linux-kernel - [PATCH] ARM: OMAP: Fix use of possibly uninitialized irq variable

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Date:   Thu,  1 Apr 2021 18:11:27 +0200
From:   Maciej Falkowski <maciej.falkowski9@...il.com>
To:     khilman@...nel.org, aaro.koskinen@....fi, tony@...mide.com,
        linux@...linux.org.uk
Cc:     linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        maciej.falkowski9@...il.com
Subject: [PATCH] ARM: OMAP: Fix use of possibly uninitialized irq variable

The current control flow of IRQ number assignment to `irq` variable
allows a request of IRQ of unspecified value,
generating a warning under Clang compilation with omap1_defconfig on linux-next:

arch/arm/mach-omap1/pm.c:656:11: warning: variable 'irq' is used uninitialized whenever
'if' condition is false [-Wsometimes-uninitialized]
        else if (cpu_is_omap16xx())
                 ^~~~~~~~~~~~~~~~~
./arch/arm/mach-omap1/include/mach/soc.h:123:30: note: expanded from macro 'cpu_is_omap16xx'
                                        ^~~~~~~~~~~~~
arch/arm/mach-omap1/pm.c:658:18: note: uninitialized use occurs here
        if (request_irq(irq, omap_wakeup_interrupt, 0, "peripheral wakeup",
                        ^~~
arch/arm/mach-omap1/pm.c:656:7: note: remove the 'if' if its condition is always true
        else if (cpu_is_omap16xx())
             ^~~~~~~~~~~~~~~~~~~~~~
arch/arm/mach-omap1/pm.c:611:9: note: initialize the variable 'irq' to silence this warning
        int irq;
               ^
                = 0
1 warning generated.

The patch provides a default value to the `irq` variable
along with a validity check.

Signed-off-by: Maciej Falkowski <maciej.falkowski9@...il.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1324
---
 arch/arm/mach-omap1/pm.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/arm/mach-omap1/pm.c b/arch/arm/mach-omap1/pm.c
index 2c1e2b32b9b3..a745d64d4699 100644
--- a/arch/arm/mach-omap1/pm.c
+++ b/arch/arm/mach-omap1/pm.c
@@ -655,9 +655,13 @@ static int __init omap_pm_init(void)
 		irq = INT_7XX_WAKE_UP_REQ;
 	else if (cpu_is_omap16xx())
 		irq = INT_1610_WAKE_UP_REQ;
-	if (request_irq(irq, omap_wakeup_interrupt, 0, "peripheral wakeup",
-			NULL))
-		pr_err("Failed to request irq %d (peripheral wakeup)\n", irq);
+	else
+		irq = -1;
+
+	if (irq >= 0) {
+		if (request_irq(irq, omap_wakeup_interrupt, 0, "peripheral wakeup", NULL))
+			pr_err("Failed to request irq %d (peripheral wakeup)\n", irq);
+	}
 
 	/* Program new power ramp-up time
 	 * (0 for most boards since we don't lower voltage when in deep sleep)
-- 
2.26.3