mac80211: sample survey implementation for mac80211 & hwsim

This adds the survey function to both mac80211 itself and to mac80211_hwsim.
For the latter driver, we simply invent some noise level.A real driver which
cannot determine the real channel noise MUST NOT report any noise, especially
not a magically conjured one :-)

Signed-off-by: Holger Schurig <holgerschurig@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 4edd73c..f97dda7 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -410,6 +410,17 @@
 	return ret;
 }
 
+static int ieee80211_dump_survey(struct wiphy *wiphy, struct net_device *dev,
+				 int idx, struct survey_info *survey)
+{
+	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
+
+	if (!local->ops->get_survey)
+		return -EOPNOTSUPP;
+
+	return drv_get_survey(local, idx, survey);
+}
+
 static int ieee80211_get_station(struct wiphy *wiphy, struct net_device *dev,
 				 u8 *mac, struct station_info *sinfo)
 {
@@ -1507,6 +1518,7 @@
 	.change_station = ieee80211_change_station,
 	.get_station = ieee80211_get_station,
 	.dump_station = ieee80211_dump_station,
+	.dump_survey = ieee80211_dump_survey,
 #ifdef CONFIG_MAC80211_MESH
 	.add_mpath = ieee80211_add_mpath,
 	.del_mpath = ieee80211_del_mpath,