1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_
3 #define _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_
4
5 #include <asm/types.h>
6 #include <asm/bitsperlong.h>
7
8 /**
9 * __ffs - find first bit in word.
10 * @word: The word to search
11 *
12 * Undefined if no bit exists, so code should check against 0 first.
13 */
14 static __always_inline unsigned int __ffs(unsigned long word)
15 {
16 unsigned int num = 0;
17
18 #if __BITS_PER_LONG == 64
19 if ((word & 0xffffffff) == 0) {
20 num += 32;
21 word >>= 32;
22 }
23 #endif
24 if ((word & 0xffff) == 0) {
25 num += 16;
26 word >>= 16;
27 }
28 if ((word & 0xff) == 0) {
29 num += 8;
30 word >>= 8;
31 }
32 if ((word & 0xf) == 0) {
33 num += 4;
34 word >>= 4;
35 }
36 if ((word & 0x3) == 0) {
37 num += 2;
38 word >>= 2;
39 }
40 if ((word & 0x1) == 0)
41 num += 1;
42 return num;
43 }
44
45 #endif /* _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_ */
46
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