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Subject[PATCH v1 2/2] lib/math: Move int_pow() from pwm_bl.c for wider use
Date
The integer exponentiation is used in few places and might be used
in the future by other call sites. Move it to wider use.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
drivers/video/backlight/pwm_bl.c | 15 ---------------
include/linux/kernel.h | 1 +
lib/math/Makefile | 2 +-
lib/math/int_pow.c | 32 ++++++++++++++++++++++++++++++++
4 files changed, 34 insertions(+), 16 deletions(-)
create mode 100644 lib/math/int_pow.c

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 53b8ceea9bde..fb45f866b923 100644
--- 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 bb8958690b69..d327fe835f2c 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -500,6 +500,7 @@ 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 b75878420da6..583bbfebfc09 100644
--- 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
index 000000000000..622fc1ab3c74
--- /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);
--
2.20.1
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