lib/math: move int_pow() from pwm_bl.c for wider use

The integer exponentiation is used in few places and might be used in
the future by other call sites.  Move it to wider use.

Link: http://lkml.kernel.org/r/20190323172531.80025-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Ray Jui <rjui@broadcom.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 53b8cee..fb45f86 100644 (file)
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -155,21 +155,6 @@ static const struct backlight_ops pwm_backlight_ops = {
 #ifdef CONFIG_OF
 #define PWM_LUMINANCE_SCALE    10000 /* luminance scale */
 
-/* An integer based power function */
-static u64 int_pow(u64 base, int exp)
-{
-       u64 result = 1;
-
-       while (exp) {
-               if (exp & 1)
-                       result *= base;
-               exp >>= 1;
-               base *= base;
-       }
-
-       return result;
-}
-
 /*
  * CIE lightness to PWM conversion.
  *

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index a3b59d1..74b1ee9 100644 (file)
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -484,6 +484,7 @@ extern int __kernel_text_address(unsigned long addr);
 extern int kernel_text_address(unsigned long addr);
 extern int func_ptr_is_kernel_text(void *ptr);
 
+u64 int_pow(u64 base, unsigned int exp);
 unsigned long int_sqrt(unsigned long);
 
 #if BITS_PER_LONG < 64

diff --git a/lib/math/Makefile b/lib/math/Makefile
index b758784..583bbfe 100644 (file)
--- a/lib/math/Makefile
+++ b/lib/math/Makefile
@@ -1,4 +1,4 @@
-obj-y += div64.o gcd.o lcm.o int_sqrt.o reciprocal_div.o
+obj-y += div64.o gcd.o lcm.o int_pow.o int_sqrt.o reciprocal_div.o
 
 obj-$(CONFIG_CORDIC)           += cordic.o
 obj-$(CONFIG_PRIME_NUMBERS)    += prime_numbers.o

diff --git a/lib/math/int_pow.c b/lib/math/int_pow.c
new file mode 100644 (file)
index 0000000..622fc1a
--- /dev/null
+++ b/lib/math/int_pow.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * An integer based power function
+ *
+ * Derived from drivers/video/backlight/pwm_bl.c
+ */
+
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+
+/**
+ * int_pow - computes the exponentiation of the given base and exponent
+ * @base: base which will be raised to the given power
+ * @exp: power to be raised to
+ *
+ * Computes: pow(base, exp), i.e. @base raised to the @exp power
+ */
+u64 int_pow(u64 base, unsigned int exp)
+{
+       u64 result = 1;
+
+       while (exp) {
+               if (exp & 1)
+                       result *= base;
+               exp >>= 1;
+               base *= base;
+       }
+
+       return result;
+}
+EXPORT_SYMBOL_GPL(int_pow);