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

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Message-ID: <ca399c86-5bfc-057b-6f9f-50614b91a9b9@csgroup.eu>
Date:   Thu, 26 Jan 2023 08:14:49 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Arnd Bergmann <arnd@...db.de>,
        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



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().

Christophe


> 
> Fixes: 9091373ab7ea ("gpio: remove less important #ifdef around declarations")
> Signed-off-by: Pierluigi Passaro <pierluigi.p@...iscite.com>
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>   include/linux/gpio/driver.h | 23 +++++++++++++++++++++--
>   1 file changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
> index 26a808fb8a25..67990908a040 100644
> --- a/include/linux/gpio/driver.h
> +++ b/include/linux/gpio/driver.h
> @@ -751,6 +751,8 @@ gpiochip_remove_pin_ranges(struct gpio_chip *gc)
>   
>   #endif /* CONFIG_PINCTRL */
>   
> +#ifdef CONFIG_GPIOLIB
> +
>   struct gpio_desc *gpiochip_request_own_desc(struct gpio_chip *gc,
>   					    unsigned int hwnum,
>   					    const char *label,
> @@ -758,8 +760,6 @@ struct gpio_desc *gpiochip_request_own_desc(struct gpio_chip *gc,
>   					    enum gpiod_flags dflags);
>   void gpiochip_free_own_desc(struct gpio_desc *desc);
>   
> -#ifdef CONFIG_GPIOLIB
> -
>   /* lock/unlock as IRQ */
>   int gpiochip_lock_as_irq(struct gpio_chip *gc, unsigned int offset);
>   void gpiochip_unlock_as_irq(struct gpio_chip *gc, unsigned int offset);
> @@ -769,6 +769,25 @@ struct gpio_chip *gpiod_to_chip(const struct gpio_desc *desc);
>   
>   #else /* CONFIG_GPIOLIB */
>   
> +#include <linux/gpio/machine.h>
> +#include <linux/gpio/consumer.h>
> +
> +static inline struct gpio_desc *gpiochip_request_own_desc(struct gpio_chip *gc,
> +					    unsigned int hwnum,
> +					    const char *label,
> +					    enum gpio_lookup_flags lflags,
> +					    enum gpiod_flags dflags)
> +{
> +	/* GPIO can never have been requested */
> +	WARN_ON(1);
> +	return ERR_PTR(-ENODEV);
> +}
> +
> +static inline void gpiochip_free_own_desc(struct gpio_desc *desc)
> +{
> +	WARN_ON(1);
> +}
> +
>   static inline struct gpio_chip *gpiod_to_chip(const struct gpio_desc *desc)
>   {
>   	/* GPIO can never have been requested */