linux-kernel - Re: [PATCH v1 1/1] gpiolib: sysfs: Do unexport GPIO when user asks for it

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Date:   Mon, 14 Aug 2023 18:13:44 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andy@...nel.org>,
        Marek Behún <kabel@...nel.org>
Subject: Re: [PATCH v1 1/1] gpiolib: sysfs: Do unexport GPIO when user asks
 for it

On Mon, Aug 14, 2023 at 1:19 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> It seems that sysfs interface implicitly relied on the gpiod_free()
> to unexport the line. This is not good and prone to regressions.
> Fix it by explicitly calling gpiod_unexport().
>

I wouldn't say it's prone to regressions, it's literally just that
gpiod_free() should not deal with sysfs.

How about that for commit message (I can change it when applying):

It seems that sysfs interface implicitly relied on the gpiod_free()
to unexport the line. This is logically incorrect as core gpiolib should
not deal with sysfs so instead of restoring it, let's call gpiod_unexport()
from sysfs code.

Bart

> Fixes: b0ce9ce408b6 ("gpiolib: Do not unexport GPIO on freeing")
> Reported-by: Marek Behún <kabel@...nel.org>
> Closes: https://lore.kernel.org/r/20230808102828.4a9eac09@dellmb
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Tested-by: Marek Behún <kabel@...nel.org>
> ---
>  drivers/gpio/gpiolib-sysfs.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
> index 530dfd19d7b5..50503a4525eb 100644
> --- a/drivers/gpio/gpiolib-sysfs.c
> +++ b/drivers/gpio/gpiolib-sysfs.c
> @@ -515,8 +515,9 @@ static ssize_t unexport_store(const struct class *class,
>          * they may be undone on its behalf too.
>          */
>         if (test_and_clear_bit(FLAG_SYSFS, &desc->flags)) {
> +               gpiod_unexport(desc);
> +               gpiod_free(desc);
>                 status = 0;
> -               gpiod_free(desc);
>         }
>  done:
>         if (status)
> @@ -781,8 +782,10 @@ void gpiochip_sysfs_unregister(struct gpio_device *gdev)
>         mutex_unlock(&sysfs_lock);
>
>         /* unregister gpiod class devices owned by sysfs */
> -       for_each_gpio_desc_with_flag(chip, desc, FLAG_SYSFS)
> +       for_each_gpio_desc_with_flag(chip, desc, FLAG_SYSFS) {
> +               gpiod_unexport(desc);
>                 gpiod_free(desc);
> +       }
>  }
>
>  static int __init gpiolib_sysfs_init(void)
> --
> 2.40.0.1.gaa8946217a0b
>