linux-kernel - [PATCH] media: videodev2.h: Fix shifting signed 32-bit value by 31 bits problem

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Message-Id: <20190613005652.7423-1-skhan@linuxfoundation.org>
Date:   Wed, 12 Jun 2019 18:56:52 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     mchehab@...nel.org, hverkuil-cisco@...all.nl
Cc:     Shuah Khan <skhan@...uxfoundation.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] media: videodev2.h: Fix shifting signed 32-bit value by 31 bits problem

Fix v4l2_fourcc define to use "U" cast to avoid shifting signed 32-bit
value by 31 bits problem. This isn't a problem for kernel builds with
gcc.

This could be problem since this header is part of public API which
could be included for builds using compilers that don't handle this
condition safely resulting in undefined behavior.

Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
---
 include/uapi/linux/videodev2.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 1050a75fb7ef..9d9705ceda76 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -80,7 +80,7 @@
 /*  Four-character-code (FOURCC) */
 #define v4l2_fourcc(a, b, c, d)\
 	((__u32)(a) | ((__u32)(b) << 8) | ((__u32)(c) << 16) | ((__u32)(d) << 24))
-#define v4l2_fourcc_be(a, b, c, d)	(v4l2_fourcc(a, b, c, d) | (1 << 31))
+#define v4l2_fourcc_be(a, b, c, d)	(v4l2_fourcc(a, b, c, d) | (1U << 31))
 
 /*
  *	E N U M S
-- 
2.17.1