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/kernel.h>
15 
16 /* straight from the datasheet */
17 #define LM75_TEMP_MIN (-55000)
18 #define LM75_TEMP_MAX 125000
19 #define LM75_SHUTDOWN 0x01
20 
21 /*
22  * TEMP: 0.001C/bit (-55C to +125C)
23  * REG: (0.5C/bit, two's complement) << 7
24  */
LM75_TEMP_TO_REG(long temp)25 static inline u16 LM75_TEMP_TO_REG(long temp)
26 {
27 	int ntemp = clamp_val(temp, LM75_TEMP_MIN, LM75_TEMP_MAX);
28 
29 	ntemp += (ntemp < 0 ? -250 : 250);
30 	return (u16)((ntemp / 500) << 7);
31 }
32 
LM75_TEMP_FROM_REG(u16 reg)33 static inline int LM75_TEMP_FROM_REG(u16 reg)
34 {
35 	/*
36 	 * use integer division instead of equivalent right shift to
37 	 * guarantee arithmetic shift and preserve the sign
38 	 */
39 	return ((s16)reg / 128) * 500;
40 }
41