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

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Message-ID: <CAMRc=McaZV=tUkzDGMYxXqkuEYw_KasKcv8QGdjw709UYZuGhg@mail.gmail.com>
Date: Tue, 7 Oct 2025 15:13:29 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Srinivas Kandagatla <srini@...nel.org>
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>, 
	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 Mon, Oct 6, 2025 at 11:55 PM Srinivas Kandagatla <srini@...nel.org> wrote:
>
> >
> > If they were called "reset-gpios" then we could (and should) use
> > Krzysztof's reset-gpio driver here, but we have many cases where
> > that's not the case and the names (and implied functions) are
>
> Yes, these codec drivers are due to be moved to use reset-gpios.
>

You will still need to keep support for the current "powerdown-gpios"
property in existing device tree sources so that doesn't change
anything. And what about shared pins other than reset? 'dc-gpios' for
display, other 'powerdown' instances, 'enable-gpios', all kinds of
uncommon names like: `dlg,cs`, `wlf,ldo2ena`, `speaker-enable`,
`maxim,enable`? It's not likely we will create a separate abstraction
for each of them. What I'm proposing is a sane, catch-all mechanism
for shared GPIOs that right now use a rather wonky hack. Also: the
drivers have no business knowing that they request GPIOs that can be
shared. This is why I want to hide it inside GPIOLIB.

Bartosz