hwmon: (adc128d818) Do proper sign extension

data->temp[index] has type s16. Because of C's promotion rules,
(data->temp[index] << 7) >> 7 is exactly the same as
data->temp[index]. The intention was to use bit 8 as a sign bit, so do
that using the existing API.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/drivers/hwmon/adc128d818.c b/drivers/hwmon/adc128d818.c
index 0625e50..ad2b47e 100644 (file)
--- a/drivers/hwmon/adc128d818.c
+++ b/drivers/hwmon/adc128d818.c
@@ -27,6 +27,7 @@
 #include <linux/err.h>
 #include <linux/regulator/consumer.h>
 #include <linux/mutex.h>
+#include <linux/bitops.h>
 
 /* Addresses to scan
  * The chip also supports addresses 0x35..0x37. Don't scan those addresses
@@ -189,7 +190,7 @@ static ssize_t adc128_show_temp(struct device *dev,
        if (IS_ERR(data))
                return PTR_ERR(data);
 
-       temp = (data->temp[index] << 7) >> 7;   /* sign extend */
+       temp = sign_extend32(data->temp[index], 8);
        return sprintf(buf, "%d\n", temp * 500);/* 0.5 degrees C resolution */
 }