The function gp2ap020a00f_get_thresh_reg() can return -EINVAL in its
error path. Yet, the function has return type of u8. Added error
checking for gp2ap020a00f_get_thresh_reg() return value.

Detected by Smatch:
drivers/iio/light/gp2ap020a00f.c:1013 gp2ap020a00f_get_thresh_reg() warn:
signedness bug returning '(-22)'

Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Ethan Tidmore <ethantidmore06@gmail.com>
---
v4:
- Added Reviewed-by: tag from Andy Shevchenko.
v3:
- Remove Fixes: tag.
- Added Smatch warning.
v2:
- Fixed gp2ap020a00f_get_thresh_reg() parameter alignment.
- Removed unneeded whitespace between assignment and check.

 drivers/iio/light/gp2ap020a00f.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/light/gp2ap020a00f.c b/drivers/iio/light/gp2ap020a00f.c
index 91fdcb980111..deca9fd77fdd 100644
--- a/drivers/iio/light/gp2ap020a00f.c
+++ b/drivers/iio/light/gp2ap020a00f.c
@@ -993,8 +993,8 @@ static irqreturn_t gp2ap020a00f_trigger_handler(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
-static u8 gp2ap020a00f_get_thresh_reg(const struct iio_chan_spec *chan,
-					     enum iio_event_direction event_dir)
+static int gp2ap020a00f_get_thresh_reg(const struct iio_chan_spec *chan,
+				       enum iio_event_direction event_dir)
 {
 	switch (chan->type) {
 	case IIO_PROXIMITY:
@@ -1024,11 +1024,14 @@ static int gp2ap020a00f_write_event_val(struct iio_dev *indio_dev,
 	struct gp2ap020a00f_data *data = iio_priv(indio_dev);
 	bool event_en = false;
 	u8 thresh_val_id;
-	u8 thresh_reg_l;
+	int thresh_reg_l;
 
 	guard(mutex)(&data->lock);
 
 	thresh_reg_l = gp2ap020a00f_get_thresh_reg(chan, dir);
+	if (thresh_reg_l < 0)
+		return thresh_reg_l;
+
 	thresh_val_id = GP2AP020A00F_THRESH_VAL_ID(thresh_reg_l);
 	if (thresh_val_id > GP2AP020A00F_THRESH_PH)
 		return -EINVAL;
@@ -1070,11 +1073,13 @@ static int gp2ap020a00f_read_event_val(struct iio_dev *indio_dev,
 				       int *val, int *val2)
 {
 	struct gp2ap020a00f_data *data = iio_priv(indio_dev);
-	u8 thresh_reg_l;
+	int thresh_reg_l;
 
 	guard(mutex)(&data->lock);
 
 	thresh_reg_l = gp2ap020a00f_get_thresh_reg(chan, dir);
+	if (thresh_reg_l < 0)
+		return thresh_reg_l;
 	if (thresh_reg_l > GP2AP020A00F_PH_L_REG)
 		return -EINVAL;
 
-- 
2.53.0