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    SubjectRe: [PATCH 2/4] dt-bindings: pwm-backlight: add a num-interpolation-steps property.
    On Wed, Jan 10, 2018 at 11:30:44PM +0100, Enric Balletbo i Serra wrote:
    > The num-interpolated-steps property specifies the number of
    > interpolated steps between each value of brightness-level table. This is
    > useful for high resolution PWMs to not have to list out every possible
    > value in the brightness-level array.
    >
    > Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
    > ---
    > .../bindings/leds/backlight/pwm-backlight.txt | 21 +++++++++++++++++++++
    > 1 file changed, 21 insertions(+)
    >
    > diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
    > index 310810906613..605432c910c5 100644
    > --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
    > +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
    > @@ -21,6 +21,11 @@ Optional properties:
    > and enabling the backlight using GPIO.
    > - pwm-off-delay-ms: Delay in ms between disabling the backlight using GPIO
    > and setting PWM value to 0.
    > + - num-interpolated-steps: Number of interpolated steps between each value
    > + of brightness-levels table. This way a high
    > + resolution pwm duty cycle can be used without
    > + having to list out every possible value in the
    > + brightness-level array.
    >
    > [0]: Documentation/devicetree/bindings/pwm/pwm.txt
    > [1]: Documentation/devicetree/bindings/gpio/gpio.txt
    > @@ -39,3 +44,19 @@ Example:
    > post-pwm-on-delay-ms = <10>;
    > pwm-off-delay-ms = <10>;
    > };
    > +
    > +Example using num-interpolation-steps:
    > +
    > + backlight {
    > + compatible = "pwm-backlight";
    > + pwms = <&pwm 0 5000000>;
    > +
    > + brightness-levels = <0 65535>;
    > + num-interpolated-steps = <4096>;

    How does this make sense with only 2 defined levels other than having
    fewer steps? I thought the purpose of this was to have a piecewise
    linear curve.

    > + default-brightness-level = <6>;

    Aren't valid values 0, 16, 32, 48, etc.?

    Rob

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