drivers/hwmon/lm75.h

   1 /*
   2     lm75.h - Part of lm_sensors, Linux kernel modules for hardware
   3               monitoring
   4     Copyright (c) 2003 Mark M. Hoffman <mhoffman@lightlink.com>
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License
  17     along with this program; if not, write to the Free Software
  18     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19 */
  20
  21 /*
  22     This file contains common code for encoding/decoding LM75 type
  23     temperature readings, which are emulated by many of the chips
  24     we support.  As the user is unlikely to load more than one driver
  25     which contains this code, we don't worry about the wasted space.
  26 */
  27
  28 #include <linux/kernel.h>
  29
  30 /* straight from the datasheet */
  31 #define LM75_TEMP_MIN (-55000)
  32 #define LM75_TEMP_MAX 125000
  33 #define LM75_SHUTDOWN 0x01
  34
  35 /* TEMP: 0.001C/bit (-55C to +125C)
  36    REG: (0.5C/bit, two's complement) << 7 */
  37 static inline u16 LM75_TEMP_TO_REG(long temp)
  38 {
  39         int ntemp = clamp_val(temp, LM75_TEMP_MIN, LM75_TEMP_MAX);
  40         ntemp += (ntemp < 0 ? -250 : 250);
  41         return (u16)((ntemp / 500) << 7);
  42 }
  43
  44 static inline int LM75_TEMP_FROM_REG(u16 reg)
  45 {
  46         /* use integer division instead of equivalent right shift to
  47            guarantee arithmetic shift and preserve the sign */
  48         return ((s16)reg / 128) * 500;
  49 }