1 files changed, 62 insertions, 1 deletions

diff --git a/net/dsa/master.c b/net/dsa/master.c
index c90ee3227dea..71bb15f491c8 100644
--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@@ -158,8 +158,59 @@ static void dsa_master_ethtool_teardown(struct net_device *dev)
 	cpu_dp->orig_ethtool_ops = NULL;
 }
 
+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 *cpu_dp = dev->dsa_ptr;
+
+	return sprintf(buf, "%s\n",
+		       dsa_tag_protocol_to_str(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_master_set_mtu(struct net_device *dev, struct dsa_port *cpu_dp)
+{
+	unsigned int mtu = ETH_DATA_LEN + cpu_dp->tag_ops->overhead;
+	int err;
+
+	rtnl_lock();
+	if (mtu <= dev->max_mtu) {
+		err = dev_set_mtu(dev, mtu);
+		if (err)
+			netdev_dbg(dev, "Unable to set MTU to include for DSA overheads\n");
+	}
+	rtnl_unlock();
+}
+
+static void dsa_master_reset_mtu(struct net_device *dev)
+{
+	int err;
+
+	rtnl_lock();
+	err = dev_set_mtu(dev, ETH_DATA_LEN);
+	if (err)
+		netdev_dbg(dev,
+			   "Unable to reset MTU to exclude DSA overheads\n");
+	rtnl_unlock();
+}
+
 int dsa_master_setup(struct net_device *dev, struct dsa_port *cpu_dp)
 {
+	int ret;
+
+	dsa_master_set_mtu(dev,  cpu_dp);
+
 	/* If we use a tagging format that doesn't have an ethertype
 	 * field, make sure that all packets from this point on get
 	 * sent to the tag format's receive function.
@@ -168,12 +219,22 @@ int dsa_master_setup(struct net_device *dev, struct dsa_port *cpu_dp)
 
 	dev->dsa_ptr = cpu_dp;
 
-	return dsa_master_ethtool_setup(dev);
+	ret = dsa_master_ethtool_setup(dev);
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_group(&dev->dev.kobj, &dsa_group);
+	if (ret)
+		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_ethtool_teardown(dev);
+	dsa_master_reset_mtu(dev);
 
 	dev->dsa_ptr = NULL;