Based on kernel version 4.9. Page generated on 2016-12-21 14:35 EST.
1 One-shot LED Trigger 2 ==================== 3 4 This is a LED trigger useful for signaling the user of an event where there are 5 no clear trap points to put standard led-on and led-off settings. Using this 6 trigger, the application needs only to signal the trigger when an event has 7 happened, than the trigger turns the LED on and than keeps it off for a 8 specified amount of time. 9 10 This trigger is meant to be usable both for sporadic and dense events. In the 11 first case, the trigger produces a clear single controlled blink for each 12 event, while in the latter it keeps blinking at constant rate, as to signal 13 that the events are arriving continuously. 14 15 A one-shot LED only stays in a constant state when there are no events. An 16 additional "invert" property specifies if the LED has to stay off (normal) or 17 on (inverted) when not rearmed. 18 19 The trigger can be activated from user space on led class devices as shown 20 below: 21 22 echo oneshot > trigger 23 24 This adds sysfs attributes to the LED that are documented in: 25 Documentation/ABI/testing/sysfs-class-led-trigger-oneshot 26 27 Example use-case: network devices, initialization: 28 29 echo oneshot > trigger # set trigger for this led 30 echo 33 > delay_on # blink at 1 / (33 + 33) Hz on continuous traffic 31 echo 33 > delay_off 32 33 interface goes up: 34 35 echo 1 > invert # set led as normally-on, turn the led on 36 37 packet received/transmitted: 38 39 echo 1 > shot # led starts blinking, ignored if already blinking 40 41 interface goes down 42 43 echo 0 > invert # set led as normally-off, turn the led off