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

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Message-ID: <AM6PR08MB4376030EDCFAD7F5FD5313D2FFCF9@AM6PR08MB4376.eurprd08.prod.outlook.com>
Date:   Thu, 26 Jan 2023 13:41:45 +0000
From:   Pierluigi Passaro <pierluigi.p@...iscite.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        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>,
        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 02:29PM +0100, Arnd Bergmann wrote:
> 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
> 
I've received the following messages:
- https://lore.kernel.org/all/202301240409.tZdm0o0a-lkp@intel.com/
- https://lore.kernel.org/all/202301240439.wYz6uU0k-lkp@intel.com/
- https://lore.kernel.org/all/20230124075600.649bd7bb@canb.auug.org.au/
Please let me know if you need further details.
Regards
Pier