vax_sgmap_init
void vax_sgmap_init(bus_dma_tag_t, struct vax_sgmap *, const char *,
vax_sgmap_init(t, &sc->uv_sgmap, "uba_sgmap", 0, sc->uv_size, pte, 0);
vax_sgmap_init(dmat, &sc->sc_sgmap, "tc_sgmap", dmat->_wbase,
vax_sgmap_init(t, &sc->sc_sgmap, "vsbus_sgmap", t->_wbase, t->_wsize, pte, 0);