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

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Message-ID: <CAEktqcuxS1sPfkGVCgSy1ki8fmUDmuUsHrdAT+zFKy5vGSoKPw@mail.gmail.com>
Date:   Tue, 28 Nov 2023 11:55:34 +0100
From:   Börge Strümpfel <boerge.struempfel@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Andy Shevchenko <andy@...nel.org>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org, bstruempfel@...ratronik.de
Subject: Re: [PATCH] gpiolib: sysfs: Fix improper error handling on failed export

Hi Andy,

On Thu, Nov 23, 2023 at 4:01 PM Börge Strümpfel
<boerge.struempfel@...il.com> wrote:
>
> Hi Andy
>
> thank you for your feedback
>
> On Thu, Nov 23, 2023 at 3:25 PM Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
> >
> > On Thu, Nov 23, 2023 at 3:30 PM Boerge Struempfel
> > <boerge.struempfel@...il.com> wrote:
> > >
> > > If gpio_set_transitory fails, we should free the gpio again. Most
> >
> > We refer to functions as func() in the text and comments (note parentheses).
> >
> > GPIO
>
> Thanks for letting me know, I will update the the commit message in
> regards to this.
>
> >
> > > notably, the flag FLAG_REQUESTED has previously been set in
> > > gpiod_request_commit, and should be reset on failure.
> >
> > Same about func().
> >
> > ...
> >
> > Seems the correct fix, but you may also add that no existing user is
> > returning anything except 0 or ENOTSUPP that is converted to 0 in
> > GPIOLIB core code. Hence no Fixes tag is needed, but still possible if
> > maintainers want it.
> >
>
> You are right. For now, all mainline users are returning 0. We only found
> this due to downstream-specific code. I'll add a comment about this not
> affecting any existing users to the commit message.
>

A small update:
I looked through the possible users again, and there seems to be at least
the possibility for some other return values. The reason for this is, that
the .set_config() of the specific gpio driver is called during the
gpiod_set_transitory() call. For example the .set_config() of gpio-aspeed
might in certain (somewhat unlikely) cases return -EPROBE_DEFER as
well as -EINVAL.

However I don't think, that these conditional paths can be reached on a
properly configured system.

Kind Regards,
Börge Strümpfel