linux-kernel - Re: (subset) [PATCH RFC 0/9] gpio: improve support for shared GPIOs

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Message-ID: <176000470857.91617.1046632810440589541.b4-ty@linaro.org>
Date: Thu,  9 Oct 2025 12:12:27 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: 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>,
	Bartosz Golaszewski <brgl@...ev.pl>
Cc: Bartosz Golaszewski <bartosz.golaszewski@...aro.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
Subject: Re: (subset) [PATCH RFC 0/9] gpio: improve support for shared GPIOs

From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>


On Wed, 24 Sep 2025 16:51:28 +0200, Bartosz Golaszewski wrote:
> Here's a functional RFC for improving the handling of shared GPIOs in
> linux.
> 
> Problem statement: GPIOs are implemented as a strictly exclusive
> resource in the kernel but there are lots of platforms on which single
> pin is shared by multiple devices which don't communicate so need some
> way of properly sharing access to a GPIO. What we have now is the
> GPIOD_FLAGS_BIT_NONEXCLUSIVE flag which was introduced as a hack and
> doesn't do any locking or arbitration of access - it literally just hand
> the same GPIO descriptor to all interested users.
> 
> [...]

I'm picking this one up for fixes as it addresses a locking bug.

[1/9] gpio: wcd934x: mark the GPIO controller as sleeping
      https://git.kernel.org/brgl/linux/c/83d314fac266a3d9de61e4a4490c4f2eafc86b05

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>