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diff --git a/Documentation/leds/ledtrig-oneshot.rst b/Documentation/leds/ledtrig-oneshot.rst new file mode 100644 index 000000000000..69fa3ea1d554 --- /dev/null +++ b/Documentation/leds/ledtrig-oneshot.rst @@ -0,0 +1,44 @@ +==================== +One-shot LED Trigger +==================== + +This is a LED trigger useful for signaling the user of an event where there are +no clear trap points to put standard led-on and led-off settings. Using this +trigger, the application needs only to signal the trigger when an event has +happened, than the trigger turns the LED on and than keeps it off for a +specified amount of time. + +This trigger is meant to be usable both for sporadic and dense events. In the +first case, the trigger produces a clear single controlled blink for each +event, while in the latter it keeps blinking at constant rate, as to signal +that the events are arriving continuously. + +A one-shot LED only stays in a constant state when there are no events. An +additional "invert" property specifies if the LED has to stay off (normal) or +on (inverted) when not rearmed. + +The trigger can be activated from user space on led class devices as shown +below:: + + echo oneshot > trigger + +This adds sysfs attributes to the LED that are documented in: +Documentation/ABI/testing/sysfs-class-led-trigger-oneshot + +Example use-case: network devices, initialization:: + + echo oneshot > trigger # set trigger for this led + echo 33 > delay_on # blink at 1 / (33 + 33) Hz on continuous traffic + echo 33 > delay_off + +interface goes up:: + + echo 1 > invert # set led as normally-on, turn the led on + +packet received/transmitted:: + + echo 1 > shot # led starts blinking, ignored if already blinking + +interface goes down:: + + echo 0 > invert # set led as normally-off, turn the led off |