uint64_state interface.The optional function signal_current_level can be called when a new target is connected.
SIM_INTERFACE(multi_level_signal) {
void (*signal_level_change)(conf_object_t *NOTNULL obj, uint64 level);
void (*signal_current_level)(conf_object_t *NOTNULL obj, uint64 level);
};
#define MULTI_LEVEL_SIGNAL_INTERFACE "multi_level_signal"