mac80211: allow disabling 40MHz on 2.4GHz

In some situations it is required that a system be
configured with no support for 40 MHz channels in
the 2.4 GHz band. Rather than imposing any such
restrictions on everybody, allow configuration a
system like that with a module parameter. It is
writable at runtime but only takes effect at the
time of the next association.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index e1293e8..25f5209 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -33,6 +33,12 @@
 #include "cfg.h"
 #include "debugfs.h"
 
+
+bool ieee80211_disable_40mhz_24ghz;
+module_param(ieee80211_disable_40mhz_24ghz, bool, 0644);
+MODULE_PARM_DESC(ieee80211_disable_40mhz_24ghz,
+		 "Disable 40MHz support in the 2.4GHz band");
+
 void ieee80211_configure_filter(struct ieee80211_local *local)
 {
 	u64 mc;