net: dsa: make "label" property optional for dsa2

In the new DTS bindings for DSA (dsa2), the "ethernet" and "link"
phandles are respectively mandatory and exclusive to CPU port and DSA
link device tree nodes.

Simplify dsa2.c a bit by checking the presence of such phandle instead
of checking the redundant "label" property.

Then the Linux philosophy for Ethernet switch ports is to expose them to
userspace as standard NICs by default. Thus use the standard enumerated
"eth%d" device name if no "label" property is provided for a user port.
This allows to save DTS files from subjective net device names.

If one wants to rename an interface, udev rules can be used as usual.

Of course the current behavior is unchanged, and the optional "label"
property for user ports has precedence over the enumerated name.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Acked-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/dsa/dsa.txt

@@ -34,26 +34,27 @@ Required properties:
 
 Each port children node must have the following mandatory properties:
 - reg			: Describes the port address in the switch
-- label			: Describes the label associated with this port, which
-                          will become the netdev name. Special labels are
-			  "cpu" to indicate a CPU port and "dsa" to
-			  indicate an uplink/downlink port between switches in
-			  the cluster.
 
-A port labelled "dsa" has the following mandatory property:
+An uplink/downlink port between switches in the cluster has the following
+mandatory property:
 
 - link			: Should be a list of phandles to other switch's DSA
 			  port. This port is used as the outgoing port
 			  towards the phandle ports. The full routing
 			  information must be given, not just the one hop
 			  routes to neighbouring switches.
 
-A port labelled "cpu" has the following mandatory property:
+A CPU port has the following mandatory property:
 
 - ethernet		: Should be a phandle to a valid Ethernet device node.
                           This host device is what the switch port is
 			  connected to.
 
+A user port has the following optional property:
+
+- label			: Describes the label associated with this port, which
+                          will become the netdev name.
+
 Port child nodes may also contain the following optional standardised
 properties, described in binding documents:
 
@@ -107,7 +108,6 @@ linked into one DSA cluster.
 
 			switch0port5: port@5 {
 				reg = <5>;
-				label = "dsa";
 				phy-mode = "rgmii-txid";
 				link = <&switch1port6
 					&switch2port9>;
@@ -119,7 +119,6 @@ linked into one DSA cluster.
 
 			port@6 {
 				reg = <6>;
-				label = "cpu";
 				ethernet = <&fec1>;
 				fixed-link {
 					speed = <100>;
@@ -165,7 +164,6 @@ linked into one DSA cluster.
 
 			switch1port5: port@5 {
 				reg = <5>;
-				label = "dsa";
 				link = <&switch2port9>;
 				phy-mode = "rgmii-txid";
 				fixed-link {
@@ -176,7 +174,6 @@ linked into one DSA cluster.
 
 			switch1port6: port@6 {
 				reg = <6>;
-				label = "dsa";
 				phy-mode = "rgmii-txid";
 				link = <&switch0port5>;
 				fixed-link {
@@ -255,7 +252,6 @@ linked into one DSA cluster.
 
 			switch2port9: port@9 {
 				reg = <9>;
-				label = "dsa";
 				phy-mode = "rgmii-txid";
 				link = <&switch1port5
 					&switch0port5>;

net/dsa/dsa2.c

@@ -81,30 +81,12 @@ static void dsa_dst_del_ds(struct dsa_switch_tree *dst,
 
 static bool dsa_port_is_dsa(struct device_node *port)
 {
-	const char *name;
-
-	name = of_get_property(port, "label", NULL);
-	if (!name)
-		return false;
-
-	if (!strcmp(name, "dsa"))
-		return true;
-
-	return false;
+	return !!of_parse_phandle(port, "link", 0);
 }
 
 static bool dsa_port_is_cpu(struct device_node *port)
 {
-	const char *name;
-
-	name = of_get_property(port, "label", NULL);
-	if (!name)
-		return false;
-
-	if (!strcmp(name, "cpu"))
-		return true;
-
-	return false;
+	return !!of_parse_phandle(port, "ethernet", 0);
 }
 
 static bool dsa_ds_find_port(struct dsa_switch *ds,
@@ -268,6 +250,8 @@ static int dsa_user_port_apply(struct device_node *port, u32 index,
 	int err;
 
 	name = of_get_property(port, "label", NULL);
+	if (!name)
+		name = "eth%d";
 
 	err = dsa_slave_create(ds, ds->dev, index, name);
 	if (err) {