linux-kernel - Re: [PATCH 3/3] gpio: shared: allow sharing a reset-gpios pin between reset-gpio and gpiolib

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Message-ID: <0bce9429-1cff-4a62-bdae-57697daf2920@sirena.org.uk>
Date: Thu, 8 Jan 2026 15:46:12 +0000
From: Mark Brown <broonie@...nel.org>
To: Bartosz Golaszewski <bartosz.golaszewski@....qualcomm.com>
Cc: Linus Walleij <linusw@...nel.org>,
	Bartosz Golaszewski <brgl@...nel.org>, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>, Aishwarya.TCV@....com
Subject: Re: [PATCH 3/3] gpio: shared: allow sharing a reset-gpios pin
 between reset-gpio and gpiolib

On Mon, Dec 22, 2025 at 11:01:28AM +0100, Bartosz Golaszewski wrote:
> We currently support sharing GPIOs between multiple devices whose drivers
> use either the GPIOLIB API *OR* the reset control API but not both at
> the same time.

We're seeing futher issues which bisect to this patch in today's
next/pending-fixes on db845c:

<1>[   18.348426] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008

...

<4>[   18.799534] Call trace:
<4>[   18.799536]  gpiod_direction_output_nonotify+0x14/0x194 (P)
<4>[   18.799541]  gpiod_configure_flags+0xb0/0x364
<4>[   18.799543]  gpiod_find_and_request+0x144/0x504
<4>[   18.832617]  gpiod_get_index+0x58/0x90
<4>[   18.836657]  devm_gpiod_get_index+0x20/0xb0
<4>[   18.841139]  devm_gpiod_get_optional+0x18/0x34
<4>[   18.845881]  lt9611_probe+0x130/0x488 [lontium_lt9611]

Some prior instances were fixed by:

   https://lore.kernel.org/all/20260106-gpio-shared-fixes-v2-0-c7091d2f7581@oss.qualcomm.com/

but that's only in next/master, not next/pending-fixes, and in any case
the issue also appears in next/master which should include them.

git bisect start
# status: waiting for both good and bad commits
# bad: [fc4e91c639c0af93d63c3d5bc0ee45515dd7504a] Add linux-next specific files for 20260108
git bisect bad fc4e91c639c0af93d63c3d5bc0ee45515dd7504a
# status: waiting for good commit(s), bad commit known
# bad: [53ebf42e14b480288f52fa86811bf68703fece4e] Merge branch 'for-linux-next-fixes' of https://gitlab.freedesktop.org/drm/misc/kernel.git
git bisect bad 53ebf42e14b480288f52fa86811bf68703fece4e
# status: waiting for good commit(s), bad commit known
# good: [f0b9d8eb98dfee8d00419aa07543bdc2c1a44fb1] Merge tag 'nfsd-6.19-3' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux
git bisect good f0b9d8eb98dfee8d00419aa07543bdc2c1a44fb1
# good: [a64e2a609fbd406cc424ba13bfcf1941c3b004ea] Merge branch 'for-linus' of https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git
git bisect good a64e2a609fbd406cc424ba13bfcf1941c3b004ea
# good: [1d1d206d257d645c8e3b910d69a1d4b0105de146] Merge branch 'fixes' of git://linuxtv.org/media-ci/media-pending.git
git bisect good 1d1d206d257d645c8e3b910d69a1d4b0105de146
# good: [fc6818ad09fcdcd3670755c8dbe9785561f8ef1e] Merge branch 'riscv-dt-fixes' of https://git.kernel.org/pub/scm/linux/kernel/git/conor/linux.git
git bisect good fc6818ad09fcdcd3670755c8dbe9785561f8ef1e
# bad: [158eb9119b536341cf39b07c6f9408c15516f77e] Merge branch 'rust-fixes' of https://github.com/Rust-for-Linux/linux.git
git bisect bad 158eb9119b536341cf39b07c6f9408c15516f77e
# bad: [51018b3e4652074f726aea6cd66e89edcef34e76] Merge branch 'gpio/for-current' of https://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git
git bisect bad 51018b3e4652074f726aea6cd66e89edcef34e76
# bad: [014a17deb41201449f76df2b20c857a9c3294a7c] gpio: pca953x: handle short interrupt pulses on PCAL devices
git bisect bad 014a17deb41201449f76df2b20c857a9c3294a7c
# good: [cb0451e33be047fff7137f58d9996370e11fb344] gpio: shared: verify con_id when adding proxy lookup
git bisect good cb0451e33be047fff7137f58d9996370e11fb344
# bad: [a7ac22d53d0990152b108c3f4fe30df45fcb0181] gpiolib: fix race condition for gdev->srcu
git bisect bad a7ac22d53d0990152b108c3f4fe30df45fcb0181
# bad: [49416483a953662aa53c6d9bef651757d4a95ba5] gpio: shared: allow sharing a reset-gpios pin between reset-gpio and gpiolib
git bisect bad 49416483a953662aa53c6d9bef651757d4a95ba5
# first bad commit: [49416483a953662aa53c6d9bef651757d4a95ba5] gpio: shared: allow sharing a reset-gpios pin between reset-gpio and gpiolib

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