drivers/hwmon/adm1021.c: support high precision ADM1023 remote sensor

The ADM1023 temperature sensor supports higher resolution for its external
sensor (sensitivity of 1/8 deg C).  This patch makes this higher
resolution available through the appropriate temperature sysfs nodes.

Curiously, this functionality was available in the 2.4 kernel driver (but
formatted in a less helpful manner).

Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Michael Abbott <michael.abbott@diamond.ac.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 23 insertions, 24 deletions

diff --git a/drivers/hwmon/adm1021.c b/drivers/hwmon/adm1021.c
index b11e06f644b1..de84398775b6 100644
--- a/drivers/hwmon/adm1021.c
+++ b/drivers/hwmon/adm1021.c
@@ -85,14 +85,11 @@ struct adm1021_data {
         char valid;             /* !=0 if following fields are valid */
         unsigned long last_updated;     /* In jiffies */
 
-        s8 temp_max[2];         /* Register values */
-        s8 temp_min[2];
-        s8 temp[2];
+        int temp_max[2];                /* Register values */
+        int temp_min[2];
+        int temp[2];
         u8 alarms;
         /* Special values for ADM1023 only */
-        u8 remote_temp_prec;
-        u8 remote_temp_os_prec;
-        u8 remote_temp_hyst_prec;
         u8 remote_temp_offset;
         u8 remote_temp_offset_prec;
 };
@@ -141,7 +138,7 @@ static ssize_t show_temp(struct device *dev,
         int index = to_sensor_dev_attr(devattr)->index;
         struct adm1021_data *data = adm1021_update_device(dev);
 
-        return sprintf(buf, "%d\n", 1000 * data->temp[index]);
+        return sprintf(buf, "%d\n", data->temp[index]);
 }
 
 static ssize_t show_temp_max(struct device *dev,
@@ -150,7 +147,7 @@ static ssize_t show_temp_max(struct device *dev,
         int index = to_sensor_dev_attr(devattr)->index;
         struct adm1021_data *data = adm1021_update_device(dev);
 
-        return sprintf(buf, "%d\n", 1000 * data->temp_max[index]);
+        return sprintf(buf, "%d\n", data->temp_max[index]);
 }
 
 static ssize_t show_temp_min(struct device *dev,
@@ -159,7 +156,7 @@ static ssize_t show_temp_min(struct device *dev,
         int index = to_sensor_dev_attr(devattr)->index;
         struct adm1021_data *data = adm1021_update_device(dev);
 
-        return sprintf(buf, "%d\n", 1000 * data->temp_min[index]);
+        return sprintf(buf, "%d\n", data->temp_min[index]);
 }
 
 static ssize_t show_alarm(struct device *dev, struct device_attribute *attr,
@@ -412,25 +409,27 @@ static struct adm1021_data *adm1021_update_device(struct device *dev)
                 dev_dbg(&client->dev, "Starting adm1021 update\n");
 
                 for (i = 0; i < 2; i++) {
-                        data->temp[i] = i2c_smbus_read_byte_data(client,
-                                                ADM1021_REG_TEMP(i));
-                        data->temp_max[i] = i2c_smbus_read_byte_data(client,
-                                                ADM1021_REG_TOS_R(i));
-                        data->temp_min[i] = i2c_smbus_read_byte_data(client,
-                                                ADM1021_REG_THYST_R(i));
+                        data->temp[i] = 1000 *
+                                (s8) i2c_smbus_read_byte_data(
+                                        client, ADM1021_REG_TEMP(i));
+                        data->temp_max[i] = 1000 *
+                                (s8) i2c_smbus_read_byte_data(
+                                        client, ADM1021_REG_TOS_R(i));
+                        data->temp_min[i] = 1000 *
+                                (s8) i2c_smbus_read_byte_data(
+                                        client, ADM1021_REG_THYST_R(i));
                 }
                 data->alarms = i2c_smbus_read_byte_data(client,
                                                 ADM1021_REG_STATUS) & 0x7c;
                 if (data->type == adm1023) {
-                        data->remote_temp_prec =
-                                i2c_smbus_read_byte_data(client,
-                                                ADM1023_REG_REM_TEMP_PREC);
-                        data->remote_temp_os_prec =
-                                i2c_smbus_read_byte_data(client,
-                                                ADM1023_REG_REM_TOS_PREC);
-                        data->remote_temp_hyst_prec =
-                                i2c_smbus_read_byte_data(client,
-                                                ADM1023_REG_REM_THYST_PREC);
+                        /* The ADM1023 provides 3 extra bits of precision for
+                         * the remote sensor in extra registers. */
+                        data->temp[1] += 125 * (i2c_smbus_read_byte_data(
+                                client, ADM1023_REG_REM_TEMP_PREC) >> 5);
+                        data->temp_max[1] += 125 * (i2c_smbus_read_byte_data(
+                                client, ADM1023_REG_REM_TOS_PREC) >> 5);
+                        data->temp_min[1] += 125 * (i2c_smbus_read_byte_data(
+                                client, ADM1023_REG_REM_THYST_PREC) >> 5);
                         data->remote_temp_offset =
                                 i2c_smbus_read_byte_data(client,
                                                 ADM1023_REG_REM_OFFSET);