linux-kernel - Re: Linux logs new warning `gpio gpiochip0: gpiochip_add_data_with_key: get

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Message-ID: <Z78jjr8LMa165CZP@smile.fi.intel.com>
Date: Wed, 26 Feb 2025 16:22:06 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Cc: Linus Walleij <linus.walleij@...aro.org>, brgl@...ev.pl,
	Paul Menzel <pmenzel@...gen.mpg.de>, linux-gpio@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org,
	regressions@...ts.linux.dev
Subject: Re: Linux logs new warning `gpio gpiochip0:
 gpiochip_add_data_with_key: get_direction failed: -22`

On Wed, Feb 26, 2025 at 03:14:24PM +0100, Bartosz Golaszewski wrote:
> On Wed, 26 Feb 2025 at 14:47, Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> > On Wed, Feb 26, 2025 at 03:37:47PM +0200, Andy Shevchenko wrote:
> > > On Tue, Feb 25, 2025 at 10:25:00PM +0100, Linus Walleij wrote:
> > > > On Mon, Feb 24, 2025 at 9:51 AM <brgl@...ev.pl> wrote:
> > > >
> > > > > In any case: Linus: what should be our policy here? There are some pinctrl
> > > > > drivers which return EINVAL if the pin in question is not in GPIO mode. I don't
> > > > > think this is an error. Returning errors should be reserved for read failures
> > > > > and so on. Are you fine with changing the logic here to explicitly default to
> > > > > INPUT as until recently all errors would be interpreted as such anyway?
> > > >
> > > > Oh hm I guess. There was no defined semantic until now anyway. Maybe
> > > > Andy has something to say about it though, it's very much his pin controller.
> > >
> > > Driver is doing correct things. If you want to be pedantic, we need to return
> > > all possible pin states (which are currently absent from GPIO get_direction()
> > > perspective) and even though it's not possible to tell from the pin muxer
> > > p.o.v. If function is I2C, it's open-drain, if some other, it may be completely
> > > different, but pin muxer might only guesstimate the state of the particular
> > > function is and I do not think guesstimation is a right approach.
> > >
> > > We may use the specific error code, though. and document that semantics.
> >
> > Brief looking at the error descriptions and the practical use the best (and
> > unique enough) choice may be EBADSLT.
> 
> In any case, I proposed to revert to the previous behavior in
> gpiochip_add_data() in my follow-up series so the issue should soon go
> away.

Yes, I noted. The above is a material to discuss. We can make that semantics
documented and strict and then one may filter out those errors if/when
required.

-- 
With Best Regards,
Andy Shevchenko