linux-kernel - Re: [PATCH 0/4] gpio: mxc: silence warning about GPIO base being statically allocated

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Message-ID: <CAMRc=MdYB_XHCaurs1mO+KGX7rB5zFT3zCi=UbNY0rSbMEJdWw@mail.gmail.com>
Date: Wed, 15 Jan 2025 17:52:14 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc: Andy Shevchenko <andy.shevchenko@...il.com>, Linus Walleij <linus.walleij@...aro.org>, 
	Andy Whitcroft <apw@...onical.com>, Joe Perches <joe@...ches.com>, 
	Dwaipayan Ray <dwaipayanray1@...il.com>, Lukas Bulwahn <lukas.bulwahn@...il.com>, 
	Fabio Estevam <festevam@...il.com>, Shawn Guo <shawnguo@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>, 
	Dario Binacchi <dario.binacchi@...rulasolutions.com>, Haibo Chen <haibo.chen@....com>, 
	Catalin Popescu <catalin.popescu@...ca-geosystems.com>, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, imx@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/4] gpio: mxc: silence warning about GPIO base being
 statically allocated

On Tue, Jan 14, 2025 at 10:55 AM Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:
>
> Hi Andy,
>
> On 14.01.25 10:46, Andy Shevchenko wrote:
> > On Tue, Jan 14, 2025 at 12:19 AM Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:
> >>
> >> The i.MX GPIO driver has had deterministic numbering for the GPIOs
> >> for more than 12 years.
> >>
> >> Reverting this to dynamically numbered will break existing setups in the
> >> worst manner possible: The build will succeed, the kernel will not print
> >> warnings, but users will find their devices essentially toggling GPIOs
> >> at random with the potential of permanent damage. We thus want to keep
> >> the numbering as-is until the SysFS API is removed and script fail
> >> instead of toggling GPIOs dependent on probe order.
> >
> > While I understand the issue this tends to get never fixed until the
> > entire support of iMX boards will be dropped.
>
> i.MX is an actively developed and widely used platform. Why should support
> be dropped?
>
> > Personally I do not like
> > this series at all. Rather let's try to go the hard way and understand
> > what's going on to fix the current issues.
>
> /sys/class/gpio is deprecated and when it is finally removed, this series can
> be reverted again. The alternatives are either do nothing and live with 6 kernel
> warnings cluttering every boot or show users the finger as described in
> the cover letter.
>
> Do you see a different path forward?
>

I recently wrote a user-space compatibility layer for sysfs[1]. While
right now it doesn't support static base numbers, I'm very open to
adding it except that I wasn't sure how to approach it.

Is this of any use to you and could it help you switch to libgpiod
without changing your user-space set-up (given the support for static
GPIO numbering)? If so, how would you like to see this implemented? A
config file at /etc that would list chip labels and their desired GPIO
base?

Bartosz

[1] https://github.com/brgl/gpiod-sysfs-proxy