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Mauro Carvalho Chehab8dab9192019-06-28 09:20:20 -03001====================
Fabio Baltieri5e417282012-06-07 06:11:05 +08002One-shot LED Trigger
3====================
4
5This is a LED trigger useful for signaling the user of an event where there are
6no clear trap points to put standard led-on and led-off settings. Using this
7trigger, the application needs only to signal the trigger when an event has
8happened, than the trigger turns the LED on and than keeps it off for a
9specified amount of time.
10
11This trigger is meant to be usable both for sporadic and dense events. In the
12first case, the trigger produces a clear single controlled blink for each
13event, while in the latter it keeps blinking at constant rate, as to signal
14that the events are arriving continuously.
15
16A one-shot LED only stays in a constant state when there are no events. An
17additional "invert" property specifies if the LED has to stay off (normal) or
18on (inverted) when not rearmed.
19
20The trigger can be activated from user space on led class devices as shown
Mauro Carvalho Chehab8dab9192019-06-28 09:20:20 -030021below::
Fabio Baltieri5e417282012-06-07 06:11:05 +080022
23 echo oneshot > trigger
24
Rafał Miłecki1f70cb42016-08-26 16:19:36 +020025This adds sysfs attributes to the LED that are documented in:
26Documentation/ABI/testing/sysfs-class-led-trigger-oneshot
Fabio Baltieri5e417282012-06-07 06:11:05 +080027
Mauro Carvalho Chehab8dab9192019-06-28 09:20:20 -030028Example use-case: network devices, initialization::
Fabio Baltieri5e417282012-06-07 06:11:05 +080029
30 echo oneshot > trigger # set trigger for this led
31 echo 33 > delay_on # blink at 1 / (33 + 33) Hz on continuous traffic
32 echo 33 > delay_off
33
Mauro Carvalho Chehab8dab9192019-06-28 09:20:20 -030034interface goes up::
Fabio Baltieri5e417282012-06-07 06:11:05 +080035
36 echo 1 > invert # set led as normally-on, turn the led on
37
Mauro Carvalho Chehab8dab9192019-06-28 09:20:20 -030038packet received/transmitted::
Fabio Baltieri5e417282012-06-07 06:11:05 +080039
40 echo 1 > shot # led starts blinking, ignored if already blinking
41
Mauro Carvalho Chehab8dab9192019-06-28 09:20:20 -030042interface goes down::
Fabio Baltieri5e417282012-06-07 06:11:05 +080043
44 echo 0 > invert # set led as normally-off, turn the led off