BBC_GPIO_PORT1_DATA
r = bus_space_read_1(sc->sc_iot, sc->sc_gpioh, BBC_GPIO_PORT1_DATA);
bus_space_write_1(sc->sc_iot, sc->sc_gpioh, BBC_GPIO_PORT1_DATA, r);
bus_space_read_1(sc->sc_iot, sc->sc_gpioh, BBC_GPIO_PORT1_DATA);