mac80211: implement packet loss notification

For drivers that have accurate TX status reporting
we can report the number of consecutive lost packets
to userspace using the new cfg80211 CQM event. The
threshold is fixed right now, this may need to be
improved in the future.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/sta_info.h

@@ -248,6 +248,7 @@ enum plink_state {
  * @sta: station information we share with the driver
  * @dead: set to true when sta is unlinked
  * @uploaded: set to true when sta is uploaded to the driver
+ * @lost_packets: number of consecutive lost packets
  */
 struct sta_info {
 	/* General information, mostly static */
@@ -335,6 +336,8 @@ struct sta_info {
 	} debugfs;
 #endif
 
+	unsigned int lost_packets;
+
 	/* keep last! */
 	struct ieee80211_sta sta;
 };