linux-kernel - Re: [PATCH] gpiolib: enable CONFIG_GPIOLIB

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Message-ID: <CAMuHMdUSsKeY-Uj1xA4SatDk+Mb0e4LJyOU=aS52YbA3DSMLrA@mail.gmail.com>
Date: Tue, 29 Jul 2025 14:12:21 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: Arnd Bergmann <arnd@...nel.org>, Linus Walleij <linus.walleij@...aro.org>, 
	Bartosz Golaszewski <brgl@...ev.pl>, Alexander Sverdlin <alexander.sverdlin@...il.com>, 
	kernel test robot <lkp@...el.com>, Peng Fan <peng.fan@....com>, 
	Koichiro Den <koichiro.den@...onical.com>, Lee Jones <lee@...nel.org>, 
	Geert Uytterhoeven <geert+renesas@...der.be>, André Draszik <andre.draszik@...aro.org>, 
	Niko Pasaloukos <nikolaos.pasaloukos@...ize.com>, 
	Thomas Richard <thomas.richard@...tlin.com>, Yixun Lan <dlan@...too.org>, 
	Lars-Peter Clausen <lars@...afoo.de>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	"open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpiolib: enable CONFIG_GPIOLIB_LEGACY even for !GPIOLIB

Hi Arnd,

On Tue, 29 Jul 2025 at 13:58, Arnd Bergmann <arnd@...db.de> wrote:
> On Tue, Jul 29, 2025, at 12:47, Geert Uytterhoeven wrote:
> >>
> >> -if GPIOLIB
> >> -
> >>  config GPIOLIB_LEGACY
> >>         def_bool y
> >>
> >> +if GPIOLIB
> >> +
> >>  config GPIOLIB_FASTPATH_LIMIT
> >>         int "Maximum number of GPIOs for fast path"
> >>         range 32 512
> >
> > This won't work for everything.
> > While I now get CONFIG_GPIOLIB_LEGACY=y in all m68k defconfigs, and
> > simple inline functions like gpio_is_valid() are now available, more
> > complex functions will still fail, as drivers/gpio/gpiolib-legacy.c
> > is not built.
> >
> > drivers/Makefile:
> >
> >     obj-$(CONFIG_GPIOLIB)           += gpio/

> Do you have an example config that shows this problem?
> I've tried a couple of configurations on m68k now but are unable
> to reproduce this, using 'defconfig' (without GPIOLIB) and
> 'm5475evb_defconfig' (with GPIOLIB).
>
> The intention of this patch (in combination with the previous one)
> was that the legacy interfaces would still behave exactly like
> before, falling back to the stubs when GPIOLIB is disabled.

I haven't seen any actual failures.  When discovering
CONFIG_GPIOLIB_LEGACY=y in all m68k defconfigs, my initial worry
was that it would increase kernel size by needlessly including
gpiolib-legacy.o. When that didn't turn out to be true, I started
wondering how your commit would fix anything without including
gpiolib-legacy.o.  Looks like any users just uses the simple static
inlines...
Sorry for confusing you.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds