net: mdio: warn once if addr parameter is invalid in mdiobus_get_phy()

If mdiobus_get_phy() is called with an invalid addr parameter, then the
caller has a bug. Print a call trace to help identifying the caller.

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/daec3f08-6192-ba79-f74b-5beb436cab6c@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/mdio_bus.c

@@ -109,9 +109,10 @@ EXPORT_SYMBOL(mdiobus_unregister_device);
 
 struct phy_device *mdiobus_get_phy(struct mii_bus *bus, int addr)
 {
+	bool addr_valid = addr >= 0 && addr < ARRAY_SIZE(bus->mdio_map);
 	struct mdio_device *mdiodev;
 
-	if (addr < 0 || addr >= ARRAY_SIZE(bus->mdio_map))
+	if (WARN_ONCE(!addr_valid, "addr %d out of range\n", addr))
 		return NULL;
 
 	mdiodev = bus->mdio_map[addr];