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

From: Bartosz Golaszewski <brgl@bgdev.pl>
To: Thorsten Leemhuis <regressions@leemhuis.info>
Cc: Linus Walleij <linus.walleij@linaro.org>,
	 Marcelo Roberto Jimenez <marcelo.jimenez@gmail.com>,
	stable <stable@vger.kernel.org>,
	 regressions@lists.linux.dev,
	 "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	Thierry Reding <treding@nvidia.com>,
	 Vidya Sagar <vidyas@nvidia.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	 Stephen Rothwell <sfr@canb.auug.org.au>,
	Edmond Chung <edmondchung@google.com>,
	 Andrew Chant <achant@google.com>,
	Will McVicker <willmcvicker@google.com>,
	 Sergio Tanzilli <tanzilli@acmesystems.it>
Subject: Re: [PATCH] gpio: Revert regression in sysfs-gpio (gpiolib.c)
Date: Mon, 7 Mar 2022 10:58:51 +0100	[thread overview]
Message-ID: <CAMRc=MfbeOBim5mAMGghUYX_uvAKnCikEqftF-k4EZE6g48cNg@mail.gmail.com> (raw)
In-Reply-To: <cadc5208-2eb1-beb1-4f6d-d07939072ca3@leemhuis.info>

On Fri, Mar 4, 2022 at 8:13 AM Thorsten Leemhuis
<regressions@leemhuis.info> wrote:
>
> Hi, this is your Linux kernel regression tracker.
>
> On 16.02.22 15:40, Bartosz Golaszewski wrote:
> > On Tue, Feb 15, 2022 at 10:56 PM Linus Walleij <linus.walleij@linaro.org> wrote:
> >>
> >> On Mon, Feb 14, 2022 at 12:24 AM Marcelo Roberto Jimenez
> >> <marcelo.jimenez@gmail.com> wrote:
> >>> On Sat, Feb 12, 2022 at 1:55 PM Linus Walleij <linus.walleij@linaro.org> wrote:
> >>
> >>>> I am curious about the usecases and how deeply you have built
> >>>> yourselves into this.
> >>>
> >>> I don't know if I understand what you mean, sorry.
> >>
> >> Why does the user need the sysfs ABI? What is it used for?
> >>
> >> I.e what is the actual use case?
> >>
> >>>>> In any case, the upstream file should be enough to test the issue reported here.
> >>>>
> >>>> The thing is that upstream isn't super happy that you have been
> >>>> making yourselves dependent on features that we are actively
> >>>> discouraging and then demanding that we support these features.
> >>>
> >>> Hum, demanding seems to be a strong word for what I am doing here.
> >>>
> >>> Deprecated should not mean broken. My point is: the API seems to be
> >>> currently broken. User space apps got broken, that's a fact. I even
> >>> took the time to bisect the kernel and show you which commit broke it.
> >>> So, no, I am not demanding. More like reporting and providing a
> >>> temporary solution to those with a similar problem.
> >>>
> >>> Maybe it is time to remove the API, but this is up to "upstream".
> >>> Leaving the API broken seems pointless and unproductive.
> >>>
> >>> Sorry for the "not super happiness of upstream", but maybe upstream
> >>> got me wrong.
> >>>
> >>> We are not "making ourselves dependent on features ...". The API was
> >>> there. We used it. Now it is deprecated, ok, we should move on. I got
> >>> the message.
> >>
> >> Ouch I deserved some slamming for this.
> >>
> >> I'm sorry if I came across as harsh :(
> >>
> >> I just don't know how to properly push for this.
> >>
> >> I have even pushed the option of the deprecated sysfs ABI
> >> behind the CONFIG_EXPERT option, which should mean that
> >> the kernel config has been made by someone who has checked
> >> the option "yes I am an expert I know what I am doing"
> >> yet failed to observe that this ABI is obsoleted since 5 years
> >> and hence failed to be an expert.
> >>
> >> Of course the ABI (not API really) needs to be fixed if we can find the
> >> problem. It's frustrating that fixing it seems to fix broken other
> >> features which are not deprecated, hence the annoyance on my
> >> part.
> >>
> >
> > I'm afraid we'll earn ourselves a good old LinusRant if we keep
> > pushing the character device as a solution to the problem here.
> > Marcelo is right after all: he used an existing user interface, the
> > interface broke, it must be fixed.
> >
> > I would prefer to find a solution that fixes Marcelo's issue while
> > keeping the offending patches in tree but it seems like the issue is
> > more complicated and will require some rework of the sysfs interface.
> >
> > In which case unless there are objections I lean towards reverting the
> > relevant commits.
>
> Sounds good to me, but that was two weeks ago and afaics nothing
> happened since then. Or did the discussion continue somewhere else?
>

Now queued for fixes, thanks for the reminder.

Bart

> >>> And I will also tell the dev team that they must use the GPIO char dev
> >>> and libgpiod from now on and must port everything to it. And we will
> >>> likely have another group of people who are not super happy, but
> >>> that's life... :)
> >>
> >> I'm happy to hear this!
>
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
>
> P.S.: As the Linux kernel's regression tracker I'm getting a lot of
> reports on my table. I can only look briefly into most of them and lack
> knowledge about most of the areas they concern. I thus unfortunately
> will sometimes get things wrong or miss something important. I hope
> that's not the case here; if you think it is, don't hesitate to tell me
> in a public reply, it's in everyone's interest to set the public record
> straight.
>
> #regzbot poke