media: v4l: subdev: Add trivial set_routing support

Add trivial S_ROUTING IOCTL support for drivers where routing is static.
Essentially this means returning the same information G_ROUTING call would
have done.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Co-developed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Julien Massot <julien.massot@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

drivers/media/v4l2-core/v4l2-subdev.c

@@ -1013,6 +1013,20 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
 				return -EINVAL;
 		}
 
+		/*
+		 * If the driver doesn't support setting routing, just return
+		 * the routing table.
+		 */
+		if (!v4l2_subdev_has_op(sd, pad, set_routing)) {
+			memcpy((struct v4l2_subdev_route *)(uintptr_t)routing->routes,
+			       state->routing.routes,
+			       min(state->routing.num_routes, routing->len_routes) *
+			       sizeof(*state->routing.routes));
+			routing->num_routes = state->routing.num_routes;
+
+			return 0;
+		}
+
 		krouting.num_routes = routing->num_routes;
 		krouting.len_routes = routing->len_routes;
 		krouting.routes = routes;