Re: [Xen-devel] [PATCH 2/3] xen/kbdif: Add unique input device identifier

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Jun 07, 2018 at 04:40:48PM +0300, Oleksandr Andrushchenko wrote:
> On 06/07/2018 04:28 PM, Konrad Rzeszutek Wilk wrote:
> > On Wed, May 23, 2018 at 09:19:22AM +0300, Oleksandr Andrushchenko wrote:
> > > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> > > 
> > > If frontend is configured to expose multiple input device instances
> > > then backend may require a way to uniquely identify concrete input
> > > device within the frontend. This is useful for use-cases where
> > > virtual input device needs to be matched to physical input device.
> > > Add XenBus "unique-id" node parameter, so this sort of use-cases can
> > > be implemented.
> > > 
> > > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> > > ---
> > >   xen/include/public/io/kbdif.h | 10 ++++++++++
> > >   1 file changed, 10 insertions(+)
> > > 
> > > diff --git a/xen/include/public/io/kbdif.h b/xen/include/public/io/kbdif.h
> > > index a68da0f1a37f..45e4ff5b0a05 100644
> > > --- a/xen/include/public/io/kbdif.h
> > > +++ b/xen/include/public/io/kbdif.h
> > > @@ -82,6 +82,15 @@
> > >    *      for pointer devices should set this to 1. Raw (unscaled) values 
> > > have
> > >    *      a range of [0, 0x7fff].
> > >    *
> > > + *-----------------------  Device Instance Parameters 
> > > ------------------------
> > > + *
> > > + * unique-id
> > > + *      Values:         <uint32_t>
> > Wouldn't a string be easier? That way you can extend this in the future
> > to also have an UUID or so?
> Much easier. We were thinking about that as well, but sndif already has it
> as uint32_t. If you are ok to change uniquie-id for sndif to string then
> that
> would be much better: UUID as you mention + all protocols have unique-id
> consistently defined as string.
> sndif's unique-id is not used by the frontend driver and we are about
> to start libx/xl support for sound, so I think this is the right time for
> such a change.
> If you are fine with that then I'll send yet another patch for sndif.

Please do and feel free to add 

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

on it.

Also pls CC Juergen so he can release-ack it.
> > > + *
> > > + *      After device instance initialization it is assigned a unique ID
> > > + *      (within the front driver), so every instance of the frontend can 
> > > be
> > > + *      identified by the backend by this ID.
> > > + *
> > >    *------------------------- Pointer Device Parameters 
> > > ------------------------
> > >    *
> > >    * width
> > > @@ -204,6 +213,7 @@
> > >   #define XENKBD_FIELD_MT_WIDTH          "multi-touch-width"
> > >   #define XENKBD_FIELD_MT_HEIGHT         "multi-touch-height"
> > >   #define XENKBD_FIELD_MT_NUM_CONTACTS   "multi-touch-num-contacts"
> > > +#define XENKBD_FIELD_UNIQUE_ID         "unique-id"
> > >   /* OBSOLETE, not recommended for use */
> > >   #define XENKBD_FIELD_RING_REF          "page-ref"
> > > -- 
> > > 2.17.0
> > > 
> 

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