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

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Message-ID: <CAMRc=McVc2aYFX-DKjtNNNs0eZLcq_jahR+_q3EP1T352XhP+Q@mail.gmail.com>
Date: Wed, 24 Sep 2025 20:58:14 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: Kees Cook <kees@...nel.org>, Mika Westerberg <westeri@...nel.org>, 
	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>, 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 RFC 0/9] gpio: improve support for shared GPIOs

On Wed, Sep 24, 2025 at 8:25 PM Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
>
> Hi Bartosz,
>
> On Wed, Sep 24, 2025 at 04:51:28PM +0200, Bartosz Golaszewski wrote:
> > Here's a functional RFC for improving the handling of shared GPIOs in
> > linux.
> >

[snip]

> >
> > The practical use-case for this are the powerdown GPIOs shared by
> > speakers on Qualcomm db845c platform, however I have also extensively
> > tested it using gpio-virtuser on arm64 qemu with various DT
> > configurations.
>
> How is this different from the existing gpio-backed regulator/supply?
> IMO GPIOs are naturally exclusive-use resources (in cases when you need
> to control them, not simply read their state), and when there is a need
> to share them there are more appropriate abstractions that are built on
> top of GPIOs...
>

I think you have never been on the receiving end of Krzysztof's wrath
when trying to model a simple shared pin as a nonexistent reset
provider or a fixed regulator in device-tree. :)

Unless you mean some other abstractions I am missing.

Bartosz