Commit | Line | Data |
---|---|---|
5e417281 FB |
1 | One-shot LED Trigger |
2 | ==================== | |
3 | ||
4 | This is a LED trigger useful for signaling the user of an event where there are | |
5 | no clear trap points to put standard led-on and led-off settings. Using this | |
6 | trigger, the application needs only to signal the trigger when an event has | |
7 | happened, than the trigger turns the LED on and than keeps it off for a | |
8 | specified amount of time. | |
9 | ||
10 | This trigger is meant to be usable both for sporadic and dense events. In the | |
11 | first case, the trigger produces a clear single controlled blink for each | |
12 | event, while in the latter it keeps blinking at constant rate, as to signal | |
13 | that the events are arriving continuously. | |
14 | ||
15 | A one-shot LED only stays in a constant state when there are no events. An | |
16 | additional "invert" property specifies if the LED has to stay off (normal) or | |
17 | on (inverted) when not rearmed. | |
18 | ||
19 | The trigger can be activated from user space on led class devices as shown | |
20 | below: | |
21 | ||
22 | echo oneshot > trigger | |
23 | ||
24 | This adds the following sysfs attributes to the LED: | |
25 | ||
26 | delay_on - specifies for how many milliseconds the LED has to stay at | |
27 | LED_FULL brightness after it has been armed. | |
28 | Default to 100 ms. | |
29 | ||
30 | delay_off - specifies for how many milliseconds the LED has to stay at | |
31 | LED_OFF brightness after it has been armed. | |
32 | Default to 100 ms. | |
33 | ||
34 | invert - reverse the blink logic. If set to 0 (default) blink on for delay_on | |
35 | ms, then blink off for delay_off ms, leaving the LED normally off. If | |
36 | set to 1, blink off for delay_off ms, then blink on for delay_on ms, | |
37 | leaving the LED normally on. | |
38 | Setting this value also immediately change the LED state. | |
39 | ||
40 | shot - write any non-empty string to signal an events, this starts a blink | |
41 | sequence if not already running. | |
42 | ||
43 | Example use-case: network devices, initialization: | |
44 | ||
45 | echo oneshot > trigger # set trigger for this led | |
46 | echo 33 > delay_on # blink at 1 / (33 + 33) Hz on continuous traffic | |
47 | echo 33 > delay_off | |
48 | ||
49 | interface goes up: | |
50 | ||
51 | echo 1 > invert # set led as normally-on, turn the led on | |
52 | ||
53 | packet received/transmitted: | |
54 | ||
55 | echo 1 > shot # led starts blinking, ignored if already blinking | |
56 | ||
57 | interface goes down | |
58 | ||
59 | echo 0 > invert # set led as normally-off, turn the led off |