On 06/05/2014 01:53 AM, Peter Meerwald wrote:
i2c_smbus_read_word_data() does host endian conversion already,
no need for le16_to_cpu()
Signed-off-by: Peter Meerwald <pmeerw@xxxxxxxxxx>
---
drivers/iio/magnetometer/ak8975.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
index 09ea5c4..ea08313 100644
--- a/drivers/iio/magnetometer/ak8975.c
+++ b/drivers/iio/magnetometer/ak8975.c
@@ -373,8 +373,6 @@ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
{
struct ak8975_data *data = iio_priv(indio_dev);
struct i2c_client *client = data->client;
- u16 meas_reg;
- s16 raw;
int ret;
mutex_lock(&data->lock);
@@ -422,16 +420,11 @@ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
dev_err(&client->dev, "Read axis data fails\n");
goto exit;
}
- meas_reg = ret;
mutex_unlock(&data->lock);
- /* Endian conversion of the measured values. */
- raw = (s16) (le16_to_cpu(meas_reg));
-
/* Clamp to valid range. */
- raw = clamp_t(s16, raw, -4096, 4095);
- *val = raw;
+ *val = clamp_t(s16, ret, -4096, 4095);
return IIO_VAL_INT;
exit:
I did some experiments on little-endian platforms, so your change
won't hurt on x86.
Read as word data -> Reg 3 (LB) and Reg 4(HB)
[ 1529.699617] Word read reg->3:ffc8
Read as byte separately LB and HB
[ 1529.711619] Byte read reg->3:c8 reg->4:ff
x86 platform is le, so no change in output by call to le16_to_cpu
[ 1529.711634] Raw value final ffffffc8
Don't we need to convert for big-endian platforms?
When I trace the path for i2c, I don't see any host order
conversion.
Path:
i2c_smbus_read_word_data->i2c_smbus_xfer->i2c_smbus_xfer_emulated
i2c_smbus_xfer_emulated
{
(for designware) bus
// Send command part
adap->algo->master_xfer->i2c_dw_xfer_msg ->
// Rx data
via i2c_dw_read, don't see any host order conversion
\
{
order word according to SMBUS specification, low byte on the bus first
case I2C_SMBUS_WORD_DATA:
case I2C_SMBUS_PROC_CALL:
data->word = msgbuf1[0] | (msgbuf1[1] << 8);
break;
}
But there is no host order conversion?
}
Thanks,
Srinivas
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