mac80211: revamp beacon configuration

This patch changes mac80211's beacon configuration handling
to never pass skbs to the driver directly but rather always
require the driver to use ieee80211_beacon_get(). Additionally,
it introduces "change flags" on the config_interface() call
to enable drivers to figure out what is changing. Finally, it
removes the beacon_update() driver callback in favour of
having IBSS beacon delivered by ieee80211_beacon_get() as well.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath5k/base.c b/drivers/net/wireless/ath5k/base.c
index a43e9b2..217d506 100644
--- a/drivers/net/wireless/ath5k/base.c
+++ b/drivers/net/wireless/ath5k/base.c
@@ -207,7 +207,6 @@
 	.get_tx_stats 	= ath5k_get_tx_stats,
 	.get_tsf 	= ath5k_get_tsf,
 	.reset_tsf 	= ath5k_reset_tsf,
-	.beacon_update 	= ath5k_beacon_update,
 };
 
 /*
@@ -2785,6 +2784,18 @@
 		 * a clean way of letting us retrieve this yet. */
 		ath5k_hw_set_associd(ah, ah->ah_bssid, 0);
 	}
+
+	if (conf->changed & IEEE80211_IFCC_BEACON &&
+	    vif->type == IEEE80211_IF_TYPE_IBSS) {
+		struct sk_buff *beacon = ieee80211_beacon_get(hw, vif);
+		if (!beacon) {
+			ret = -ENOMEM;
+			goto unlock;
+		}
+		/* call old handler for now */
+		ath5k_beacon_update(hw, beacon);
+	}
+
 	mutex_unlock(&sc->lock);
 
 	return ath5k_reset(hw);