linux-kernel - Re: [PATCH v2 1/3] ARM: imx: Allow user to disable pinctrl

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Message-Id: <5881df5a-9495-49b9-9956-0538055bba60@app.fastmail.com>
Date: Wed, 27 Nov 2024 10:18:22 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Rasmus Villemoes" <ravi@...vas.dk>, "Fabio Estevam" <festevam@...il.com>
Cc: "Guenter Roeck" <linux@...ck-us.net>,
 "Linus Walleij" <linus.walleij@...aro.org>,
 "Esben Haabendal" <esben@...nix.com>, "Russell King" <linux@...linux.org.uk>,
 "Shawn Guo" <shawnguo@...nel.org>, "Sascha Hauer" <s.hauer@...gutronix.de>,
 "Pengutronix Kernel Team" <kernel@...gutronix.de>,
 "Dong Aisheng" <aisheng.dong@....com>, "Jacky Bai" <ping.bai@....com>,
 linux-arm-kernel@...ts.infradead.org, imx@...ts.linux.dev,
 linux-kernel@...r.kernel.org,
 "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
 "Fabio Estevam" <festevam@...x.de>
Subject: Re: [PATCH v2 1/3] ARM: imx: Allow user to disable pinctrl

On Wed, Nov 27, 2024, at 10:13, Rasmus Villemoes wrote:
> On Tue, Nov 26 2024, Fabio Estevam <festevam@...il.com> wrote:
>>> Fabio submitted a patch enabling PINCTRL for imx_v4_v5_defconfig and
>>> imx_v6_v7_defconfig explicitly [1]. I don't know if that fixes the
>>> problem for good - I see CONFIG_ARCH_MXC in other configurations as
>>> well.
>>
>> Good point. I can send a v2 adding CONFIG_PINCTRL=y to the other defconfigs.
>>
>
> Instead of doing that, isn't this exactly what the 'imply' keyword is
> for?
>
> - weak reverse dependencies: "imply" <symbol> ["if" <expr>]
>
>   This is similar to "select" as it enforces a lower limit on another
>   symbol except that the "implied" symbol's value may still be set to n
>   from a direct dependency or with a visible prompt.
>
>
> So how about adding 'imply PINCTRL' in lieu of the previous 'select
> PINCTRL'? And that would also better match the intention of the patch in
> question (namely that the user needs to take explicit action to disable
> PINCTRL).

Please never use imply. Even if you think it's the right
thing in a particular case, it will come back to bite you
later.

See also https://en.wikipedia.org/wiki/COMEFROM ;-)

I would prefer we completely kill off that keyword from the Kconfig
language and replace it with the reverse 'default'. In this
particular case, having 'default ARCH_IMX' in 'PINCTRL'
would of course not be a great idea, but for the exact same
reason, the 'imply' is wrong here.

       Arnd