plumvideo_backlight
static void plumvideo_backlight(struct plumvideo_softc *, int);
plumvideo_backlight(sc, 0);
plumvideo_backlight(sc, 1);
plumvideo_backlight(sc, dispparam->curval);
plumvideo_backlight(sc, 1);
plumvideo_backlight(sc, 0);