linux-kernel - Re: [PATCH v2 1/5] gpio: sysfs: use cleanup guards for gpiod

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Message-ID: <CAMRc=Mcd8vVCwDvRysMxB00xUD77zmJK1EApFuAEfWpwOhkviw@mail.gmail.com>
Date: Fri, 25 Oct 2024 16:08:00 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Kent Gibson <warthog618@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v2 1/5] gpio: sysfs: use cleanup guards for gpiod_data::mutex

On Fri, Oct 25, 2024 at 3:24 PM Kent Gibson <warthog618@...il.com> wrote:
>
> On Fri, Oct 25, 2024 at 02:18:51PM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > Shrink the code and drop some goto labels by using lock guards around
> > gpiod_data::mutex.
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > ---
> >  drivers/gpio/gpiolib-sysfs.c | 81 ++++++++++++++++----------------------------
> >  1 file changed, 29 insertions(+), 52 deletions(-)
> >
> > @@ -139,19 +132,17 @@ static ssize_t value_store(struct device *dev,
> >       long value;
> >
> >       status = kstrtol(buf, 0, &value);
> > +     if (status)
> > +             return status;
> >
> > -     mutex_lock(&data->mutex);
> > +     guard(mutex)(&data->mutex);
> >
> > -     if (!test_bit(FLAG_IS_OUT, &desc->flags)) {
> > -             status = -EPERM;
> > -     } else if (status == 0) {
> > -             gpiod_set_value_cansleep(desc, value);
> > -             status = size;
> > -     }
> > +     if (!test_bit(FLAG_IS_OUT, &desc->flags))
> > +             return -EPERM;
> >
> > -     mutex_unlock(&data->mutex);
> > +     gpiod_set_value_cansleep(desc, value);
> >
> > -     return status;
> > +     return size;
> >  }
>
> This is a behavioural change as you've moved the decode check before the
> permission check.  Not sure if that is significant or not, so in my
> suggestion I retained the old order.
>
> Cheers,
> Kent.

Yeah, I don't know why it was done. Typically you want to sanitize the
input before anything else and this is what's done almost everywhere
else. I'd keep it like that.

Bart