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Message-ID: <Pine.LNX.4.64.0701300543420.17991@CPE00045a9c397f-CM001225dbafb6>
Date: Tue, 30 Jan 2007 06:06:00 -0500 (EST)
From: "Robert P. J. Day" <rpjday@...dspring.com>
To: Linux kernel mailing list <linux-kernel@...r.kernel.org>
cc: Andrew Morton <akpm@...l.org>, Paul Mackerras <paulus@...ba.org>,
dhowells@...hat.com, galak@...nel.crashing.org
Subject: [PATCH] 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@...dspring.com>
---
while people are coming up with more and more clever ways to do
rounding, we can at least add the check for power-of-2 now, so we can
start the cleanup.
arch/powerpc/mm/pgtable_32.c | 5 +----
arch/ppc/mm/pgtable.c | 5 +----
arch/ppc/syslib/ppc85xx_rio.c | 2 --
drivers/net/gianfar_ethtool.c | 2 --
include/linux/log2.h | 11 +++++++++++
5 files changed, 13 insertions(+), 12 deletions(-)
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 1891dbe..bd02272 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 354a940..82b06a1 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 05b0e94..2b09780 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 6d71bea..0d6943d 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 d02e1a5..99922be 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))
--
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA
http://www.fsdev.dreamhosters.com/wiki/index.php?title=Main_Page
========================================================================
-
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