There is also rec_notify_trigger - called when Canon firmware announces "recording" - shoot.c, PROP_HANDLER(PROP_SHOOTING_TYPE).
Or you may want to enable it when you send the button press.
Polling is used to keep the LED on, if some other events happen to turn it off.
Or you may want to enable it when you send the button press.
Polling is used to keep the LED on, if some other events happen to turn it off.