tools: gpio: fix -c option of gpio-event-mon

Following line should listen for a rising edge and exit after the first
one since '-c 1' is provided.

    # gpio-event-mon -n gpiochip1 -o 0 -r -c 1

It works with kernel 4.19 but it doesn't work with 5.10. In 5.10 the
above command doesn't exit after the first rising edge it keep listening
for an event forever. The '-c 1' is not taken into an account.
The problem is in commit 62757c32d5db ("tools: gpio: add multi-line
monitoring to gpio-event-mon").
Before this commit the iterator 'i' in monitor_device() is used for
counting of the events (loops). In the case of the above command (-c 1)
we should start from 0 and increment 'i' only ones and hit the 'break'
statement and exit the process. But after the above commit counting
doesn't start from 0, it start from 1 when we listen on one line.
It is because 'i' is used from one more purpose, counting of lines
(num_lines) and it isn't restore to 0 after following code

    for (i = 0; i < num_lines; i++)
        gpiotools_set_bit(&values.mask, i);

This patch just restore the initial value of the iterator to 0 in
order to allow counting of loops to work for any cases.

Fixes: 62757c32d5db ("tools: gpio: add multi-line monitoring to gpio-event-mon")
Signed-off-by: Ivo Borisov Shopov <ivoshopov@gmail.com>
---
 tools/gpio/gpio-event-mon.c | 1 +
 1 file changed, 1 insertion(+)

On Thu, Jan 26, 2023 at 3:11 PM Ivo Borisov Shopov <ivoshopov@gmail.com> wrote:
>
> Following line should listen for a rising edge and exit after the first
> one since '-c 1' is provided.
>
>     # gpio-event-mon -n gpiochip1 -o 0 -r -c 1
>
> It works with kernel 4.19 but it doesn't work with 5.10. In 5.10 the
> above command doesn't exit after the first rising edge it keep listening
> for an event forever. The '-c 1' is not taken into an account.
> The problem is in commit 62757c32d5db ("tools: gpio: add multi-line
> monitoring to gpio-event-mon").
> Before this commit the iterator 'i' in monitor_device() is used for
> counting of the events (loops). In the case of the above command (-c 1)
> we should start from 0 and increment 'i' only ones and hit the 'break'
> statement and exit the process. But after the above commit counting
> doesn't start from 0, it start from 1 when we listen on one line.
> It is because 'i' is used from one more purpose, counting of lines
> (num_lines) and it isn't restore to 0 after following code
>
>     for (i = 0; i < num_lines; i++)
>         gpiotools_set_bit(&values.mask, i);
>
> This patch just restore the initial value of the iterator to 0 in

s/This patch just restore/Restore/

> order to allow counting of loops to work for any cases.

Very good explanation for the issue, thanks!
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

P.S. No need to resend to address above, I think Bart can amend that
when applying.

> Fixes: 62757c32d5db ("tools: gpio: add multi-line monitoring to gpio-event-mon")
> Signed-off-by: Ivo Borisov Shopov <ivoshopov@gmail.com>
> ---
>  tools/gpio/gpio-event-mon.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/tools/gpio/gpio-event-mon.c b/tools/gpio/gpio-event-mon.c
> index 6c122952c589..5dee2b98ab60 100644
> --- a/tools/gpio/gpio-event-mon.c
> +++ b/tools/gpio/gpio-event-mon.c
> @@ -86,6 +86,7 @@ int monitor_device(const char *device_name,
>                         gpiotools_test_bit(values.bits, i));
>         }
>
> +       i = 0;
>         while (1) {
>                 struct gpio_v2_line_event event;
>
> --
> 2.20.1
>

On Thu, Jan 26, 2023 at 2:11 PM Ivo Borisov Shopov <ivoshopov@gmail.com> wrote:
>
> Following line should listen for a rising edge and exit after the first
> one since '-c 1' is provided.
>
>     # gpio-event-mon -n gpiochip1 -o 0 -r -c 1
>
> It works with kernel 4.19 but it doesn't work with 5.10. In 5.10 the
> above command doesn't exit after the first rising edge it keep listening
> for an event forever. The '-c 1' is not taken into an account.
> The problem is in commit 62757c32d5db ("tools: gpio: add multi-line
> monitoring to gpio-event-mon").
> Before this commit the iterator 'i' in monitor_device() is used for
> counting of the events (loops). In the case of the above command (-c 1)
> we should start from 0 and increment 'i' only ones and hit the 'break'
> statement and exit the process. But after the above commit counting
> doesn't start from 0, it start from 1 when we listen on one line.
> It is because 'i' is used from one more purpose, counting of lines
> (num_lines) and it isn't restore to 0 after following code
>
>     for (i = 0; i < num_lines; i++)
>         gpiotools_set_bit(&values.mask, i);
>
> This patch just restore the initial value of the iterator to 0 in
> order to allow counting of loops to work for any cases.
>
> Fixes: 62757c32d5db ("tools: gpio: add multi-line monitoring to gpio-event-mon")
> Signed-off-by: Ivo Borisov Shopov <ivoshopov@gmail.com>
> ---
>  tools/gpio/gpio-event-mon.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/tools/gpio/gpio-event-mon.c b/tools/gpio/gpio-event-mon.c
> index 6c122952c589..5dee2b98ab60 100644
> --- a/tools/gpio/gpio-event-mon.c
> +++ b/tools/gpio/gpio-event-mon.c
> @@ -86,6 +86,7 @@ int monitor_device(const char *device_name,
>                         gpiotools_test_bit(values.bits, i));
>         }
>
> +       i = 0;
>         while (1) {
>                 struct gpio_v2_line_event event;
>
> --
> 2.20.1
>

Queued for fixes with the commit message tweaked.

Bart