pwm-backlight.txt

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    1 pwm-backlight bindings
    2 
    3 Required properties:
    4   - compatible: "pwm-backlight"
    5   - pwms: OF device-tree PWM specification (see PWM binding[0])
    6   - power-supply: regulator for supply voltage
    7 
    8 Optional properties:
    9   - pwm-names: a list of names for the PWM devices specified in the
   10                "pwms" property (see PWM binding[0])
   11   - enable-gpios: contains a single GPIO specifier for the GPIO which enables
   12                   and disables the backlight (see GPIO binding[1])
   13   - post-pwm-on-delay-ms: Delay in ms between setting an initial (non-zero) PWM
   14                           and enabling the backlight using GPIO.
   15   - pwm-off-delay-ms: Delay in ms between disabling the backlight using GPIO
   16                       and setting PWM value to 0.
   17   - brightness-levels: Array of distinct brightness levels. Typically these
   18                        are in the range from 0 to 255, but any range starting at
   19                        0 will do. The actual brightness level (PWM duty cycle)
   20                        will be interpolated from these values. 0 means a 0% duty
   21                        cycle (darkest/off), while the last value in the array
   22                        represents a 100% duty cycle (brightest).
   23   - default-brightness-level: The default brightness level (index into the
   24                               array defined by the "brightness-levels" property).
   25   - num-interpolated-steps: Number of interpolated steps between each value
   26                             of brightness-levels table. This way a high
   27                             resolution pwm duty cycle can be used without
   28                             having to list out every possible value in the
   29                             brightness-level array.
   30 
   31 [0]: Documentation/devicetree/bindings/pwm/pwm.txt
   32 [1]: Documentation/devicetree/bindings/gpio/gpio.txt
   33 
   34 Example:
   35 
   36         backlight {
   37                 compatible = "pwm-backlight";
   38                 pwms = <&pwm 0 5000000>;
   39 
   40                 brightness-levels = <0 4 8 16 32 64 128 255>;
   41                 default-brightness-level = <6>;
   42 
   43                 power-supply = <&vdd_bl_reg>;
   44                 enable-gpios = <&gpio 58 0>;
   45                 post-pwm-on-delay-ms = <10>;
   46                 pwm-off-delay-ms = <10>;
   47         };
   48 
   49 Example using num-interpolation-steps:
   50 
   51         backlight {
   52                 compatible = "pwm-backlight";
   53                 pwms = <&pwm 0 5000000>;
   54 
   55                 brightness-levels = <0 2048 4096 8192 16384 65535>;
   56                 num-interpolated-steps = <2048>;
   57                 default-brightness-level = <4096>;
   58 
   59                 power-supply = <&vdd_bl_reg>;
   60                 enable-gpios = <&gpio 58 0>;
   61         };

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FreeBSD/Linux Kernel Cross Reference sys/contrib/device-tree/Bindings/leds/backlight/pwm-backlight.txt

FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/leds/backlight/pwm-backlight.txt