vax_sgmap_alloc
int vax_sgmap_alloc(bus_dmamap_t, bus_size_t, struct vax_sgmap *, int);
error = vax_sgmap_alloc(map, vax_round_page(size),
error = vax_sgmap_alloc(map, (endva - va), sgmap, flags);
error = vax_sgmap_alloc(map, vax_round_page(size),