linux-kernel - [PATCH] UAPI/ioctl: Improve parameter name of ioctl request definition helpers

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Message-ID: <20240712093524.905556-2-u.kleine-koenig@baylibre.com>
Date: Fri, 12 Jul 2024 11:35:23 +0200
From: Uwe Kleine-König <u.kleine-koenig@...libre.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] UAPI/ioctl: Improve parameter name of ioctl request definition helpers

The third parameter to _IOR et al is a type name, not a size. So the
parameter being named "size" is irritating. Rename it to "argtype"
instead to reduce confusion.

There is a very minor chance that this breaks stuff. It only hurts
however if there is a variable (or macro) in userspace that is called
"argtype" *and* it's used in the parameters of _IOR and friends. IMHO
this is negligible because usually definitions making use of these
macros are provided by kernel headers (i.e. us) or if they are
replicated in userspace code, they are replicated and so supposed to
match the kernel definitions (e.g. to make them usable by programs
without the need to update the kernel headers used to compile the
program).

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...libre.com>
---
Hello,

if there are doubts about using "argtype": Would "_argtype" be better?

Best regards
Uwe

 include/uapi/asm-generic/ioctl.h | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/uapi/asm-generic/ioctl.h b/include/uapi/asm-generic/ioctl.h
index a84f4db8a250..e3290a5824c9 100644
--- a/include/uapi/asm-generic/ioctl.h
+++ b/include/uapi/asm-generic/ioctl.h
@@ -82,13 +82,13 @@
  * NOTE: _IOW means userland is writing and kernel is reading. _IOR
  * means userland is reading and kernel is writing.
  */
-#define _IO(type,nr)		_IOC(_IOC_NONE,(type),(nr),0)
-#define _IOR(type,nr,size)	_IOC(_IOC_READ,(type),(nr),(_IOC_TYPECHECK(size)))
-#define _IOW(type,nr,size)	_IOC(_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
-#define _IOWR(type,nr,size)	_IOC(_IOC_READ|_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
-#define _IOR_BAD(type,nr,size)	_IOC(_IOC_READ,(type),(nr),sizeof(size))
-#define _IOW_BAD(type,nr,size)	_IOC(_IOC_WRITE,(type),(nr),sizeof(size))
-#define _IOWR_BAD(type,nr,size)	_IOC(_IOC_READ|_IOC_WRITE,(type),(nr),sizeof(size))
+#define _IO(type,nr)			_IOC(_IOC_NONE,(type),(nr),0)
+#define _IOR(type,nr,argtype)		_IOC(_IOC_READ,(type),(nr),(_IOC_TYPECHECK(argtype)))
+#define _IOW(type,nr,argtype)		_IOC(_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(argtype)))
+#define _IOWR(type,nr,argtype)		_IOC(_IOC_READ|_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(argtype)))
+#define _IOR_BAD(type,nr,argtype)	_IOC(_IOC_READ,(type),(nr),sizeof(argtype))
+#define _IOW_BAD(type,nr,argtype)	_IOC(_IOC_WRITE,(type),(nr),sizeof(argtype))
+#define _IOWR_BAD(type,nr,argtype)	_IOC(_IOC_READ|_IOC_WRITE,(type),(nr),sizeof(argtype))
 
 /* used to decode ioctl numbers.. */
 #define _IOC_DIR(nr)		(((nr) >> _IOC_DIRSHIFT) & _IOC_DIRMASK)

base-commit: 3fe121b622825ff8cc995a1e6b026181c48188db
prerequisite-patch-id: 816efa50518af0814a168f7f0ac5904b7128e5b1
-- 
2.43.0