[bug report] net: dsa: mt7530: Add the support of MT7531 switch

[Dan Carpenter]

Hello Landen Chao,

The patch c288575f7810: "net: dsa: mt7530: Add the support of MT7531
switch" from Sep 11, 2020, leads to the following static checker
warning:

	drivers/net/dsa/mt7530.c:2298 mt7531_cpu_port_config()
	error: uninitialized symbol 'interface'.

drivers/net/dsa/mt7530.c
  2273  static int
  2274  mt7531_cpu_port_config(struct dsa_switch *ds, int port)
  2275  {
  2276          struct mt7530_priv *priv = ds->priv;
  2277          phy_interface_t interface;
  2278          int speed;
  2279  
  2280          switch (port) {
  2281          case 5:
  2282                  if (mt7531_is_rgmii_port(priv, port))
  2283                          interface = PHY_INTERFACE_MODE_RGMII;
  2284                  else
  2285                          interface = PHY_INTERFACE_MODE_2500BASEX;
  2286  
  2287                  priv->p5_interface = interface;
  2288                  break;
  2289          case 6:
  2290                  interface = PHY_INTERFACE_MODE_2500BASEX;
  2291  
  2292                  mt7531_pad_setup(ds, interface);
  2293  
  2294                  priv->p6_interface = interface;
  2295                  break;

Does this need a default case?  Smatch thinks "port" can be 0-6.

  2296          }
  2297  
  2298          if (interface == PHY_INTERFACE_MODE_2500BASEX)
  2299                  speed = SPEED_2500;
  2300          else
  2301                  speed = SPEED_1000;
  2302  
  2303          mt7531_mac_config(ds, port, MLO_AN_FIXED, interface);
  2304          mt7530_write(priv, MT7530_PMCR_P(port),
  2305                       PMCR_CPU_PORT_SETTING(priv->id));
  2306          mt753x_phylink_mac_link_up(ds, port, MLO_AN_FIXED, interface, NULL,
  2307                                     speed, DUPLEX_FULL, true, true);
  2308  
  2309          return 0;
  2310  }

regards,
dan carpenter