Re: [PATCH 1/3] gpiolib: don't use gpiochip_get_direction() when registering a chip

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Tue, Feb 25, 2025 at 2:22 PM Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>
> On Tue, Feb 25, 2025 at 12:56:23PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxxxx>
>
> --
> With Best Regards,
> Andy Shevchenko
>
>