Re: [PATCH] gpiolib: don't allow setting values on input lines

[Andy Shevchenko]

On Wed, Apr 09, 2025 at 06:43:47PM +0200, Bartosz Golaszewski wrote:
> On Wed, Apr 9, 2025 at 4:38 PM Andy Shevchenko
> <andriy.shevchenko@xxxxxxxxx> wrote:
> > On Fri, Mar 14, 2025 at 11:35:21AM +0100, Bartosz Golaszewski wrote:
> > > On Fri, Mar 14, 2025 at 11:33 AM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> > > > On Tue, Mar 11, 2025 at 3:20 PM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
> > > >
> > > > > From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> > > > >
> > > > > Some drivers as well as the character device and sysfs code check
> > > > > whether the line actually is in output mode before allowing the user to
> > > > > set a value.
> > > > >
> > > > > However, GPIO value setters now return integer values and can indicate
> > > > > failures. This allows us to move these checks into the core code.
> > > > >
> > > > > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> > > >
> > > > Makes sense, if there are regressions let's smoke them out
> > > > in linux-next.
> > > >
> > > > Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> > >
> > > Thanks. I decided not to queue it for v6.15 for exactly that reason,
> > > I'll pick it up early into the v6.16 cycle and let it sit in next for
> > > several weeks.
> >
> > As far as I can tell from the reading of the code, this will break the open
> > drain emulation. Am I mistaken?
> 
> Could you produce a call trace where this could result in a breakage?

I can't right now, my comment was based on the my (mis)understanding of
the code flow.

> I tested open-drain and open-source emulation but maybe I'm missing
> something.

I;m glad to know that you tested this! So, it means that I misunderstood
something.

-- 
With Best Regards,
Andy Shevchenko