[PATCH] iio: si7020: Fix endianness for I2C reads

[PATCH] iio: si7020: Fix endianness for I2C reads

[Andrey Smirnov]

Si7020 outputs most significant byte of the measurement result first
and least significant byte last. As a result the data returned by
i2c_smbus_read_word_data appears as big endian. Fix this by making a
call to an approbriate byte conversion routine.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
---
 drivers/iio/humidity/si7020.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/humidity/si7020.c b/drivers/iio/humidity/si7020.c
index fa3b809..5c89e14 100644
--- a/drivers/iio/humidity/si7020.c
+++ b/drivers/iio/humidity/si7020.c
@@ -56,7 +56,7 @@ static int si7020_read_raw(struct iio_dev *indio_dev,
 					       SI7020CMD_RH_HOLD);
 		if (ret < 0)
 			return ret;
-		*val = ret >> 2;
+		*val = be16_to_cpu(ret) >> 2;
 		if (chan->type == IIO_HUMIDITYRELATIVE)
 			*val &= GENMASK(11, 0);
 		return IIO_VAL_INT;
--
2.1.0

Re: [PATCH] iio: si7020: Fix endianness for I2C reads

[Lars-Peter Clausen]

On 03/13/2015 03:53 AM, Andrey Smirnov wrote:
> Si7020 outputs most significant byte of the measurement result first
> and least significant byte last. As a result the data returned by
> i2c_smbus_read_word_data appears as big endian. Fix this by making a
> call to an approbriate byte conversion routine.

i2c_smbus_read_word_data() returns data in native endianess. But it 
interprets the word on the bus as little-endian (As specified by the SMBus 
spec). If your chip returns data in big-endian use 
i2c_smbus_read_word_data_swapped().

- Lars

Re: [PATCH] iio: si7020: Fix endianness for I2C reads

[Andrey Smirnov]

>
> i2c_smbus_read_word_data() returns data in native endianess. But it
> interprets the word on the bus as little-endian (As specified by the SMBus
> spec). If your chip returns data in big-endian use
> i2c_smbus_read_word_data_swapped().
>
> - Lars

Ah, good to know. I'll update the patch accordingly.

Thanks