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Commit ab53d472 authored by Rusty Russell's avatar Rusty Russell
Browse files

bitmap: find_last_bit() 



Impact: New API

As the name suggests.  For the moment everyone uses the generic one.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 0db5d3d2

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



/**

lib/Kconfig

+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

lib/Makefile

+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

lib/find_last_bit.c

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);