linux-kernel - Re: [PATCH v4 03/10] gpiolib: implement low-level, shared GPIO support

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Message-ID: <CAMRc=Mexa9eSe+qy9dm_q=+gBKtc-EZ7M0RXsgSe6fhWj1FV4A@mail.gmail.com>
Date: Wed, 26 Nov 2025 16:47:54 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Cosmin Tanislav <demonsingur@...il.com>
Cc: Kees Cook <kees@...nel.org>, Mika Westerberg <westeri@...nel.org>, 
	Dmitry Torokhov <dmitry.torokhov@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Linus Walleij <linus.walleij@...aro.org>, Manivannan Sadhasivam <mani@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Saravana Kannan <saravanak@...gle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Andy Shevchenko <andy@...nel.org>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Srinivas Kandagatla <srini@...nel.org>, Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, 
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>, 
	Alexey Klimov <alexey.klimov@...aro.org>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, linux-hardening@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-sound@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v4 03/10] gpiolib: implement low-level, shared GPIO support

On Wed, Nov 26, 2025 at 4:34 PM Cosmin Tanislav <demonsingur@...il.com> wrote:
>
> > +
> > +             count = of_count_phandle_with_args(curr, prop->name,
> > +                                                "#gpio-cells");
>
> This call causes error messages to be printed for gpio-hog entries, like
> this one from arch/arm64/boot/dts/renesas/rzt2h-n2h-evk-common.dtsi:
>

Thanks for the report.

Please trim your responses to just the relevant context though, you
included the entire huge patch.

>         sdhi0-emmc-iovs-hog {
>                 gpio-hog;
>                 gpios = <RZT2H_GPIO(2, 6) GPIO_ACTIVE_HIGH>;
>                 output-high;
>                 line-name = "SD0_IOVS";
>         };
>
> For gpio-hog entries, the first element is not a phandle (gpio-hog is
> already under its parent).
>
> of_count_phandle_with_args() will however try to interpret it as a
> parent either way, causing the following error to be printed.
>
> OF: /soc/pinctrl@...c0000/sdhi0-emmc-iovs-hog: could not get #gpio-cells
> for /soc/ethernet@...10000/mdio/ethernet-phy@2
>
> RZT2H_GPIO(2, 6) expands to 22, or 0x16.
>
> Coincidentally, in the decompiled dts file we have:
>
> ethernet-phy@2 {
>         ...
>         phandle = <0x16>;
> };
>

Yes, because behind the scenes, a phandle really is nothing more than
an integer.

> Maybe a check for gpio-hogs should be added?
>
> Something like the following before the call to
> of_count_phandle_with_args().
>
> if (strcmp(prop->name, "gpios") == 0 &&
>      of_property_present(curr, "gpio-hog"))
>         continue;
>

Yes, that's a good idea, thanks. Let me cook up a patch.

Bart