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Andy ShevchenkoandLee Jones
6ebff754c4
Adjust documentation of brightness sysfs node about accepted value range. The code accepts only decimal values. We may not relax that due to different readings for, e.g., octal 0100, which becomes 64 instead of currently parsed 100. Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Link: https://patch.msgid.link/20260513220620.369825-1-andriy.shevchenko@linux.intel.com Signed-off-by: Lee Jones <lee@kernel.org>
90 lines
2.8 KiB
Plaintext
90 lines
2.8 KiB
Plaintext
What: /sys/class/leds/<led>/brightness
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Date: March 2006
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KernelVersion: 2.6.17
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Contact: Richard Purdie <rpurdie@rpsys.net>
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Description:
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Set the brightness of the LED.
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Most LEDs don't have hardware brightness support, so will
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just be turned on for non-zero brightness settings.
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.. Note::
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For multicolor LEDs, writing to this file will update all
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LEDs within the group to a calculated percentage of what
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each color LED intensity is set to.
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The percentage is calculated for each grouped LED via
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the equation below::
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led_brightness = brightness * multi_intensity/max_brightness
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For additional details please refer to
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Documentation/leds/leds-class-multicolor.rst.
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The value is between 0 and /sys/class/leds/<led>/max_brightness
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and is represented by as a decimal.
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Writing 0 to this file clears active trigger.
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Writing non-zero to this file while trigger is active changes the
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top brightness trigger is going to use.
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What: /sys/class/leds/<led>/max_brightness
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Date: March 2006
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KernelVersion: 2.6.17
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Contact: Richard Purdie <rpurdie@rpsys.net>
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Description:
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Maximum brightness level for this LED, default is 255 (LED_FULL).
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If the LED does not support different brightness levels, this
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should be 1.
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What: /sys/class/leds/<led>/brightness_hw_changed
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Date: January 2017
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KernelVersion: 4.11
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Description:
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Last hardware set brightness level for this LED. Some LEDs
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may be changed autonomously by hardware/firmware. Only LEDs
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where this happens and the driver can detect this, will have
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this file.
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This file supports poll() to detect when the hardware changes
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the brightness.
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Reading this file will return the last brightness level set
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by the hardware, this may be different from the current
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brightness. Reading this file when no hw brightness change
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event has happened will return an ENODATA error.
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What: /sys/class/leds/<led>/trigger
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Date: March 2006
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KernelVersion: 2.6.17
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Contact: Richard Purdie <rpurdie@rpsys.net>
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Description:
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Set the trigger for this LED. A trigger is a kernel based source
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of LED events.
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You can change triggers in a similar manner to the way an IO
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scheduler is chosen. Trigger specific parameters can appear in
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/sys/class/leds/<led> once a given trigger is selected. For
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their documentation see `sysfs-class-led-trigger-*`.
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Writing "none" removes the trigger for this LED.
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Writing "default" sets the trigger to the LED's default trigger
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(which would often be configured in the device tree for the
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hardware).
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What: /sys/class/leds/<led>/inverted
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Date: January 2011
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KernelVersion: 2.6.38
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Contact: Richard Purdie <rpurdie@rpsys.net>
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Description:
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Invert the LED on/off state. This parameter is specific to
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gpio and backlight triggers. In case of the backlight trigger,
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it is useful when driving a LED which is intended to indicate
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a device in a standby like state.
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