asm-generic/bitops/__ffs.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #ifndef _ASM_GENERIC_BITOPS___FFS_H_
0003 #define _ASM_GENERIC_BITOPS___FFS_H_
0004
0005 #include <asm/types.h>
0006
0007 /**
0008  * __ffs - find first bit in word.
0009  * @word: The word to search
0010  *
0011  * Undefined if no bit exists, so code should check against 0 first.
0012  */
0013 static __always_inline unsigned long __ffs(unsigned long word)
0014 {
0015     int num = 0;
0016
0017 #if BITS_PER_LONG == 64
0018     if ((word & 0xffffffff) == 0) {
0019         num += 32;
0020         word >>= 32;
0021     }
0022 #endif
0023     if ((word & 0xffff) == 0) {
0024         num += 16;
0025         word >>= 16;
0026     }
0027     if ((word & 0xff) == 0) {
0028         num += 8;
0029         word >>= 8;
0030     }
0031     if ((word & 0xf) == 0) {
0032         num += 4;
0033         word >>= 4;
0034     }
0035     if ((word & 0x3) == 0) {
0036         num += 2;
0037         word >>= 2;
0038     }
0039     if ((word & 0x1) == 0)
0040         num += 1;
0041     return num;
0042 }
0043
0044 #endif /* _ASM_GENERIC_BITOPS___FFS_H_ */