Re: [PATCH v3 5/7] dt-bindings: mfd: Add synology,microp device

[Markus Probst <markus.probst@posteo.de>]

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On Sat, 2026-03-14 at 09:49 +0100, Krzysztof Kozlowski wrote:
> On 13/03/2026 21:29, Markus Probst wrote:
> > 
> > > This is not an "MFD" device.
> > It now uses the MFD APIs. By the definiton of @Lee (assuming I
> > understood it correctly), this device should now qualify as "MFD"
> > device.
> 
> No. Using Linux framework does not make this device MFD, since there is
> no such term of hardware as MFD. Otherwise please explain or link to
> verifiable external source describing what sort of device class is MFD
I assumed these comments would also apply for the dt bindings:
-
https://lore.kernel.org/rust-for-linux/DGYAFNSJ7576.1E0JZ2W499ZQ7@kernel.org/
-
https://lore.kernel.org/rust-for-linux/20260309151555.GU183676@google.com/

given that using linux MFD APIs also changes the structure of the dt
bindings with added sub-devices.

But it seems no?

> because for sure this is not MFD how Wikipedia defines it.

Wikipedia defines it as a synonym for a "multi-function
product/printer/peripheral"
https://en.wikipedia.org/wiki/Multifunction_device

> 
> > 
> > > > +
> > > > +    mcu {
> > > 
> > > Please read previous comments.
> > 
> > You are likly trying to refer to this comment from you:
> > > Depending what this is. MCU is generic purpose unit where you load
> > your
> > > different FW for different purposes and you have here specific - to
> > > handle certain aspects of this entire machine. This looks like EC, so
> > > should be called embedded-controller and placed in that directory.
> > Synology uses Microchip PIC for this purpose. On a Synology DS215j, it
> > uses a "Microchip PIC16F1829". At least to me, this looks like a
> 
> It does not matter what chip is used. Every component uses some sort of
> chip.
I would be interested in what does matter then.

I did not actually find an exact definition for what
Documentation/devicetree/bindings/mfd
and
Documentation/devicetree/bindings/embedded-controller
is for in the kernel tree or in the devicetree spec.

> 
> > general purpose microcontroller with firmware from synology flashed
> > onto it. Therefore it is a MCU.
> 
> Every chip is then an MCU with such logic. Every PMIC, every EC.
> 
> This is for me clearly embedded controller and that's where this should
> be placed and called.
In that case I will move it to
Documentation/devicetree/bindings/embedded-controller and update the
node name used in the example.

I will wait a bit for the other patches to be reviewed before sending a
next revision.

But I wonder how
Documentation/devicetree/bindings/mfd/qnap,ts433-mcu.yaml
got in there then, given it is pretty similar to this device in the
functionality it provides.

> 
> Best regards,
> Krzysztof

Thanks
- Markus Probst

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