lib: add lib/gcd.c

This patch adds lib/gcd.c which contains a greatest common divider
implementation taken from sound/core/pcm_timer.c

Several usages of this new library function will be sent to subsystem
maintainers.

[[email protected]: use swap() (pointed out by Joe)]
[[email protected]: just add gcd.o to obj-y, remove Kconfig changes]
Signed-off-by: Florian Fainelli <[email protected]>
Cc: Sergei Shtylyov <[email protected]>
Cc: Takashi Iwai <[email protected]>
Cc: Simon Horman <[email protected]>
Cc: Julius Volz <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Patrick McHardy <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/gcd.h

@@ -0,0 +1,8 @@
+#ifndef _GCD_H
+#define _GCD_H
+
+#include <linux/compiler.h>
+
+unsigned long gcd(unsigned long a, unsigned long b) __attribute_const__;
+
+#endif /* _GCD_H */

lib/Makefile

@@ -21,7 +21,7 @@ lib-y	+= kobject.o kref.o klist.o
 
 obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
 	 bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \
-	 string_helpers.o
+	 string_helpers.o gcd.o
 
 ifeq ($(CONFIG_DEBUG_KOBJECT),y)
 CFLAGS_kobject.o += -DDEBUG

lib/gcd.c

@@ -0,0 +1,18 @@
+#include <linux/kernel.h>
+#include <linux/gcd.h>
+#include <linux/module.h>
+
+/* Greatest common divisor */
+unsigned long gcd(unsigned long a, unsigned long b)
+{
+	unsigned long r;
+
+	if (a < b)
+		swap(a, b);
+	while ((r = a % b) != 0) {
+		a = b;
+		b = r;
+	}
+	return b;
+}
+EXPORT_SYMBOL_GPL(gcd);