Add the V4L2_CID_VBLANK control to the list of mandatory controls the sensor driver has to report and document the new requirement. The vertical blanking control is used to calculate the frame duration. Signed-off-by: Jacopo Mondi <jacopo@jmondi.org> Signed-off-by: Naushir Patuck <naush@raspberrypi.com> Reviewed-by: Naushir Patuck <naush@raspberrypi.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>