Re: [Qemu-devel] Can we improve virtio data structures with QOM?

[Anthony Liguori]

On 06/01/2012 12:48 AM, Markus Armbruster wrote:
> Anthony Liguori<address@hidden>  writes:
>
> [On how to model virtio devices in QOM:]
> > Basically, it should look like:
> >
> > VirtioPCIDevice is-a PCIDevice
> >
> > VirtioPCIDevice has-a link<VirtioDevice>
>
> Could you explain why this is link<>  and not child<>?

So you can do:

qemu -device virtio-pci,id=foo,vdev=bar -device virtio-blk,id=bar,bus=foo

The alternative would be:

qemu -device virtio-pci,id=foo,child_type=virtio-blk

But that feels ugly to me.  If you want to have a variable type of device, a 
link is the right tool.

BTW, I make no mention of BusState here.  That's intentional.  There's no need 
to involve buses IMHO.

Regards,

Anthony Liguori

> > VirtioDevice is-a DeviceState
> >
> > VirtioBlk is-a VirtioDevice
> > VirtioNet is-a VirtioDevice
> > ...
> >
> > VirtioPCIBlk is-a VirtioPCIDevice
> > VirtioPCIBlk has-a child<VirtioBlk>
> >
> > This gives us backwards compat while also providing a cleaner
> > model. VirtioPCIBlk et al would be deprecated eventually (but not any
> > time soon).