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authorRusty Russell <rusty@rustcorp.com.au>2009-01-01 10:12:19 +1030
committerRusty Russell <rusty@rustcorp.com.au>2009-01-01 10:12:19 +1030
commitab53d472e785e51fdfc08fc1d66252c1153e6c0f (patch)
tree19abab13d2e4e8fe00f960c0ac475e14bfb1a44e /lib/find_last_bit.c
parent0db5d3d2f58804edb394e8008c7d9744110338a2 (diff)
downloadlinux-ab53d472e785e51fdfc08fc1d66252c1153e6c0f.tar.gz
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/find_last_bit.c')
-rw-r--r--lib/find_last_bit.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/lib/find_last_bit.c b/lib/find_last_bit.c
new file mode 100644
index 00000000000..5d202e36bdd
--- /dev/null
+++ b/lib/find_last_bit.c
@@ -0,0 +1,45 @@
+/* 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);