IIC_IDBR
bus_space_write_4(sc->sc_st, sc->sc_sh, IIC_IDBR, idbr);
*bytep = bus_space_read_4(sc->sc_st, sc->sc_sh, IIC_IDBR);
bus_space_write_4(sc->sc_st, sc->sc_sh, IIC_IDBR, byte);