grfunmap
rv = grfunmap(dev, sc->mfb_sc, *(void **)data, l->l_proc);
int grfunmap(dev_t, struct macfb_softc *, void *, struct proc *);
error = grfunmap(dev, *(void **)data, l->l_proc);
(void) grfunmap(dev, (void *) 0, curproc);
static int grfunmap(dev_t, void *, struct proc *);