| ==================== | |
| 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, then the trigger turns the LED on and then 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 |