summaryrefslogtreecommitdiffstats
path: root/Documentation/leds/ledtrig-oneshot.rst
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/leds/ledtrig-oneshot.rst')
-rw-r--r--Documentation/leds/ledtrig-oneshot.rst44
1 files changed, 44 insertions, 0 deletions
diff --git a/Documentation/leds/ledtrig-oneshot.rst b/Documentation/leds/ledtrig-oneshot.rst
new file mode 100644
index 000000000000..69fa3ea1d554
--- /dev/null
+++ b/Documentation/leds/ledtrig-oneshot.rst
@@ -0,0 +1,44 @@
+====================
+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 sysfs attributes to the LED that are documented in:
+Documentation/ABI/testing/sysfs-class-led-trigger-oneshot
+
+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