LM73 bug fix for negative temperatures and cleanup

When the LM73 temperature sensor measures a temperature below 0 C, the
current driver does not perform sign extension, so the result returned is
512 C too high.  This patch fixes the problem, and does general cleanup
of the code.

Signed-off-by: Larry Johnson <lrj@acm.org>

diff --git a/drivers/hwmon/lm73.c b/drivers/hwmon/lm73.c
index db8ef662adc27194bf6cf96c212fbcbb3f48d247..98e8bd298476e4150811ebdbd0482e6893b75dd9 100644 (file)
--- a/drivers/hwmon/lm73.c
+++ b/drivers/hwmon/lm73.c
@@ -1,5 +1,5 @@
 /*
- * (C) Copyright 2007
+ * (C) Copyright 2007-2008
  * Larry Johnson, lrj@acm.org
  *
  * based on dtt/lm75.c which is ...
@@ -39,10 +39,10 @@
  */
 #define DTT_I2C_DEV_CODE 0x48  /* National Semi's LM73 device */
 
-int dtt_read(int sensor, int reg)
+int dtt_read(int const sensor, int const reg)
 {
        int dlen;
-       uchar data[2];
+       uint8_t data[2];
 
        /*
         * Validate 'reg' param and get register size.
@@ -62,27 +62,24 @@ int dtt_read(int sensor, int reg)
                return -1;
        }
        /*
-        * Calculate sensor address and register.
+        * Try to read the register at the calculated sensor address.
         */
-       sensor = DTT_I2C_DEV_CODE + (sensor & 0x07);    /* calculate LM73 addr */
-       /*
-        * Now try to read the register.
-        */
-       if (i2c_read(sensor, reg, 1, data, dlen) != 0)
+       if (0 !=
+           i2c_read(DTT_I2C_DEV_CODE + (sensor & 0x07), reg, 1, data, dlen))
                return -1;
        /*
         * Handle 2 byte result.
         */
        if (2 == dlen)
-               return ((int)((short)data[1] + (((short)data[0]) << 8)));
+               return (int)((unsigned)data[0] << 8 | (unsigned)data[1]);
 
        return (int)data[0];
 } /* dtt_read() */
 
-int dtt_write(int sensor, int reg, int val)
+int dtt_write(int const sensor, int const reg, int const val)
 {
        int dlen;
-       uchar data[2];
+       uint8_t data[2];
 
        /*
         * Validate 'reg' param and handle register size
@@ -91,28 +88,25 @@ int dtt_write(int sensor, int reg, int val)
        case DTT_CONFIG:
        case DTT_CONTROL:
                dlen = 1;
-               data[0] = (char)(val & 0xff);
+               data[0] = (uint8_t) val;
                break;
        case DTT_TEMP_HIGH:
        case DTT_TEMP_LOW:
                dlen = 2;
-               data[0] = (char)((val >> 8) & 0xff);    /* MSB first */
-               data[1] = (char)(val & 0xff);
+               data[0] = (uint8_t) (val >> 8); /* MSB first */
+               data[1] = (uint8_t) val;
                break;
        default:
                return -1;
        }
        /*
-        * Calculate sensor address and register.
-        */
-       sensor = DTT_I2C_DEV_CODE + (sensor & 0x07);    /* calculate LM73 addr */
-       /*
-        * Write value to register.
+        * Write value to register at the calculated sensor address.
         */
-       return i2c_write(sensor, reg, 1, data, dlen) != 0;
+       return 0 != i2c_write(DTT_I2C_DEV_CODE + (sensor & 0x07), reg, 1, data,
+                             dlen);
 } /* dtt_write() */
 
-static int _dtt_init(int sensor)
+static int _dtt_init(int const sensor)
 {
        int val;
 
@@ -120,31 +114,31 @@ static int _dtt_init(int sensor)
         * Validate the Identification register
         */
        if (0x0190 != dtt_read(sensor, DTT_ID))
-               return 1;
+               return -1;
        /*
         * Setup THIGH (upper-limit) and TLOW (lower-limit) registers
         */
        val = CFG_DTT_MAX_TEMP << 7;
        if (dtt_write(sensor, DTT_TEMP_HIGH, val))
-               return 1;
+               return -1;
 
        val = CFG_DTT_MIN_TEMP << 7;
        if (dtt_write(sensor, DTT_TEMP_LOW, val))
-               return 1;
+               return -1;
        /*
         * Setup configuraton register
         */
        /* config = alert active low, disabled, and reset */
        val = 0x64;
        if (dtt_write(sensor, DTT_CONFIG, val))
-               return 1;
+               return -1;
        /*
         * Setup control/status register
         */
        /* control = temp resolution 0.25C */
        val = 0x00;
        if (dtt_write(sensor, DTT_CONTROL, val))
-               return 1;
+               return -1;
 
        dtt_read(sensor, DTT_CONTROL);  /* clear temperature flags */
        return 0;
@@ -157,7 +151,7 @@ int dtt_init(void)
        const char *const header = "DTT:   ";
 
        for (i = 0; i < sizeof(sensors); i++) {
-               if (_dtt_init(sensors[i]) != 0)
+               if (0 != _dtt_init(sensors[i]))
                        printf("%s%d FAILED INIT\n", header, i + 1);
                else
                        printf("%s%d is %i C\n", header, i + 1,
@@ -166,7 +160,13 @@ int dtt_init(void)
        return 0;
 } /* dtt_init() */
 
-int dtt_get_temp(int sensor)
+int dtt_get_temp(int const sensor)
 {
-       return (dtt_read(sensor, DTT_READ_TEMP) + 0x0040) >> 7;
+       int const ret = dtt_read(sensor, DTT_READ_TEMP);
+
+       if (ret < 0) {
+               printf("DTT temperature read failed.\n");
+               return 0;
+       }
+       return (int)((int16_t) ret + 0x0040) >> 7;
 } /* dtt_get_temp() */