linux-kernel - Re: [PATCH v4 00/10] gpio: sysfs: add a per-chip export/unexport attribute pair

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Message-ID: <CAMRc=Mc7HaVjchDWN_oWUuqgVZbj3ZVYvU-bwiA+ZUH+0gEXSQ@mail.gmail.com>
Date: Sun, 13 Jul 2025 10:48:03 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>, Kent Gibson <warthog618@...il.com>, 
	Jan Lübbe <jlu@...gutronix.de>, Marek Vasut <marex@...x.de>, 
	Geert Uytterhoeven <geert+renesas@...der.be>, Linus Walleij <linus.walleij@...aro.org>, 
	Andy Shevchenko <andriy.shevchenko@...el.com>, Bartosz Golaszewski <brgl@...ev.pl>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v4 00/10] gpio: sysfs: add a per-chip export/unexport
 attribute pair

On Fri, Jul 4, 2025 at 2:58 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> Following our discussion[1], here's a proposal for extending the sysfs
> interface with attributes not referring to GPIO lines by their global
> numbers in a backward compatible way.
>
> Long story short: there is now a new class device for each GPIO chip.
> It's called chipX where X is the ID of the device as per the driver
> model and it lives next to the old gpiochipABC where ABC is the GPIO
> base. Each new chip class device has a pair of export/unexport
> attributes which work similarly to the global ones under /sys/class/gpio
> but take hardware offsets within the chip as input, instead of the
> global numbers. Finally, each exported line appears at the same time as
> the global /sys/class/gpio/gpioABC as well as per-chip
> /sys/class/gpio/chipX/gpioY sysfs group except that the latter only
> implements a minimal subset of the functionality of the former, namely:
> only the 'direction' and 'value' attributes and it doesn't support event
> polling.
>
> The series contains the implementation of a parallel GPIO chip entry not
> containing the base GPIO number in the name and the corresponding sysfs
> attribute group for each exported line that lives under the new chip
> class device as well as a way to allow to compile out the legacy parts
> leaving only the new elements of the sysfs ABI.
>
> This series passes the compatibility tests I wrote while working on the
> user-space compatibility layer for sysfs[2].
>
> [1] https://lore.kernel.org/all/CAMRc=McUCeZcU6co1aN54rTudo+JfPjjForu4iKQ5npwXk6GXA@mail.gmail.com/
> [2] https://github.com/brgl/gpio-sysfs-compat-tests
>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> ---

Alright, so what are we doing about this? Should I queue these patches
for v6.17? Kent, any additional comments? Geert, Jan: did you have the
chance to test it?

Bart