led_attach
led_attach("indicator", (void *)(gpio_base + reg[0]),
if (led_attach(label, pin, gpioleds_get, gpioleds_set) == NULL)
l->led = led_attach(n, l, pcagpio_get, pcagpio_set);
led_attach(name, l, pcf8574_get_led, pcf8574_set_led);
void * led_attach(const char *, void *, led_getstate_fn, led_setstate_fn);