = TYPE_X86_IOMMU_DEVICE,
>>> +    .parent        = TYPE_SYS_BUS_DEVICE,
>>> +    .instance_size = sizeof(X86IOMMUState),
>>> +    .class_init    = x86_iommu_class_init,
>>> +    .class_size    = sizeof(X86IOMMUClass),
>>> +    .abstract      = true,
>>> +};
>>
>> As I suspected am having some trouble parenting a PCI device from a
>> Bus device but I will investigate further to see if I can manage
>> something.
>>
> 
> You cannot derive from both SYS_BUS_DEVICE and PCI_DEVICE.
> You would need a composition; your device would be a SYS_BUS_DEVICE
> and its state would include a PCI_DEVICE (or the other way around).
> Then you can divide the responsibilities between them.

Given that the AMD IOMMU is more a platform than a PCI device, I would
also go for deriving from SYS_BUS_DEVICE (and later on a common x86
IOMMU class) and embedding a PCI_DEVICE. And the Intel IOMMU has no PCI
device feature at all.

Jan



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