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

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Message-ID: <Z78ZK8Sh0cOhMEsH@black.fi.intel.com>
Date: Wed, 26 Feb 2025 15:37:47 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: brgl@...ev.pl, Paul Menzel <pmenzel@...gen.mpg.de>,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	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 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.

-- 
With Best Regards,
Andy Shevchenko