| 1 | What: /sys/class/leds/<led>/brightness |
| 2 | Date: March 2006 |
| 3 | KernelVersion: 2.6.17 |
| 4 | Contact: Richard Purdie <[email protected]> |
| 5 | Description: |
| 6 | Set the brightness of the LED. |
| 7 | |
| 8 | Most LEDs don't have hardware brightness support, so will |
| 9 | just be turned on for non-zero brightness settings. |
| 10 | |
| 11 | .. Note:: |
| 12 | |
| 13 | For multicolor LEDs, writing to this file will update all |
| 14 | LEDs within the group to a calculated percentage of what |
| 15 | each color LED intensity is set to. |
| 16 | |
| 17 | The percentage is calculated for each grouped LED via |
| 18 | the equation below:: |
| 19 | |
| 20 | led_brightness = brightness * multi_intensity/max_brightness |
| 21 | |
| 22 | For additional details please refer to |
| 23 | Documentation/leds/leds-class-multicolor.rst. |
| 24 | |
| 25 | The value is between 0 and /sys/class/leds/<led>/max_brightness |
| 26 | and is represented by as a decimal. |
| 27 | |
| 28 | Writing 0 to this file clears active trigger. |
| 29 | |
| 30 | Writing non-zero to this file while trigger is active changes the |
| 31 | top brightness trigger is going to use. |
| 32 | |
| 33 | |
| 34 | |
| 35 | What: /sys/class/leds/<led>/max_brightness |
| 36 | Date: March 2006 |
| 37 | KernelVersion: 2.6.17 |
| 38 | Contact: Richard Purdie <[email protected]> |
| 39 | Description: |
| 40 | Maximum brightness level for this LED, default is 255 (LED_FULL). |
| 41 | |
| 42 | If the LED does not support different brightness levels, this |
| 43 | should be 1. |
| 44 | |
| 45 | What: /sys/class/leds/<led>/brightness_hw_changed |
| 46 | Date: January 2017 |
| 47 | KernelVersion: 4.11 |
| 48 | Description: |
| 49 | Last hardware set brightness level for this LED. Some LEDs |
| 50 | may be changed autonomously by hardware/firmware. Only LEDs |
| 51 | where this happens and the driver can detect this, will have |
| 52 | this file. |
| 53 | |
| 54 | This file supports poll() to detect when the hardware changes |
| 55 | the brightness. |
| 56 | |
| 57 | Reading this file will return the last brightness level set |
| 58 | by the hardware, this may be different from the current |
| 59 | brightness. Reading this file when no hw brightness change |
| 60 | event has happened will return an ENODATA error. |
| 61 | |
| 62 | What: /sys/class/leds/<led>/trigger |
| 63 | Date: March 2006 |
| 64 | KernelVersion: 2.6.17 |
| 65 | Contact: Richard Purdie <[email protected]> |
| 66 | Description: |
| 67 | Set the trigger for this LED. A trigger is a kernel based source |
| 68 | of LED events. |
| 69 | |
| 70 | You can change triggers in a similar manner to the way an IO |
| 71 | scheduler is chosen. Trigger specific parameters can appear in |
| 72 | /sys/class/leds/<led> once a given trigger is selected. For |
| 73 | their documentation see `sysfs-class-led-trigger-*`. |
| 74 | |
| 75 | Writing "none" removes the trigger for this LED. |
| 76 | |
| 77 | Writing "default" sets the trigger to the LED's default trigger |
| 78 | (which would often be configured in the device tree for the |
| 79 | hardware). |
| 80 | |
| 81 | What: /sys/class/leds/<led>/inverted |
| 82 | Date: January 2011 |
| 83 | KernelVersion: 2.6.38 |
| 84 | Contact: Richard Purdie <[email protected]> |
| 85 | Description: |
| 86 | Invert the LED on/off state. This parameter is specific to |
| 87 | gpio and backlight triggers. In case of the backlight trigger, |
| 88 | it is useful when driving a LED which is intended to indicate |
| 89 | a device in a standby like state. |