ieee802154: add support for listen-before-talk in wpan_phy

Listen-before-talk is an alternative to CSMA in uncoordinated networks
and prescribed by european regulations if one wants to have a device
with radio duty cycles above 10% (or less in some bands). Add a phy
property to enable/disable LBT in the phy, including support in the
at86rf230 driver for RF212 chips.

Signed-off-by: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/mac802154.h b/include/net/mac802154.h
index 8bd2785..521edcb 100644
--- a/include/net/mac802154.h
+++ b/include/net/mac802154.h
@@ -117,6 +117,11 @@
  * set_txpower:
  *	  Set radio transmit power in dB. Called with pib_lock held.
  *	  Returns either zero, or negative errno.
+ *
+ * set_lbt
+ *	  Enables or disables listen before talk on the device. Called with
+ *	  pib_lock held.
+ *	  Returns either zero, or negative errno.
  */
 struct ieee802154_ops {
 	struct module	*owner;
@@ -134,6 +139,7 @@
 	int		(*ieee_addr)(struct ieee802154_dev *dev,
 				     u8 addr[IEEE802154_ADDR_LEN]);
 	int		(*set_txpower)(struct ieee802154_dev *dev, int db);
+	int		(*set_lbt)(struct ieee802154_dev *dev, bool on);
 };
 
 /* Basic interface to register ieee802154 device */