linux-kernel - Re: [PATCH 1/3] gpiolib: don't use gpiochip_get

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMRc=MdTKCtwrDouTV4YHoWa1F8cenSVEtTXicSUdrmEk3TxCQ@mail.gmail.com>
Date: Tue, 25 Feb 2025 15:43:29 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, Marek Szyprowski <m.szyprowski@...sung.com>, 
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 1/3] gpiolib: don't use gpiochip_get_direction() when
 registering a chip

On Tue, Feb 25, 2025 at 2:22 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Tue, Feb 25, 2025 at 12:56:23PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > During chip registration we should neither check the return value of
> > gc->get_direction() nor hold the SRCU lock when calling it. The former
> > is because pin controllers may have pins set to alternate functions and
> > return errors from their get_direction() callbacks. That's alright - we
> > should default to the safe INPUT state and not bail-out. The latter is
> > not needed because we haven't registered the chip yet so there's nothing
> > to protect against dynamic removal. In fact: we currently hit a lockdep
> > splat. Revert to calling the gc->get_direction() callback directly not
> > not checking its value.
>
> ...
>
> I think the below code deserves a commit (as a summary of the above commit
> message).
>

Can you rephrase? I'm not getting this one.

Bart

> > +             if (gc->get_direction && gpiochip_line_is_valid(gc, desc_index))
> > +                     assign_bit(FLAG_IS_OUT, &desc->flags,
> > +                                !gc->get_direction(gc, desc_index));
> > +             else
> >                       assign_bit(FLAG_IS_OUT,
> >                                  &desc->flags, !gc->direction_input);
>
> Otherwise LGTM,
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
>
> --
> With Best Regards,
> Andy Shevchenko
>
>