bcm2835_mbox_write
bcm2835_mbox_write(sc->sc_iot, sc->sc_ioh, chan, data);
void bcm2835_mbox_write(bus_space_tag_t, bus_space_handle_t, uint8_t,
bcm2835_mbox_write(iot, ioh, BCMMBOX_CHANARM2VC,
bcm2835_mbox_write(iot, ioh, BCMMBOX_CHANPM, (
bcm2835_mbox_write(iot, ioh, BCMMBOX_CHANARM2VC,