1 /* SPDX-License-Identifier: GPL-2.0 */ 1
2 #ifndef _ASM_GENERIC_BITOPS_FFS_H_
3 #define _ASM_GENERIC_BITOPS_FFS_H_
4
5 /**
6 * generic_ffs - find first bit set
7 * @x: the word to search
8 *
9 * This is defined the same way as
10 * the libc and compiler builtin ffs routines,
11 * differs in spirit from ffz (man ffs).
12 */
13 static inline int generic_ffs(int x)
14 {
15 int r = 1;
16
17 if (!x)
18 return 0;
19 if (!(x & 0xffff)) {
20 x >>= 16;
21 r += 16;
22 }
23 if (!(x & 0xff)) {
24 x >>= 8;
25 r += 8;
26 }
27 if (!(x & 0xf)) {
28 x >>= 4;
29 r += 4;
30 }
31 if (!(x & 3)) {
32 x >>= 2;
33 r += 2;
34 }
35 if (!(x & 1)) {
36 x >>= 1;
37 r += 1;
38 }
39 return r;
40 }
41
42 #ifndef __HAVE_ARCH_FFS
43 #define ffs(x) generic_ffs(x)
44 #endif
45
46 #endif /* _ASM_GENERIC_BITOPS_FFS_H_ */
47
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