[POWERPC] Add "is_power_of_2" checking to log2.h.

Add the inline function "is_power_of_2()" to log2.h, where the value
zero is *not* considered to be a power of two.
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

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.

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.

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;

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);
 

include/linux/log2.h

@@ -43,6 +43,17 @@ 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
  */