1What:		/sys/class/leds/<led>/pattern
2Date:		September 2018
3KernelVersion:	4.20
4Description:
5		Specify a software pattern for the LED, that supports altering
6		the brightness for the specified duration with one software
7		timer. It can do gradual dimming and step change of brightness.
8
9		The pattern is given by a series of tuples, of brightness and
10		duration (ms). The LED is expected to traverse the series and
11		each brightness value for the specified duration. Duration of
12		0 means brightness should immediately change to new value, and
13		writing malformed pattern deactivates any active one.
14
15		1. For gradual dimming, the dimming interval now is set as 50
16		milliseconds. So the tuple with duration less than dimming
17		interval (50ms) is treated as a step change of brightness,
18		i.e. the subsequent brightness will be applied without adding
19		intervening dimming intervals.
20
21		The gradual dimming format of the software pattern values should be:
22		"brightness_1 duration_1 brightness_2 duration_2 brightness_3
23		duration_3 ...". For example:
24
25		echo 0 1000 255 2000 > pattern
26
27		It will make the LED go gradually from zero-intensity to max (255)
28		intensity in 1000 milliseconds, then back to zero intensity in 2000
29		milliseconds:
30
31		LED brightness
32		    ^
33		255-|       / \            / \            /
34		    |      /    \         /    \         /
35		    |     /       \      /       \      /
36		    |    /          \   /          \   /
37		  0-|   /             \/             \/
38		    +---0----1----2----3----4----5----6------------> time (s)
39
40		2. To make the LED go instantly from one brightness value to another,
41		we should use zero-time lengths (the brightness must be same as
42		the previous tuple's). So the format should be:
43		"brightness_1 duration_1 brightness_1 0 brightness_2 duration_2
44		brightness_2 0 ...". For example:
45
46		echo 0 1000 0 0 255 2000 255 0 > pattern
47
48		It will make the LED stay off for one second, then stay at max brightness
49		for two seconds:
50
51		LED brightness
52		    ^
53		255-|        +---------+    +---------+
54		    |        |         |    |         |
55		    |        |         |    |         |
56		    |        |         |    |         |
57		  0-|   -----+         +----+         +----
58		    +---0----1----2----3----4----5----6------------> time (s)
59
60What:		/sys/class/leds/<led>/hw_pattern
61Date:		September 2018
62KernelVersion:	4.20
63Description:
64		Specify a hardware pattern for the LED, for LED hardware that
65		supports autonomously controlling brightness over time, according
66		to some preprogrammed hardware patterns. It deactivates any active
67		software pattern.
68
69		Since different LED hardware can have different semantics of
70		hardware patterns, each driver is expected to provide its own
71		description for the hardware patterns in their ABI documentation
72		file.
73
74What:		/sys/class/leds/<led>/repeat
75Date:		September 2018
76KernelVersion:	4.20
77Description:
78		Specify a pattern repeat number. -1 means repeat indefinitely,
79		other negative numbers and number 0 are invalid.
80
81		This file will always return the originally written repeat
82		number.
83