Re: [PATCH v12 4/4] net: dsa: add basic initial driver for MxL862xx switches

On Mon, Feb 02, 2026 at 12:23:26PM +0200, Vladimir Oltean wrote:

On Sun, Feb 01, 2026 at 02:25:13AM +0000, Daniel Golle wrote:

quoted

+static int mxl862xx_setup_mdio(struct dsa_switch *ds)
+{
+	struct mxl862xx_priv *priv = ds->priv;
+	struct device *dev = ds->dev;
+	struct device_node *mdio_np;
+	struct mii_bus *bus;
+	int ret;
+
+	bus = devm_mdiobus_alloc(dev);
+	if (!bus)
+		return -ENOMEM;
+
+	bus->priv = priv;
+	ds->user_mii_bus = bus;
+	bus->name = KBUILD_MODNAME "-mii";
+	snprintf(bus->id, MII_BUS_ID_SIZE, "%s-mii", dev_name(dev));
+	bus->read_c45 = mxl862xx_phy_read_c45_mii_bus;
+	bus->write_c45 = mxl862xx_phy_write_c45_mii_bus;
+	bus->read = mxl862xx_phy_read_mii_bus;
+	bus->write = mxl862xx_phy_write_mii_bus;
+	bus->parent = dev;
+	bus->phy_mask = ~ds->phys_mii_mask;
+
+	mdio_np = of_get_child_by_name(dev->of_node, "mdio");
+	if (!mdio_np)
+		return -ENODEV;

As per the dt-bindings patch, the "mdio" child node is not required.
But here it is.

Now that ports are counted from 0, and 0 being the microcontroller, the
port number no longer matches the PHY ID, so I suppose I got to change
the dt-bindigns as that kinda makes the mdio node mandatory for anything
to work.

All user ports are given a valid non-NULL dp->cpu_dp pointer. I strongly
oppose introducing FUD in the code. If there are valid reasons behind
this I'm all ears, but there aren't.

Looking at other drivers I thought that, and regret not having challenged the
AI commenting on this...