iio: light: bu27008: Fix scale format

The driver is expecting accuracy of NANOs for intensity scale in
raw_write. The IIO core is however defaulting to MICROs. This leads the
raw-write of smallest scales to never succeed as correct selector(s) are
not found.

Fix this by implementing the .write_raw_get_fmt callback to use NANO
accuracy for writes of IIO_CHAN_INFO_SCALE.

Fixes: 41ff93d1 ("iio: light: ROHM BU27008 color sensor")
Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Link: https://lore.kernel.org/r/e4778b74cde41431f77bc8dd88ec18605da0b400.1686648422.git.mazziesaccount@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/rohm-bu27008.c

@@ -633,7 +633,7 @@ static int bu27008_try_find_new_time_gain(struct bu27008_data *data, int val,
 	for (i = 0; i < data->gts.num_itime; i++) {
 		new_time_sel = data->gts.itime_table[i].sel;
 		ret = iio_gts_find_gain_sel_for_scale_using_time(&data->gts,
-					new_time_sel, val, val2 * 1000, gain_sel);
+					new_time_sel, val, val2, gain_sel);
 		if (!ret)
 			break;
 	}
@@ -662,7 +662,7 @@ static int bu27008_set_scale(struct bu27008_data *data,
 		goto unlock_out;
 
 	ret = iio_gts_find_gain_sel_for_scale_using_time(&data->gts, time_sel,
-						val, val2 * 1000, &gain_sel);
+						val, val2, &gain_sel);
 	if (ret) {
 		ret = bu27008_try_find_new_time_gain(data, val, val2, &gain_sel);
 		if (ret)
@@ -677,6 +677,21 @@ static int bu27008_set_scale(struct bu27008_data *data,
 	return ret;
 }
 
+static int bu27008_write_raw_get_fmt(struct iio_dev *indio_dev,
+				     struct iio_chan_spec const *chan,
+				     long mask)
+{
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		return IIO_VAL_INT_PLUS_NANO;
+	case IIO_CHAN_INFO_INT_TIME:
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		return -EINVAL;
+	}
+}
+
 static int bu27008_write_raw(struct iio_dev *idev,
 			     struct iio_chan_spec const *chan,
 			     int val, int val2, long mask)
@@ -756,6 +771,7 @@ static int bu27008_update_scan_mode(struct iio_dev *idev,
 static const struct iio_info bu27008_info = {
 	.read_raw = &bu27008_read_raw,
 	.write_raw = &bu27008_write_raw,
+	.write_raw_get_fmt = &bu27008_write_raw_get_fmt,
 	.read_avail = &bu27008_read_avail,
 	.update_scan_mode = bu27008_update_scan_mode,
 	.validate_trigger = iio_validate_own_trigger,