On Tue, Oct 08, 2013 at 02:53:26PM +0200, Cornelia Huck wrote:
> On Tue, 8 Oct 2013 15:26:38 +0300
> "Michael S. Tsirkin" <> wrote:
>
> > On Tue, Oct 08, 2013 at 02:16:06PM +0200, Cornelia Huck wrote:
> > > On Tue, 8 Oct 2013 15:12:39 +0300
> > > "Michael S. Tsirkin" <> wrote:
> > >
> > > > This reminds me - our use of the SenseID format for device
> > > > identification is not in the spec, is it?
> > > > We should probably add it - want to do this?
> > >
> > > I don't think there's a need to do so, as it is a standard channel
> > > command. Every control unit/device since 1973 supports it :)
> >
> > The format of the command is standard, yes.
> > But I really meant which virtio field goes into which field
> > and how does a driver match.
> >
> > Linux guest does: CCW_DEVICE(0x3832, 0)
> > so it ignores device type and model, and
> > matches controller model against virtio device ID.
> >
> > This really should be documented in spec - it's not good
> > that people need to look at guest code to write hypervisors.
>
> Ah, I see what you mean. It is already there in 2.3.3.1., but we could
> it more explicit:
>
> ===
>
> SenseID will return the following information for a virtio-ccw proxy
> device:
>
> ----------------------------------------------
> | control unit type | 0x3832 |
> |-----------------------|--------------------|
> | control unit model | <virtio device id> |
> |-----------------------|--------------------|
> | device type | zeroes (unset) |
> |-----------------------|--------------------|
> | device model | zeroes (unset) |
> |-----------------------|--------------------|
> | extended SenseId data | zeroes (unset) |
> ----------------------------------------------
>
> A driver for virtio-ccw devices should look for a control unit type of
> 0x3832 and ignore the device type.
>
> ===
>
> I think ignoring the device type is obvious, though.
I think it's a MUST, not a should, right?
It's not really obvious - if you just describe what hardware
does then drivers just think they can make assumptions.
If we want drivers to do something we really must write it
explicitly.
