Re: [PATCH v7 1/2] dt-bindings: iio: proximity: add ST VL53L1X ToF sensor

[Jonathan Cameron]

On Wed, 25 Mar 2026 15:18:05 +0600
Sirat <email@xxxxxxxx> wrote:

> On Wed, Mar 25, 2026 at 2:58 PM Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote:
> >
> > On 25/03/2026 09:48, Sirat wrote:  
> > > On Wed, Mar 25, 2026 at 2:05 PM Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote:  
> > >>
> > >> On Wed, Mar 25, 2026 at 12:32:22PM +0600, Siratul Islam wrote:  
> > >>> Add device tree binding documentation for the STMicroelectronics
> > >>> VL53L1X Time-of-Flight ranging sensor connected via I2C.
> > >>>
> > >>> Make vdd-supply required. The device requires power to operate
> > >>> and the property should have been required from the start.  
> > >>
> > >> That's ABI break and device for many years was working fine, so this
> > >> should not be changed.
> > >>  
> > > Jonathan and David asked that vdd-supply be made required. I feel like
> > > there is a conflict here that I am not able to resolve myself.
> > >
> > > What I think about it is the binding does not correctly describe the
> > > hardware and we should consider this a bug and fix it.
> > > The driver worked because of a fallback mechanism (dummy/fake
> > > regulator) and not because power was optional.
> > >  
> >
> >
> > I looked at v6 and v5 and I do not see such comment for binding that
> > existing device should change ABI. Can you point me to it?
> >  
> "Make it required and add a note to the commit message to say why the
> requirement should always have been there. Devices tend not to work
> with no power." - Jonathan (v3:
> https://lore.kernel.org/linux-iio/20260322115704.10b2e0d4@jic23-huawei)
> 
> "No, bindings should not depend on driver implementation." - David
> (When I asked if I should  drop the hard requirement in the binding,
> v6: https://lore.kernel.org/linux-iio/55e92148-b5de-4fb8-af0b-9476235341bc@xxxxxxxxxxxx/)
> 
> "From the point of view of the devicetree, it doesn't matter what the
> driver does. It matters that the chip can't work without power. ;-)" -
> David (v1: https://lore.kernel.org/linux-iio/d0ec6a2f-6d30-4774-8950-15dd3c4b020b@xxxxxxxxxxxx)
> 
> I'm not sure if this is the correct way to quote. But I have added the links.

This came up a few years back - though I doubt I can track down the
exact discussion however.

From a Linux point of view we are breaking binding checks only if the
supply (that should always have been there as chips tend not to work
well without power) is not present.  We absolutely have to
keep the driver running whether or not the supply is specified.
Do other DT users provide such a constraint? I've no idea.

If the DT maintainer preference is leave it not required (perhaps
with a comment saying new users of the binding should supply it)
then that's fine by me. I'll keep it in mind for future similar changes.

Thanks,

Jonathan

> 
> Thanks,
> Sirat
> 
>