Re: [PATCH 1/2] dt-bindings: leds: backlight: add Kinetic KTD3137

[Roman Vivchar]

On Tuesday, November 3rd, 2026 at 4:42 PM, Daniel Thompson <danielt@xxxxxxxxxx> wrote:

> On Tue, Nov 03, 2026 at 02:34:02PM +0000, Roman Vivchar wrote:
> > Hi Daniel,
> >
> > On Tuesday, November 3rd, 2026 at 4:05 PM, Daniel Thompson <danielt@xxxxxxxxxx> wrote:
> > > On Mon, Nov 02, 2026 at 09:58:48PM +0200, Roman Vivchar via B4 Relay wrote:
> > > > +  led-max-microamp:
> > > > +    minimum: 5000
> > > > +    maximum: 29800
> > > > +    default: 20200
> > > > +
> > > > +  vin-supply: true
> > > > +
> > > > +required:
> > > > +  - compatible
> > > > +  - reg
> > > > +  - vin-supply
> > >
> > > Why is vin-supply required?
> > >
> >
> > The chip cannot function without VIN power supply. Even if it's on the
> > always-on power rail on certain board, there's always a chance it might be
> > accidentally left disabled on the other. It's better to document supply in
> > the bindings as far as I understand.
>
> You haven't just documented the binding, you have also made the property
> mandatory by adding it to required.
>
> So what I am asking is why is this property listed as required. You
> didn't implement the driver in a way that makes the supply mandatory.

Not sure I follow.

In the driver I've used devm_regulator_get_enable(), rather than _optional(),
since my understanding is that the non-optional helper is a standard kernel
API for required supplies (with regulator core warning and fallback to dummy
regulator in case DT omits it).

Do you suggest dropping vin-supply from required: ? On my board it's connected
to an always-on supply, though I can't tell about others. I can proceed with
this if the DT maintainers are okay with that.

>
> Daniel.
>