Re: [PATCH] dt-bindings: hwmon: microchip,emc2305: add vcc-supply and #cooling-cells

[Guenter Roeck]

On 8/24/26 10:00, Conor Dooley wrote:
> On Mon, Aug 24, 2026 at 05:42:59PM +0200, Vincent Jardin via B4 Relay wrote:
> > From: Vincent Jardin <vjardin@xxxxxxx>
> >
> > Both properties are missing, so a board that supplies either fails with
> > dtbs_check:
> >
> >    fan-controller@2c (microchip,emc2305): '#cooling-cells', 'vcc-supply'
> >    do not match any of the regexes: '^fan@[0-4]$', '^pinctrl-[0-9]+$'
> >
> > The #cooling-cells property belongs to the controller node, which is
> > where the driver actually registers.
> >
> > Two cells is what that registration needs: a cooling-maps entry
> > references the fan as <&emc2305 min max>.
> >
> > Two cells also documents what the driver supports today. The
> > pwm-separate path registers one cooling device per PWM against the same
> > node, and they all get cdev_id 0, so no cell count can tell them apart.
> > That is a driver issue, noted here but not addressed.
> >
> > The examples in this binding put that property on the fan@N subnodes
> > instead, which does not match what the driver does: they are left alone
> > here rather than changed blind.
>
> That seems correct though and putting it in the device node when there's 4
> fans that could interact with different zones seems wrong. Shouldn't the
> driver be fixed instead?

I am a bit (or, rather, more than a bit) concerned about Sashiko's feedback:

New issues:
- [Medium] The commit message makes materially false claims about the driver's
  device tree parsing logic to justify leaving the binding examples unchanged.

Guenter

> > vcc-supply describes the chip's own rail, which matters on boards where
> > the sensor sits behind a switched supply.
> >
> > Signed-off-by: Vincent Jardin <vjardin@xxxxxxx>
> > ---
> >   Documentation/devicetree/bindings/hwmon/microchip,emc2305.yaml | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/hwmon/microchip,emc2305.yaml b/Documentation/devicetree/bindings/hwmon/microchip,emc2305.yaml
> > index 8c2548539d7fd..47640214de100 100644
> > --- a/Documentation/devicetree/bindings/hwmon/microchip,emc2305.yaml
> > +++ b/Documentation/devicetree/bindings/hwmon/microchip,emc2305.yaml
> > @@ -44,6 +44,11 @@ properties:
> >              - 0 (Open-Drain)
> >              - 1 (Push-Pull)
> >   
> > +  vcc-supply: true
> > +
> > +  "#cooling-cells":
> > +    const: 2
> > +
> >   patternProperties:
> >     '^fan@[0-4]$':
> >       $ref: fan-common.yaml#
> >
> > ---
> > base-commit: 0a0d1d55dad570724bf8c7ea83409639cfb4be9b
> > change-id: 20260824-for-upstream-dt-emc2305-vcc-cooling-251655c99ef8
> >
> > Best regards,
> > --
> > Vincent Jardin <vjardin@xxxxxxx>