linux-kernel - [PATCH] tools: gpio: fix -c option of gpio-event-mon

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Message-Id: <20230126131033.23011-1-ivoshopov@gmail.com>
Date:   Thu, 26 Jan 2023 15:10:33 +0200
From:   Ivo Borisov Shopov <ivoshopov@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     ivoshopov@...il.com, Bartosz Golaszewski <brgl@...ev.pl>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Kent Gibson <warthog618@...il.com>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] 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@...il.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