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linux/bits.h: make BIT(), GENMASK(), and friends available in assembly 

BIT(),  GENMASK(), etc. are useful to define register bits of hardware.
However, low-level code is often written in assembly, where they are
not available due to the hard-coded 1UL, 0UL.

In fact, in-kernel headers such as arch/arm64/include/asm/sysreg.h
use _BITUL() instead of BIT() so that the register bit macros are
available in assembly.

Using macros in include/uapi/linux/const.h have two reasons:

[1] For use in uapi headers
  We should use underscore-prefixed variants for user-space.

[2] For use in assembly code
  Since _BITUL() uses UL(1) instead of 1UL, it can be used as an
  alternative of BIT().

For [2], it is pretty easy to change BIT() etc. for use in assembly.

This allows to replace _BUTUL() in kernel-space headers with BIT().

Link: http://lkml.kernel.org/r/20190609153941.17249-1-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Masahiro Yamada 2019-07-16 16:26:57 -07:00 committed by Linus Torvalds
parent 65f50f2553
commit 95b980d62d
1 changed files with 10 additions and 7 deletions
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17
include/linux/bits.h
View File

@ -1,13 +1,15 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_BITS_H
#define __LINUX_BITS_H
#include <linux/const.h>
#include <asm/bitsperlong.h>
#define BIT(nr) (1UL << (nr))
#define BIT_ULL(nr) (1ULL << (nr))
#define BIT_MASK(nr) (1UL << ((nr) % BITS_PER_LONG))
#define BIT(nr) (UL(1) << (nr))
#define BIT_ULL(nr) (ULL(1) << (nr))
#define BIT_MASK(nr) (UL(1) << ((nr) % BITS_PER_LONG))
#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
#define BIT_ULL_MASK(nr) (1ULL << ((nr) % BITS_PER_LONG_LONG))
#define BIT_ULL_MASK(nr) (ULL(1) << ((nr) % BITS_PER_LONG_LONG))
#define BIT_ULL_WORD(nr) ((nr) / BITS_PER_LONG_LONG)
#define BITS_PER_BYTE 8
@ -17,10 +19,11 @@
* GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
*/
#define GENMASK(h, l) \
(((~0UL) - (1UL << (l)) + 1) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
(((~UL(0)) - (UL(1) << (l)) + 1) & \
(~UL(0) >> (BITS_PER_LONG - 1 - (h))))
#define GENMASK_ULL(h, l) \
(((~0ULL) - (1ULL << (l)) + 1) & \
(~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))
(((~ULL(0)) - (ULL(1) << (l)) + 1) & \
(~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h))))
#endif /* __LINUX_BITS_H */