| Rusty Russell | ab53d47 | 2009-01-01 10:12:19 +1030 | [diff] [blame] | 1 | /* 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> |
| 14 | #include <linux/module.h> |
| 15 | #include <asm/types.h> |
| 16 | #include <asm/byteorder.h> |
| 17 | |
| 18 | unsigned long find_last_bit(const unsigned long *addr, unsigned long size) |
| 19 | { |
| 20 | unsigned long words; |
| 21 | unsigned long tmp; |
| 22 | |
| 23 | /* Start at final word. */ |
| 24 | words = size / BITS_PER_LONG; |
| 25 | |
| 26 | /* Partial final word? */ |
| 27 | if (size & (BITS_PER_LONG-1)) { |
| 28 | tmp = (addr[words] & (~0UL >> (BITS_PER_LONG |
| 29 | - (size & (BITS_PER_LONG-1))))); |
| 30 | if (tmp) |
| 31 | goto found; |
| 32 | } |
| 33 | |
| 34 | while (words) { |
| 35 | tmp = addr[--words]; |
| 36 | if (tmp) { |
| 37 | found: |
| 38 | return words * BITS_PER_LONG + __fls(tmp); |
| 39 | } |
| 40 | } |
| 41 | |
| 42 | /* Not found */ |
| 43 | return size; |
| 44 | } |
| 45 | EXPORT_SYMBOL(find_last_bit); |