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

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Message-ID: <CAMRc=MdfueZQts=ur-+hVBATWs-oO_jowbbi=mqX6Bp-zhkUVQ@mail.gmail.com>
Date:   Tue, 17 Jan 2023 10:34:03 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Pierluigi Passaro <pierluigi.p@...iscite.com>
Cc:     Alexander Stein <alexander.stein@...tq-group.com>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        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 8:44 AM Pierluigi Passaro
<pierluigi.p@...iscite.com> wrote:
>
> 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 */

If someone calls these functions without GPIOLIB enabled then they
deserve lots of warnings to remind them to fix their config. :)

Let's keep it like in other places.

Bart