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

[me@herrie.org]

On 2026-06-05 15:04, Jonathan Cameron wrote:
> 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
> 
Hard to say, my old HP TouchPad needs 100 as a value here (taken from 
legacy 2.6.35
kernel and binaries). So we probably don't need precision, but I have no 
other
references to substantiate.

Thanks
Herman
> 
> 
>> 
>> > 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
>> >