From 1dd7093742517b4aa362d22eaff8eef133d876ce Mon Sep 17 00:00:00 2001 From: Krzysztof Kozlowski Date: Wed, 9 Jan 2019 15:44:45 +0100 Subject: dt-bindings: leds: Add pattern initialization from Device Tree Document new led-pattern property for initialization of LED triggers. The property format is trigger-specific (except being array of integers). For pattern trigger, the explanation of pattern format was moved to a common file shared with sysfs ABI. Signed-off-by: Krzysztof Kozlowski Acked-by: Pavel Machek Reviewed-by: Rob Herring Signed-off-by: Jacek Anaszewski --- Documentation/devicetree/bindings/leds/common.txt | 12 ++++++ .../bindings/leds/leds-trigger-pattern.txt | 49 ++++++++++++++++++++++ 2 files changed, 61 insertions(+) create mode 100644 Documentation/devicetree/bindings/leds/leds-trigger-pattern.txt (limited to 'Documentation/devicetree/bindings') diff --git a/Documentation/devicetree/bindings/leds/common.txt b/Documentation/devicetree/bindings/leds/common.txt index aa1399814a2a..70876ac11367 100644 --- a/Documentation/devicetree/bindings/leds/common.txt +++ b/Documentation/devicetree/bindings/leds/common.txt @@ -37,6 +37,18 @@ Optional properties for child nodes: "ide-disk" - LED indicates IDE disk activity (deprecated), in new implementations use "disk-activity" "timer" - LED flashes at a fixed, configurable rate + "pattern" - LED alters the brightness for the specified duration with one + software timer (requires "led-pattern" property) + +- led-pattern : Array of integers with default pattern for certain triggers. + Each trigger may parse this property differently: + - one-shot : two numbers specifying delay on and delay off (in ms), + - timer : two numbers specifying delay on and delay off (in ms), + - pattern : the pattern is given by a series of tuples, of + brightness and duration (in ms). The exact format is + described in: + Documentation/devicetree/bindings/leds/leds-trigger-pattern.txt + - led-max-microamp : Maximum LED supply current in microamperes. This property can be made mandatory for the board configurations 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 000000000000..d3696680bfc8 --- /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) -- cgit v1.2.3-59-g8ed1b