1 files changed, 82 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-pattern b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
new file mode 100644
index 000000000000..fb3d1e03b881
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
@@ -0,0 +1,82 @@
+What:		/sys/class/leds/<led>/pattern
+Date:		September 2018
+KernelVersion:	4.20
+Description:
+		Specify a software pattern for the LED, that supports altering
+		the brightness for the specified duration with one software
+		timer. It can do gradual dimming and step change of brightness.
+
+		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:
+
+		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 brigntess value to another,
+		we should use 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:
+
+		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)
+
+What:		/sys/class/leds/<led>/hw_pattern
+Date:		September 2018
+KernelVersion:	4.20
+Description:
+		Specify a hardware pattern for the LED, for LED hardware that
+		supports autonomously controlling brightness over time, according
+		to some preprogrammed hardware patterns. It deactivates any active
+		software pattern.
+
+		Since different LED hardware can have different semantics of
+		hardware patterns, each driver is expected to provide its own
+		description for the hardware patterns in their ABI documentation
+		file.
+
+What:		/sys/class/leds/<led>/repeat
+Date:		September 2018
+KernelVersion:	4.20
+Description:
+		Specify a pattern repeat number. -1 means repeat indefinitely,
+		other negative numbers and number 0 are invalid.
+
+		This file will always return the originally written repeat
+		number.