6lowpan: add support for getting short address

In case of sending RA messages we need some way to get the short address
from an 802.15.4 6LoWPAN interface. This patch will add a temporary
debugfs entry for experimental userspace api.
Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Alexander Aring <aar@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/6lowpan/debugfs.c

@@ -245,6 +245,41 @@ static const struct file_operations lowpan_context_fops = {
 	.release	= single_release,
 };
 
+static int lowpan_short_addr_get(void *data, u64 *val)
+{
+	struct wpan_dev *wdev = data;
+
+	rtnl_lock();
+	*val = le16_to_cpu(wdev->short_addr);
+	rtnl_unlock();
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(lowpan_short_addr_fops, lowpan_short_addr_get,
+			NULL, "0x%04llx\n");
+
+static int lowpan_dev_debugfs_802154_init(const struct net_device *dev,
+					  struct lowpan_dev *ldev)
+{
+	struct dentry *dentry, *root;
+
+	if (!lowpan_is_ll(dev, LOWPAN_LLTYPE_IEEE802154))
+		return 0;
+
+	root = debugfs_create_dir("ieee802154", ldev->iface_debugfs);
+	if (!root)
+		return -EINVAL;
+
+	dentry = debugfs_create_file("short_addr", 0444, root,
+				     lowpan_802154_dev(dev)->wdev->ieee802154_ptr,
+				     &lowpan_short_addr_fops);
+	if (!dentry)
+		return -EINVAL;
+
+	return 0;
+}
+
 int lowpan_dev_debugfs_init(struct net_device *dev)
 {
 	struct lowpan_dev *ldev = lowpan_dev(dev);
@@ -272,6 +307,10 @@ int lowpan_dev_debugfs_init(struct net_device *dev)
 			goto remove_root;
 	}
 
+	ret = lowpan_dev_debugfs_802154_init(dev, ldev);
+	if (ret < 0)
+		goto remove_root;
+
 	return 0;
 
 remove_root: