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authorRusty Russell <rusty@rustcorp.com.au>2008-12-31 18:42:19 -0500
committerRusty Russell <rusty@rustcorp.com.au>2008-12-31 18:42:19 -0500
commitab53d472e785e51fdfc08fc1d66252c1153e6c0f (patch)
tree19abab13d2e4e8fe00f960c0ac475e14bfb1a44e /lib
parent0db5d3d2f58804edb394e8008c7d9744110338a2 (diff)
bitmap: find_last_bit()
Impact: New API As the name suggests. For the moment everyone uses the generic one. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig4
-rw-r--r--lib/Makefile1
-rw-r--r--lib/find_last_bit.c45
3 files changed, 50 insertions, 0 deletions
diff --git a/lib/Kconfig b/lib/Kconfig
index 2ba43c4a5b07..fc5f5ee50bc2 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -13,6 +13,10 @@ config GENERIC_FIND_FIRST_BIT
13config GENERIC_FIND_NEXT_BIT 13config GENERIC_FIND_NEXT_BIT
14 bool 14 bool
15 15
16config GENERIC_FIND_LAST_BIT
17 bool
18 default y
19
16config CRC_CCITT 20config CRC_CCITT
17 tristate "CRC-CCITT functions" 21 tristate "CRC-CCITT functions"
18 help 22 help
diff --git a/lib/Makefile b/lib/Makefile
index 80fe8a3ec12a..32b0e64ded27 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -37,6 +37,7 @@ lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
37lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o 37lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
38lib-$(CONFIG_GENERIC_FIND_FIRST_BIT) += find_next_bit.o 38lib-$(CONFIG_GENERIC_FIND_FIRST_BIT) += find_next_bit.o
39lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o 39lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o
40lib-$(CONFIG_GENERIC_FIND_LAST_BIT) += find_last_bit.o
40obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o 41obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o
41obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o 42obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o
42obj-$(CONFIG_PLIST) += plist.o 43obj-$(CONFIG_PLIST) += plist.o
diff --git a/lib/find_last_bit.c b/lib/find_last_bit.c
new file mode 100644
index 000000000000..5d202e36bdd8
--- /dev/null
+++ b/lib/find_last_bit.c
@@ -0,0 +1,45 @@
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/module.h>
15#include <asm/types.h>
16#include <asm/byteorder.h>
17
18unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
19{
20 unsigned long words;
21 unsigned long tmp;
22
23 /* Start at final word. */
24 words = size / BITS_PER_LONG;
25
26 /* Partial final word? */
27 if (size & (BITS_PER_LONG-1)) {
28 tmp = (addr[words] & (~0UL >> (BITS_PER_LONG
29 - (size & (BITS_PER_LONG-1)))));
30 if (tmp)
31 goto found;
32 }
33
34 while (words) {
35 tmp = addr[--words];
36 if (tmp) {
37found:
38 return words * BITS_PER_LONG + __fls(tmp);
39 }
40 }
41
42 /* Not found */
43 return size;
44}
45EXPORT_SYMBOL(find_last_bit);