net: dsa: Expose tagging protocol to user-space

There is no way for user-space to know what a given DSA network device's
tagging protocol is. Expose this information through a dsa/tagging
attribute which reflects the tagging protocol currently in use.

This is helpful for configuration (e.g: none behaves dramatically
different wrt. bridges) as well as for packet capture tools when there
is not a proper Ethernet type available.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 28 insertions, 0 deletions

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 1c45c1d6d241..3f840b6eea69 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1058,6 +1058,27 @@ static struct device_type dsa_type = {
 	.name	= "dsa",
 };
 
+static ssize_t tagging_show(struct device *d, struct device_attribute *attr,
+			    char *buf)
+{
+	struct net_device *dev = to_net_dev(d);
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+
+	return sprintf(buf, "%s\n",
+		       dsa_tag_protocol_to_str(dp->cpu_dp->tag_ops));
+}
+static DEVICE_ATTR_RO(tagging);
+
+static struct attribute *dsa_slave_attrs[] = {
+	&dev_attr_tagging.attr,
+	NULL
+};
+
+static const struct attribute_group dsa_group = {
+	.name	= "dsa",
+	.attrs	= dsa_slave_attrs,
+};
+
 static void dsa_slave_phylink_validate(struct net_device *dev,
 				       unsigned long *supported,
 				       struct phylink_link_state *state)
@@ -1353,8 +1374,14 @@ int dsa_slave_create(struct dsa_port *port)
 		goto out_phy;
 	}
 
+	ret = sysfs_create_group(&slave_dev->dev.kobj, &dsa_group);
+	if (ret)
+		goto out_unreg;
+
 	return 0;
 
+out_unreg:
+	unregister_netdev(slave_dev);
 out_phy:
 	rtnl_lock();
 	phylink_disconnect_phy(p->dp->pl);
@@ -1378,6 +1405,7 @@ void dsa_slave_destroy(struct net_device *slave_dev)
 	rtnl_unlock();
 
 	dsa_slave_notify(slave_dev, DSA_PORT_UNREGISTER);
+	sysfs_remove_group(&slave_dev->dev.kobj, &dsa_group);
 	unregister_netdev(slave_dev);
 	phylink_destroy(dp->pl);
 	free_percpu(p->stats64);