linux-kernel - [PATCH 2/2] drivers/hwmon/adc128d818.c: Do proper sign extension

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Date:	Thu, 22 Jan 2015 23:44:14 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Jean Delvare <jdelvare@...e.de>, Guenter Roeck <linux@...ck-us.net>
Cc:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	lm-sensors@...sensors.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] drivers/hwmon/adc128d818.c: 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@...musvillemoes.dk>
---
 drivers/hwmon/adc128d818.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/adc128d818.c b/drivers/hwmon/adc128d818.c
index 0625e50d7a6e..ad2b47e40345 100644
--- 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 */
 }
 
-- 
2.1.3

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