[PATCH] iio: temperature: tsys02d: Fix state desynchronization on resolution write error

[Salah Triki]

In tsys02d_write_raw(), dev_data->res_index is updated before checking
the return value of ms_sensors_write_resolution(). If the hardware I2C
write operation fails, dev_data->res_index remains updated with the
new index despite the physical sensor remaining in its previous state.

This leads to a state desynchronization where subsequent reads via
tsys02d_read_raw() return an incorrect sampling frequency.

Fix this by performing the I2C write first and updating dev_data->res_index
only if ms_sensors_write_resolution() succeeds.

Fixes: 53bf4d067d51 ("Add tsys02d meas-spec driver support")
Signed-off-by: Salah Triki <salah.triki@xxxxxxxxx>
---
 drivers/iio/temperature/tsys02d.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/temperature/tsys02d.c b/drivers/iio/temperature/tsys02d.c
index 3ef72347456e..f50426beacdd 100644
--- a/drivers/iio/temperature/tsys02d.c
+++ b/drivers/iio/temperature/tsys02d.c
@@ -73,8 +73,9 @@ static int tsys02d_write_raw(struct iio_dev *indio_dev,
 		if (i < 0)
 			return -EINVAL;
 		mutex_lock(&dev_data->lock);
-		dev_data->res_index = i;
 		ret = ms_sensors_write_resolution(dev_data, i);
+		if (!ret)
+			dev_data->res_index = i;
 		mutex_unlock(&dev_data->lock);
 
 		return ret;
-- 
2.43.0