[PATCH net-next v4 4/5] net: mdio: realtek-rtl9300: reject duplicate MDIO bus IDs

[Markus Stockhausen <markus.stockhausen@gmx.de>]

The reg property identifies the hardware MDIO bus and is used as an
index into the per-bus state. However, duplicate bus IDs are currently
not rejected explicitly and only fail later during MDIO bus
registration due to the duplicate bus ID.

Keep track of successfully registered buses and reject a duplicate reg
value before allocating another bus. For this use the already existing
but currently unused priv->bus[] property.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
---
 drivers/net/mdio/mdio-realtek-rtl9300.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/mdio/mdio-realtek-rtl9300.c b/drivers/net/mdio/mdio-realtek-rtl9300.c
index 8ca917d9aea3..45cbefc52100 100644
--- a/drivers/net/mdio/mdio-realtek-rtl9300.c
+++ b/drivers/net/mdio/mdio-realtek-rtl9300.c
@@ -845,6 +845,9 @@ static int otto_emdio_probe_one(struct device *dev, struct otto_emdio_priv *priv
 		return dev_err_probe(dev, -EINVAL,
 				     "illegal (dangling) smi bus number %d\n", mdio_bus);
 
+	if (priv->bus[mdio_bus])
+		return dev_err_probe(dev, -EINVAL, "duplicated smi bus number %d\n", mdio_bus);
+
 	bus = devm_mdiobus_alloc_size(dev, sizeof(*chan));
 	if (!bus)
 		return -ENOMEM;
@@ -868,6 +871,8 @@ static int otto_emdio_probe_one(struct device *dev, struct otto_emdio_priv *priv
 	if (err)
 		return dev_err_probe(dev, err, "cannot register MDIO bus\n");
 
+	priv->bus[mdio_bus] = bus;
+
 	return 0;
 }
 
-- 
2.55.0