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

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Date:   Fri, 1 Dec 2023 10:45:33 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Boerge Struempfel <boerge.struempfel@...il.com>
Cc:     andy@...nel.org, Linus Walleij <linus.walleij@...aro.org>,
        Andrew Jeffery <andrew@...id.au>,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Rob Herring <robh@...nel.org>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org, bstruempfel@...ratronik.de
Subject: Re: [PATCH v3] gpiolib: sysfs: Fix error handling on failed export

On Wed, Nov 29, 2023 at 4:23 PM Boerge Struempfel
<boerge.struempfel@...il.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@...il.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