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Diffstat (limited to 'kernel/Documentation/leds/ledtrig-oneshot.txt')
| -rw-r--r-- | kernel/Documentation/leds/ledtrig-oneshot.txt | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/kernel/Documentation/leds/ledtrig-oneshot.txt b/kernel/Documentation/leds/ledtrig-oneshot.txt new file mode 100644 index 000000000..07cd1fa41 --- /dev/null +++ b/kernel/Documentation/leds/ledtrig-oneshot.txt @@ -0,0 +1,59 @@ +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 the following sysfs attributes to the LED: + + delay_on - specifies for how many milliseconds the LED has to stay at + LED_FULL brightness after it has been armed. + Default to 100 ms. + + delay_off - specifies for how many milliseconds the LED has to stay at + LED_OFF brightness after it has been armed. + Default to 100 ms. + + invert - reverse the blink logic. If set to 0 (default) blink on for delay_on + ms, then blink off for delay_off ms, leaving the LED normally off. If + set to 1, blink off for delay_off ms, then blink on for delay_on ms, + leaving the LED normally on. + Setting this value also immediately change the LED state. + + shot - write any non-empty string to signal an events, this starts a blink + sequence if not already running. + +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 |