About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / leds / ledtrig-oneshot.txt




Custom Search

Based on kernel version 4.9. Page generated on 2016-12-21 14:35 EST.

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 sysfs attributes to the LED that are documented in:
25	Documentation/ABI/testing/sysfs-class-led-trigger-oneshot
26	
27	Example use-case: network devices, initialization:
28	
29	  echo oneshot > trigger # set trigger for this led
30	  echo 33 > delay_on     # blink at 1 / (33 + 33) Hz on continuous traffic
31	  echo 33 > delay_off
32	
33	interface goes up:
34	
35	  echo 1 > invert # set led as normally-on, turn the led on
36	
37	packet received/transmitted:
38	
39	  echo 1 > shot # led starts blinking, ignored if already blinking
40	
41	interface goes down
42	
43	  echo 0 > invert # set led as normally-off, turn the led off
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.