linux-kernel - Re: [PATCH 1/4] gpiolib: add opt-out for existing drivers with static GPIO base

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Message-ID: <CAHp75VfAmqzKxgXTc9TqeFOeGSr_D3NmCa0M7+4Zf37CofrHeg@mail.gmail.com>
Date: Tue, 14 Jan 2025 21:38:25 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc: Linus Walleij <linus.walleij@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>, 
	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 1/4] gpiolib: add opt-out for existing drivers with static
 GPIO base

On Tue, Jan 14, 2025 at 12:06 PM Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:
> On 14.01.25 10:49, Andy Shevchenko wrote:
> > On Tue, Jan 14, 2025 at 12:20 AM Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:
> >>
> >> Some drivers have had deterministic GPIO numbering for most of
> >> their existence, e.g. the i.MX GPIO since commit 7e6086d9e54a
> >> ("gpio/mxc: specify gpio base for device tree probe"), more than
> >> 12 years ago.
> >>
> >> 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.
> >>
> >> As these concerns won't go away until the sysfs interface is removed,
> >> let's add a new struct gpio_chip::legacy_static_base member that can be
> >> used by existing drivers that have been grandfathered in to suppress
> >> the warning currently being printed:
> >>
> >>   gpio gpiochip0: Static allocation of GPIO base is deprecated,
> >>   use dynamic allocation.
> >
> > Warning is harmless and still a good reminder for the stuff that needs
> > more love.
> > NAK.
>
> A warning is a call-to-action and it's counterproductive to keep tricking
> people into removing the static base and breaking other users' scripts.

Are you prepared to say the same when the entire GPIO SYSFS will be
removed? Because that's exactly what I referred to in the reply to the
cover letter as an impediment to move forward.

> I don't understand what love you think this will spawn with regards
> to the i.MX GPIO driver. Can you explain?

To fix the bugs you found. If it's not the GPIO driver a culprit, we
need to find the real one and fix that.

-- 
With Best Regards,
Andy Shevchenko