[media] v4l: Implement v4l2_subdev_link_validate()

v4l2_subdev_link_validate() is the default op for validating a link. In V4L2
subdev context, it is used to call a pad op which performs the proper link
check without much extra work.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 7e85035..1c2318b 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -470,6 +470,11 @@
 			     struct v4l2_subdev_selection *sel);
 	int (*set_selection)(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh,
 			     struct v4l2_subdev_selection *sel);
+#ifdef CONFIG_MEDIA_CONTROLLER
+	int (*link_validate)(struct v4l2_subdev *sd, struct media_link *link,
+			     struct v4l2_subdev_format *source_fmt,
+			     struct v4l2_subdev_format *sink_fmt);
+#endif /* CONFIG_MEDIA_CONTROLLER */
 };
 
 struct v4l2_subdev_ops {
@@ -602,6 +607,13 @@
 	return sd->host_priv;
 }
 
+#ifdef CONFIG_MEDIA_CONTROLLER
+int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd,
+				      struct media_link *link,
+				      struct v4l2_subdev_format *source_fmt,
+				      struct v4l2_subdev_format *sink_fmt);
+int v4l2_subdev_link_validate(struct media_link *link);
+#endif /* CONFIG_MEDIA_CONTROLLER */
 void v4l2_subdev_init(struct v4l2_subdev *sd,
 		      const struct v4l2_subdev_ops *ops);