drm: Add a SET_CLIENT_CAP ioctl

This ioctl can be used to turn some knobs in a DRM driver. The client
can ask the DRM core for an alternate view of the reality: it can be
useful to be able to instruct the core that the DRM client can handle
new functionnality that would otherwise break current ABI.

v2: Rename to ioctl from SET_CAP to SET_CLIENT_CAP (Chris Wilson)

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 1e09e8f..526baed 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -627,6 +627,12 @@
 	__u64 value;
 };
 
+/** DRM_IOCTL_SET_CLIENT_CAP ioctl argument type */
+struct drm_set_client_cap {
+	__u64 capability;
+	__u64 value;
+};
+
 #define DRM_CLOEXEC O_CLOEXEC
 struct drm_prime_handle {
 	__u32 handle;
@@ -659,6 +665,7 @@
 #define DRM_IOCTL_GEM_FLINK		DRM_IOWR(0x0a, struct drm_gem_flink)
 #define DRM_IOCTL_GEM_OPEN		DRM_IOWR(0x0b, struct drm_gem_open)
 #define DRM_IOCTL_GET_CAP		DRM_IOWR(0x0c, struct drm_get_cap)
+#define DRM_IOCTL_SET_CLIENT_CAP	DRM_IOW( 0x0d, struct drm_set_client_cap)
 
 #define DRM_IOCTL_SET_UNIQUE		DRM_IOW( 0x10, struct drm_unique)
 #define DRM_IOCTL_AUTH_MAGIC		DRM_IOW( 0x11, struct drm_auth)