bitops: introduce for_each_clear_bit()
authorAkinobu Mita <akinobu.mita@gmail.com>
Fri, 23 Mar 2012 22:02:04 +0000 (15:02 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 23 Mar 2012 23:58:34 +0000 (16:58 -0700)
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 <akinobu.mita@gmail.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Stefano Panella <stefano.panella@csr.com>
Cc: David Vrabel <david.vrabel@csr.com>
Cc: Sergei Shtylyov <sshtylyov@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/bitops.h

index 348b1dc..a3b6b82 100644 (file)
@@ -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;