media: subdev: add v4l2_subdev_set_routing helper()

Add a helper function to set the subdev routing. The helper can be used
from subdev driver's set_routing op to store the routing table.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

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

@@ -12,6 +12,7 @@
 #include <linux/ioctl.h>
 #include <linux/mm.h>
 #include <linux/module.h>
+#include <linux/overflow.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/version.h>
@@ -1208,6 +1209,36 @@ int v4l2_subdev_get_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state,
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_get_fmt);
 
+int v4l2_subdev_set_routing(struct v4l2_subdev *sd,
+			    struct v4l2_subdev_state *state,
+			    const struct v4l2_subdev_krouting *routing)
+{
+	struct v4l2_subdev_krouting *dst = &state->routing;
+	const struct v4l2_subdev_krouting *src = routing;
+	struct v4l2_subdev_krouting new_routing = { 0 };
+	size_t bytes;
+
+	if (unlikely(check_mul_overflow((size_t)src->num_routes,
+					sizeof(*src->routes), &bytes)))
+		return -EOVERFLOW;
+
+	lockdep_assert_held(state->lock);
+
+	if (src->num_routes > 0) {
+		new_routing.routes = kmemdup(src->routes, bytes, GFP_KERNEL);
+		if (!new_routing.routes)
+			return -ENOMEM;
+	}
+
+	new_routing.num_routes = src->num_routes;
+
+	kfree(dst->routes);
+	*dst = new_routing;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_set_routing);
+
 #endif /* CONFIG_VIDEO_V4L2_SUBDEV_API */
 
 #endif /* CONFIG_MEDIA_CONTROLLER */

include/media/v4l2-subdev.h

@@ -1424,6 +1424,22 @@ v4l2_subdev_lock_and_get_active_state(struct v4l2_subdev *sd)
 int v4l2_subdev_get_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state,
 			struct v4l2_subdev_format *format);
 
+/**
+ * v4l2_subdev_set_routing() - Set given routing to subdev state
+ * @sd: The subdevice
+ * @state: The subdevice state
+ * @routing: Routing that will be copied to subdev state
+ *
+ * This will release old routing table (if any) from the state, allocate
+ * enough space for the given routing, and copy the routing.
+ *
+ * This can be used from the subdev driver's set_routing op, after validating
+ * the routing.
+ */
+int v4l2_subdev_set_routing(struct v4l2_subdev *sd,
+			    struct v4l2_subdev_state *state,
+			    const struct v4l2_subdev_krouting *routing);
+
 #endif /* CONFIG_VIDEO_V4L2_SUBDEV_API */
 
 #endif /* CONFIG_MEDIA_CONTROLLER */