+
+
+Link validation
+---------------
+
+Link validation is performed by media_entity_pipeline_start() for any
+entity which has sink pads in the pipeline. The
+media_entity::link_validate() callback is used for that purpose. In
+link_validate() callback, entity driver should check that the properties of
+the source pad of the connected entity and its own sink pad match. It is up
+to the type of the entity (and in the end, the properties of the hardware)
+what matching actually means.
+
+Subsystems should facilitate link validation by providing subsystem specific
+helper functions to provide easy access for commonly needed information, and
+in the end provide a way to use driver-specific callbacks.