| 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 |
