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Message-Id: <200812011848.31552.rusty@rustcorp.com.au>
Date: Mon, 1 Dec 2008 18:48:31 +1030
From: Rusty Russell <rusty@...tcorp.com.au>
To: linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...hat.com>, Mike Travis <travis@....com>
Subject: [PATCH 5/6] 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@...tcorp.com.au>
---
include/linux/bitops.h | 13 ++++++++++++-
lib/Kconfig | 4 ++++
lib/Makefile | 1 +
lib/find_next_bit.c | 31 +++++++++++++++++++++++++++++++
4 files changed, 48 insertions(+), 1 deletion(-)
diff -r 22df8a8dec81 include/linux/bitops.h
--- a/include/linux/bitops.h Sat Oct 18 04:46:13 2008 +1100
+++ b/include/linux/bitops.h Tue Oct 21 17:06:35 2008 +1100
@@ -134,8 +134,19 @@ extern unsigned long find_first_bit(cons
*/
extern unsigned long find_first_zero_bit(const unsigned long *addr,
unsigned long size);
+#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
-#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
diff -r 22df8a8dec81 lib/Kconfig
--- a/lib/Kconfig Sat Oct 18 04:46:13 2008 +1100
+++ b/lib/Kconfig Tue Oct 21 17:06:35 2008 +1100
@@ -12,6 +12,10 @@ 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"
diff -r 22df8a8dec81 lib/Makefile
--- a/lib/Makefile Sat Oct 18 04:46:13 2008 +1100
+++ b/lib/Makefile Tue Oct 21 17:06:35 2008 +1100
@@ -37,6 +37,7 @@ lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) +=
lib-$(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-$(CONFIG_GENERIC_FIND_LAST_BIT) += find_next_bit.o
obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o
obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o
obj-$(CONFIG_PLIST) += plist.o
diff -r 22df8a8dec81 lib/find_next_bit.c
--- a/lib/find_next_bit.c Sat Oct 18 04:46:13 2008 +1100
+++ b/lib/find_next_bit.c Tue Oct 21 17:06:35 2008 +1100
@@ -159,6 +159,37 @@ EXPORT_SYMBOL(find_first_zero_bit);
EXPORT_SYMBOL(find_first_zero_bit);
#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
+#ifdef CONFIG_GENERIC_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 /* CONFIG_GENERIC_FIND_LAST_BIT */
+
#ifdef __BIG_ENDIAN
/* include/linux/byteorder does not support "unsigned long" type */
--
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