hwmon: (f71882fg) Fix negative temperature

[ Upstream commit 4aaaaf0f279836f06d3b9d0ffeec7a1e1a04ceef ]

All temperature of Fintek superio hwmonitor that using 1-byte reg will use
2's complement.

In show_temp()
	temp = data->temp[nr] * 1000;

When data->temp[nr] read as 255, it indicate -1C, but this code will report
255C to userspace. It'll be ok when change to:
	temp = ((s8)data->temp[nr]) * 1000;

Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com>
Link: https://lore.kernel.org/r/20220418090706.6339-1-hpeter+linux_kernel@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/hwmon/f71882fg.c b/drivers/hwmon/f71882fg.c
index ca54ce5c8e10c0ef04261b5ef804b56b0e888cae..4010b61743f5bc5259557b12f1242976136859e7 100644 (file)
--- a/drivers/hwmon/f71882fg.c
+++ b/drivers/hwmon/f71882fg.c
@@ -1590,8 +1590,9 @@ static ssize_t show_temp(struct device *dev, struct device_attribute *devattr,
                temp *= 125;
                if (sign)
                        temp -= 128000;
-       } else
-               temp = data->temp[nr] * 1000;
+       } else {
+               temp = ((s8)data->temp[nr]) * 1000;
+       }
 
        return sprintf(buf, "%d\n", temp);
 }