linux-kernel - Re: [PATCH v2] gpio: mxc: configure dynamic GPIO base for CONFIG_GPIO

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Message-ID: <CACRpkdaBrxwWd4JPAJCZRj1Ov8a_6U+idGzi2pnEr4MJ0Eyf2Q@mail.gmail.com>
Date: Tue, 13 May 2025 15:04:28 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc: Bartosz Golaszewski <brgl@...ev.pl>, Shawn Guo <shawnguo@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>, 
	Fabio Estevam <festevam@...il.com>, linux-gpio@...r.kernel.org, 
	Dario Binacchi <dario.binacchi@...rulasolutions.com>, Haibo Chen <haibo.chen@....com>, 
	Catalin Popescu <catalin.popescu@...ca-geosystems.com>, imx@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] gpio: mxc: configure dynamic GPIO base for CONFIG_GPIO_SYSFS=n

On Wed, May 7, 2025 at 3:07 PM Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:

> i.MX GPIO numbering has been deterministic since commit 7e6086d9e54a
> ("gpio/mxc: specify gpio base for device tree probe"), a year after
> device tree support was first added back in 2011.
>
> Reverting to dynamically allocated GPIO base now would break most
> systems making use of the sysfs API. These systems will be eventually
> broken by the removal of the sysfs API, but that would result in GPIO
> scripts not working instead of essentially toggling at random according
> to probe order, which would happen if we unconditionally set base to -1.
>
> Yet, the warning is annoying and has resulted in many rejected attempts
> to remove it over the years[1][2][3].
>
> As the i.MX GPIO driver is device tree only, GPIO_SYSFS is the only
> consumer of the deterministic GPIO numbering. Let's therefore restrict the
> static base and the warning that comes with it to configurations
> with CONFIG_GPIO_SYSFS enabled.
>
> [1]: https://lore.kernel.org/all/20230226205319.1013332-1-dario.binacchi@amarulasolutions.com/
> [2]: https://lore.kernel.org/all/20230506085928.933737-2-haibo.chen@nxp.com/
> [3]: https://lore.kernel.org/all/20241121145515.3087855-1-catalin.popescu@leica-geosystems.com/
>
> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>

Well that is an interesting way to do it. OK I guess!

Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij