Re: [PATCH net-next v3 1/2] dt-bindings: net: pse-pd: Add bindings for LTC4266 PSE Controller

[Rob Herring]

On Sat, Oct 10, 2026 at 07:30:50AM +0000, Kyle Swenson wrote:
> Hello Rob,
> 
> On Wed, Oct 07, 2026 at 04:04:54PM -0500, Rob Herring wrote:
> > On Sun, Sep 27, 2026 at 09:29:48PM +0000, Kyle Swenson wrote:
> > > Add the LTC4266 Power Sourcing Equipment controller device tree bindings
> > > documentation.
> > > 
> > > Signed-off-by: Kyle Swenson <kyle.swenson@xxxxxxxx>
> > > ---
> > >  .../bindings/net/pse-pd/lltc,ltc4266.yaml     | 180 ++++++++++++++++++
> > >  1 file changed, 180 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/net/pse-pd/lltc,ltc4266.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/net/pse-pd/lltc,ltc4266.yaml b/Documentation/devicetree/bindings/net/pse-pd/lltc,ltc4266.yaml
> > > new file mode 100644
> > > index 000000000000..e11c9d601eee
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/net/pse-pd/lltc,ltc4266.yaml
> > > @@ -0,0 +1,180 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/net/pse-pd/lltc,ltc4266.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Linear Technology LTC4266 Power Sourcing Equipment controller
> > > +
> > > +maintainers:
> > > +  - Kyle Swenson <kyle.swenson@xxxxxxxx>
> > > +
> > > +allOf:
> > > +  - $ref: pse-controller.yaml#
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - lltc,ltc4266
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  interrupts:
> > > +    maxItems: 1
> > > +
> > > +  channels:
> > > +    type: object
> > > +    additionalProperties: false
> > > +    description:
> > > +      Defines the 4 physical delivery channels on the controller that can be
> > > +      referenced by PSE PIs through their "pairsets" property. The actual port
> > > +      matrix mapping is created when PSE PIs reference these channels in their
> > > +      pairsets.
> > > +
> > > +    properties:
> > > +      '#address-cells':
> > > +        const: 1
> > > +
> > > +      '#size-cells':
> > > +        const: 0
> > > +
> > > +    patternProperties:
> > > +      '^channel@[0-3]$':
> > > +        type: object
> > > +        additionalProperties: false
> > > +
> > > +        properties:
> > > +          reg:
> > > +            maxItems: 1
> > > +
> > > +          sense-resistor-micro-ohms:
> > > +            description: Sense resistor connected to the channel's MOSFET, used
> > > +              for current measurement and for overcurrent detection. The I_CUT
> > > +              and I_LIM register encodings depend on which value is fitted, so
> > > +              a wrong value programs the wrong thresholds.
> > > +            enum: [250000, 500000]
> > > +
> > > +        required:
> > > +          - reg
> > > +          - sense-resistor-micro-ohms
> > > +
> > > +    required:
> > > +      - '#address-cells'
> > > +      - '#size-cells'
> > > +
> > > +  pse-pis:
> > > +    type: object
> > > +    additionalProperties: false
> > > +
> > > +    properties:
> > > +      '#address-cells':
> > > +        const: 1
> > > +
> > > +      '#size-cells':
> > > +        const: 0
> > > +
> > > +    patternProperties:
> > > +      '^pse-pi@[0-3]$':
> > > +        type: object
> > > +        additionalProperties: true
> > 
> > This cannot be true. That allows adding any property.
> > 
> 
> So my intent with the additionalProperties: true was to avoid
> replicating the entire pse-pis node from pse-controller.yaml.
> Conceptually, my goal was to inherit everything from the
> pse-controller.yaml binding, except limit the maxItems to 1 (since the
> LTC4266 only supports power over a single PI).

pse-controller.yaml doesn't have the constraint there either. It is fine 
if the constraint is there. However, that means custom properties are not 
allowed in pse-pi nodes. Maybe that's fine and is certainly easier for 
the schema. If you do forsee a need for device specific properties in 
this node, then you need a $ref in this node with all the common 
properties. IOW, similar to how the graph schema is structured.


> > > +        properties:
> > > +          pairsets:
> > > +            description: The LTC4266 delivers power to a PI over a single
> > > +              pairset, driven by one of the controller's four channels. There
> > > +              is no 4-pair mode spreading a PI over two channels, so exactly
> > > +              one channel phandle is expected.
> > > +            maxItems: 1
> > > +          pairset-names:
> > > +            maxItems: 1
> > 
> > An empty node is valid? Needs 'required'.
> 
> I thought the 'required' comes from the pse-controller.yaml binding.
> If I adjust the example dts in the binding with something like

Indeed. My mistake.

> 
>            pse_pi2: pse-pi@2 {
> -            reg = <2>;
> -            #pse-cells = <0>;
> -            pairset-names = "alternative-a";
> -            pairsets = <&phys2>;
> -            polarity-supported = "MDI";
> -            vpwr-supply = <&vreg_pse>;

If instead, you add 'foo-bar' property, you won't see any failure. 
That's the 1st issue.

Rob