net: dsa: ksz9477: report 0 as value when returning error

Most register accesses via the ksz_read* functions don't expect that
they can fail and don't check for an error. This assumption is wrong if
there is a problem with the underlying transport, e.g. an I2C bus.

In that case, the functions would return an error code that mostly goes
unchecked and *val is set to an uninitialized value.

The original Linux driver suffers from a similar problem: There, *val is
only set on success, but if the read fails, there's a warning printed
to log, but still the uninitialized variable in the caller function will
be used instead.

This likely goes unnoticed, because GCC builds on Linux have
-Wno-maybe-uninitialized, but we have implicit -W-maybe-uninitialized in
barebox.

As we sync the code from Linux, one should probably fix this there
first, but let's improve the situation a bit by not reporting an
uninitialized value, but a deterministic zero.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20240502151757.3964461-2-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/net/ksz_common.h b/drivers/net/ksz_common.h
index 291488fe34..44b5055ee3 100644
--- a/drivers/net/ksz_common.h
+++ b/drivers/net/ksz_common.h
@@ -20,7 +20,7 @@ struct ksz_switch {
 
 static inline int ksz_read8(struct ksz_switch *priv, u32 reg, u8 *val)
 {
-	unsigned int value;
+	unsigned int value = 0;
 	int ret = regmap_read(priv->regmap[0], reg, &value);
 
 	*val = value;
@@ -29,7 +29,7 @@ static inline int ksz_read8(struct ksz_switch *priv, u32 reg, u8 *val)
 
 static inline int ksz_read16(struct ksz_switch *priv, u32 reg, u16 *val)
 {
-	unsigned int value;
+	unsigned int value = 0;
 	int ret = regmap_read(priv->regmap[1], reg, &value);
 
 	*val = value;
@@ -38,7 +38,7 @@ static inline int ksz_read16(struct ksz_switch *priv, u32 reg, u16 *val)
 
 static inline int ksz_read32(struct ksz_switch *priv, u32 reg, u32 *val)
 {
-	unsigned int value;
+	unsigned int value = 0;
 	int ret = regmap_read(priv->regmap[2], reg, &value);
 
 	*val = value;