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 */ 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 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