media: subdev: add v4l2_subdev_has_pad_interdep()

Add a v4l2_subdev_has_pad_interdep() helper function which can be used
for media_entity_operations.has_pad_interdep op.

It considers two pads interdependent if there is an active route between
pad0 and pad1.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

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

@@ -1073,6 +1073,37 @@ int v4l2_subdev_link_validate(struct media_link *link)
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_link_validate);
 
+bool v4l2_subdev_has_pad_interdep(struct media_entity *entity,
+				  unsigned int pad0, unsigned int pad1)
+{
+	struct v4l2_subdev *sd = media_entity_to_v4l2_subdev(entity);
+	struct v4l2_subdev_krouting *routing;
+	struct v4l2_subdev_state *state;
+	unsigned int i;
+
+	state = v4l2_subdev_lock_and_get_active_state(sd);
+
+	routing = &state->routing;
+
+	for (i = 0; i < routing->num_routes; ++i) {
+		struct v4l2_subdev_route *route = &routing->routes[i];
+
+		if (!(route->flags & V4L2_SUBDEV_ROUTE_FL_ACTIVE))
+			continue;
+
+		if ((route->sink_pad == pad0 && route->source_pad == pad1) ||
+		    (route->source_pad == pad0 && route->sink_pad == pad1)) {
+			v4l2_subdev_unlock_state(state);
+			return true;
+		}
+	}
+
+	v4l2_subdev_unlock_state(state);
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_has_pad_interdep);
+
 struct v4l2_subdev_state *
 __v4l2_subdev_state_alloc(struct v4l2_subdev *sd, const char *lock_name,
 			  struct lock_class_key *lock_key)

include/media/v4l2-subdev.h

@@ -1246,6 +1246,24 @@ int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd,
  */
 int v4l2_subdev_link_validate(struct media_link *link);
 
+/**
+ * v4l2_subdev_has_pad_interdep - MC has_pad_interdep implementation for subdevs
+ *
+ * @entity: pointer to &struct media_entity
+ * @pad0: pad number for the first pad
+ * @pad1: pad number for the second pad
+ *
+ * This function is an implementation of the
+ * media_entity_operations.has_pad_interdep operation for subdevs that
+ * implement the multiplexed streams API (as indicated by the
+ * V4L2_SUBDEV_FL_STREAMS subdev flag).
+ *
+ * It considers two pads interdependent if there is an active route between pad0
+ * and pad1.
+ */
+bool v4l2_subdev_has_pad_interdep(struct media_entity *entity,
+				  unsigned int pad0, unsigned int pad1);
+
 /**
  * __v4l2_subdev_state_alloc - allocate v4l2_subdev_state
  *