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

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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>
This commit is contained in:
Andy Shevchenko 2019-05-14 15:43:08 -07:00 committed by Linus Torvalds
parent 2c64e9cb0b
commit 9f61589469
4 changed files with 34 additions and 16 deletions
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15
drivers/video/backlight/pwm_bl.c
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@ -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.
*

1
include/linux/kernel.h
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@ -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

2
lib/math/Makefile
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@ -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

32
lib/math/int_pow.c Normal file
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@ -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);