linux-kernel - Re: regression from commit b0ce9ce408b6 ("gpiolib: Do not unexport GPIO on freeing")

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Message-ID: <ZNYKjnPjIRWIYVot@smile.fi.intel.com>
Date:   Fri, 11 Aug 2023 13:16:46 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Marek Behún <kabel@...nel.org>
Cc:     Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        linux-gpio@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: regression from commit b0ce9ce408b6 ("gpiolib: Do not unexport
 GPIO on freeing")

On Tue, Aug 08, 2023 at 10:28:28AM +0200, Marek Behún wrote:
> Hi,
> 
> the commit b0ce9ce408b6 ("gpiolib: Do not unexport GPIO on freeing")
> 
>   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b0ce9ce408b6
> 
> causes a regression on my mvebu arm board (haven't tested on other
> systems), wherein if I export a GPIO to sysfs and then unexport it, it
> does not disasppear from the /sys/class/gpio directory, and subsequent
> writes to the export and unexport files for the gpio fail.
> 
>   $ cd /sys/class/gpio
>   $ ls
>   export       gpiochip0    gpiochip32   gpiochip512  unexport
>   $ echo 43 >export
>   $ ls
>   export       gpio43       gpiochip0    gpiochip32   gpiochip512
>   unexport
>   $ cat gpio43/value
>   1
>   $ echo 43 >unexport
>   $ ls
>   export       gpio43       gpiochip0    gpiochip32   gpiochip512
>   unexport
>   $ echo 43 >unexport
>   ash: write error: Invalid argument
>   $ echo 43 >export
>   ash: write error: Operation not permitted

Can you test the following change (I'll submit a formal patch if it works)?

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 530dfd19d7b5..b10a9b5598b2 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)

-- 
With Best Regards,
Andy Shevchenko