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| -rw-r--r-- | Documentation/devicetree/bindings/leds/leds-trigger-pattern.txt | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/leds/leds-trigger-pattern.txt b/Documentation/devicetree/bindings/leds/leds-trigger-pattern.txt new file mode 100644 index 0000000000..d3696680bf --- /dev/null +++ b/Documentation/devicetree/bindings/leds/leds-trigger-pattern.txt @@ -0,0 +1,49 @@ +* Pattern format for LED pattern trigger + +The pattern is given by a series of tuples, of brightness and duration (ms). +The LED is expected to traverse the series and each brightness value for the +specified duration. Duration of 0 means brightness should immediately change to +new value, and writing malformed pattern deactivates any active one. + +1. For gradual dimming, the dimming interval now is set as 50 milliseconds. So +the tuple with duration less than dimming interval (50ms) is treated as a step +change of brightness, i.e. the subsequent brightness will be applied without +adding intervening dimming intervals. + +The gradual dimming format of the software pattern values should be: +"brightness_1 duration_1 brightness_2 duration_2 brightness_3 duration_3 ...". +For example (using sysfs interface): + +echo 0 1000 255 2000 > pattern + +It will make the LED go gradually from zero-intensity to max (255) intensity in +1000 milliseconds, then back to zero intensity in 2000 milliseconds: + +LED brightness + ^ +255-| / \ / \ / + | / \ / \ / + | / \ / \ / + | / \ / \ / + 0-| / \/ \/ + +---0----1----2----3----4----5----6------------> time (s) + +2. To make the LED go instantly from one brightness value to another, we should +use zero-time lengths (the brightness must be same as the previous tuple's). So +the format should be: "brightness_1 duration_1 brightness_1 0 brightness_2 +duration_2 brightness_2 0 ...". +For example (using sysfs interface): + +echo 0 1000 0 0 255 2000 255 0 > pattern + +It will make the LED stay off for one second, then stay at max brightness for +two seconds: + +LED brightness + ^ +255-| +---------+ +---------+ + | | | | | + | | | | | + | | | | | + 0-| -----+ +----+ +---- + +---0----1----2----3----4----5----6------------> time (s) |