[media] v4l: subdev: Extend default link validation to cover field order

The field order must match between the source and sink pads, or the sink
pad field order must be NONE. This allows connecting an interlaced
source to a bridge that has no hardware support for interlaced formats.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Enrico Butera <ebutera@users.sourceforge.net>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

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

@@ -501,11 +501,20 @@ int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd,
 				      struct v4l2_subdev_format *source_fmt,
 				      struct v4l2_subdev_format *sink_fmt)
 {
+	/* The width, height and code must match. */
 	if (source_fmt->format.width != sink_fmt->format.width
 	    || source_fmt->format.height != sink_fmt->format.height
 	    || source_fmt->format.code != sink_fmt->format.code)
 		return -EINVAL;
 
+	/* The field order must match, or the sink field order must be NONE
+	 * to support interlaced hardware connected to bridges that support
+	 * progressive formats only.
+	 */
+	if (source_fmt->format.field != sink_fmt->format.field &&
+	    sink_fmt->format.field != V4L2_FIELD_NONE)
+		return -EINVAL;
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_link_validate_default);