1 /* SPDX-License-Identifier: GPL-2.0 */ 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, therefore 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