find_last_bit.c

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/* find_last_bit.c: fallback find next bit implementation
 *
 * Copyright (C) 2008 IBM Corporation
 * Written by Rusty Russell <[email protected]>
 * (Inspired by David Howell's find_next_bit implementation)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/bitops.h>
#include <linux/export.h>
#include <asm/types.h>
#include <asm/byteorder.h>

#ifndef find_last_bit

unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
{
    unsigned long words;
    unsigned long tmp;

    /* Start at final word. */
    words = size / BITS_PER_LONG;

    /* Partial final word? */
    if (size & (BITS_PER_LONG-1)) {
        tmp = (addr[words] & (~0UL >> (BITS_PER_LONG
                     - (size & (BITS_PER_LONG-1)))));
        if (tmp)
            goto found;
    }

    while (words) {
        tmp = addr[--words];
        if (tmp) {
found:
            return words * BITS_PER_LONG + __fls(tmp);
        }
    }

    /* Not found */
    return size;
}
EXPORT_SYMBOL(find_last_bit);

#endif