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