drivers/hwmon/lm75.h

   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 }