Re: [PATCH RFC] virtio-spec: flexible configuration layout

Michael S. Tsirkin
2011-11-09T10:49:03Z

On Wed, Nov 09, 2011 at 12:26:08PM +0200, Sasha Levin wrote:
> On Wed, 2011-11-09 at 12:13 +0200, Michael S. Tsirkin wrote:
> > On Wed, Nov 09, 2011 at 10:46:06AM +0200, Sasha Levin wrote:
> > > The device initialization sequence might use an update as well.
> >
> > What is needed? Add an item where the driver scans the PCI capability
> > list to detect the layout?
>
> Yup, something similar like that - just to make it obvious.
>
> > > Maybe
> > > also a description of how device handles missing structure IDs.
> > >
> > > [snip]
> >
> > Hmm. I just have
> > 'Drivers should fall back on this legacy structure if a
> > Virtio Structure capability is missing in the PCI capability
> > list'.
> >
> > What else would be helpful? An example?
>
> I just remembered from your patch that you could define some structure
> IDs, but not necessarily all of them, if it's not longer the case then
> ignore me. If it is, then the scenario of a missing structure should be
> specified (For example, if the ISR structure wasn't defined, fall back
> to...).

Yes, this was the intent of the text above. I'll make that explicit.

> > > I'm not sure what capability length is, can't find it in the spec
> > > either.
> > >
> > > [snip]
> >
> > It's the legth of the vendor specific capability structure in bytes.
> > 'the byte immediately following the “Next”
> > pointer in the capability structure is defined to be a length field'
> > It's on page 330 in my copy.
>
> Right, I was looking only at the regular cap definition.
>
> --
>
> Sasha.