Re: [PATCH v2 1/6] dt-bindings: mfd: add NXP MC33978/MC34978 MSDI

[Krzysztof Kozlowski <krzk@kernel.org>]

On 04/03/2026 10:06, David Jander wrote:
> 
> Hi Krzysztof,
> 
> On Wed, 4 Mar 2026 09:05:11 +0100
> Krzysztof Kozlowski <krzk@kernel.org> wrote:
> 
>> On Tue, Mar 03, 2026 at 05:10:20PM +0100, Oleksij Rempel wrote:
>>> Hi Krzysztof and Rob,
>>>
>>> On Tue, Mar 03, 2026 at 08:40:55AM -0600, Rob Herring (Arm) wrote:  
>>>>>  .../devicetree/bindings/mfd/nxp,mc33978.yaml  | 114 ++++++++++++++++++
>>>>>  .../bindings/pinctrl/nxp,mc33978-pinctrl.yaml |  82 +++++++++++++
>>>>>  2 files changed, 196 insertions(+)
>>>>>  create mode 100644 Documentation/devicetree/bindings/mfd/nxp,mc33978.yaml
>>>>>  create mode 100644 Documentation/devicetree/bindings/pinctrl/nxp,mc33978-pinctrl.yaml
>>>>>   
>>>>
>>>> My bot found errors running 'make dt_binding_check' on your patch:
>>>>
>>>> yamllint warnings/errors:
>>>>
>>>> dtschema/dtc warnings/errors:
>>>> /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/mfd/nxp,mc33978.example.dtb: gpio@0 (nxp,mc33978): $nodename:0: 'gpio@0' does not match '^mux-controller(@.*|-([0-9]|[1-9][0-9]+))?$'
>>>> 	from schema $id: http://devicetree.org/schemas/mux/mux-controller.yaml
>>>>   
>>>
>>> Folding the mux node into the parent as suggested [1] causes this error.
>>> Because the parent now has #mux-control-cells, the generic
>>> mux-controller.yaml forces the node name to be mux-controller. Since
>>> this chip is primarily a switch/GPIO controller, naming the parent SPI
>>> node mux-controller@0 is misleading.
>>>
>>> What is the preferred way to go here?  
>>
>> https://www.nxp.com/products/interfaces/multi-switch-detection-interface/22-i-o-msdi-programmable-current-analog-mux:MC33978
>>
>> Name of the mc33978 device is "programmable analog mux" and further
>> description says "analog multiplexer for reading analog inputs ", so I
>> don't find "mux-controller" a confusing name. It is EXACTLY a
>> mux, so mux-controller.
> 
> Sorry to chime in here. I'm afraid the NXP description on that link you posted
> is a typo. It is not correct. This chip is primarily a "Switch Detection
> Interface", or in other wordt a switch input interface. Wee here for the same
> page for the MC34978, which is the exact same chip:
> 
> https://www.nxp.com/products/interfaces/multi-switch-detection-interface/switch-detection-interface-22-i-os-programmable-wetting-current-temp-sensor-3-3-v-5-0-v-spi:MC34978

That's MC34978 and I commented on MC33978.

What is the primary function of MC33978 being described here as the base?

> 
> It has an additional function that can be used as an analog MUX, but it is an
> extra feature and definitely NOT its primary function.
> 
> Not sure if this is relevant, but I fear there might be some confusion.
> 
> Best regards,
> 
>> Anyway if you want gpio, then please add a patch extending the pattern
>> in mux-controller.yaml to allow "gpio".
>>
>> Alternative, because it is rather a mux than a controller of a mux,
>> would be to call it just "mux" or "io-mux" (maybe the latter, since we
>> have "i2c-mux" in the spec) and allow that pattern to be in
>> mux-controller.
>>
>>
>> Best regards,
>> Krzysztof
> 


Best regards,
Krzysztof