linux-kernel - Re: [PATCH RFC/RFT] pinctrl: qcom: make the pinmuxing strict

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Message-ID: <CAMRc=Md=ABd+aSc7DE-2dsR5rMnpnvbetuexw8vmrf7_zzT31Q@mail.gmail.com>
Date: Fri, 27 Jun 2025 10:26:22 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>, Linus Walleij <linus.walleij@...aro.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org, 
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH RFC/RFT] pinctrl: qcom: make the pinmuxing strict

On Thu, Jun 26, 2025 at 9:06 PM Konrad Dybcio
<konrad.dybcio@....qualcomm.com> wrote:
>
> On 6/25/25 5:37 PM, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > The strict flag in struct pinmux_ops disallows the usage of the same pin
> > as a GPIO and for another function. Without it, a rouge user-space
> > process with enough privileges (or even a buggy driver) can request a
> > used pin as GPIO and drive it, potentially confusing devices or even
> > crashing the system. Set it globally for all pinctrl-msm users.
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > ---
>
> SC8280XP CRD breaks with this.. looks like there's a conflict between
> regulator-fixed accessing the pin with gpiod APIs and setting a pinmux:
>
> [    5.095688] sc8280xp-tlmm f100000.pinctrl: pin GPIO_25 already requested by regulator-edp-3p3; cannot claim for f100000.pinctrl:570
> [    5.107822] sc8280xp-tlmm f100000.pinctrl: error -EINVAL: pin-25 (f100000.pinctrl:570)
>
>
> Konrad

Yeah, I would be surprised if nothing broke.It's probably worth
looking into the implementation of the strict flag as it makes every
muxed pin unavailable as GPIO even if - like in this case - the
function *is* "gpio". Of course the "gpio" string has no real meaning
to the pinctrl core, it's just a name but it would be awesome if we
could say for a given function that this means GPIO and as such should
be available to the GPIOLIB API.

Bart