2023-11-29 15:23:29

by Boerge Struempfel

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

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 <[email protected]>

---

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

2023-11-29 16:10:44

by Andy Shevchenko

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

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 <[email protected]>

--
With Best Regards,
Andy Shevchenko

2023-12-01 09:46:12

by Bartosz Golaszewski

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

On Wed, Nov 29, 2023 at 4:23 PM Boerge Struempfel
<[email protected]> 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 <[email protected]>
>
> ---
>
> 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