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References: <20230126131033.23011-1-ivoshopov@gmail.com>
In-Reply-To: <20230126131033.23011-1-ivoshopov@gmail.com>
From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Thu, 26 Jan 2023 15:26:13 +0200
Message-ID: <CAHp75VcsdPfYt9O8GFDa1r8EzUy9dTDH09ttb50qBWPNkJuokQ@mail.gmail.com>
Subject: Re: [PATCH] tools: gpio: fix -c option of gpio-event-mon
To:     Ivo Borisov Shopov <ivoshopov@gmail.com>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <brgl@bgdev.pl>,
        Kent Gibson <warthog618@gmail.com>, linux-gpio@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Precedence: bulk

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
>


-- 
With Best Regards,
Andy Shevchenko