Mauro Carvalho Chehab | 8dab919 | 2019-06-28 09:20:20 -0300 | [diff] [blame] | 1 | ==================== |
Fabio Baltieri | 5e41728 | 2012-06-07 06:11:05 +0800 | [diff] [blame] | 2 | One-shot LED Trigger |
| 3 | ==================== |
| 4 | |
| 5 | This is a LED trigger useful for signaling the user of an event where there are |
| 6 | no clear trap points to put standard led-on and led-off settings. Using this |
| 7 | trigger, the application needs only to signal the trigger when an event has |
| 8 | happened, than the trigger turns the LED on and than keeps it off for a |
| 9 | specified amount of time. |
| 10 | |
| 11 | This trigger is meant to be usable both for sporadic and dense events. In the |
| 12 | first case, the trigger produces a clear single controlled blink for each |
| 13 | event, while in the latter it keeps blinking at constant rate, as to signal |
| 14 | that the events are arriving continuously. |
| 15 | |
| 16 | A one-shot LED only stays in a constant state when there are no events. An |
| 17 | additional "invert" property specifies if the LED has to stay off (normal) or |
| 18 | on (inverted) when not rearmed. |
| 19 | |
| 20 | The trigger can be activated from user space on led class devices as shown |
Mauro Carvalho Chehab | 8dab919 | 2019-06-28 09:20:20 -0300 | [diff] [blame] | 21 | below:: |
Fabio Baltieri | 5e41728 | 2012-06-07 06:11:05 +0800 | [diff] [blame] | 22 | |
| 23 | echo oneshot > trigger |
| 24 | |
Rafał Miłecki | 1f70cb4 | 2016-08-26 16:19:36 +0200 | [diff] [blame] | 25 | This adds sysfs attributes to the LED that are documented in: |
| 26 | Documentation/ABI/testing/sysfs-class-led-trigger-oneshot |
Fabio Baltieri | 5e41728 | 2012-06-07 06:11:05 +0800 | [diff] [blame] | 27 | |
Mauro Carvalho Chehab | 8dab919 | 2019-06-28 09:20:20 -0300 | [diff] [blame] | 28 | Example use-case: network devices, initialization:: |
Fabio Baltieri | 5e41728 | 2012-06-07 06:11:05 +0800 | [diff] [blame] | 29 | |
| 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 Chehab | 8dab919 | 2019-06-28 09:20:20 -0300 | [diff] [blame] | 34 | interface goes up:: |
Fabio Baltieri | 5e41728 | 2012-06-07 06:11:05 +0800 | [diff] [blame] | 35 | |
| 36 | echo 1 > invert # set led as normally-on, turn the led on |
| 37 | |
Mauro Carvalho Chehab | 8dab919 | 2019-06-28 09:20:20 -0300 | [diff] [blame] | 38 | packet received/transmitted:: |
Fabio Baltieri | 5e41728 | 2012-06-07 06:11:05 +0800 | [diff] [blame] | 39 | |
| 40 | echo 1 > shot # led starts blinking, ignored if already blinking |
| 41 | |
Mauro Carvalho Chehab | 8dab919 | 2019-06-28 09:20:20 -0300 | [diff] [blame] | 42 | interface goes down:: |
Fabio Baltieri | 5e41728 | 2012-06-07 06:11:05 +0800 | [diff] [blame] | 43 | |
| 44 | echo 0 > invert # set led as normally-off, turn the led off |