/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_UNITS_H
#define _LINUX_UNITS_H

#include <linux/bits.h>
#include <linux/math.h>

/* Metric prefixes in accordance with Système international (d'unités) */
#define PETA    1000000000000000ULL
#define TERA    1000000000000ULL
#define GIGA    1000000000UL
#define MEGA    1000000UL
#define KILO    1000UL
#define HECTO   100UL
#define DECA    10UL
#define DECI    10UL
#define CENTI   100UL
#define MILLI   1000UL
#define MICRO   1000000UL
#define NANO    1000000000UL
#define PICO    1000000000000ULL
#define FEMTO   1000000000000000ULL

/*
 * Percentage and related scaling units
 *
 * These macros define scaling factors used to convert between ratio and
 * percentage-based representations with different decimal resolutions.
 * They are used for precise fractional calculations in engineering, finance,
 * and measurement applications.
 *
 * Examples:
 *   1%     = 0.01    = 1 / PERCENT
 *   0.1%   = 0.001   = 1 / PERMILLE
 *   0.01%  = 0.0001  = 1 / PERMYRIAD (1 basis point)
 *   0.001% = 0.00001 = 1 / PERCENTMILLE
 */
#define PERCENT         100
#define PERMILLE        1000
#define PERMYRIAD       10000
#define PERCENTMILLE    100000

#define NANOHZ_PER_HZ           1000000000UL
#define MICROHZ_PER_HZ          1000000UL
#define MILLIHZ_PER_HZ          1000UL

/* Hz based multipliers */
#define HZ_PER_KHZ              1000UL
#define HZ_PER_MHZ              1000000UL
#define HZ_PER_GHZ              1000000000UL

/* kHz based multipliers */
#define KHZ_PER_MHZ             1000UL
#define KHZ_PER_GHZ             1000000UL

#define MILLIWATT_PER_WATT      1000UL
#define MICROWATT_PER_MILLIWATT 1000UL
#define MICROWATT_PER_WATT      1000000UL

#define BYTES_PER_KBIT          (KILO / BITS_PER_BYTE)
#define BYTES_PER_MBIT          (MEGA / BITS_PER_BYTE)
#define BYTES_PER_GBIT          (GIGA / BITS_PER_BYTE)

#define ABSOLUTE_ZERO_MILLICELSIUS -273150

static inline long milli_kelvin_to_millicelsius(long t)
{
        return t + ABSOLUTE_ZERO_MILLICELSIUS;
}

static inline long millicelsius_to_milli_kelvin(long t)
{
        return t - ABSOLUTE_ZERO_MILLICELSIUS;
}

#define MILLIDEGREE_PER_DEGREE 1000
#define MILLIDEGREE_PER_DECIDEGREE 100

static inline long kelvin_to_millicelsius(long t)
{
        return milli_kelvin_to_millicelsius(t * MILLIDEGREE_PER_DEGREE);
}

static inline long millicelsius_to_kelvin(long t)
{
        t = millicelsius_to_milli_kelvin(t);

        return DIV_ROUND_CLOSEST(t, MILLIDEGREE_PER_DEGREE);
}

static inline long deci_kelvin_to_celsius(long t)
{
        t = milli_kelvin_to_millicelsius(t * MILLIDEGREE_PER_DECIDEGREE);

        return DIV_ROUND_CLOSEST(t, MILLIDEGREE_PER_DEGREE);
}

static inline long celsius_to_deci_kelvin(long t)
{
        t = millicelsius_to_milli_kelvin(t * MILLIDEGREE_PER_DEGREE);

        return DIV_ROUND_CLOSEST(t, MILLIDEGREE_PER_DECIDEGREE);
}

/**
 * deci_kelvin_to_millicelsius_with_offset - convert Kelvin to Celsius
 * @t: temperature value in decidegrees Kelvin
 * @offset: difference between Kelvin and Celsius in millidegrees
 *
 * Return: temperature value in millidegrees Celsius
 */
static inline long deci_kelvin_to_millicelsius_with_offset(long t, long offset)
{
        return t * MILLIDEGREE_PER_DECIDEGREE - offset;
}

static inline long deci_kelvin_to_millicelsius(long t)
{
        return milli_kelvin_to_millicelsius(t * MILLIDEGREE_PER_DECIDEGREE);
}

static inline long millicelsius_to_deci_kelvin(long t)
{
        t = millicelsius_to_milli_kelvin(t);

        return DIV_ROUND_CLOSEST(t, MILLIDEGREE_PER_DECIDEGREE);
}

static inline long kelvin_to_celsius(long t)
{
        return t + DIV_ROUND_CLOSEST(ABSOLUTE_ZERO_MILLICELSIUS,
                                     MILLIDEGREE_PER_DEGREE);
}

static inline long celsius_to_kelvin(long t)
{
        return t - DIV_ROUND_CLOSEST(ABSOLUTE_ZERO_MILLICELSIUS,
                                     MILLIDEGREE_PER_DEGREE);
}

#endif /* _LINUX_UNITS_H */