[PATCH] bitops: generic ext2_{set,clear,test,find_first_zero,find_next_zero}_bit()

This patch introduces the C-language equivalents of the functions below:

int ext2_set_bit(int nr, volatile unsigned long *addr);
int ext2_clear_bit(int nr, volatile unsigned long *addr);
int ext2_test_bit(int nr, const volatile unsigned long *addr);
unsigned long ext2_find_first_zero_bit(const unsigned long *addr,
                                       unsigned long size);
unsinged long ext2_find_next_zero_bit(const unsigned long *addr,
                                      unsigned long size);

In include/asm-generic/bitops/ext2-non-atomic.h

This code largely copied from:

include/asm-powerpc/bitops.h
include/asm-parisc/bitops.h

Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 73 insertions, 0 deletions

diff --git a/lib/find_next_bit.c b/lib/find_next_bit.c
index 9c90853b44..bda0d71a25 100644
--- a/lib/find_next_bit.c
+++ b/lib/find_next_bit.c
@@ -12,6 +12,7 @@
 #include <linux/bitops.h>
 #include <linux/module.h>
 #include <asm/types.h>
+#include <asm/byteorder.h>
 
 #define BITOP_WORD(nr)          ((nr) / BITS_PER_LONG)
 
@@ -106,3 +107,75 @@ found_middle:
 }
 
 EXPORT_SYMBOL(find_next_zero_bit);
+
+#ifdef __BIG_ENDIAN
+
+/* include/linux/byteorder does not support "unsigned long" type */
+static inline unsigned long ext2_swabp(const unsigned long * x)
+{
+#if BITS_PER_LONG == 64
+        return (unsigned long) __swab64p((u64 *) x);
+#elif BITS_PER_LONG == 32
+        return (unsigned long) __swab32p((u32 *) x);
+#else
+#error BITS_PER_LONG not defined
+#endif
+}
+
+/* include/linux/byteorder doesn't support "unsigned long" type */
+static inline unsigned long ext2_swab(const unsigned long y)
+{
+#if BITS_PER_LONG == 64
+        return (unsigned long) __swab64((u64) y);
+#elif BITS_PER_LONG == 32
+        return (unsigned long) __swab32((u32) y);
+#else
+#error BITS_PER_LONG not defined
+#endif
+}
+
+unsigned long generic_find_next_zero_le_bit(const unsigned long *addr, unsigned
+                long size, unsigned long offset)
+{
+        const unsigned long *p = addr + BITOP_WORD(offset);
+        unsigned long result = offset & ~(BITS_PER_LONG - 1);
+        unsigned long tmp;
+
+        if (offset >= size)
+                return size;
+        size -= result;
+        offset &= (BITS_PER_LONG - 1UL);
+        if (offset) {
+                tmp = ext2_swabp(p++);
+                tmp |= (~0UL >> (BITS_PER_LONG - offset));
+                if (size < BITS_PER_LONG)
+                        goto found_first;
+                if (~tmp)
+                        goto found_middle;
+                size -= BITS_PER_LONG;
+                result += BITS_PER_LONG;
+        }
+
+        while (size & ~(BITS_PER_LONG - 1)) {
+                if (~(tmp = *(p++)))
+                        goto found_middle_swap;
+                result += BITS_PER_LONG;
+                size -= BITS_PER_LONG;
+        }
+        if (!size)
+                return result;
+        tmp = ext2_swabp(p);
+found_first:
+        tmp |= ~0UL << size;
+        if (tmp == ~0UL)        /* Are any bits zero? */
+                return result + size; /* Nope. Skip ffz */
+found_middle:
+        return result + ffz(tmp);
+
+found_middle_swap:
+        return result + ffz(ext2_swab(tmp));
+}
+
+EXPORT_SYMBOL(generic_find_next_zero_le_bit);
+
+#endif /* __BIG_ENDIAN */