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

[Thorsten Leemhuis <regressions@xxxxxxxxxxxxx>]

On 16.02.22 15:40, Bartosz Golaszewski wrote:
> On Tue, Feb 15, 2022 at 10:56 PM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
>>
>> On Mon, Feb 14, 2022 at 12:24 AM Marcelo Roberto Jimenez
>> <marcelo.jimenez@xxxxxxxxx> wrote:
>>> On Sat, Feb 12, 2022 at 1:55 PM Linus Walleij <linus.walleij@xxxxxxxxxx> 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.

Reviving and old thread, hence a quick reminder: The patch at the start
of this thread was applied and then reverted in 56e337f2cf13 with this text:

```
This commit - while attempting to fix a regression - has caused a number
of other problems. As the fallout from it is more significant than the
initial problem itself, revert it for now before we find a correct
solution.
```

I still have this on my list of open regressions and that made me
wonder: is anyone working on a "correct solution" (or was one even
applied and I missed it)? Or is the situation so tricky that we better
leave everything as it is? Marcelo, do you still care?

Ciao, Thorsten