linux-kernel - [PATCH] Fix _IOC_TYPECHECK sparse error

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Message-ID: <533A64EC.2090106@xs4all.nl>
Date:	Tue, 01 Apr 2014 09:04:12 +0200
From:	Hans Verkuil <hverkuil@...all.nl>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
CC:	Sparse Mailing-list <linux-sparse@...r.kernel.org>,
	Linux Media Mailing List <linux-media@...r.kernel.org>,
	Christopher Li <sparse@...isli.org>
Subject: [PATCH] Fix _IOC_TYPECHECK sparse error

When running sparse over drivers/media/v4l2-core/v4l2-ioctl.c I get these
errors:

drivers/media/v4l2-core/v4l2-ioctl.c:2043:9: error: bad integer constant expression
drivers/media/v4l2-core/v4l2-ioctl.c:2044:9: error: bad integer constant expression
drivers/media/v4l2-core/v4l2-ioctl.c:2045:9: error: bad integer constant expression
drivers/media/v4l2-core/v4l2-ioctl.c:2046:9: error: bad integer constant expression

etc.

The root cause of that turns out to be in include/asm-generic/ioctl.h:

#include <uapi/asm-generic/ioctl.h>

/* provoke compile error for invalid uses of size argument */
extern unsigned int __invalid_size_argument_for_IOC;
#define _IOC_TYPECHECK(t) \
        ((sizeof(t) == sizeof(t[1]) && \
          sizeof(t) < (1 << _IOC_SIZEBITS)) ? \
          sizeof(t) : __invalid_size_argument_for_IOC)

If it is defined as this (as is already done if __KERNEL__ is not defined):

#define _IOC_TYPECHECK(t) (sizeof(t))

then all is well with the world.

This patch allows sparse to work correctly.

Signed-off-by: Hans Verkuil <hans.verkuil@...co.com>

diff --git a/include/asm-generic/ioctl.h b/include/asm-generic/ioctl.h
index d17295b..297fb0d 100644
--- a/include/asm-generic/ioctl.h
+++ b/include/asm-generic/ioctl.h
@@ -3,10 +3,15 @@
 
 #include <uapi/asm-generic/ioctl.h>
 
+#ifdef __CHECKER__
+#define _IOC_TYPECHECK(t) (sizeof(t))
+#else
 /* provoke compile error for invalid uses of size argument */
 extern unsigned int __invalid_size_argument_for_IOC;
 #define _IOC_TYPECHECK(t) \
 	((sizeof(t) == sizeof(t[1]) && \
 	  sizeof(t) < (1 << _IOC_SIZEBITS)) ? \
 	  sizeof(t) : __invalid_size_argument_for_IOC)
+#endif
+
 #endif /* _ASM_GENERIC_IOCTL_H */

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