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authorAkinobu Mita <mita@miraclelinux.com>2006-03-26 04:39:08 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-26 11:57:10 -0500
commitc1226a005ec400e966f4993dfcc0e99fd7baa6a1 (patch)
tree7c69ee952fae6209b7e760c1b7de83e2d9f05d25 /include/asm-generic
parent4117b02132d1cf96a3e1c57148e302c4801c974d (diff)
[PATCH] bitops: generic __ffs()
This patch introduces the C-language equivalent of the function: unsigned long __ffs(unsigned long word); In include/asm-generic/bitops/__ffs.h This code largely copied from: include/asm-sparc/bitops.h Signed-off-by: Akinobu Mita <mita@miraclelinux.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/bitops/__ffs.h43
1 files changed, 43 insertions, 0 deletions
diff --git a/include/asm-generic/bitops/__ffs.h b/include/asm-generic/bitops/__ffs.h
new file mode 100644
index 000000000000..9a3274aecf83
--- /dev/null
+++ b/include/asm-generic/bitops/__ffs.h
@@ -0,0 +1,43 @@
1#ifndef _ASM_GENERIC_BITOPS___FFS_H_
2#define _ASM_GENERIC_BITOPS___FFS_H_
3
4#include <asm/types.h>
5
6/**
7 * __ffs - find first bit in word.
8 * @word: The word to search
9 *
10 * Undefined if no bit exists, so code should check against 0 first.
11 */
12static inline unsigned long __ffs(unsigned long word)
13{
14 int num = 0;
15
16#if BITS_PER_LONG == 64
17 if ((word & 0xffffffff) == 0) {
18 num += 32;
19 word >>= 32;
20 }
21#endif
22 if ((word & 0xffff) == 0) {
23 num += 16;
24 word >>= 16;
25 }
26 if ((word & 0xff) == 0) {
27 num += 8;
28 word >>= 8;
29 }
30 if ((word & 0xf) == 0) {
31 num += 4;
32 word >>= 4;
33 }
34 if ((word & 0x3) == 0) {
35 num += 2;
36 word >>= 2;
37 }
38 if ((word & 0x1) == 0)
39 num += 1;
40 return num;
41}
42
43#endif /* _ASM_GENERIC_BITOPS___FFS_H_ */