linux-kernel - [PATCH] leds: trigger: ledtrig-cpu:: Fix a warning when compiling with W=1

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Date:   Sat, 23 Sep 2023 09:15:38 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
        Bryan Wu <bryan.wu@...onical.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Jamie Iles <jamie@...ieiles.com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        linux-leds@...r.kernel.org
Subject: [PATCH] leds: trigger: ledtrig-cpu:: Fix a warning when compiling with W=1

In order to teach the compiler that 'trig->name' will never be truncated,
we need to tell it that 'cpu' is not negative.

When building with W=1, this fixes the following warnings:

  drivers/leds/trigger/ledtrig-cpu.c: In function ‘ledtrig_cpu_init’:
  drivers/leds/trigger/ledtrig-cpu.c:155:56: error: ‘%d’ directive output may be truncated writing between 1 and 11 bytes into a region of size 5 [-Werror=format-truncation=]
    155 |                 snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
        |                                                        ^~
  drivers/leds/trigger/ledtrig-cpu.c:155:52: note: directive argument in the range [-2147483648, 7]
    155 |                 snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
        |                                                    ^~~~~~~
  drivers/leds/trigger/ledtrig-cpu.c:155:17: note: ‘snprintf’ output between 5 and 15 bytes into a destination of size 8
    155 |                 snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
        |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fixes: 8f88731d052d ("led-triggers: create a trigger for CPU activity")
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
 drivers/leds/trigger/ledtrig-cpu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-cpu.c b/drivers/leds/trigger/ledtrig-cpu.c
index 8af4f9bb9cde..05848a2fecff 100644
--- a/drivers/leds/trigger/ledtrig-cpu.c
+++ b/drivers/leds/trigger/ledtrig-cpu.c
@@ -130,7 +130,7 @@ static int ledtrig_prepare_down_cpu(unsigned int cpu)
 
 static int __init ledtrig_cpu_init(void)
 {
-	int cpu;
+	unsigned int cpu;
 	int ret;
 
 	/* Supports up to 9999 cpu cores */
@@ -152,7 +152,7 @@ static int __init ledtrig_cpu_init(void)
 		if (cpu >= 8)
 			continue;
 
-		snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
+		snprintf(trig->name, MAX_NAME_LEN, "cpu%u", cpu);
 
 		led_trigger_register_simple(trig->name, &trig->_trig);
 	}
-- 
2.34.1