linux-kernel - Re: [PATCH 8/8] gpiolib: sanitize the return value of gpio_chip::get

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Message-ID: <CAMRc=Md-bMUEKgF7srLFqwdetDcTDB-0YzrisccQmReDs-Ndvg@mail.gmail.com>
Date: Mon, 24 Feb 2025 20:55:26 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Andy Shevchenko <andriy.shevchenko@...el.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 8/8] gpiolib: sanitize the return value of gpio_chip::get_direction()

On Mon, Feb 24, 2025 at 5:33 PM Andy Shevchenko
<andriy.shevchenko@...el.com> wrote:
>
> On Mon, Feb 10, 2025 at 11:52:02AM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > As per the API contract, the get_direction() callback can only
> > return 0, 1 or a negative error number. Add a wrapper around the callback
> > calls that filters out anything else.
>
> ...
>
> > +static int gpiochip_get_direction(struct gpio_chip *gc, unsigned int offset)
> > +{
> > +     int ret;
> > +
> > +     lockdep_assert_held(&gc->gpiodev->srcu);
> > +
> > +     if (WARN_ON(!gc->get_direction))
> > +             return -EOPNOTSUPP;
> > +
> > +     ret = gc->get_direction(gc, offset);
> > +     if (ret > 1)
>
> Would it be better to use the respective GPIO*... macro instead of 1?
>

I did consider it but I don't like comparing against enums, it doesn't
feel right as the value behind the name can change. I think I prefer
it like this even if it's not the best solution either. Maybe we could
be more explicit and say:

    if (!(ret == IN || ret == OUT || ret < 0)

?

Bart