linux-kernel - RE: [PATCH 1/1] dt-bindings: backlight: mp3309c: remove two required properties

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Date:   Wed, 25 Oct 2023 07:02:02 +0000
From:   Flavio Suligoi <f.suligoi@...m.it>
To:     Conor Dooley <conor@...nel.org>
CC:     Lee Jones <lee@...nel.org>,
        Daniel Thompson <daniel.thompson@...aro.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>
Subject: RE: [PATCH 1/1] dt-bindings: backlight: mp3309c: remove two required
 properties

Hi Conor,

...

> > > > > > The two properties:
> > > > > >
> > > > > > - max-brightness
> > > > > > - default brightness
> > > > > >
> > > > > > are not really required, so they can be removed from the "required"
> > > > > > section.
> > > > >
> > > > > Why are they not required? You need to provide an explanation.
> > > >
> > > > The "max-brightness" is not more used now in the driver (I used it
> > > > in the first version of the driver).
> > >
> > > If it is not used any more, what happens when someone passes an old
> > > devicetree to the kernel, that contains max-brightness, but not any
> > > of your new properties?
> >
> > This is not a problem, because the device driver has not yet been included in
> any kernel.
> > My patch for the device driver is still being analyzed by the maintainers.
> > Only this dt-binding yaml file is already included in the
> > "for-backlight-next" branch of the "backlight" kernel repository.
> > At the moment, this driver is used only in a i.MX8MM board produced in
> > my company, under my full control. No other developer is using it now.
> 
> Right. This is exactly the sort of commentary that you need to provide up
> front, to have us spent a bunch of time going back and forth to figure out :(

I'm sorry for wasting your time, I'll add this information in the next commit.

> 
> > > > The "default-brightness", if omitted in the DT, is managed by the
> > > > device driver, using a default value. This depends on the dimming
> > > > mode
> > > used:
> > >
> > > For default-brightness, has here always been support in the driver
> > > for the property being omitted, or is this newly added?
> >
> > In the first version of the driver this property was a "required
> > property", but nobody has used this driver before, so this should be not a
> problem.
> 
> > > What I would like is an explanation in the commit message as to why
> > > the revised example is more helpful than the existing (and
> > > must-remain-valid) one.
> >
> > As said before, no one may have ever used this device driver, so I
> > would leave only this new version of the example.
> 
> Okay. Please improve the commit message explaining why it is okay to make
> these changes & send a v2.
> The alternative is that Lee drops the dt-binding patch & you submit a revised
> version of the binding alongside the next iteration of the driver.

Ok, I'll send a new commit v2, explaining the reasons for the changes.

> 
> Cheers,
> Conor.

Thank you Conor,
Flavio.