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

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Message-ID: <CACRpkdbgv5BhP_iv1fV7-=w6qF3H+=GiUJz=hQko3rcd6uq4BQ@mail.gmail.com>
Date: Wed, 15 Jan 2025 13:00:18 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc: 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>, Andy Shevchenko <andy.shevchenko@...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 Mon, Jan 13, 2025 at 11:19 PM Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:

> 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:

I think entire drivers, pertaining to in worst case several generations
of SoCs is not the way to approach this. It could be a SoC or, more
likely, single systems using a SoC, that has a problem with this.

If you want to safeguard this I would use some code loop in the
gpiolib(-sysfs) that looks at of_machine_is_compatible("foo,bar-machine")
to match the top-level compatible for known problematic machines
so we can be fine-grained of this so when that machines retires
the driver can start using dynamic GPIO number allotment.

Yours,
Linus Walleij