Re: [Bug]:LAGER: GPIO-KEYS: Warning occurs after unbinding the e6051000.gpio

[Cao Minh Hiep <cm-hiep@jinso.co.jp>]

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Hi Linus-san
Thanks for your reply!

On 04/26/2016 06:20 PM, Linus Walleij wrote:
> On Mon, Apr 25, 2016 at 11:32 AM, Cao Minh Hiep <cm-hiep@jinso.co.jp> wrote:
>
>> Hello Linus Walleij-san
>>
>> We have tested Linux upstream v4.6-rc2 on Renesas's Lager board.
>> When we tried to unbind the e6051000.gpio, the following warning messages
>> occurs:
>>
>> "root@linaro-nano:/sys/bus/platform/drivers/gpio_rcar# echo e6051000.gpio >
>> unbind
>> [  241.511034] ------------[ cut here ]------------
>> [  241.525054] WARNING: CPU: 0 PID: 2104 at fs/proc/generic.c:575
>> remove_proc_entry+0x13c/0x160
>> [  241.550456] remove_proc_entry: removing non-empty directory 'irq/169',
>> leaking at least '6-0039'
> Do you mean that you set up a handler in userspace, using the
> deprecated sysfs ABI and then unbind the module providing the
> IRQ resource?
>
Please see the attach file for procedure test of this case.
In order to make sure that driver works normally after unbind and rebind 
the device.

>> And we found a patch between v4.5 and v4.6-rc2 that causing of this issue.
>> The patch is "ff2b1359 gpio: make the gpiochip a real device"
> It seems the issue is not a bug in the kernel, the issue is that the
> kernel is warning you about something that was wrong also before
> but you didn't get a warning for it until now.
>
> It is not OK to unbind a driver providing IRQs.
>
> It is even unclear if we should even allow modules to provide
> IRQs because there is no way to handle irqchips going away
> when it has consumers.
>
> Maybe we should just do this?
>
> diff --git a/drivers/gpio/gpio-rcar.c b/drivers/gpio/gpio-rcar.c
> index 3fe8e773d95c..ae5e81358ec5 100644
> --- a/drivers/gpio/gpio-rcar.c
> +++ b/drivers/gpio/gpio-rcar.c
> @@ -562,6 +562,7 @@ static struct platform_driver gpio_rcar_device_driver = {
>          .driver         = {
>                  .name   = "gpio_rcar",
>                  .of_match_table = of_match_ptr(gpio_rcar_of_table),
> +               .suppress_bind_attrs = true,
>          }
>   };
>
I have just tried to patch this patch on v4.6-rc2, then make a test.
The results is: I could not unbind the device.

"Welcome to Linaro 14.04 (GNU/Linux 4.6.0-rc2-dirty armv7l)

  * Documentation:  https://wiki.linaro.org/
root@linaro-nano:~# uname -a
Linux linaro-nano 4.6.0-rc2-dirty #8 SMP Wed Apr 27 13:40:12 JST 2016 
armv7l armv7l armv7l GNU/Linux
root@linaro-nano:~# cd /sys/bus/platform/drivers/gpio-keys; ls -d keyboard
keyboard
root@linaro-nano:/sys/bus/platform/drivers/gpio-keys# echo keyboard > unbind
root@linaro-nano:/sys/bus/platform/drivers/gpio-keys# cd
root@linaro-nano:~#
root@linaro-nano:~# cd /sys/bus/platform/drivers/gpio_rcar; ls -d 
e6051000.gpio
e6051000.gpio
root@linaro-nano:/sys/bus/platform/drivers/gpio_rcar# echo e6051000.gpio 
 > unbind
-bash: unbind: Permission denied

root@linaro-nano:/sys/bus/platform/drivers/gpio_rcar# ls
e6050000.gpio  e6052000.gpio  e6054000.gpio  uevent
e6051000.gpio  e6053000.gpio  e6055000.gpio
root@linaro-nano:/sys/bus/platform/drivers/gpio_rcar#
"

before patching the patch, gpio-rcar devices are shown as below:

"root@linaro-nano:~# cd /sys/bus/platform/drivers/gpio_rcar; ls
bind           e6051000.gpio  e6053000.gpio  e6055000.gpio  unbind
e6050000.gpio  e6052000.gpio  e6054000.gpio  uevent
root@linaro-nano:/sys/bus/platform/drivers/gpio_rcar# "


Best Regards,
Jinso/Cao Minh Hiep.


[-- Attachment #2: gpio-rcar-unbind-rebind-procedure.txt --]
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1.Booting kernel.

2.Confirm the gpio keys device.
# cd /sys/bus/platform/drivers/gpio-keys; ls -d keyboard
keyboard

3.Do unbind the device
# cd /sys/bus/platform/drivers/gpio-keys; echo keyboard > unbind

4. Confirm the gpio rcars device
# cd /sys/bus/platform/drivers/gpio_rcar; ls -d e6051000.gpio
e6051000.gpio

5.Do unbind the device.
# cd /sys/bus/platform/drivers/gpio_rcar; echo e6051000.gpio > unbind

6.Confirm the gpio rcars device
# cd /sys/bus/platform/drivers/gpio_rcar; ls -d e6051000.gpio
ls: cannot access e6051000.gpio: No such file or directory

7. Do rebind the gpio rcar device.
cd /sys/bus/platform/drivers/gpio_rcar; echo e6051000.gpio > bind

8. Do rebind the gpio keys device.
# cd /sys/bus/platform/drivers/gpio-keys;  echo keyboard > bind

9. Confirm.