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Diffstat (limited to 'Documentation/ABI/testing/sysfs-class-led')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-class-led | 64 |
1 files changed, 58 insertions, 6 deletions
diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led index 3646ec85d513..0313b82644f2 100644 --- a/Documentation/ABI/testing/sysfs-class-led +++ b/Documentation/ABI/testing/sysfs-class-led @@ -3,17 +3,61 @@ Date: March 2006 KernelVersion: 2.6.17 Contact: Richard Purdie <rpurdie@rpsys.net> 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. The value is between 0 and + 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 <rpurdie@rpsys.net> Description: - Maximum brightness level for this led, default is 255 (LED_FULL). + 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 @@ -21,10 +65,18 @@ KernelVersion: 2.6.17 Contact: Richard Purdie <rpurdie@rpsys.net> Description: Set the trigger for this LED. A trigger is a kernel based source - of led events. + 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. + /sys/class/leds/<led> once a given trigger is selected. For + their documentation see `sysfs-class-led-trigger-*`. + + Writing "none" removes the trigger for this LED. + + Writing "default" sets the trigger to the LED's default trigger + (which would often be configured in the device tree for the + hardware). What: /sys/class/leds/<led>/inverted Date: January 2011 |