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linux-next/include/uapi/linux/const.h
H. Peter Anvin 2fc016c5bd linux/const.h: Add _BITUL() and _BITULL()
Add macros for single bit definitions of a specific type.  These are
similar to the BIT() macro that already exists, but with a few
exceptions:

1. The namespace is such that they can be used in uapi definitions.
2. The type is set with the _AC() macro to allow it to be used in
   assembly.
3. The type is explicitly specified to be UL or ULL.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/n/tip-nbca8p7cg6jyjoit7klh3o91@git.kernel.org
2013-06-25 15:50:04 -07:00

28 lines
673 B
C

/* const.h: Macros for dealing with constants. */
#ifndef _LINUX_CONST_H
#define _LINUX_CONST_H
/* Some constant macros are used in both assembler and
* C code. Therefore we cannot annotate them always with
* 'UL' and other type specifiers unilaterally. We
* use the following macros to deal with this.
*
* Similarly, _AT() will cast an expression with a type in C, but
* leave it unchanged in asm.
*/
#ifdef __ASSEMBLY__
#define _AC(X,Y) X
#define _AT(T,X) X
#else
#define __AC(X,Y) (X##Y)
#define _AC(X,Y) __AC(X,Y)
#define _AT(T,X) ((T)(X))
#endif
#define _BITUL(x) (_AC(1,UL) << (x))
#define _BITULL(x) (_AC(1,ULL) << (x))
#endif /* !(_LINUX_CONST_H) */