[PATCH] drivers: iio: pressure: dps310: Fix failure to read negative numbers

[George Liu]

The dps310 chip driver fails to read the temperature when the
temperature reaches below zero.

The dps310_calculate_temp method will return the current temperature
(rc). If the temperature drops to 0 degrees, then rc < 0, it will
return directly without assigning a value to `val`.

Tested: When the temperature reaches below 0 degrees
1. without this patch:
```
cat /sys/bus/i2c/drivers/dps310/7-0076/iio\:device2/in_temp_input
cat: read error: Unknown error 2370
```

2. with this patch:
```
cat /sys/bus/i2c/drivers/dps310/7-0076/iio\:device2/in_temp_input
cat: read error: Unknown error -3370
```

Signed-off-by: George Liu <liuxiwei at ieisystem.com>
---
 drivers/iio/pressure/dps310.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 1ff091b2f764..fcbfdc5e85b7 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -730,7 +730,7 @@ static int dps310_read_pressure(struct dps310_data *data, int *val, int *val2,
 	}
 }
 
-static int dps310_calculate_temp(struct dps310_data *data)
+static int dps310_calculate_temp(struct dps310_data *data, int *val)
 {
 	s64 c0;
 	s64 t;
@@ -746,7 +746,9 @@ static int dps310_calculate_temp(struct dps310_data *data)
 	t = c0 + ((s64)data->temp_raw * (s64)data->c1);
 
 	/* Convert to milliCelsius and scale the temperature */
-	return (int)div_s64(t * 1000LL, kt);
+	*val = (int)div_s64(t * 1000LL, kt);
+
+	return 0;
 }
 
 static int dps310_read_temp(struct dps310_data *data, int *val, int *val2,
@@ -768,11 +770,10 @@ static int dps310_read_temp(struct dps310_data *data, int *val, int *val2,
 		if (rc)
 			return rc;
 
-		rc = dps310_calculate_temp(data);
+		rc = dps310_calculate_temp(data, val);
 		if (rc < 0)
 			return rc;
 
-		*val = rc;
 		return IIO_VAL_INT;
 
 	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
-- 
2.34.1