linux/drivers/hwmon/lm75.h

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * lm75.h - Part of lm_sensors, Linux kernel modules for hardware monitoring
 * Copyright (c) 2003 Mark M. Hoffman <mhoffman@lightlink.com>
 */

/*
 * This file contains common code for encoding/decoding LM75 type
 * temperature readings, which are emulated by many of the chips
 * we support.  As the user is unlikely to load more than one driver
 * which contains this code, we don't worry about the wasted space.
 */

#include <linux/minmax.h>
#include <linux/types.h>

/* straight from the datasheet */
#define LM75_TEMP_MIN (-55000)
#define LM75_TEMP_MAX 125000
#define LM75_SHUTDOWN 0x01

/*
 * TEMP: 0.001C/bit (-55C to +125C)
 * REG: (0.5C/bit, two's complement) << 7
 */
static inline u16 LM75_TEMP_TO_REG(long temp)
{
	int ntemp = clamp_val(temp, LM75_TEMP_MIN, LM75_TEMP_MAX);

	ntemp += (ntemp < 0 ? -250 : 250);
	return (u16)((ntemp / 500) << 7);
}

static inline int LM75_TEMP_FROM_REG(u16 reg)
{
	/*
	 * use integer division instead of equivalent right shift to
	 * guarantee arithmetic shift and preserve the sign
	 */
	return ((s16)reg / 128) * 500;
}