[Qemu-devel] Re: [PATCH] piix: use pci_config_set_prog_interface()

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

On Wed, Dec 29, 2010 at 11:26:32AM +0100, Sebastian Herbszt wrote:
> Michael S. Tsirkin wrote:
> >On Tue, Dec 28, 2010 at 07:48:23PM +0100, Sebastian Herbszt wrote:
> >>Michael S. Tsirkin wrote:
> >>>On Tue, Dec 28, 2010 at 05:24:06PM +0100, Sebastian Herbszt wrote:
> >>>>Michael S. Tsirkin wrote:
> >>>>>On Mon, Dec 20, 2010 at 10:18:01PM +0100, Sebastian Herbszt wrote:
> >>>>>>Use pci_config_set_prog_interface().
> >>>>>>
> >>>>>>Signed-off-by: Sebastian Herbszt <herbszt@gmx.de>
> >>>>>
> >>>>>Since I was asked explicitly - I don't have a problem
> >>>>>with these changes: both class and prog interface.
> >>>>>However, they aren't all that useful in themselves.
> >>>>>
> >>>>>For class, what I would like to see is a system where
> >>>>>the device class is put in the qdev info table,
> >>>>>and where -device ?
> >>>>>(and hopefully the legacy -help, -nic etc as well)
> >>>>>use this information.
> >>>>
> >>>>I am not sure if you mean something like the patch below.
> >>>
> >>>Not exactly
> >>>
> >>>- I'd like to keep the pci_config_set_class in the devices,
> >>> just make it do an assert.
> >>
> >>Assert on which condition?
> >
> >That PCI class matches device type defined in qdev.
> >This will serve to verify that all devices are converted properly.
> >
> >>>- Nics already have DEFINE_NIC_PROPERTIES - can this be used somehow?
> >>> Same for other devices ...
> >>
> >>We got DEFINE_NIC_PROPERTIES and DEFINE_BLOCK_PROPERTIES.
> >>Something like DEFINE_PCI_PROPERTIES could be introduced, but i am not sure
> >
> >This shouldn't have to do anything with PCI.
> >We should define the device type as NIC,
> >PCI class can be derived from that.
> 
> So you want to introduce a device property like "device_type" and set it to "NIC" and
> then translate "NIC" to the correct PCI class code. Are you sure this is unambiguous?
> "NIC" could be ethernet or token ring. A generic name like "HBA" could translate to even
> more codes (scsi, ide, raid, sata, ...).
> 
> >>which device properties it should hold (vendor_id, device_id, class, etc?).
> >>Those will then be user-modifiable with e.g. -device e1000,pci_class=1234.
> >>
> >>Sebastian
> >
> >Why is this helpful?
> >- tweaking class will just break guests
> >- binary representation is unfriendly, let's not require users to read
> > pci spec just to run qemu.
> 
> "pci_class" is optional.
> I just wanted to show that qdev device properties are
> user-modifiable and i didn't find a way to prevent this.

Ah, ok.
I think properties starting with x- are internal.
It's a kind of undocumented thing.

-- 
MST