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

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Date:   Tue, 17 Jan 2023 07:44:41 +0000
From:   Pierluigi Passaro <pierluigi.p@...iscite.com>
To:     Alexander Stein <alexander.stein@...tq-group.com>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "brgl@...ev.pl" <brgl@...ev.pl>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Eran Matityahu <eran.m@...iscite.com>,
        Nate Drude <Nate.D@...iscite.com>,
        Francesco Ferraro <francesco.f@...iscite.com>,
        "pierluigi.passaro@...il.com" <pierluigi.passaro@...il.com>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] gpiolib: fix linker errors when GPIOLIB is disabled

On Tue, Jan 17, 2023 at 7:23 AM Alexander Stein <alexander.stein@...tq-group.com> wrote:
> Hi,
>
> Am Montag, 16. Januar 2023, 15:08:11 CET schrieb Pierluigi Passaro:
> > 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 protototypes under "#ifdef CONFIG_GPIOLIB" and provide
> > reasonable definitions in the "#else" branch.
> >
> > Signed-off-by: Pierluigi Passaro <pierluigi.p@...iscite.com>
> > Reported-by: kernel test robot <lkp@...el.com>
> > ---
> >  include/linux/gpio/driver.h | 20 ++++++++++++++++++--
> >  1 file changed, 18 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
> > index 44783fc16125..ed77c6fc0beb 100644
> > --- a/include/linux/gpio/driver.h
> > +++ b/include/linux/gpio/driver.h
> > @@ -758,6 +758,8 @@ 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,
> > @@ -765,8 +767,6 @@ 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);
> > @@ -776,6 +776,22 @@ struct gpio_chip *gpiod_to_chip(const struct gpio_desc
> > *desc);
> >
> >  #else /* CONFIG_GPIOLIB */
> >
> > +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);
>
> This will raise the warning on each invocation. How about using
> WARN_ON_ONCE(1), or even WARN_ONCE("Kernel compiled without CONFIG_GPIOLIB
> support")?
>
No problem on my side, but this would create a misalignment with all other
GPIOLIB "dummy" calls.
Personally I would prefer WARN_ONCE("Kernel compiled without CONFIG_GPIOLIB
support").
Please confirm your preferences and I'll provide a patch v2.
Thanks
>
> > +     return ERR_PTR(-ENODEV);
> > +}
> > +
> > +static inline void gpiochip_free_own_desc(struct gpio_desc *desc)
> > +{
> > +     WARN_ON(1);
>
> Same as above.
>
> Best regards,
> Alexander
>
> > +}
> > +
> >  static inline struct gpio_chip *gpiod_to_chip(const struct gpio_desc *desc)
> > {
> >       /* GPIO can never have been requested */