Re: [Qemu-devel] [PATCH] virtio: make bindings typesafe

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Dec 17, 2012 at 10:13:11PM +0100, Andreas Färber wrote:
> Am 17.12.2012 21:48, schrieb Michael S. Tsirkin:
> > On Mon, Dec 17, 2012 at 07:25:08PM +0100, Andreas Färber wrote:
> >> Am 17.12.2012 19:21, schrieb Paolo Bonzini:
> >>> Il 17/12/2012 18:55, Andreas Färber ha scritto:
> >>>> Am 17.12.2012 16:45, schrieb Michael S. Tsirkin:
> >>>>> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> >>>>> index 3ea4140..63ae888 100644
> >>>>> --- a/hw/virtio-pci.c
> >>>>> +++ b/hw/virtio-pci.c
> >>>>> @@ -98,34 +98,34 @@ bool virtio_is_big_endian(void);
> >>>>>  
> >>>>>  /* virtio device */
> >>>>>  
> >>>>> -static void virtio_pci_notify(void *opaque, uint16_t vector)
> >>>>> +static void virtio_pci_notify(DeviceState *d, uint16_t vector)
> >>>>>  {
> >>>>> -    VirtIOPCIProxy *proxy = opaque;
> >>>>> +    VirtIOPCIProxy *proxy = container_of(d, VirtIOPCIProxy, pci_dev.qdev);
> >>>>
> >>>> Nack. This is going the wrong direction QOM-wise and you among all
> >>>> others know that from PCI host bridges!
> >>>
> >>> Well, that's just a difference of VIRTIO_PCI_PROXY(d) vs. container_of.
> >>
> >> VIRTIO_PCI_PROXY(d) would be acceptable, sure. But as-is this patch just
> >> pushes unnecessary work on Fred, me, you or anyone else who works with QOM.
> > 
> > What's VIRTIO_PCI_PROXY? Note this is data path we do not want extra
> > code.
> 
> My complaint is the direct access of pci_dev, qdev, etc. parent fields
> in many places as the main change of this patch. Those mean more places
> to touch in a future patch.
> 
> Use of any new-style macro hiding these - wherever the particular one
> suggested may be defined or whether it needs to be added - is better.
> 
> If performance of dynamic_cast is an issue - something I'd leave you to
> discuss with Anthony - you can just do a C cast directly. Just don't
> spread this qdev paradigm further please.
> 
> Regards,
> Andreas

OK so just

#define VIRTIO_PCI_PROXY(d) container_of(d, VirtIOPCIProxy, pci_dev.qdev)

is OK with you?


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