net: dsa: Add helper function to obtain PHY device of a given port

In preparation for having more call sites attempting to obtain a
reference against a PHY device corresponding to a particular port,
introduce a helper function for that purpose.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/port.c

@@ -273,25 +273,38 @@ int dsa_port_vlan_del(struct dsa_port *dp,
 	return 0;
 }
 
-static int dsa_port_setup_phy_of(struct dsa_port *dp, bool enable)
+static struct phy_device *dsa_port_get_phy_device(struct dsa_port *dp)
 {
-	struct device_node *port_dn = dp->dn;
 	struct device_node *phy_dn;
-	struct dsa_switch *ds = dp->ds;
 	struct phy_device *phydev;
-	int port = dp->index;
-	int err = 0;
 
-	phy_dn = of_parse_phandle(port_dn, "phy-handle", 0);
+	phy_dn = of_parse_phandle(dp->dn, "phy-handle", 0);
 	if (!phy_dn)
-		return 0;
+		return NULL;
 
 	phydev = of_phy_find_device(phy_dn);
 	if (!phydev) {
-		err = -EPROBE_DEFER;
-		goto err_put_of;
+		of_node_put(phy_dn);
+		return ERR_PTR(-EPROBE_DEFER);
 	}
 
+	return phydev;
+}
+
+static int dsa_port_setup_phy_of(struct dsa_port *dp, bool enable)
+{
+	struct dsa_switch *ds = dp->ds;
+	struct phy_device *phydev;
+	int port = dp->index;
+	int err = 0;
+
+	phydev = dsa_port_get_phy_device(dp);
+	if (!phydev)
+		return 0;
+
+	if (IS_ERR(phydev))
+		return PTR_ERR(phydev);
+
 	if (enable) {
 		err = genphy_config_init(phydev);
 		if (err < 0)
@@ -317,8 +330,6 @@ static int dsa_port_setup_phy_of(struct dsa_port *dp, bool enable)
 
 err_put_dev:
 	put_device(&phydev->mdio.dev);
-err_put_of:
-	of_node_put(phy_dn);
 	return err;
 }