HI Daniel,

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+required:
+  - compatible
+  - reg
+  - max-brightness

Why is this mandatory?

There's no point in setting max-brightness when running in I2C
mode
(max- brightness should default to 31 in that case).

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+  - default-brightness

Again. I'm not clear why this needs to be mandatory.

Ok, you are right, I'll remove max-brightness and
default-brightness from required properties list. I think to
change these properties, for the pwm dimming, into a clearer:

- brightness-levels (uint32)
- default-brightness-levels (uint32).

For example:

  brightness-levels:
    description:
      Number of brightness levels. The actual brightness
      level (PWM duty cycle) will be interpolated from 0 to this value.
      0 means a  0% duty cycle (darkest/off), while the
brightness-levels

represents

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      a 100% duty cycle (brightest).
    $ref: /schemas/types.yaml#/definitions/uint32

  default-brightness-level:
    description:
      The default brightness level (from 0 to brightness-levels)
    $ref: /schemas/types.yaml#/definitions/uint32

Example:
brightness-levels = <10>;
default-brightness-level = <6>;

What do you think about this solution?

If you want to introduce a brightness-levels property then I would
expect it to be defined with the same meaning as pwm-backlight
(it's not relevant to the bindings but ideally it would be
implemented by refactoring and reusing the code from pwm_bl.c).

ok, I'll use the brightness-levels property as used in pwm-backlight

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Same with default-brightness-level although I'm not sure why one
wouldn't just use default-brightness for new bindings (doesn't
default-brightness-level simply do exactly the same thing as
default-

brightness).

ok for default-brightness instead of default-brightness-level

Just a question: default-brightness-level is the index into the brightness-

levels array.

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But, if I use default-brightness instead of default-brightness-level,
should I consider default-brightness also as an index into brightness-levels

array?

Yes.

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Or, in this case, have the default-brightness to be equal to one of
the values inside the brightness-levels array?

When there is a brightness array (and there is no interpolation) then it is
indexed by brightness. The values in the array are not brightness (e.g. the
controlable value describing the output of the hardware). The values in the
table are merely the PWM duty cycle...

ok

Main difference is, with a correct table the brightness can use an appropriate
logarithmic power scale (which matches how humans perceive
brightness) instead of the linear scale provided by the PWM duty cycle.


Daniel.


Brightness and "index into the brightness-levels array" should be one and the
same thing

ok, I'll use default-brightness, thanks for the explanations!

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Daniel.

Thanks an best regards,
Flavio

Thanks,

Flavio

Flavio