bitmap: find_last_bit() (ab53d472) · Commits · 戴 / test

include/linux/bitops.h

+12 −1

Original line number	Diff line number	Diff line
		@@ -134,9 +134,20 @@ extern unsigned long find_first_bit(const unsigned long *addr,
		*/
		extern unsigned long find_first_zero_bit(const unsigned long *addr,
		unsigned long size);

		#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */

		#ifdef CONFIG_GENERIC_FIND_LAST_BIT
		/**
		* find_last_bit - find the last set bit in a memory region
		* @addr: The address to start the search at
		* @size: The maximum size to search
		*
		* Returns the bit number of the first set bit, or size.
		*/
		extern unsigned long find_last_bit(const unsigned long *addr,
		unsigned long size);
		#endif /* CONFIG_GENERIC_FIND_LAST_BIT */

		#ifdef CONFIG_GENERIC_FIND_NEXT_BIT

		/**

+4 −0

Original line number	Diff line number	Diff line
		@@ -13,6 +13,10 @@ config GENERIC_FIND_FIRST_BIT
		config GENERIC_FIND_NEXT_BIT
		bool

		config GENERIC_FIND_LAST_BIT
		bool
		default y

		config CRC_CCITT
		tristate "CRC-CCITT functions"
		help

+1 −0

Original line number	Diff line number	Diff line
		@@ -37,6 +37,7 @@ lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
		lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
		lib-$(CONFIG_GENERIC_FIND_FIRST_BIT) += find_next_bit.o
		lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o
		lib-$(CONFIG_GENERIC_FIND_LAST_BIT) += find_last_bit.o
		obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o
		obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o
		obj-$(CONFIG_PLIST) += plist.o

0 → 100644

+45 −0

Original line number	Diff line number	Diff line
		/* find_last_bit.c: fallback find next bit implementation
		*
		* Copyright (C) 2008 IBM Corporation
		* Written by Rusty Russell <rusty@rustcorp.com.au>
		* (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/module.h>
		#include <asm/types.h>
		#include <asm/byteorder.h>

		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);