linux-kernel - Re: [PATCH 1/5] dt-bindings: pinctrl: document the STMFX pinctrl bindings

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Message-ID: <b9005dd8-8214-ceab-0f88-ff1a51b44e34@st.com>
Date:   Wed, 16 May 2018 15:01:10 +0000
From:   Amelie DELAUNAY <amelie.delaunay@...com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Lee Jones <lee.jones@...aro.org>
CC:     Rob Herring <robh@...nel.org>, Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/5] dt-bindings: pinctrl: document the STMFX pinctrl
 bindings



On 05/16/2018 04:20 PM, Linus Walleij wrote:
> On Wed, May 9, 2018 at 9:56 AM, Amelie DELAUNAY <amelie.delaunay@...com> wrote:
> 
>> Indeed, stmfx has other functions than GPIO. But, after comments done
>> here: [1] and there: [2], it has been decided to move MFD parent/GPIO
>> child drivers into a single PINCTRL/GPIO driver because of the following
>> reasons:
>> - Other stmfx functions (IDD measurement and TouchScreen controller) are
>> not used on any of the boards using an stmfx and supported by Linux, so
>> no way to test these functions, and no need to maintain them while they
>> are not being used.
>> - But, in the case a new board will use more than GPIO function on
>> stmfx, the actual implementation allow to easily extract common init
>> part of stmfx and put it in an MFD driver.
>>
>> So I could remove gpio sub-node and put its contents in stmfx node and
>> keep single PINCTRL/GPIO driver for the time being.
>> Please advise,
> 
> I would normally advice to use the right modeling from the start, create
> the MFD driver and spawn the devices from there. It is confusing
> if the layout of the driver(s) doesn't really match the layout of the
> hardware.
> 
> I understand that it is a pain to write new MFD drivers to get your
> things going and it would be "nice to get this working really quick
> now" but in my experience it is better to do it right from the start.
> 

Hi Linus,

Thanks for your advice. I understand the point.
So, the right modeling would be to:
- create an MFD driver with the common init part of stmfx
- remove all common init part of stmfx-pinctrl driver and keep only all 
gpio/pinctrl functions.

I will not develop the other stmfx functions (IDD measurement driver and 
TouchScreen controller driver) because, as explained ealier, they are 
not used on any of the boards using an stmfx and supported by Linux, so 
no way to test these functions, and no need to maintain them while they 
are not being used.

Lee, are you OK with that ?

Regards,
Amelie