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

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Message-ID: <Y9JTPAL7VDXNPy5h@smile.fi.intel.com>
Date:   Thu, 26 Jan 2023 12:17:32 +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 09:40:18AM +0100, Arnd Bergmann wrote:
> On Thu, Jan 26, 2023, at 09:14, 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().
> 
> There are only a handful of files calling these functions:
> 
> $ git grep -l gpiochip_request_own_desc
> Documentation/driver-api/gpio/driver.rst
> arch/arm/mach-omap1/ams-delta-fiq.c
> arch/arm/mach-omap1/board-ams-delta.c
> drivers/gpio/gpio-mvebu.c
> drivers/gpio/gpiolib-acpi.c
> drivers/gpio/gpiolib.c
> drivers/hid/hid-cp2112.c
> drivers/memory/omap-gpmc.c
> drivers/net/wireless/broadcom/brcm80211/brcmsmac/led.c
> drivers/power/supply/collie_battery.c
> drivers/spi/spi-bcm2835.c
> include/linux/gpio/driver.h
> 
> All of these should already prevent the link failure through
> a Kconfig 'depends on GPIOLIB' for the driver, or 'select GPIOLIB'
> for the platform code. I checked all of the above and they seem fine.
> If anything else calls the function, I'd add the same dependency
> there.

So, you think it's worth to send a few separate fixes as adding that
dependency? But doesn't it feel like a papering over the issue with
that APIs used in some of the drivers in the first place?

-- 
With Best Regards,
Andy Shevchenko