[PATCH v3] gpiolib: sysfs: Fix error handling on failed export

[PATCH v3] gpiolib: sysfs: Fix error handling on failed export

[Boerge Struempfel]

If gpio_set_transitory() fails, we should free the GPIO again. Most
notably, the flag FLAG_REQUESTED has previously been set in
gpiod_request_commit(), and should be reset on failure.

To my knowledge, this does not affect any current users, since the
gpio_set_transitory() mainly returns 0 and -ENOTSUPP, which is converted
to 0. However the gpio_set_transitory() function calles the .set_config()
function of the corresponding GPIO chip and there are some GPIO drivers in
which some (unlikely) branches return other values like -EPROBE_DEFER,
and -EINVAL. In these cases, the above mentioned FLAG_REQUESTED would not
be reset, which results in the pin being blocked until the next reboot.

Fixes: e10f72bf4b3e ("gpio: gpiolib: Generalise state persistence beyond sleep")
Signed-off-by: Boerge Struempfel <boerge.struempfel@gmail.com>

---

V2: https://lore.kernel.org/linux-gpio/CAEktqcv8NC0Cy+wo7nRGOp9USoBdta=n=mrbo-WomxgcmWN5nQ@mail.gmail.com/T/#t
V1: https://lore.kernel.org/linux-gpio/CAEktqcuxS1sPfkGVCgSy1ki8fmUDmuUsHrdAT+zFKy5vGSoKPw@mail.gmail.com/T/#t

Changes from V2:
	- Capitalized all occurances of GPIO in commit message
	- Added Missing - in front of Error Code in commit message
	- Added Fixes Tag in commit message

Changes from V1:
	- Marked all functions in commit message with parenthesis
	- Elaborated in commit message

 drivers/gpio/gpiolib-sysfs.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 6f309a3b2d9a..12d853845bb8 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -474,14 +474,17 @@ static ssize_t export_store(const struct class *class,
 		goto done;
 
 	status = gpiod_set_transitory(desc, false);
-	if (!status) {
-		status = gpiod_export(desc, true);
-		if (status < 0)
-			gpiod_free(desc);
-		else
-			set_bit(FLAG_SYSFS, &desc->flags);
+	if (status) {
+		gpiod_free(desc);
+		goto done;
 	}
 
+	status = gpiod_export(desc, true);
+	if (status < 0)
+		gpiod_free(desc);
+	else
+		set_bit(FLAG_SYSFS, &desc->flags);
+
 done:
 	if (status)
 		pr_debug("%s: status %d\n", __func__, status);
-- 
2.42.0

Re: [PATCH v3] gpiolib: sysfs: Fix error handling on failed export

[Andy Shevchenko]

On Wed, Nov 29, 2023 at 04:23:07PM +0100, Boerge Struempfel wrote:
> If gpio_set_transitory() fails, we should free the GPIO again. Most
> notably, the flag FLAG_REQUESTED has previously been set in
> gpiod_request_commit(), and should be reset on failure.
> 
> To my knowledge, this does not affect any current users, since the
> gpio_set_transitory() mainly returns 0 and -ENOTSUPP, which is converted
> to 0. However the gpio_set_transitory() function calles the .set_config()
> function of the corresponding GPIO chip and there are some GPIO drivers in
> which some (unlikely) branches return other values like -EPROBE_DEFER,
> and -EINVAL. In these cases, the above mentioned FLAG_REQUESTED would not
> be reset, which results in the pin being blocked until the next reboot.

Thank you!
Reviewed-by: Andy Shevchenko <andy@kernel.org>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3] gpiolib: sysfs: Fix error handling on failed export

[Bartosz Golaszewski]

On Wed, Nov 29, 2023 at 4:23 PM Boerge Struempfel
<boerge.struempfel@gmail.com> wrote:
>
> If gpio_set_transitory() fails, we should free the GPIO again. Most
> notably, the flag FLAG_REQUESTED has previously been set in
> gpiod_request_commit(), and should be reset on failure.
>
> To my knowledge, this does not affect any current users, since the
> gpio_set_transitory() mainly returns 0 and -ENOTSUPP, which is converted
> to 0. However the gpio_set_transitory() function calles the .set_config()
> function of the corresponding GPIO chip and there are some GPIO drivers in
> which some (unlikely) branches return other values like -EPROBE_DEFER,
> and -EINVAL. In these cases, the above mentioned FLAG_REQUESTED would not
> be reset, which results in the pin being blocked until the next reboot.
>
> Fixes: e10f72bf4b3e ("gpio: gpiolib: Generalise state persistence beyond sleep")
> Signed-off-by: Boerge Struempfel <boerge.struempfel@gmail.com>
>
> ---
>
> V2: https://lore.kernel.org/linux-gpio/CAEktqcv8NC0Cy+wo7nRGOp9USoBdta=n=mrbo-WomxgcmWN5nQ@mail.gmail.com/T/#t
> V1: https://lore.kernel.org/linux-gpio/CAEktqcuxS1sPfkGVCgSy1ki8fmUDmuUsHrdAT+zFKy5vGSoKPw@mail.gmail.com/T/#t
>
> Changes from V2:
>         - Capitalized all occurances of GPIO in commit message
>         - Added Missing - in front of Error Code in commit message
>         - Added Fixes Tag in commit message
>
> Changes from V1:
>         - Marked all functions in commit message with parenthesis
>         - Elaborated in commit message
>
>  drivers/gpio/gpiolib-sysfs.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
> index 6f309a3b2d9a..12d853845bb8 100644
> --- a/drivers/gpio/gpiolib-sysfs.c
> +++ b/drivers/gpio/gpiolib-sysfs.c
> @@ -474,14 +474,17 @@ static ssize_t export_store(const struct class *class,
>                 goto done;
>
>         status = gpiod_set_transitory(desc, false);
> -       if (!status) {
> -               status = gpiod_export(desc, true);
> -               if (status < 0)
> -                       gpiod_free(desc);
> -               else
> -                       set_bit(FLAG_SYSFS, &desc->flags);
> +       if (status) {
> +               gpiod_free(desc);
> +               goto done;
>         }
>
> +       status = gpiod_export(desc, true);
> +       if (status < 0)
> +               gpiod_free(desc);
> +       else
> +               set_bit(FLAG_SYSFS, &desc->flags);
> +
>  done:
>         if (status)
>                 pr_debug("%s: status %d\n", __func__, status);
> --
> 2.42.0
>

Applied, thanks!

Bart