1 What: /sys/class/leds/<led>/brightne 1 What: /sys/class/leds/<led>/brightness
2 Date: March 2006 2 Date: March 2006
3 KernelVersion: 2.6.17 3 KernelVersion: 2.6.17
4 Contact: Richard Purdie <rpurdie@rpsys.n 4 Contact: Richard Purdie <rpurdie@rpsys.net>
5 Description: 5 Description:
6 Set the brightness of the LED. 6 Set the brightness of the LED.
7 7
8 Most LEDs don't have hardware 8 Most LEDs don't have hardware brightness support, so will
9 just be turned on for non-zero 9 just be turned on for non-zero brightness settings.
10 10
11 .. Note:: 11 .. Note::
12 12
13 For multicolor LEDs, writing 13 For multicolor LEDs, writing to this file will update all
14 LEDs within the group to a c 14 LEDs within the group to a calculated percentage of what
15 each color LED intensity is 15 each color LED intensity is set to.
16 16
17 The percentage is calculated 17 The percentage is calculated for each grouped LED via
18 the equation below:: 18 the equation below::
19 19
20 led_brightness = brightnes 20 led_brightness = brightness * multi_intensity/max_brightness
21 21
22 For additional details pleas 22 For additional details please refer to
23 Documentation/leds/leds-clas 23 Documentation/leds/leds-class-multicolor.rst.
24 24
25 The value is between 0 and 25 The value is between 0 and
26 /sys/class/leds/<led>/max_brig 26 /sys/class/leds/<led>/max_brightness.
27 27
28 Writing 0 to this file clears 28 Writing 0 to this file clears active trigger.
29 29
30 Writing non-zero to this file 30 Writing non-zero to this file while trigger is active changes the
31 top brightness trigger is goin 31 top brightness trigger is going to use.
32 32
33 33
34 34
35 What: /sys/class/leds/<led>/max_brig 35 What: /sys/class/leds/<led>/max_brightness
36 Date: March 2006 36 Date: March 2006
37 KernelVersion: 2.6.17 37 KernelVersion: 2.6.17
38 Contact: Richard Purdie <rpurdie@rpsys.n 38 Contact: Richard Purdie <rpurdie@rpsys.net>
39 Description: 39 Description:
40 Maximum brightness level for t 40 Maximum brightness level for this LED, default is 255 (LED_FULL).
41 41
42 If the LED does not support di 42 If the LED does not support different brightness levels, this
43 should be 1. 43 should be 1.
44 44
45 What: /sys/class/leds/<led>/brightne 45 What: /sys/class/leds/<led>/brightness_hw_changed
46 Date: January 2017 46 Date: January 2017
47 KernelVersion: 4.11 47 KernelVersion: 4.11
48 Description: 48 Description:
49 Last hardware set brightness l 49 Last hardware set brightness level for this LED. Some LEDs
50 may be changed autonomously by 50 may be changed autonomously by hardware/firmware. Only LEDs
51 where this happens and the dri 51 where this happens and the driver can detect this, will have
52 this file. 52 this file.
53 53
54 This file supports poll() to d 54 This file supports poll() to detect when the hardware changes
55 the brightness. 55 the brightness.
56 56
57 Reading this file will return 57 Reading this file will return the last brightness level set
58 by the hardware, this may be d 58 by the hardware, this may be different from the current
59 brightness. Reading this file 59 brightness. Reading this file when no hw brightness change
60 event has happened will return 60 event has happened will return an ENODATA error.
61 61
62 What: /sys/class/leds/<led>/trigger 62 What: /sys/class/leds/<led>/trigger
63 Date: March 2006 63 Date: March 2006
64 KernelVersion: 2.6.17 64 KernelVersion: 2.6.17
65 Contact: Richard Purdie <rpurdie@rpsys.n 65 Contact: Richard Purdie <rpurdie@rpsys.net>
66 Description: 66 Description:
67 Set the trigger for this LED. 67 Set the trigger for this LED. A trigger is a kernel based source
68 of LED events. 68 of LED events.
69 69
70 You can change triggers in a s 70 You can change triggers in a similar manner to the way an IO
71 scheduler is chosen. Trigger s 71 scheduler is chosen. Trigger specific parameters can appear in
72 /sys/class/leds/<led> once a g 72 /sys/class/leds/<led> once a given trigger is selected. For
73 their documentation see `sysfs 73 their documentation see `sysfs-class-led-trigger-*`.
74 74
75 What: /sys/class/leds/<led>/inverted 75 What: /sys/class/leds/<led>/inverted
76 Date: January 2011 76 Date: January 2011
77 KernelVersion: 2.6.38 77 KernelVersion: 2.6.38
78 Contact: Richard Purdie <rpurdie@rpsys.n 78 Contact: Richard Purdie <rpurdie@rpsys.net>
79 Description: 79 Description:
80 Invert the LED on/off state. T 80 Invert the LED on/off state. This parameter is specific to
81 gpio and backlight triggers. I 81 gpio and backlight triggers. In case of the backlight trigger,
82 it is useful when driving a LE 82 it is useful when driving a LED which is intended to indicate
83 a device in a standby like sta 83 a device in a standby like state.
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