ledtrig-oneshot.rst (1557B)
1==================== 2One-shot LED Trigger 3==================== 4 5This is a LED trigger useful for signaling the user of an event where there are 6no clear trap points to put standard led-on and led-off settings. Using this 7trigger, the application needs only to signal the trigger when an event has 8happened, than the trigger turns the LED on and than keeps it off for a 9specified amount of time. 10 11This trigger is meant to be usable both for sporadic and dense events. In the 12first case, the trigger produces a clear single controlled blink for each 13event, while in the latter it keeps blinking at constant rate, as to signal 14that the events are arriving continuously. 15 16A one-shot LED only stays in a constant state when there are no events. An 17additional "invert" property specifies if the LED has to stay off (normal) or 18on (inverted) when not rearmed. 19 20The trigger can be activated from user space on led class devices as shown 21below:: 22 23 echo oneshot > trigger 24 25This adds sysfs attributes to the LED that are documented in: 26Documentation/ABI/testing/sysfs-class-led-trigger-oneshot 27 28Example use-case: network devices, initialization:: 29 30 echo oneshot > trigger # set trigger for this led 31 echo 33 > delay_on # blink at 1 / (33 + 33) Hz on continuous traffic 32 echo 33 > delay_off 33 34interface goes up:: 35 36 echo 1 > invert # set led as normally-on, turn the led on 37 38packet received/transmitted:: 39 40 echo 1 > shot # led starts blinking, ignored if already blinking 41 42interface goes down:: 43 44 echo 0 > invert # set led as normally-off, turn the led off