[PATCH 3/6] vduse: Add API v2 definition

["Eugenio Pérez" <eperezma@redhat.com>]

Introduce the definition for VDUSE API V2.  This version serves as a
gateway for feature negotiation.

The kernel uses this version to determine if the userspace device
supports feature flags. Devices that do not explicitly negotiate API V2
will be blocked from querying available VDUSE features, ensuring
backward compatibility.

The next patches implement the new feature incrementally, only enabling
the VDUSE device to set the V2 API version by the end of the series.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 include/uapi/linux/vduse.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
index 68b4287f9fac..dea89ed281a7 100644
--- a/include/uapi/linux/vduse.h
+++ b/include/uapi/linux/vduse.h
@@ -14,6 +14,10 @@
 
 #define VDUSE_API_VERSION_1	1
 
+/* Features support */
+
+#define VDUSE_API_VERSION_2	2
+
 /*
  * Get the version of VDUSE API that kernel supported (VDUSE_API_VERSION).
  * This is used for future extension.
-- 
2.52.0