ga_dmatag
sc->sc_dmat = ga->ga_dmatag;
if (bus_dmamem_alloc(ga->ga_dmatag, sc->sc_msize, NBPG, 0,
if (bus_dmamem_map(ga->ga_dmatag, &seg, rseg, sc->sc_msize,
bus_dmamem_free(ga->ga_dmatag, &seg, rseg);
sc->sc_dmat = ga->ga_dmatag;
sc->sc_dmat = ga->ga_dmatag;
sc->sc_siop.sc_c.sc_dmat = ga->ga_dmatag;