Re: [PATCH v1] iio: hid-sensor-attributes: Convert to use int_pow()

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 19 Jun 2019 17:07:02 +0300
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> Instead of linear approach to calculate power of 10, use generic int_pow()
> which does it better.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Hi Andy,

Looks good to me, but I would like Srinivas to take a look and
preferably test this a bit just to check we aren't all missing something
subtle!

+CC Srinivas

Thanks,

Jonathan
> ---
>  .../hid-sensors/hid-sensor-attributes.c       | 53 ++++++++-----------
>  1 file changed, 22 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> index a8a3fe428d8d..b9dd19b34267 100644
> --- a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> +++ b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> @@ -8,6 +8,7 @@
>  #include <linux/module.h>
>  #include <linux/interrupt.h>
>  #include <linux/irq.h>
> +#include <linux/kernel.h>
>  #include <linux/slab.h>
>  #include <linux/hid-sensor-hub.h>
>  #include <linux/iio/iio.h>
> @@ -68,16 +69,6 @@ static struct {
>  	{HID_USAGE_SENSOR_HUMIDITY, 0, 1000, 0},
>  };
>  
> -static int pow_10(unsigned power)
> -{
> -	int i;
> -	int ret = 1;
> -	for (i = 0; i < power; ++i)
> -		ret = ret * 10;
> -
> -	return ret;
> -}
> -
>  static void simple_div(int dividend, int divisor, int *whole,
>  				int *micro_frac)
>  {
> @@ -96,14 +87,14 @@ static void simple_div(int dividend, int divisor, int *whole,
>  			rem *= 10;
>  			exp++;
>  		}
> -		*micro_frac = (rem / divisor) * pow_10(6-exp);
> +		*micro_frac = (rem / divisor) * int_pow(10, 6 - exp);
>  	}
>  }
>  
>  static void split_micro_fraction(unsigned int no, int exp, int *val1, int *val2)
>  {
> -	*val1 = no/pow_10(exp);
> -	*val2 = no%pow_10(exp) * pow_10(6-exp);
> +	*val1 = no / int_pow(10, exp);
> +	*val2 = no % int_pow(10, exp) * int_pow(10, 6 - exp);
>  }
>  
>  /*
> @@ -125,7 +116,7 @@ static void convert_from_vtf_format(u32 value, int size, int exp,
>  	}
>  	exp = hid_sensor_convert_exponent(exp);
>  	if (exp >= 0) {
> -		*val1 = sign * value * pow_10(exp);
> +		*val1 = sign * value * int_pow(10, exp);
>  		*val2 = 0;
>  	} else {
>  		split_micro_fraction(value, -exp, val1, val2);
> @@ -145,10 +136,10 @@ static u32 convert_to_vtf_format(int size, int exp, int val1, int val2)
>  		sign = -1;
>  	exp = hid_sensor_convert_exponent(exp);
>  	if (exp < 0) {
> -		value = abs(val1) * pow_10(-exp);
> -		value += abs(val2) / pow_10(6+exp);
> +		value = abs(val1) * int_pow(10, -exp);
> +		value += abs(val2) / int_pow(10, 6 + exp);
>  	} else
> -		value = abs(val1) / pow_10(exp);
> +		value = abs(val1) / int_pow(10, exp);
>  	if (sign < 0)
>  		value =  ((1LL << (size * 8)) - value);
>  
> @@ -211,12 +202,12 @@ int hid_sensor_write_samp_freq_value(struct hid_sensor_common *st,
>  	if (val1 < 0 || val2 < 0)
>  		return -EINVAL;
>  
> -	value = val1 * pow_10(6) + val2;
> +	value = val1 * int_pow(10, 6) + val2;
>  	if (value) {
>  		if (st->poll.units == HID_USAGE_SENSOR_UNITS_MILLISECOND)
> -			value = pow_10(9)/value;
> +			value = int_pow(10, 9) / value;
>  		else if (st->poll.units == HID_USAGE_SENSOR_UNITS_SECOND)
> -			value = pow_10(6)/value;
> +			value = int_pow(10, 6) / value;
>  		else
>  			value = 0;
>  	}
> @@ -311,34 +302,34 @@ static void adjust_exponent_nano(int *val0, int *val1, int scale0,
>  	int rem;
>  
>  	if (exp > 0) {
> -		*val0 = scale0 * pow_10(exp);
> +		*val0 = scale0 * int_pow(10, exp);
>  		res = 0;
>  		if (exp > 9) {
>  			*val1 = 0;
>  			return;
>  		}
>  		for (i = 0; i < exp; ++i) {
> -			x = scale1 / pow_10(8 - i);
> -			res += (pow_10(exp - 1 - i) * x);
> -			scale1 = scale1 % pow_10(8 - i);
> +			x = scale1 / int_pow(10, 8 - i);
> +			res += int_pow(10, exp - 1 - i) * x;
> +			scale1 = scale1 % int_pow(10, 8 - i);
>  		}
>  		*val0 += res;
> -		*val1 = scale1 * pow_10(exp);
> +		*val1 = scale1 * int_pow(10, exp);
>  	} else if (exp < 0) {
>  		exp = abs(exp);
>  		if (exp > 9) {
>  			*val0 = *val1 = 0;
>  			return;
>  		}
> -		*val0 = scale0 / pow_10(exp);
> -		rem = scale0 % pow_10(exp);
> +		*val0 = scale0 / int_pow(10, exp);
> +		rem = scale0 % int_pow(10, exp);
>  		res = 0;
>  		for (i = 0; i < (9 - exp); ++i) {
> -			x = scale1 / pow_10(8 - i);
> -			res += (pow_10(8 - exp - i) * x);
> -			scale1 = scale1 % pow_10(8 - i);
> +			x = scale1 / int_pow(10, 8 - i);
> +			res += int_pow(10, 8 - exp - i) * x;
> +			scale1 = scale1 % int_pow(10, 8 - i);
>  		}
> -		*val1 = rem * pow_10(9 - exp) + res;
> +		*val1 = rem * int_pow(10, 9 - exp) + res;
>  	} else {
>  		*val0 = scale0;
>  		*val1 = scale1;