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: <11982b12-a359-467a-a6fc-e39adccca413@ti.com>
Date: Thu, 6 Mar 2025 03:13:33 +0530
From: "Vankar, Chintan" <c-vankar@...com>
To: Rob Herring <robh@...nel.org>
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

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.


Regards,
Chintan.


> Rob