SM502_GPIO_DIR0
reg = bus_space_read_4(sc->sc_memt, sc->sc_regh, SM502_GPIO_DIR0);
bus_space_write_4(sc->sc_memt, sc->sc_regh, SM502_GPIO_DIR0, reg);
voyager_twiddle_bits(cookie, SM502_GPIO_DIR0, m_and, m_or)