linux-kernel - RE: [PATCH v3 1/2] dt-bindings: backlight: Add MPS MP3309C

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Date:   Tue, 3 Oct 2023 09:43:15 +0000
From:   Flavio Suligoi <f.suligoi@...m.it>
To:     Daniel Thompson <daniel.thompson@...aro.org>
CC:     Lee Jones <lee@...nel.org>, Jingoo Han <jingoohan1@...il.com>,
        Helge Deller <deller@....de>, Pavel Machek <pavel@....cz>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh@...nel.org>
Subject: RE: [PATCH v3 1/2] dt-bindings: backlight: Add MPS MP3309C

Hi Daniel,

...

> > +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).
> 
> 
> > +  - 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
      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?

> Daniel.

Thanks for your help,
Flavio