ATI_REG_PHYS_OUT_ADDR
bus_space_write_4(iot, ioh, ATI_REG_PHYS_OUT_ADDR, data);
bus_space_write_4(iot, ioh, ATI_REG_PHYS_OUT_ADDR, value);
value = bus_space_read_4(iot, ioh, ATI_REG_PHYS_OUT_ADDR);