Re: [PATCH v3 2/3] dt-bindings: iio: light: isl29018: add isil,cover-comp-gain

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 4 Jun 2026 18:01:08 +0100
Conor Dooley <conor@kernel.org> wrote:

> On Thu, Jun 04, 2026 at 12:06:16PM +0200, Herman van Hazendonk wrote:
> > Document the new optional property that seeds the ISL29018 calibration
> > scale factor at boot from firmware, allowing boards with tinted cover
> > glass to ship with correct luminance readings without a userspace helper.
> > 
> > The value is a positive integer (minimum 1, maximum 65535) that is
> > multiplied with the raw lux reading.  Userspace can still override it
> > at runtime through in_illuminance0_calibscale.
> > 
> > Signed-off-by: Herman van Hazendonk <github.com@herrie.org>
> > ---
> >  .../devicetree/bindings/iio/light/isl29018.yaml     | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/light/isl29018.yaml b/Documentation/devicetree/bindings/iio/light/isl29018.yaml
> > index 0ea278b07d1c..92ea2742bbd3 100644
> > --- a/Documentation/devicetree/bindings/iio/light/isl29018.yaml
> > +++ b/Documentation/devicetree/bindings/iio/light/isl29018.yaml
> > @@ -34,6 +34,19 @@ properties:
> >    vcc-supply:
> >      description: Regulator that provides power to the sensor
> >  
> > +  isil,cover-comp-gain:
> > +    description: |
> > +      Multiplier applied to the ambient-light reading at startup to
> > +      compensate for optical loss in the board's cover glass. Boards
> > +      that mount the sensor under a tinted or coated window typically
> > +      need a value between a few and a few hundred.  

Is it useful to support decimal points on these values?  The userspace interface
does and you mention the 'right' answer might be only a few which means precision
at that range will be terrible - less of an issue if 100s!

Thanks

Jonathan



> 
> > The value seeds
> > +      in_illuminance0_calibscale, so it can still be retuned at
> > +      runtime through sysfs.  
> 
> Delete this, driver implementation stuff isn't relevant to the
> devicetree binding.
> 
> With that gone,
> Acked-by: Conor Dooley <conor.dooley@microchip.com>
> 
> pw-bot: changes-requested
> 
> Cheers,
> Conor.
> 
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    minimum: 1
> > +    maximum: 65535
> > +    default: 1
> > +
> >  required:
> >    - compatible
> >    - reg
> > -- 
> > 2.43.0
> >