We must not use any information in the passed var besides xoffset,
yoffset and vmode as otherwise applications might abuse it.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Guan Xuetao <gxt@mprc.pku.edu.cn>
Acked-by: Guan Xuetao <gxt@mprc.pku.edu.cn>