1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3  * lm75.h - Part of lm_sensors, Linux kernel modules for hardware monitoring
4  * Copyright (c) 2003 Mark M. Hoffman <mhoffman@lightlink.com>
5  */
6 
7 /*
8  * This file contains common code for encoding/decoding LM75 type
9  * temperature readings, which are emulated by many of the chips
10  * we support.  As the user is unlikely to load more than one driver
11  * which contains this code, we don't worry about the wasted space.
12  */
13 
14 #include <linux/minmax.h>
15 #include <linux/types.h>
16 
17 /* straight from the datasheet */
18 #define LM75_TEMP_MIN (-55000)
19 #define LM75_TEMP_MAX 125000
20 #define LM75_SHUTDOWN 0x01
21 
22 /*
23  * TEMP: 0.001C/bit (-55C to +125C)
24  * REG: (0.5C/bit, two's complement) << 7
25  */
LM75_TEMP_TO_REG(long temp)26 static inline u16 LM75_TEMP_TO_REG(long temp)
27 {
28 	int ntemp = clamp_val(temp, LM75_TEMP_MIN, LM75_TEMP_MAX);
29 
30 	ntemp += (ntemp < 0 ? -250 : 250);
31 	return (u16)((ntemp / 500) << 7);
32 }
33 
LM75_TEMP_FROM_REG(u16 reg)34 static inline int LM75_TEMP_FROM_REG(u16 reg)
35 {
36 	/*
37 	 * use integer division instead of equivalent right shift to
38 	 * guarantee arithmetic shift and preserve the sign
39 	 */
40 	return ((s16)reg / 128) * 500;
41 }
42