Re: Phandles

Kyle Bonnici
2026-04-12T16:37:44Z

> On 12 Apr 2026, at 17:40, Herve Codina <herve.codina@bootlin.com> wrote:
>
> Hi Kyle,
>
> +Cc Kernel device-tree maintainers
>
> On Sun, 12 Apr 2026 13:51:35 +0000
> Kyle Bonnici <kylebonnici@hotmail.com> wrote:
>
>>> On 12 Apr 2026, at 14:51, Herve Codina <herve.codina@bootlin.com> wrote:
>>>
>>> Hi Kyle,
>>>
>>> On Sat, 11 Apr 2026 18:33:33 +0000
>>> Kyle Bonnici <kylebonnici@hotmail.com> wrote:
>>>
>>>> Hi
>>>>
>>>> I have been looking at the the code for the compiler and I am wondering which specifications marks the below properties MUST BE Nexus Properties hence the validation.
>>>>
>>>> WARNING_PROPERTY_PHANDLE_CELLS(clocks, "clocks", "#clock-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(cooling_device, "cooling-device", "#cooling-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(dmas, "dmas", "#dma-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(hwlocks, "hwlocks", "#hwlock-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(interrupts_extended, "interrupts-extended", "#interrupt-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(io_channels, "io-channels", "#io-channel-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(iommus, "iommus", "#iommu-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(mboxes, "mboxes", "#mbox-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(msi_parent, "msi-parent", "#msi-cells", true);
>>>> WARNING_PROPERTY_PHANDLE_CELLS(mux_controls, "mux-controls", "#mux-control-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(phys, "phys", "#phy-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(power_domains, "power-domains", "#power-domain-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(pwms, "pwms", "#pwm-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(resets, "resets", "#reset-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(sound_dai, "sound-dai", "#sound-dai-cells");
>>>> WARNING_PROPERTY_PHANDLE_CELLS(thermal_sensors, "thermal-sensors", "#thermal-sensor-cells");
>>>
>>> All of those properties are defined as phandles.
>>>
>>> For instance, the 'pwms' property available in a node means the the node is
>>> a pwm consumer. It must follow the pwm consumer binding [1] and so a phandle
>>> is involved.
>>>
>>> This phandle can have arguments and the number of argument is defined by the
>>> #pwm-cells property set in the pwm provider node [2], [3].
>>>
>>> [1] https://elixir.bootlin.com/zephyr/v4.4.0-rc3/source/dts/bindings/pwm/pwm-controller.yaml
>>> [2] https://github.com/zephyrproject-rtos/zephyr/blob/main/dts/bindings/pwm/pwm-controller.yaml
>>> [3] https://elixir.bootlin.com/linux/v7.0-rc7/source/Documentation/devicetree/bindings/pwm/pwm.yaml
>>>
>>>>
>>>>
>>>> These can be found here: https://github.com/dgibson/dtc/blob/main/checks.c#L1498 this is relevant for https://github.com/zephyrproject-rtos/zephyr/issues/107066
>>>
>>> Examples provided in the zephyrproject issue link are, in my opinion, incorrect.
>>>
>>> Case 1:
>>> / {
>>> node1 {
>>> pwms = <1 &pwm0 1 20 PWM_POLARITY_NORMAL>;
>>>
>>> Here the first cell '1' is not a phandle.
>>
>> Here the compiler is making an assumption here that all `pwms` properties must be specifier properties and all use `pwm` specifier.
>
> I think the purpose of 'select: true' is to have the binding always applied:
> https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/pwm/pwm-consumer.yaml#L15
>

I’m having trouble finding where the Devicetree Specification (v0.4) mandates that all binding systems must extend dt-schema.
Since this requirement isn't explicitly in the spec, it follows that the WARNING_PROPERTY_PHANDLE_CELLS validation belongs in dt-validate rather than within dtc itself.

> If this is confirmed, DTC performs correct checks as this binding must always
> be applied and so the 'pwms' property must be a phandle-array property.
>
> Device-tree maintainers, can you confirm the purpose of 'select: true' set
> in a DT binding ?
>
> Best regards,
> Hervé