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    SubjectRe: [PATCH] dt-bindings: backlight: Convert common backlight bindings to DT schema
    On Mon, Jun 22, 2020 at 10:57 AM Daniel Thompson
    <daniel.thompson@linaro.org> wrote:
    >
    > On Fri, Jun 19, 2020 at 11:53:41PM +0200, Sam Ravnborg wrote:
    > > > diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.yaml
    > > > new file mode 100644
    > > > index 000000000000..7e1f109a38a4
    > > > --- /dev/null
    > > > +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.yaml
    > > > @@ -0,0 +1,98 @@
    > > > +# SPDX-License-Identifier: GPL-2.0-only
    > > > +%YAML 1.2
    > > > +---
    > > > +$id: http://devicetree.org/schemas/leds/backlight/pwm-backlight.yaml#
    > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
    > > > +
    > > > +title: pwm-backlight bindings
    > > > +
    > > > +maintainers:
    > > > + - Lee Jones <lee.jones@linaro.org>
    > > > + - Daniel Thompson <daniel.thompson@linaro.org>
    > > > + - Jingoo Han <jingoohan1@gmail.com>
    > > > +
    > > > +properties:
    > > > + compatible:
    > > > + const: pwm-backlight
    > > > +
    > > > + pwms:
    > > > + maxItems: 1
    > > > +
    > > > + pwm-names: true
    > > > +
    > > > + power-supply:
    > > > + description: regulator for supply voltage
    > > > +
    > > > + enable-gpios:
    > > > + description: Contains a single GPIO specifier for the GPIO which enables
    > > > + and disables the backlight
    > > > + maxItems: 1
    > > > +
    > > > + post-pwm-on-delay-ms:
    > > > + description: Delay in ms between setting an initial (non-zero) PWM and
    > > > + enabling the backlight using GPIO.
    > > > +
    > > > + pwm-off-delay-ms:
    > > > + description: Delay in ms between disabling the backlight using GPIO
    > > > + and setting PWM value to 0.
    > > > +
    > > > + brightness-levels:
    > > > + description: Array of distinct brightness levels. Typically these are
    > > > + in the range from 0 to 255, but any range starting at 0 will do. The
    > > > + actual brightness level (PWM duty cycle) will be interpolated from
    > > > + these values. 0 means a 0% duty cycle (darkest/off), while the last
    > > > + value in the array represents a 100% duty cycle (brightest).
    > > > + $ref: /schemas/types.yaml#/definitions/uint32-array
    > > > +
    > > > + default-brightness-level:
    > > > + description: The default brightness level (index into the array defined
    > > > + by the "brightness-levels" property).
    > > > + $ref: /schemas/types.yaml#/definitions/uint32
    > > Same comment as before...
    >
    > Sorry the "ditto" meant I didn't thing about PWM as much as I should
    > have.
    >
    > The situation for PWM is a little different to LED. That's mostly
    > because we decided not to clutter the LED code with
    > "num-interpolated-steps".
    >
    > The PWM code implements the default-brightness-level as an index into
    > the brightness array *after* it has been expanded using interpolation.
    > In other words today Linux treats the default-brightness-level more
    > like[1].
    >
    > description: The default brightness level. When
    > num-interpolated-steps is not set this is simply an index into
    > the array defined by the "brightness-levels" property. If
    > num-interpolated-steps is set the brightness array will be
    > expanded by interpolation before we index to get a default
    > level.
    >
    > This is the best I have come up with so far... but I concede it still
    > lacks elegance.

    Happy to add this or whatever folks want if there's agreement, but I
    don't want to get bogged down on re-reviewing and re-writing the
    binding on what is just a conversion. There's a mountain of bindings
    to convert.

    Rob

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