mac80211: improve HT channel handling

Currently, when one interface switches HT mode,
all others will follow along. This is clearly
undesirable, since the new one might switch to
no-HT while another one is operating in HT.

Address this issue by keeping track of the HT
mode per interface, and allowing only changes
that are compatible, i.e. switching into HT40+
is not possible when another interface is in
HT40-, in that case the second one needs to
fall back to HT20.

Also, to allow drivers to know what's going on,
store the per-interface HT mode (channel type)
in the virtual interface's bss_conf.

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

1 files changed, 70 insertions, 0 deletions

diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
index 08f3832..5d218c5 100644
--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -2,6 +2,7 @@
  * mac80211 - channel management
  */
 
+#include <linux/nl80211.h>
 #include "ieee80211_i.h"
 
 enum ieee80211_chan_mode
@@ -55,3 +56,72 @@ ieee80211_get_channel_mode(struct ieee80211_local *local,
 
 	return mode;
 }
+
+bool ieee80211_set_channel_type(struct ieee80211_local *local,
+				struct ieee80211_sub_if_data *sdata,
+				enum nl80211_channel_type chantype)
+{
+	struct ieee80211_sub_if_data *tmp;
+	enum nl80211_channel_type superchan = NL80211_CHAN_NO_HT;
+	bool result;
+
+	mutex_lock(&local->iflist_mtx);
+
+	list_for_each_entry(tmp, &local->interfaces, list) {
+		if (tmp == sdata)
+			continue;
+
+		if (!ieee80211_sdata_running(tmp))
+			continue;
+
+		switch (tmp->vif.bss_conf.channel_type) {
+		case NL80211_CHAN_NO_HT:
+		case NL80211_CHAN_HT20:
+			superchan = tmp->vif.bss_conf.channel_type;
+			break;
+		case NL80211_CHAN_HT40PLUS:
+			WARN_ON(superchan == NL80211_CHAN_HT40MINUS);
+			superchan = NL80211_CHAN_HT40PLUS;
+			break;
+		case NL80211_CHAN_HT40MINUS:
+			WARN_ON(superchan == NL80211_CHAN_HT40PLUS);
+			superchan = NL80211_CHAN_HT40MINUS;
+			break;
+		}
+	}
+
+	switch (superchan) {
+	case NL80211_CHAN_NO_HT:
+	case NL80211_CHAN_HT20:
+		/*
+		 * allow any change that doesn't go to no-HT
+		 * (if it already is no-HT no change is needed)
+		 */
+		if (chantype == NL80211_CHAN_NO_HT)
+			break;
+		superchan = chantype;
+		break;
+	case NL80211_CHAN_HT40PLUS:
+	case NL80211_CHAN_HT40MINUS:
+		/* allow smaller bandwidth and same */
+		if (chantype == NL80211_CHAN_NO_HT)
+			break;
+		if (chantype == NL80211_CHAN_HT20)
+			break;
+		if (superchan == chantype)
+			break;
+		result = false;
+		goto out;
+	}
+
+	local->_oper_channel_type = superchan;
+
+	if (sdata)
+		sdata->vif.bss_conf.channel_type = chantype;
+
+	result = true;
+ out:
+	mutex_unlock(&local->iflist_mtx);
+
+	return result;
+}