net: dsa: Add ndo_get_phys_port_name() for CPU port

There is not currently way to infer the port number through sysfs that
is being used as the CPU port number. Overlay a ndo_get_phys_port_name()
operation onto the DSA master network device in order to retrieve that
information.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -208,6 +208,11 @@ struct dsa_port {
 	 * Original copy of the master netdev ethtool_ops
 	 */
 	const struct ethtool_ops *orig_ethtool_ops;
+
+	/*
+	 * Original copy of the master netdev net_device_ops
+	 */
+	const struct net_device_ops *orig_ndo_ops;
 };
 
 struct dsa_switch {

net/dsa/master.c

@@ -126,6 +126,17 @@ static void dsa_master_get_strings(struct net_device *dev, uint32_t stringset,
 	}
 }
 
+static int dsa_master_get_phys_port_name(struct net_device *dev,
+					 char *name, size_t len)
+{
+	struct dsa_port *cpu_dp = dev->dsa_ptr;
+
+	if (snprintf(name, len, "p%d", cpu_dp->index) >= len)
+		return -EINVAL;
+
+	return 0;
+}
+
 static int dsa_master_ethtool_setup(struct net_device *dev)
 {
 	struct dsa_port *cpu_dp = dev->dsa_ptr;
@@ -158,6 +169,38 @@ static void dsa_master_ethtool_teardown(struct net_device *dev)
 	cpu_dp->orig_ethtool_ops = NULL;
 }
 
+static int dsa_master_ndo_setup(struct net_device *dev)
+{
+	struct dsa_port *cpu_dp = dev->dsa_ptr;
+	struct dsa_switch *ds = cpu_dp->ds;
+	struct net_device_ops *ops;
+
+	if (dev->netdev_ops->ndo_get_phys_port_name)
+		return 0;
+
+	ops = devm_kzalloc(ds->dev, sizeof(*ops), GFP_KERNEL);
+	if (!ops)
+		return -ENOMEM;
+
+	cpu_dp->orig_ndo_ops = dev->netdev_ops;
+	if (cpu_dp->orig_ndo_ops)
+		memcpy(ops, cpu_dp->orig_ndo_ops, sizeof(*ops));
+
+	ops->ndo_get_phys_port_name = dsa_master_get_phys_port_name;
+
+	dev->netdev_ops  = ops;
+
+	return 0;
+}
+
+static void dsa_master_ndo_teardown(struct net_device *dev)
+{
+	struct dsa_port *cpu_dp = dev->dsa_ptr;
+
+	dev->netdev_ops = cpu_dp->orig_ndo_ops;
+	cpu_dp->orig_ndo_ops = NULL;
+}
+
 static ssize_t tagging_show(struct device *d, struct device_attribute *attr,
 			    char *buf)
 {
@@ -223,16 +266,27 @@ int dsa_master_setup(struct net_device *dev, struct dsa_port *cpu_dp)
 	if (ret)
 		return ret;
 
+	ret = dsa_master_ndo_setup(dev);
+	if (ret)
+		goto out_err_ethtool_teardown;
+
 	ret = sysfs_create_group(&dev->dev.kobj, &dsa_group);
 	if (ret)
-		dsa_master_ethtool_teardown(dev);
+		goto out_err_ndo_teardown;
+
+	return ret;
 
+out_err_ndo_teardown:
+	dsa_master_ndo_teardown(dev);
+out_err_ethtool_teardown:
+	dsa_master_ethtool_teardown(dev);
 	return ret;
 }
 
 void dsa_master_teardown(struct net_device *dev)
 {
 	sysfs_remove_group(&dev->dev.kobj, &dsa_group);
+	dsa_master_ndo_teardown(dev);
 	dsa_master_ethtool_teardown(dev);
 	dsa_master_reset_mtu(dev);