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

[Rob Herring <robh@kernel.org>]

On Tue, Oct 13, 2026 at 04:57:29PM +0200, Kory Maincent wrote:
> 
> 
> On 10/10/26 09:30, 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@est.tech>
> > > > ---
> > > >   .../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@est.tech>
> > > > +
> > > > +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]$':
> > > > +        type: object
> > > > +        additionalProperties: true
> > > 
> > > This cannot be true. That allows adding any property.
> > > 
> > 
> > So my intent with the additionalProperties: true was to avoid
> > replicating the entire pse-pis node from pse-controller.yaml.
> > Conceptually, my goal was to inherit everything from the
> > pse-controller.yaml binding, except limit the maxItems to 1 (since the
> > LTC4266 only supports power over a single PI).
> > 
> > Is there a better way to express this?
> 
> I think you can do something like this:
>      patternProperties:
> 
>        '^pse-pi@[0-3]$':
> 
>          type: object
> 
>          $ref:
> pse-controller.yaml#/properties/pse-pis/patternProperties/^pse-pi@[0-9a-f]+$
> 
>          unevaluatedProperties: false

Yes, if you want/need to allow custom properties, like this is what I 
meant.

However, it is hit or miss if a $ref to a regex works. Instead, 
pse-controller.yaml would need a $defs section that the pattern and this 
schema can reference. Multiple levels of nodes and allowing them to be 
extended gets messy.

Rob