mac80211: Allow work items to use existing channel type.

Narrow channel types can function within larger channel types.
So, use existing channel type for work items when possible.
This decreases hardware channel changes significantly when
using non NO_HT channel types on the operating channel.
Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/work.c

@@ -874,6 +874,44 @@ static void ieee80211_work_rx_queued_mgmt(struct ieee80211_local *local,
 	kfree_skb(skb);
 }
 
+static bool ieee80211_work_ct_coexists(enum nl80211_channel_type wk_ct,
+				       enum nl80211_channel_type oper_ct)
+{
+	switch (wk_ct) {
+	case NL80211_CHAN_NO_HT:
+		return true;
+	case NL80211_CHAN_HT20:
+		if (oper_ct != NL80211_CHAN_NO_HT)
+			return true;
+		return false;
+	case NL80211_CHAN_HT40MINUS:
+	case NL80211_CHAN_HT40PLUS:
+		return (wk_ct == oper_ct);
+	}
+	WARN_ON(1); /* shouldn't get here */
+	return false;
+}
+
+static enum nl80211_channel_type
+ieee80211_calc_ct(enum nl80211_channel_type wk_ct,
+		  enum nl80211_channel_type oper_ct)
+{
+	switch (wk_ct) {
+	case NL80211_CHAN_NO_HT:
+		return oper_ct;
+	case NL80211_CHAN_HT20:
+		if (oper_ct != NL80211_CHAN_NO_HT)
+			return oper_ct;
+		return wk_ct;
+	case NL80211_CHAN_HT40MINUS:
+	case NL80211_CHAN_HT40PLUS:
+		return wk_ct;
+	}
+	WARN_ON(1); /* shouldn't get here */
+	return wk_ct;
+}
+
+
 static void ieee80211_work_timer(unsigned long data)
 {
 	struct ieee80211_local *local = (void *) data;
@@ -927,14 +965,22 @@ static void ieee80211_work_work(struct work_struct *work)
 			bool on_oper_chan;
 			bool tmp_chan_changed = false;
 			bool on_oper_chan2;
+			enum nl80211_channel_type wk_ct;
 			on_oper_chan = ieee80211_cfg_on_oper_channel(local);
+
+			/* Work with existing channel type if possible. */
+			wk_ct = wk->chan_type;
+			if (wk->chan == local->hw.conf.channel)
+				wk_ct = ieee80211_calc_ct(wk->chan_type,
+						local->hw.conf.channel_type);
+
 			if (local->tmp_channel)
 				if ((local->tmp_channel != wk->chan) ||
-				    (local->tmp_channel_type != wk->chan_type))
+				    (local->tmp_channel_type != wk_ct))
 					tmp_chan_changed = true;
 
 			local->tmp_channel = wk->chan;
-			local->tmp_channel_type = wk->chan_type;
+			local->tmp_channel_type = wk_ct;
 			/*
 			 * Leave the station vifs in awake mode if they
 			 * happen to be on the same channel as
@@ -1031,7 +1077,8 @@ static void ieee80211_work_work(struct work_struct *work)
 			continue;
 		if (wk->chan != local->tmp_channel)
 			continue;
-		if (wk->chan_type != local->tmp_channel_type)
+		if (ieee80211_work_ct_coexists(wk->chan_type,
+					       local->tmp_channel_type))
 			continue;
 		remain_off_channel = true;
 	}