From 984faa1fb9175720828bf6604f936dff3f17b995 Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Thu, 22 Jan 2015 23:44:13 +0100 Subject: hwmon: (ad7314) Do proper sign extension The comment above (data << 2) >> 2 explains what the intention is: To use bit 13 of the 14-bit value data as the sign bit. However, this doesn't work due to C's promotion rules. data has type s16, but data << 2 has type int. To get sign extension, that expression would have to be cast back to an s16 before being shifted (at which point C's promotion rules would then kick in again and promote the left operand to int). As it stands, both expressions are no-ops for any value of data. Avoid these subtleties by using the existing API for this. sign_extend32 works equally well for 8 and 16 bit types. Signed-off-by: Rasmus Villemoes Signed-off-by: Guenter Roeck --- drivers/hwmon/ad7314.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'drivers/hwmon/ad7314.c') diff --git a/drivers/hwmon/ad7314.c b/drivers/hwmon/ad7314.c index f4f9b219bf16..11955467fc0f 100644 --- a/drivers/hwmon/ad7314.c +++ b/drivers/hwmon/ad7314.c @@ -16,6 +16,7 @@ #include #include #include +#include /* * AD7314 temperature masks @@ -67,7 +68,7 @@ static ssize_t ad7314_show_temperature(struct device *dev, switch (spi_get_device_id(chip->spi_dev)->driver_data) { case ad7314: data = (ret & AD7314_TEMP_MASK) >> AD7314_TEMP_SHIFT; - data = (data << 6) >> 6; + data = sign_extend32(data, 9); return sprintf(buf, "%d\n", 250 * data); case adt7301: @@ -78,7 +79,7 @@ static ssize_t ad7314_show_temperature(struct device *dev, * register. 1lsb - 31.25 milli degrees centigrade */ data = ret & ADT7301_TEMP_MASK; - data = (data << 2) >> 2; + data = sign_extend32(data, 13); return sprintf(buf, "%d\n", DIV_ROUND_CLOSEST(data * 3125, 100)); -- cgit v1.2.3