applesmc_has_key
ret = applesmc_has_key(LIGHT_SENSOR_LEFT_KEY, &left_light_sensor);
ret = applesmc_has_key(LIGHT_SENSOR_RIGHT_KEY, &right_light_sensor);
ret = applesmc_has_key(MOTION_SENSOR_KEY, &s->has_accelerometer);
ret = applesmc_has_key(BACKLIGHT_KEY, &s->has_key_backlight);