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- What: /sys/class/leds/<led>/brightness
- Date: March 2006
- KernelVersion: 2.6.17
- Contact: Richard Purdie <[email protected]>
- Description:
- Set the brightness of the LED.
- Most LEDs don't have hardware brightness support, so will
- just be turned on for non-zero brightness settings.
- .. Note::
- For multicolor LEDs, writing to this file will update all
- LEDs within the group to a calculated percentage of what
- each color LED intensity is set to.
- The percentage is calculated for each grouped LED via
- the equation below::
- led_brightness = brightness * multi_intensity/max_brightness
- For additional details please refer to
- Documentation/leds/leds-class-multicolor.rst.
- The value is between 0 and
- /sys/class/leds/<led>/max_brightness.
- Writing 0 to this file clears active trigger.
- Writing non-zero to this file while trigger is active changes the
- top brightness trigger is going to use.
- What: /sys/class/leds/<led>/max_brightness
- Date: March 2006
- KernelVersion: 2.6.17
- Contact: Richard Purdie <[email protected]>
- Description:
- Maximum brightness level for this LED, default is 255 (LED_FULL).
- If the LED does not support different brightness levels, this
- should be 1.
- What: /sys/class/leds/<led>/brightness_hw_changed
- Date: January 2017
- KernelVersion: 4.11
- Description:
- Last hardware set brightness level for this LED. Some LEDs
- may be changed autonomously by hardware/firmware. Only LEDs
- where this happens and the driver can detect this, will have
- this file.
- This file supports poll() to detect when the hardware changes
- the brightness.
- Reading this file will return the last brightness level set
- by the hardware, this may be different from the current
- brightness. Reading this file when no hw brightness change
- event has happened will return an ENODATA error.
- What: /sys/class/leds/<led>/trigger
- Date: March 2006
- KernelVersion: 2.6.17
- Contact: Richard Purdie <[email protected]>
- Description:
- Set the trigger for this LED. A trigger is a kernel based source
- of LED events.
- You can change triggers in a similar manner to the way an IO
- scheduler is chosen. Trigger specific parameters can appear in
- /sys/class/leds/<led> once a given trigger is selected. For
- their documentation see `sysfs-class-led-trigger-*`.
- What: /sys/class/leds/<led>/inverted
- Date: January 2011
- KernelVersion: 2.6.38
- Contact: Richard Purdie <[email protected]>
- Description:
- Invert the LED on/off state. This parameter is specific to
- gpio and backlight triggers. In case of the backlight trigger,
- it is useful when driving a LED which is intended to indicate
- a device in a standby like state.
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