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  * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
   8  * size and improve performance, 2015.
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public License
  12  * as published by the Free Software Foundation; either version
  13  * 2 of the License, or (at your option) any later version.
  14  */
  15
  16 #include <linux/bitops.h>
  17 #include <linux/bitmap.h>
  18 #include <linux/export.h>
  19 #include <linux/kernel.h>
  20
  21 #ifndef find_last_bit
  22
  23 unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
  24 {
  25         if (size) {
  26                 unsigned long val = BITMAP_LAST_WORD_MASK(size);
  27                 unsigned long idx = (size-1) / BITS_PER_LONG;
  28
  29                 do {
  30                         val &= addr[idx];
  31                         if (val)
  32                                 return idx * BITS_PER_LONG + __fls(val);
  33
  34                         val = ~0ul;
  35                 } while (idx--);
  36         }
  37         return size;
  38 }
  39 EXPORT_SYMBOL(find_last_bit);
  40
  41 #endif