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

[Kory Maincent <kory.maincent@bootlin.com>]

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 
  

          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

>>> +        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
> 
>             pse_pi2: pse-pi@2 {
> -            reg = <2>;
> -            #pse-cells = <0>;
> -            pairset-names = "alternative-a";
> -            pairsets = <&phys2>;
> -            polarity-supported = "MDI";
> -            vpwr-supply = <&vreg_pse>;
>             };
> 
> Then make dt_binding_check will fail with
> 
>    DTEX    Documentation/devicetree/bindings/net/pse-pd/lltc,ltc4266.example.dts
>    DTC [C] Documentation/devicetree/bindings/net/pse-pd/lltc,ltc4266.example.dtb
> Documentation/devicetree/bindings/net/pse-pd/lltc,ltc4266.example.dts:83.33-84.17: Warning (unit_address_vs_reg): /example-0/i2c/ethernet-pse@2f/pse-pis/pse-pi@2: node has a unit name, but no reg or ranges property
> Documentation/devicetree/bindings/net/pse-pd/lltc,ltc4266.example.dtb: ethernet-pse@2f (lltc,ltc4266): pse-pis:pse-pi@2: 'reg' is a required property
> 	from schema $id: http://devicetree.org/schemas/net/pse-pd/lltc,ltc4266.yaml
> Documentation/devicetree/bindings/net/pse-pd/lltc,ltc4266.example.dtb: ethernet-pse@2f (lltc,ltc4266): pse-pis:pse-pi@2: '#pse-cells' is a required property
> 	from schema $id:
> 	http://devicetree.org/schemas/net/pse-pd/lltc,ltc4266.yaml
> 
> But I'm probably missing something obvious, so please don't hesitate to
> point it out or point me to docs.
You are right on this, it should not be needed.

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com