[PATCH 2/3] xen/kbdif: Add unique input device identifier

[Oleksandr Andrushchenko <andr2000@gmail.com>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

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@epam.com>
---
 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>
+ *
+ *      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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