drivers/hwmon/lm75.h

0001 /* SPDX-License-Identifier: GPL-2.0-or-later */
0002 /*
0003  * lm75.h - Part of lm_sensors, Linux kernel modules for hardware monitoring
0004  * Copyright (c) 2003 Mark M. Hoffman <mhoffman@lightlink.com>
0005  */
0006
0007 /*
0008  * This file contains common code for encoding/decoding LM75 type
0009  * temperature readings, which are emulated by many of the chips
0010  * we support.  As the user is unlikely to load more than one driver
0011  * which contains this code, we don't worry about the wasted space.
0012  */
0013
0014 #include <linux/minmax.h>
0015 #include <linux/types.h>
0016
0017 /* straight from the datasheet */
0018 #define LM75_TEMP_MIN (-55000)
0019 #define LM75_TEMP_MAX 125000
0020 #define LM75_SHUTDOWN 0x01
0021
0022 /*
0023  * TEMP: 0.001C/bit (-55C to +125C)
0024  * REG: (0.5C/bit, two's complement) << 7
0025  */
0026 static inline u16 LM75_TEMP_TO_REG(long temp)
0027 {
0028     int ntemp = clamp_val(temp, LM75_TEMP_MIN, LM75_TEMP_MAX);
0029
0030     ntemp += (ntemp < 0 ? -250 : 250);
0031     return (u16)((ntemp / 500) << 7);
0032 }
0033
0034 static inline int LM75_TEMP_FROM_REG(u16 reg)
0035 {
0036     /*
0037      * use integer division instead of equivalent right shift to
0038      * guarantee arithmetic shift and preserve the sign
0039      */
0040     return ((s16)reg / 128) * 500;
0041 }