Re: [PATCH v9 09/10] admin: conformance clauses

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

On Fri, Nov 25, 2022 at 12:42:23PM +0100, Cornelia Huck wrote:
> On Fri, Nov 25 2022, Jason Wang <jasowang@redhat.com> wrote:
> 
> > å 2022/11/24 16:36, Michael S. Tsirkin åé:
> >> On Thu, Nov 24, 2022 at 02:51:21PM +0800, Jason Wang wrote:
> >>> On Thu, Nov 24, 2022 at 5:08 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >>>> +The device MUST NOT fail a command solely because the buffers
> >>>> +provided are shorter or longer than described in this
> >>>> +specification.
> >>> I may miss something but how can it work if the buffer is shorter?
> >> driver does not care what's there.
> >>
> >> this is mostly for forward compatibility - we'll add more fields and
> >> I don't want to explain separately that old drivers post
> >> short buffers with less fields.
> >
> >
> > For example:
> >
> > The patch said:
> >
> > struct virtio_admin_cmd_list {
> >  ÂÂÂÂÂÂ /* Indicates which of the below fields were returned
> >  ÂÂÂÂÂÂ le32 device_admin_cmds[];
> > };
> >
> > Does it mean the query can still succeed even if there's no space for 
> > virtio_admin_cmd_list in the writable buffer?
> 
> Can we pick an absolute minimum length? All drivers need to be able to
> at least accommodate this one. Or is it ok for the driver to send a
> completely useless query that doesn't get any data back?

I think it might be a way to check that a group exists.

-- 
MST