[PATCH 3.18 051/144] iio: iio: Fix iio_channel_read return if channel havnt info

[Greg Kroah-Hartman]

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 65de7654d39c70c2b942f801cea01590cf7e3458 ]

When xilinx-xadc is used with hwmon driver to read voltage, offset used
for temperature is always applied whatever the channel.

iio_channel_read must return an error to avoid offset for channel
without IIO_CHAN_INFO_OFFSET property.

Signed-off-by: Fabien Proriol <fabien.proriol@xxxxxxxx>
Signed-off-by: Jonathan Cameron <jic23@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/iio/inkern.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index f0846108d006..d33590e89337 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -426,6 +426,9 @@ static int iio_channel_read(struct iio_channel *chan, int *val, int *val2,
 	if (val2 == NULL)
 		val2 = &unused;
 
+	if(!iio_channel_has_info(chan->channel, info))
+		return -EINVAL;
+
 	if (chan->indio_dev->info->read_raw_multi) {
 		ret = chan->indio_dev->info->read_raw_multi(chan->indio_dev,
 					chan->channel, INDIO_MAX_RAW_ELEMENTS,
-- 
2.17.1