linux-kernel - Re: [PATCH v2 8/9] gpio: sysfs: allow disabling the legacy parts of the GPIO sysfs interface

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Message-ID: <CAMuHMdV0W8u30yYfYd2zXhVJn_RZB0ZXj2Qyxasd-XUA4eZJpQ@mail.gmail.com>
Date: Tue, 24 Jun 2025 13:31:41 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Ahmad Fatoum <a.fatoum@...gutronix.de>, Kent Gibson <warthog618@...il.com>, 
	Jan Lübbe <jlu@...gutronix.de>, Marek Vasut <marex@...x.de>, 
	Linus Walleij <linus.walleij@...aro.org>, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v2 8/9] gpio: sysfs: allow disabling the legacy parts of
 the GPIO sysfs interface

Hi Bartosz,

On Mon, 23 Jun 2025 at 11:01, Bartosz Golaszewski <brgl@...ev.pl> wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>
> Add a Kconfig switch allowing to disable the legacy parts of the GPIO
> sysfs interface. This means that even though we keep the
> /sys/class/gpio/ directory, it no longer contains the global
> export/unexport attribute pair (instead, the user should use the
> per-chip export/unpexport) nor the gpiochip$BASE entries. This option
> default to y if GPIO sysfs is enabled but we'll default it to n at some
> point in the future.
>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

Thanks for your patch!

> --- a/drivers/gpio/gpiolib-sysfs.c
> +++ b/drivers/gpio/gpiolib-sysfs.c

> @@ -968,6 +994,7 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
>
>         guard(mutex)(&sysfs_lock);
>
> +#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)
>         /* use chip->base for the ID; it's already known to be unique */
>         data->cdev_base = device_create_with_groups(&gpio_class, parent,
>                                                     MKDEV(0, 0), data,
> @@ -979,13 +1006,16 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
>                 kfree(data);
>                 return err;
>         }
> +#endif /* CONFIG_GPIO_SYSFS_LEGACY */

"err" is always declared, but only used in this block.
Hence if CONFIG_GPIO_SYSFS_LEGACY=n:

    drivers/gpio/gpiolib-sysfs.c: In function ‘gpiochip_sysfs_register’:
    drivers/gpio/gpiolib-sysfs.c:962:13: error: unused variable ‘err’
[-Werror=unused-variable]
      962 |         int err;
          |             ^~~

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds