drm: Add a DRM_MODE_TRANSPOSE option to the DRM rotation property

Some hardware will implement transpose as a rotation operation,
which when combined with X and Y reflect can result in a rotation,
but is a discrete operation in its own right.

Add an option for transpose only.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

drivers/gpu/drm/drm_blend.c

@@ -269,6 +269,8 @@ EXPORT_SYMBOL(drm_plane_create_alpha_property);
  * 	"reflect-x"
  * DRM_MODE_REFLECT_Y:
  * 	"reflect-y"
+ * DRM_MODE_TRANSPOSE:
+ * 	"transpose"
  *
  * Rotation is the specified amount in degrees in counter clockwise direction,
  * the X and Y axis are within the source rectangle, i.e.  the X/Y axis before
@@ -286,6 +288,7 @@ int drm_plane_create_rotation_property(struct drm_plane *plane,
 		{ __builtin_ffs(DRM_MODE_ROTATE_270) - 1, "rotate-270" },
 		{ __builtin_ffs(DRM_MODE_REFLECT_X) - 1,  "reflect-x" },
 		{ __builtin_ffs(DRM_MODE_REFLECT_Y) - 1,  "reflect-y" },
+		{ __builtin_ffs(DRM_MODE_TRANSPOSE) - 1,  "transpose" },
 	};
 	struct drm_property *prop;
 

include/uapi/drm/drm_mode.h

@@ -203,6 +203,7 @@ extern "C" {
  */
 #define DRM_MODE_REFLECT_X      (1<<4)
 #define DRM_MODE_REFLECT_Y      (1<<5)
+#define DRM_MODE_TRANSPOSE      (1<<6)
 
 /*
  * DRM_MODE_REFLECT_MASK