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

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Message-Id: <a9ec7f46-dd07-40e7-ae48-a1e48d2101c5@app.fastmail.com>
Date:   Thu, 26 Jan 2023 13:56:26 +0100
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Christophe Leroy" <christophe.leroy@...roup.eu>,
        "Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>
Cc:     "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 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.

     Arnd