linux/lib/find_last_bit.c
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   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/export.h>
  15#include <asm/types.h>
  16#include <asm/byteorder.h>
  17
  18#ifndef find_last_bit
  19
  20unsigned 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);
  48
  49#endif
  50
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