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>

1 files changed, 6 insertions, 0 deletions

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 0a762a9ba4df..a7472c979c63 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -400,6 +400,12 @@ static void ieee80211_send_assoc(struct ieee80211_sub_if_data *sdata,
 
                 /* determine capability flags */
 
+                if (ieee80211_disable_40mhz_24ghz &&
+                    sband->band == IEEE80211_BAND_2GHZ) {
+                        cap &= ~IEEE80211_HT_CAP_SUP_WIDTH_20_40;
+                        cap &= ~IEEE80211_HT_CAP_SGI_40;
+                }
+
                 switch (ht_info->ht_param & IEEE80211_HT_PARAM_CHA_SEC_OFFSET) {
                 case IEEE80211_HT_PARAM_CHA_SEC_ABOVE:
                         if (flags & IEEE80211_CHAN_NO_HT40PLUS) {