Re: [PATCH] gpio: Revert regression in sysfs-gpio (gpiolib.c)

From: Michael Walle <michael@walle.cc>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>,
	Saravana Kannan <saravanak@google.com>,
	Marcelo Roberto Jimenez <marcelo.jimenez@gmail.com>,
	Andrew Chant <achant@google.com>,
	Edmond Chung <edmondchung@google.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	regressions@lists.linux.dev,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	stable <stable@vger.kernel.org>,
	Sergio Tanzilli <tanzilli@acmesystems.it>,
	Thierry Reding <treding@nvidia.com>,
	Vidya Sagar <vidyas@nvidia.com>,
	Will McVicker <willmcvicker@google.com>,
	Horatiu Vultur <horatiu.vultur@microchip.com>,
	Lars Povlsen <lars.povlsen@microchip.com>
Subject: Re: [PATCH] gpio: Revert regression in sysfs-gpio (gpiolib.c)
Date: Thu, 17 Mar 2022 09:48:28 +0100	[thread overview]
Message-ID: <8a1a46f1e5b822fd49f56f2fe50c5396@walle.cc> (raw)
In-Reply-To: <CAHp75VeoFQHAh6SbVu7fsXfziW+2RoFTWKA6jFhFswBbazzGAA@mail.gmail.com>

Am 2022-03-17 09:37, schrieb Andy Shevchenko:
> On Thu, Mar 17, 2022 at 7:36 AM Michael Walle <michael@walle.cc> wrote:
>> Am 2022-03-15 16:32, schrieb Bartosz Golaszewski:
>> > On Mon, Mar 14, 2022 at 4:55 PM Michael Walle <michael@walle.cc> wrote:
> 
> ...
> 
>> I started to try this out, but then I was wondering if there weren't
>> other gpio/pinctrl drivers with the same problem. And judging by the
>> reports [1], I'd say there are. Then I wasn't sure if this is actually
>> the correct fix here - or if that old workaround [2] doesn't work
>> anymore because it might have that empty ranges "feature".
>> 
>> To answer your question: I don't know. But I don't know if that is
>> actually the correct way of fixing this either.
>> 
>> >> Also, I'm not sure if there are any other other driver which get
>> >> broken by this. I.e. ones falling into the gpio_stub_drv category.
> 
> I know that OF is a mess, but I want to understand why in ACPI we
> haven't experienced such an issue. Any pointers would be appreciated.

During debugging I've seen that the pinctrl-microchip-sgpio will
report itself as gpio_stub_drv. You'll find that this driver
was added by the following commit:

commit 4731210c09f5977300f439b6c56ba220c65b2348
Author: Saravana Kannan <saravanak@google.com>
Date:   Fri Jan 22 11:35:59 2021 -0800

     gpiolib: Bind gpio_device to a driver to enable fw_devlink=on by 
default

The microchip driver has actually a binding which was described in
that commit message. Thus I concluded, that it makes sense this driver
falls into that workaround. That is where I stopped and wrote this mail.
Actually, I haven't found out yet where that fallback to gpio_stub_drv
is happening.

-michael