linux-kernel - Re: [RFC PATCH v2 1/2] devicetree: bindings: mux: reg-mux: Update bindings for reg-mux for new property

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Message-ID: <CAL_JsqLb5hrYD_-dqW5ELtbXohd8a1UL7nOuP2a9ZhE+3+f=eA@mail.gmail.com>
Date: Wed, 5 Mar 2025 16:14:09 -0600
From: Rob Herring <robh@...nel.org>
To: "Vankar, Chintan" <c-vankar@...com>
Cc: Conor Dooley <conor+dt@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Peter Rosin <peda@...ntia.se>, s-vadapalli@...com, danishanwar@...com, 
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	Vignesh Raghavendra <vigneshr@...com>, Nishanth Menon <nm@...com>
Subject: Re: [RFC PATCH v2 1/2] devicetree: bindings: mux: reg-mux: Update
 bindings for reg-mux for new property

On Wed, Mar 5, 2025 at 3:43 PM Vankar, Chintan <c-vankar@...com> wrote:
>
> Hello Rob,
>
> On 3/5/2025 2:10 AM, Rob Herring wrote:
> > On Tue, Mar 4, 2025 at 1:03 PM Vankar, Chintan <c-vankar@...com> wrote:
> >>
> >> Hello Rob,
> >>
> >> On 3/4/2025 9:09 PM, Rob Herring wrote:
> >>> On Tue, Mar 04, 2025 at 03:53:05PM +0530, Chintan Vankar wrote:
> >>>> DT-binding of reg-mux is defined in such a way that one need to provide
> >>>> register offset and mask in a "mux-reg-masks" property and corresponding
> >>>> register value in "idle-states" property. This constraint forces to define
> >>>> these values in such a way that "mux-reg-masks" and "idle-states" must be
> >>>> in sync with each other. This implementation would be more complex if
> >>>> specific register or set of registers need to be configured which has
> >>>> large memory space. Introduce a new property "mux-reg-masks-state" which
> >>>> allow to specify offset, mask and value as a tuple in a single property.
> >>>
> >>> Maybe in hindsight that would have been better, but having 2 ways to
> >>> specify the same thing that we have to maintain forever is not an
> >>> improvement.
> >>>
> >>> No one is making you use this binding. If you have a large number of
> >>> muxes, then maybe you should use a specific binding.
> >>>
> >>
> >> Thank you for reviewing the patch. The reason behind choosing mux
> >> subsystem is working and implementation of mmio driver. As we can see
> >> that implementing this new property in mux-controller is almost
> >> identical to mmio driver, and it would make it easier to define and
> >> extend mux-controller's functionality. If we introduce the new driver
> >> than that would be most likely a clone of mmio driver.
> >
> > I'm talking about the binding, not the driver. They are independent.
> > Generic drivers are great. I love them. Generic bindings, not so much.
> >
> >> Let me know if implementation would be accepted by adding a new
> >> compatible for it.
> >
> > Adding a new compatible to the mmio driver? Certainly. That happens
> > all the time.
> >
> > I also didn't say don't use this binding as-is. That's fine too.
> >
>
> Can you please review the following binding:
>
> oneOf:
>    - required: [ mux-reg-masks ]
>    - required: [ mux-reg-masks-state ]
>
> allOf:
>    - if:
>        required:
>          - mux-reg-masks-state
>      then:
>        properties:
>          idle-states: false
>
> required:
>    - compatible
>    - '#mux-control-cells'
>
> I think it won't disturb the current bindings and keep backward
> compatibility with existing implementation.

Wasn't that the case before? There's nothing really different here.

Rob