lib/find_last_bit.c

   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
  20 unsigned 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) {
  39 found:
  40                         return words * BITS_PER_LONG + __fls(tmp);
  41                 }
  42         }
  43
  44         /* Not found */
  45         return size;
  46 }
  47 EXPORT_SYMBOL(find_last_bit);
  48
  49 #endif