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hwmon: (adm9240) handle temperature readings below 0

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Unlike the temperature thresholds the temperature data is a 9-bit signed
value. This allows and additional 0.5 degrees of precision on the
reading but makes handling negative values slightly harder. In order to
have sign-extension applied correctly the 9-bit value is stored in the
upper bits of a signed 16-bit value. When presenting this in sysfs the
value is shifted and scaled appropriately.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Chris Packham 2016-10-05 10:40:54 +13:00 committed by Guenter Roeck
parent 1001354ca3
commit 667f4bab81
1 changed files with 3 additions and 3 deletions
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6
drivers/hwmon/adm9240.c
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@ -194,10 +194,10 @@ static struct adm9240_data *adm9240_update_device(struct device *dev)
* 0.5'C per two measurement cycles thus ignore possible
* but unlikely aliasing error on lsb reading. --Grant
*/
data->temp = ((i2c_smbus_read_byte_data(client,
data->temp = (i2c_smbus_read_byte_data(client,
ADM9240_REG_TEMP) << 8) |
i2c_smbus_read_byte_data(client,
ADM9240_REG_TEMP_CONF)) / 128;
ADM9240_REG_TEMP_CONF);
for (i = 0; i < 2; i++) { /* read fans */
data->fan[i] = i2c_smbus_read_byte_data(client,
@ -263,7 +263,7 @@ static ssize_t show_temp(struct device *dev, struct device_attribute *dummy,
char *buf)
{
struct adm9240_data *data = adm9240_update_device(dev);
return sprintf(buf, "%d\n", data->temp * 500); /* 9-bit value */
return sprintf(buf, "%d\n", data->temp / 128 * 500); /* 9-bit value */
}
static ssize_t show_max(struct device *dev, struct device_attribute *devattr,