forked from Minki/linux
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 <krzk@kernel.org> Acked-by: Pavel Machek <pavel@ucw.cz> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
This commit is contained in:
Krzysztof Kozlowski
Jacek Anaszewski
parent
bfeffd1552
commit
1dd7093742
@ -7,55 +7,10 @@ Description:
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timer. It can do gradual dimming and step change of brightness.
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The pattern is given by a series of tuples, of brightness and
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duration (ms). The LED is expected to traverse the series and
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each brightness value for the specified duration. Duration of
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0 means brightness should immediately change to new value, and
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writing malformed pattern deactivates any active one.
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duration (ms).
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1. For gradual dimming, the dimming interval now is set as 50
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milliseconds. So the tuple with duration less than dimming
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interval (50ms) is treated as a step change of brightness,
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i.e. the subsequent brightness will be applied without adding
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intervening dimming intervals.
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The gradual dimming format of the software pattern values should be:
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"brightness_1 duration_1 brightness_2 duration_2 brightness_3
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duration_3 ...". For example:
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echo 0 1000 255 2000 > pattern
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It will make the LED go gradually from zero-intensity to max (255)
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intensity in 1000 milliseconds, then back to zero intensity in 2000
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milliseconds:
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LED brightness
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^
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255-| / \ / \ /
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| / \ / \ /
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| / \ / \ /
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| / \ / \ /
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0-| / \/ \/
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+---0----1----2----3----4----5----6------------> time (s)
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2. To make the LED go instantly from one brightness value to another,
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we should use zero-time lengths (the brightness must be same as
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the previous tuple's). So the format should be:
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"brightness_1 duration_1 brightness_1 0 brightness_2 duration_2
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brightness_2 0 ...". For example:
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echo 0 1000 0 0 255 2000 255 0 > pattern
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It will make the LED stay off for one second, then stay at max brightness
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for two seconds:
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LED brightness
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^
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255-| +---------+ +---------+
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0-| -----+ +----+ +----
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+---0----1----2----3----4----5----6------------> time (s)
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The exact format is described in:
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Documentation/devicetree/bindings/leds/leds-trigger-pattern.txt
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What: /sys/class/leds/<led>/hw_pattern
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Date: September 2018
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@ -37,6 +37,18 @@ Optional properties for child nodes:
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"ide-disk" - LED indicates IDE disk activity (deprecated),
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in new implementations use "disk-activity"
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"timer" - LED flashes at a fixed, configurable rate
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"pattern" - LED alters the brightness for the specified duration with one
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software timer (requires "led-pattern" property)
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- led-pattern : Array of integers with default pattern for certain triggers.
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Each trigger may parse this property differently:
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- one-shot : two numbers specifying delay on and delay off (in ms),
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- timer : two numbers specifying delay on and delay off (in ms),
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- pattern : the pattern is given by a series of tuples, of
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brightness and duration (in ms). The exact format is
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described in:
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Documentation/devicetree/bindings/leds/leds-trigger-pattern.txt
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- led-max-microamp : Maximum LED supply current in microamperes. This property
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can be made mandatory for the board configurations
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@ -0,0 +1,49 @@
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* Pattern format for LED pattern trigger
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The pattern is given by a series of tuples, of brightness and duration (ms).
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The LED is expected to traverse the series and each brightness value for the
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specified duration. Duration of 0 means brightness should immediately change to
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new value, and writing malformed pattern deactivates any active one.
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1. For gradual dimming, the dimming interval now is set as 50 milliseconds. So
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the tuple with duration less than dimming interval (50ms) is treated as a step
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change of brightness, i.e. the subsequent brightness will be applied without
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adding intervening dimming intervals.
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The gradual dimming format of the software pattern values should be:
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"brightness_1 duration_1 brightness_2 duration_2 brightness_3 duration_3 ...".
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For example (using sysfs interface):
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echo 0 1000 255 2000 > pattern
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It will make the LED go gradually from zero-intensity to max (255) intensity in
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1000 milliseconds, then back to zero intensity in 2000 milliseconds:
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LED brightness
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^
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255-| / \ / \ /
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| / \ / \ /
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| / \ / \ /
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| / \ / \ /
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0-| / \/ \/
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+---0----1----2----3----4----5----6------------> time (s)
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2. To make the LED go instantly from one brightness value to another, we should
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use zero-time lengths (the brightness must be same as the previous tuple's). So
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the format should be: "brightness_1 duration_1 brightness_1 0 brightness_2
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duration_2 brightness_2 0 ...".
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For example (using sysfs interface):
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echo 0 1000 0 0 255 2000 255 0 > pattern
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It will make the LED stay off for one second, then stay at max brightness for
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two seconds:
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LED brightness
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^
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255-| +---------+ +---------+
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0-| -----+ +----+ +----
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+---0----1----2----3----4----5----6------------> time (s)
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