[PATCH] net: phy: Fix return value when when !CONFIG_PHYLIB

[hhtracer]

From: huhai <huhai@xxxxxxxxxx>

Many call sites of get_phy_device() and fwnode_get_phy_node(), such as
sfp_sm_probe_phy(), phylink_fwnode_phy_connect(), etc., rely on IS_ERR()
to check for errors in the returned pointer.

Furthermore, the implementations of get_phy_device() and
fwnode_get_phy_node() themselves use ERR_PTR() to return error codes.

Therefore, when CONFIG_PHYLIB is disabled, returning NULL is incorrect,
as this would bypass IS_ERR() checks and may lead to NULL pointer
dereference.

Returning ERR_PTR(-ENXIO) is the correct and consistent way to indicate
that PHY support is not available, and it avoids such issues.

Signed-off-by: huhai <huhai@xxxxxxxxxx>
---
 include/linux/phy.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/phy.h b/include/linux/phy.h
index a2bfae80c449..be299c572d73 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -1787,13 +1787,13 @@ static inline struct phy_device *device_phy_find_device(struct device *dev)
 static inline
 struct fwnode_handle *fwnode_get_phy_node(struct fwnode_handle *fwnode)
 {
-	return NULL;
+	return ERR_PTR(-ENXIO);
 }
 
 static inline
 struct phy_device *get_phy_device(struct mii_bus *bus, int addr, bool is_c45)
 {
-	return NULL;
+	return ERR_PTR(-ENXIO);
 }
 
 static inline int phy_device_register(struct phy_device *phy)
-- 
2.25.1