6lowpan: add lowpan_is_ll function

This patch adds the lowpan_is_ll function, which can be used to make a
special 6lowpan linklayer handling for a specific 6lowpan linklayer
type.
Signed-off-by: Alexander Aring <aar@pengutronix.de>
Reviewed-by: Stefan Schmidt<stefan@osg.samsung.com>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/6lowpan/6lowpan_i.h

@@ -3,6 +3,15 @@
 
 #include <linux/netdevice.h>
 
+#include <net/6lowpan.h>
+
+/* caller need to be sure it's dev->type is ARPHRD_6LOWPAN */
+static inline bool lowpan_is_ll(const struct net_device *dev,
+				enum lowpan_lltypes lltype)
+{
+	return lowpan_dev(dev)->lltype == lltype;
+}
+
 #ifdef CONFIG_6LOWPAN_DEBUGFS
 int lowpan_dev_debugfs_init(struct net_device *dev);
 void lowpan_dev_debugfs_exit(struct net_device *dev);