blob: 91ca09fbf6f97af61b9f15ee9a8766497e685558 [file] [log] [blame]
Rusty Russellab53d472009-01-01 10:12:19 +10301/* find_last_bit.c: fallback find next bit implementation
2 *
3 * Copyright (C) 2008 IBM Corporation
4 * Written by Rusty Russell <rusty@rustcorp.com.au>
5 * (Inspired by David Howell's find_next_bit implementation)
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version
10 * 2 of the License, or (at your option) any later version.
11 */
12
13#include <linux/bitops.h>
Paul Gortmaker8bc3bcc2011-11-16 21:29:17 -050014#include <linux/export.h>
Rusty Russellab53d472009-01-01 10:12:19 +103015#include <asm/types.h>
16#include <asm/byteorder.h>
17
Akinobu Mita19de85e2011-05-26 16:26:09 -070018#ifndef find_last_bit
19
Rusty Russellab53d472009-01-01 10:12:19 +103020unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
21{
22 unsigned long words;
23 unsigned long tmp;
24
25 /* Start at final word. */
26 words = size / BITS_PER_LONG;
27
28 /* Partial final word? */
29 if (size & (BITS_PER_LONG-1)) {
30 tmp = (addr[words] & (~0UL >> (BITS_PER_LONG
31 - (size & (BITS_PER_LONG-1)))));
32 if (tmp)
33 goto found;
34 }
35
36 while (words) {
37 tmp = addr[--words];
38 if (tmp) {
39found:
40 return words * BITS_PER_LONG + __fls(tmp);
41 }
42 }
43
44 /* Not found */
45 return size;
46}
47EXPORT_SYMBOL(find_last_bit);
Akinobu Mita19de85e2011-05-26 16:26:09 -070048
49#endif