linux-kernel - Re: [PATCH v1 1/5] gpiolib: fix linker errors when GPIOLIB is disabled

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Date:   Thu, 26 Jan 2023 15:29:34 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Pierluigi Passaro <pierluigi.p@...iscite.com>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v1 1/5] gpiolib: fix linker errors when GPIOLIB is
 disabled

On Thu, Jan 26, 2023 at 01:56:26PM +0100, Arnd Bergmann wrote:
> On Thu, Jan 26, 2023, at 13:44, Christophe Leroy wrote:
> > Le 26/01/2023 à 11:19, Andy Shevchenko a écrit :
> >> On Thu, Jan 26, 2023 at 08:14:49AM +0000, Christophe Leroy wrote:
> >>> Le 25/01/2023 à 21:10, Andy Shevchenko a écrit :
> >>>> From: Pierluigi Passaro <pierluigi.p@...iscite.com>
> >>>>
> >>>> Both the functions gpiochip_request_own_desc and
> >>>> gpiochip_free_own_desc are exported from
> >>>>       drivers/gpio/gpiolib.c
> >>>> but this file is compiled only when CONFIG_GPIOLIB is enabled.
> >>>> Move the prototypes under "#ifdef CONFIG_GPIOLIB" and provide
> >>>> reasonable definitions and includes in the "#else" branch.
> >>>
> >>> Can you give more details on when and why link fails ?
> >>>
> >>> You are adding a WARN(), I understand it mean the function should never
> >>> ever be called. Shouldn't it be dropped completely by the compiler ? In
> >>> that case, no call to gpiochip_request_own_desc() should be emitted and
> >>> so link should be ok.
> >>>
> >>> If link fails, it means we still have unexpected calls to
> >>> gpiochip_request_own_desc() or gpiochip_free_own_desc(), and we should
> >>> fix the root cause instead of hiding it with a WARN().
> >> 
> >> I agree, but what do you suggest exactly? I think the calls to that functions
> >> shouldn't be in the some drivers as it's layering violation (they are not a
> >> GPIO chips to begin with). Simply adding a dependency not better than this one.
> >> 
> >
> > My suggestion is to go step by step. First step is to explicitely list 
> > drivers that call those functions without selecting GPIOLIB.
> 
> I tried that and sent the list of the drivers that call these functions,
> but as I wrote, all of them already require GPIOLIB to be set.
> 
> This means either I made a mistake in my search, or the problem
> has already been fixed. Either way, I think Andy should provide
> the exact build failure he observed so we know what caller caused
> the issue.

I believe it's not me, who first reported it. So, Pierluigi, can you point
out to the LKP message that reported the issue?

P.S> LKP sometimes finds a really twisted configurations to probe on.

-- 
With Best Regards,
Andy Shevchenko