bitops: introduce for_each_clear_bit()

Introduce for_each_clear_bit() and for_each_clear_bit_from().  They are
similar to for_each_set_bit() and list_for_each_set_bit_from(), but they
iterate over all the cleared bits in a memory region.

Signed-off-by: Akinobu Mita <[email protected]>
Cc: Robert Richter <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Stefano Panella <[email protected]>
Cc: David Vrabel <[email protected]>
Cc: Sergei Shtylyov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 348b1dca477a1c9b3b579ade963c5aca57df4d4b..a3b6b82108b9ad239dd1dda1abe6c8e3f585d3b3 100644 (file)
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -32,6 +32,17 @@ extern unsigned long __sw_hweight64(__u64 w);
             (bit) < (size);                                    \
             (bit) = find_next_bit((addr), (size), (bit) + 1))
 
+#define for_each_clear_bit(bit, addr, size) \
+       for ((bit) = find_first_zero_bit((addr), (size));       \
+            (bit) < (size);                                    \
+            (bit) = find_next_zero_bit((addr), (size), (bit) + 1))
+
+/* same as for_each_clear_bit() but use bit as value to start with */
+#define for_each_clear_bit_from(bit, addr, size) \
+       for ((bit) = find_next_zero_bit((addr), (size), (bit)); \
+            (bit) < (size);                                    \
+            (bit) = find_next_zero_bit((addr), (size), (bit) + 1))
+
 static __inline__ int get_bitmask_order(unsigned int count)
 {
        int order;