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

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Message-ID: <DU2PR01MB80349344FB8CB1415BFA917DF9C4A@DU2PR01MB8034.eurprd01.prod.exchangelabs.com>
Date:   Tue, 3 Oct 2023 16:00:32 +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?
> 
> 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

> 
> 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

> 
> 
> Daniel.

Thanks an best regards,
Flavio