[PATCH v5] staging: iio: meter: add check on return variables

[Aya Mahfouz <mahfouz.saif.elyazal@gmail.com>]

adds checks on variables that are used to return values. If
the value is less than zero, this indicates that an error
occurred and hence a message is printed through dev_err.
Checks are made on negative values only since spi_* functions
return negative error codes.

The functions were found using the following script but the
aforementioned modification was what was carried out in the end:
@@
identifier len,f;
@@

-int len;
 ... when != len
     when strict
-len =
+return
        f(...);
-return len;

Signed-off-by: Aya Mahfouz <mahfouz.saif.elyazal@gmail.com>
---
v1: added checks on last calls only.
v2: added checks on all calls that return values along with labels.
v3: added changelog that was missed in v2.
v4: adjusted the patch to state how the problem was discovered, simplify
the if conditions and avoid redundant error messages.
v5: added driver specific error messages

 drivers/staging/iio/meter/ade7758_core.c | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/drivers/staging/iio/meter/ade7758_core.c b/drivers/staging/iio/meter/ade7758_core.c
index 70e96b2..7e287da 100644
--- a/drivers/staging/iio/meter/ade7758_core.c
+++ b/drivers/staging/iio/meter/ade7758_core.c
@@ -303,14 +303,15 @@ static int ade7758_reset(struct device *dev)
 	int ret;
 	u8 val;
 
-	ade7758_spi_read_reg_8(dev,
-			ADE7758_OPMODE,
-			&val);
+	ret = ade7758_spi_read_reg_8(dev, ADE7758_OPMODE, &val);
+	if (ret < 0) {
+		dev_err(dev, "Failed to read opmode reg\n");
+		return ret;
+	}
 	val |= 1 << 6; /* Software Chip Reset */
-	ret = ade7758_spi_write_reg_8(dev,
-			ADE7758_OPMODE,
-			val);
-
+	ret = ade7758_spi_write_reg_8(dev, ADE7758_OPMODE, val);
+	if (ret < 0)
+		dev_err(dev, "Failed to write opmode reg\n");
 	return ret;
 }
 
@@ -444,14 +445,15 @@ static int ade7758_stop_device(struct device *dev)
 	int ret;
 	u8 val;
 
-	ade7758_spi_read_reg_8(dev,
-			ADE7758_OPMODE,
-			&val);
+	ret = ade7758_spi_read_reg_8(dev, ADE7758_OPMODE, &val);
+	if (ret < 0) {
+		dev_err(dev, "Failed to read opmode reg\n");
+		return ret;
+	}
 	val |= 7 << 3;  /* ADE7758 powered down */
-	ret = ade7758_spi_write_reg_8(dev,
-			ADE7758_OPMODE,
-			val);
-
+	ret = ade7758_spi_write_reg_8(dev, ADE7758_OPMODE, val);
+	if (ret < 0)
+		dev_err(dev, "Failed to write opmode reg\n");
 	return ret;
 }
 
-- 
1.9.3


-- 
Kind Regards,
Aya Saif El-yazal Mahfouz