[bug report] net: pcs: xpcs: convert to phylink_pcs_ops

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Vladimir Oltean,

The patch 11059740e616: "net: pcs: xpcs: convert to phylink_pcs_ops"
from Jun 2, 2021, leads to the following static checker warning:

	drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:1237 stmmac_phy_setup()
	error: we previously assumed 'mdio_bus_data' could be null (see line 1225)

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
  1215  static int stmmac_phy_setup(struct stmmac_priv *priv)
  1216  {
  1217          struct stmmac_mdio_bus_data *mdio_bus_data = priv->plat->mdio_bus_data;
                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  1218          struct fwnode_handle *fwnode = of_fwnode_handle(priv->plat->phylink_node);
  1219          int mode = priv->plat->phy_interface;
  1220          struct phylink *phylink;
  1221  
  1222          priv->phylink_config.dev = &priv->dev->dev;
  1223          priv->phylink_config.type = PHYLINK_NETDEV;
  1224          priv->phylink_config.pcs_poll = true;
  1225          if (priv->plat->mdio_bus_data)
                    ^^^^^^^^^^^^^^^^^^^^^^^^^
This old code assumes mdio_bus_data can be NULL.

  1226                  priv->phylink_config.ovr_an_inband =
  1227                          mdio_bus_data->xpcs_an_inband;
  1228  
  1229          if (!fwnode)
  1230                  fwnode = dev_fwnode(priv->device);
  1231  
  1232          phylink = phylink_create(&priv->phylink_config, fwnode,
  1233                                   mode, &stmmac_phylink_mac_ops);
  1234          if (IS_ERR(phylink))
  1235                  return PTR_ERR(phylink);
  1236  
  1237          if (mdio_bus_data->has_xpcs) {
                    ^^^^^^^^^^^^^^^^^^^^^^^
Unchecked dereference.

  1238                  struct mdio_xpcs_args *xpcs = priv->hw->xpcs;
  1239  
  1240                  phylink_set_pcs(phylink, &xpcs->pcs);
  1241          }
  1242  
  1243          priv->phylink = phylink;
  1244          return 0;
  1245  }

regards,
dan carpenter