media: mc-entity.c: use WARN_ON, validate link pads

Use WARN_ON instead of BUG_ON.

Add two new WARN_ONs to verify that the source pad is really a source
and that the sink pad is really a sink.

Signed-off-by: Hans Verkuil <[e-mail]>
[[e-mail]: use ! instead of == NULL for source and sink]
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/mc/mc-entity.c

···
 	struct media_link *link;
 	struct media_link *backlink;
 
-	BUG_ON(source == NULL || sink == NULL);
-	BUG_ON(source_pad >= source->num_pads);
-	BUG_ON(sink_pad >= sink->num_pads);
+	if (WARN_ON(!source || !sink) ||
+	    WARN_ON(source_pad >= source->num_pads) ||
+	    WARN_ON(sink_pad >= sink->num_pads))
+		return -EINVAL;
+	if (WARN_ON(!(source->pads[source_pad].flags & MEDIA_PAD_FL_SOURCE)))
+		return -EINVAL;
+	if (WARN_ON(!(sink->pads[sink_pad].flags & MEDIA_PAD_FL_SINK)))
+		return -EINVAL;
 
 	link = media_add_link(&source->links);
 	if (link == NULL)