2024-03-07 21:43:21

by Alexander Sverdlin

Subject: [PATCH] gpio: sysfs: repair export returning -EPERM on 1st attempt

It would make sense to return -EPERM if the bit was already set (already
used), not if it was cleared. Before this fix pins can only be exported on
the 2nd attempt:

$ echo 522 > /sys/class/gpio/export
sh: write error: Operation not permitted
$ echo 522 > /sys/class/gpio/export

Fixes: 35b545332b80 ("gpio: remove gpio_lock")
Signed-off-by: Alexander Sverdlin <[email protected]>
---
drivers/gpio/gpiolib-sysfs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 67fc09a57f26..6853ecd98bcb 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -593,7 +593,7 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
if (!guard.gc)
return -ENODEV;

- if (!test_and_set_bit(FLAG_EXPORT, &desc->flags))
+ if (test_and_set_bit(FLAG_EXPORT, &desc->flags))
return -EPERM;

gdev = desc->gdev;
--
2.43.2

2024-03-08 10:50:14

by Bartosz Golaszewski

Subject: Re: [PATCH] gpio: sysfs: repair export returning -EPERM on 1st attempt

On Thu, Mar 7, 2024 at 10:43 PM Alexander Sverdlin
<[email protected]> wrote:
>
> It would make sense to return -EPERM if the bit was already set (already
> used), not if it was cleared. Before this fix pins can only be exported on
> the 2nd attempt:
>
> $ echo 522 > /sys/class/gpio/export
> sh: write error: Operation not permitted
> $ echo 522 > /sys/class/gpio/export
>
> Fixes: 35b545332b80 ("gpio: remove gpio_lock")
> Signed-off-by: Alexander Sverdlin <[email protected]>
> ---
> drivers/gpio/gpiolib-sysfs.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
> index 67fc09a57f26..6853ecd98bcb 100644
> --- a/drivers/gpio/gpiolib-sysfs.c
> +++ b/drivers/gpio/gpiolib-sysfs.c
> @@ -593,7 +593,7 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
> if (!guard.gc)
> return -ENODEV;
>
> - if (!test_and_set_bit(FLAG_EXPORT, &desc->flags))
> + if (test_and_set_bit(FLAG_EXPORT, &desc->flags))
> return -EPERM;
>
> gdev = desc->gdev;
> --
> 2.43.2
>

That's of course correct. Applied.

Bart