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

[Thorsten Leemhuis <regressions@leemhuis.info>]

[TLDR: I'm adding this regression to regzbot, the Linux kernel
regression tracking bot; most text you find below is compiled from a few
templates paragraphs some of you might have seen already.]

On 17.12.21 16:35, Marcelo Roberto Jimenez wrote:
> Some GPIO lines have stopped working after the patch
> commit 2ab73c6d8323f ("gpio: Support GPIO controllers without pin-ranges")
> 
> And this has supposedly been fixed in the following patches
> commit 89ad556b7f96a ("gpio: Avoid using pin ranges with !PINCTRL")
> commit 6dbbf84603961 ("gpiolib: Don't free if pin ranges are not defined")

There seems to be a backstory here. Are there any entries and bug
trackers or earlier discussions everyone that looks into this should be
aware of?

> But an erratic behavior where some GPIO lines work while others do not work
> has been introduced.
> 
> This patch reverts those changes so that the sysfs-gpio interface works
> properly again.
> 
> Signed-off-by: Marcelo Roberto Jimenez <marcelo.jimenez@gmail.com>
> ---
> 
> Hi,
> 
> My system is ARM926EJ-S rev 5 (v5l) (AT91SAM9G25), the board is an ACME Systems Arietta.
> 
> The system used sysfs-gpio to manage a few gpio lines, and I have noticed that some have stopped working.
> 
> The test script is very simple:
> 
> 	#! /bin/bash
> 
> 	cd /sys/class/gpio/
> 	echo 24 > export 
> 
> 	cd pioA24
> 	echo out > direction
> 
> 	echo 0 > value
> 	cat value
> 	echo 1 > value
> 	cat value
> 	echo 0 > value
> 	cat value
> 	echo 1 > value
> 	cat value
> 
> 	cd ..
> 	echo 24 > unexport
> 
> In a "good" kernel, this script outputs 0, 1, 0, 1. In a bad kernel, the output result is 1, 1, 1, 1. Also it must be possible to run this script twice without errors, that was the issue with the gpiochip_generic_free() call that had been addressed in another patch.
> 
> In my system PINCTRL is automatically selected by 
> SOC_AT91SAM9 [=y] && ARCH_AT91 [=y] && ARCH_MULTI_V5 [=y]
> 
> So it is not an option to disable it to make it work.
> 
> Best regards,
> Marcelo.
> 
> 
>  drivers/gpio/gpiolib.c | 10 ----------
>  1 file changed, 10 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index af5bb8fedfea..ac69ec8fb37a 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1804,11 +1804,6 @@ static inline void gpiochip_irqchip_free_valid_mask(struct gpio_chip *gc)
>   */
>  int gpiochip_generic_request(struct gpio_chip *gc, unsigned offset)
>  {
> -#ifdef CONFIG_PINCTRL
> -	if (list_empty(&gc->gpiodev->pin_ranges))
> -		return 0;
> -#endif
> -
>  	return pinctrl_gpio_request(gc->gpiodev->base + offset);
>  }
>  EXPORT_SYMBOL_GPL(gpiochip_generic_request);
> @@ -1820,11 +1815,6 @@ EXPORT_SYMBOL_GPL(gpiochip_generic_request);
>   */
>  void gpiochip_generic_free(struct gpio_chip *gc, unsigned offset)
>  {
> -#ifdef CONFIG_PINCTRL
> -	if (list_empty(&gc->gpiodev->pin_ranges))
> -		return;
> -#endif
> -
>  	pinctrl_gpio_free(gc->gpiodev->base + offset);
>  }
>  EXPORT_SYMBOL_GPL(gpiochip_generic_free);
> 

Hi, this is your Linux kernel regression tracker speaking.

Thanks for the report.

To be sure this issue doesn't fall through the cracks unnoticed, I'm
adding it to regzbot, my Linux kernel regression tracking bot:

#regzbot ^introduced 2ab73c6d8323f
#regzbot title gpio: some GPIO lines have stopped working
#regzbot ignore-activity

Reminder: when fixing the issue, please add a 'Link:' tag with the URL
to the report (the parent of this mail), as explained in
'Documentation/process/submitting-patches.rst' (reminder: you should use
the kernel.org redirector). Regzbot then will automatically mark the
regression as resolved once the fix lands in the appropriate tree. For
more details about regzbot see footer.

Sending this to everyone that got the initial report, to make all aware
of the tracking. I also hope that messages like this motivate people to
directly get at least the regression mailing list and ideally even
regzbot involved when dealing with regressions, as messages like this
wouldn't be needed then.

Don't worry, I'll send further messages wrt to this regression just to
the lists (with a tag in the subject so people can filter them away), as
long as they are intended just for regzbot. With a bit of luck no such
messages will be needed anyway.

Ciao, Thorsten (wearing his 'Linux kernel regression tracker' hat).

P.S.: As a Linux kernel regression tracker I'm getting a lot of reports
on my table. I can only look briefly into most of them. Unfortunately
therefore I sometimes will 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 about it in a public reply. That's in everyone's interest, as
what I wrote above might be misleading to everyone reading this; any
suggestion I gave thus might sent someone reading this down the wrong
rabbit hole, which none of us wants.

BTW, I have no personal interest in this issue, which is tracked using
regzbot, my Linux kernel regression tracking bot
(https://linux-regtracking.leemhuis.info/regzbot/). I'm only posting
this mail to get things rolling again and hence don't need to be CC on
all further activities wrt to this regression.

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