5 files changed, 13 insertions, 12 deletions

diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 1891dbeeb8..bd02272bcb 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -294,11 +294,8 @@ void __init mapin_ram(void)
         }
 }
 
-/* is x a power of 2? */
-#define is_power_of_2(x)        ((x) != 0 && (((x) & ((x) - 1)) == 0))
-
 /* is x a power of 4? */
-#define is_power_of_4(x)        ((x) != 0 && (((x) & (x-1)) == 0) && (ffs(x) & 1))
+#define is_power_of_4(x)        is_power_of_2(x) && (ffs(x) & 1))
 
 /*
  * Set up a mapping for a block of I/O.
diff --git a/arch/ppc/mm/pgtable.c b/arch/ppc/mm/pgtable.c
index 354a9408f0..82b06a1ef9 100644
--- a/arch/ppc/mm/pgtable.c
+++ b/arch/ppc/mm/pgtable.c
@@ -313,11 +313,8 @@ void __init mapin_ram(void)
         }
 }
 
-/* is x a power of 2? */
-#define is_power_of_2(x)        ((x) != 0 && (((x) & ((x) - 1)) == 0))
-
 /* is x a power of 4? */
-#define is_power_of_4(x)        ((x) != 0 && (((x) & (x-1)) == 0) && (ffs(x) & 1))
+#define is_power_of_4(x)        is_power_of_2(x) && (ffs(x) & 1))
 
 /*
  * Set up a mapping for a block of I/O.
diff --git a/arch/ppc/syslib/ppc85xx_rio.c b/arch/ppc/syslib/ppc85xx_rio.c
index 05b0e94150..2b097800cd 100644
--- a/arch/ppc/syslib/ppc85xx_rio.c
+++ b/arch/ppc/syslib/ppc85xx_rio.c
@@ -59,8 +59,6 @@
 #define DBELL_TID(x)            (*(u8 *)(x + DOORBELL_TID_OFFSET))
 #define DBELL_INF(x)            (*(u16 *)(x + DOORBELL_INFO_OFFSET))
 
-#define is_power_of_2(x)        (((x) & ((x) - 1)) == 0)
-
 struct rio_atmu_regs {
         u32 rowtar;
         u32 pad1;
diff --git a/drivers/net/gianfar_ethtool.c b/drivers/net/gianfar_ethtool.c
index 6d71bea5e9..0d6943d670 100644
--- a/drivers/net/gianfar_ethtool.c
+++ b/drivers/net/gianfar_ethtool.c
@@ -42,8 +42,6 @@
 
 #include "gianfar.h"
 
-#define is_power_of_2(x)        ((x) != 0 && (((x) & ((x) - 1)) == 0))
-
 extern void gfar_start(struct net_device *dev);
 extern int gfar_clean_rx_ring(struct net_device *dev, int rx_work_limit);
 
diff --git a/include/linux/log2.h b/include/linux/log2.h
index d02e1a547a..99922bedfc 100644
--- a/include/linux/log2.h
+++ b/include/linux/log2.h
@@ -44,6 +44,17 @@ int __ilog2_u64(u64 n)
 #endif
 
 /*
+ *  Determine whether some value is a power of two, where zero is
+ * *not* considered a power of two.
+ */
+
+static inline __attribute__((const))
+bool is_power_of_2(unsigned long n)
+{
+        return (n != 0 && ((n & (n - 1)) == 0));
+}
+
+/*
  * round up to nearest power of two
  */
 static inline __attribute__((const))