mac80211: Support ht-cap over-rides.

This implements ht-cap over-rides for mac80211 drivers.
HT may be disabled, making an /a/b/g/n station act like an
a/b/g station.  HT40 may be disabled forcing the station to
be HT20 even if the AP and local hardware support HT40.

MAX-AMSDU may be disabled.
AMPDU-Density may be increased.
AMPDU-Factor may be decreased.

This has been successfully tested with ath9k using patched
wpa_supplicant and iw.

Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 82 insertions, 1 deletions

diff --git a/net/mac80211/ht.c b/net/mac80211/ht.c
index 988c7ec0898c..7e0ac9791fd6 100644
--- a/net/mac80211/ht.c
+++ b/net/mac80211/ht.c
@@ -18,7 +18,82 @@
 #include "ieee80211_i.h"
 #include "rate.h"
 
-void ieee80211_ht_cap_ie_to_sta_ht_cap(struct ieee80211_supported_band *sband,
+bool ieee80111_cfg_override_disables_ht40(struct ieee80211_sub_if_data *sdata)
+{
+        const __le16 flg = cpu_to_le16(IEEE80211_HT_CAP_SUP_WIDTH_20_40);
+        if ((sdata->u.mgd.ht_capa_mask.cap_info & flg) &&
+            !(sdata->u.mgd.ht_capa.cap_info & flg))
+                return true;
+        return false;
+}
+
+void __check_htcap_disable(struct ieee80211_sub_if_data *sdata,
+                           struct ieee80211_sta_ht_cap *ht_cap,
+                           u16 flag)
+{
+        __le16 le_flag = cpu_to_le16(flag);
+        if (sdata->u.mgd.ht_capa_mask.cap_info & le_flag) {
+                if (!(sdata->u.mgd.ht_capa.cap_info & le_flag))
+                        ht_cap->cap &= ~flag;
+        }
+}
+
+void ieee80211_apply_htcap_overrides(struct ieee80211_sub_if_data *sdata,
+                                     struct ieee80211_sta_ht_cap *ht_cap)
+{
+        u8 *scaps = (u8 *)(&sdata->u.mgd.ht_capa.mcs.rx_mask);
+        u8 *smask = (u8 *)(&sdata->u.mgd.ht_capa_mask.mcs.rx_mask);
+        int i;
+
+        if (sdata->vif.type != NL80211_IFTYPE_STATION) {
+                WARN_ON_ONCE(sdata->vif.type != NL80211_IFTYPE_STATION);
+                return;
+        }
+
+        /* NOTE:  If you add more over-rides here, update register_hw
+         * ht_capa_mod_msk logic in main.c as well.
+         * And, if this method can ever change ht_cap.ht_supported, fix
+         * the check in ieee80211_add_ht_ie.
+         */
+
+        /* check for HT over-rides, MCS rates first. */
+        for (i = 0; i < IEEE80211_HT_MCS_MASK_LEN; i++) {
+                u8 m = smask[i];
+                ht_cap->mcs.rx_mask[i] &= ~m; /* turn off all masked bits */
+                /* Add back rates that are supported */
+                ht_cap->mcs.rx_mask[i] |= (m & scaps[i]);
+        }
+
+        /* Force removal of HT-40 capabilities? */
+        __check_htcap_disable(sdata, ht_cap, IEEE80211_HT_CAP_SUP_WIDTH_20_40);
+        __check_htcap_disable(sdata, ht_cap, IEEE80211_HT_CAP_SGI_40);
+
+        /* Allow user to disable the max-AMSDU bit. */
+        __check_htcap_disable(sdata, ht_cap, IEEE80211_HT_CAP_MAX_AMSDU);
+
+        /* Allow user to decrease AMPDU factor */
+        if (sdata->u.mgd.ht_capa_mask.ampdu_params_info &
+            IEEE80211_HT_AMPDU_PARM_FACTOR) {
+                u8 n = sdata->u.mgd.ht_capa.ampdu_params_info
+                        & IEEE80211_HT_AMPDU_PARM_FACTOR;
+                if (n < ht_cap->ampdu_factor)
+                        ht_cap->ampdu_factor = n;
+        }
+
+        /* Allow the user to increase AMPDU density. */
+        if (sdata->u.mgd.ht_capa_mask.ampdu_params_info &
+            IEEE80211_HT_AMPDU_PARM_DENSITY) {
+                u8 n = (sdata->u.mgd.ht_capa.ampdu_params_info &
+                        IEEE80211_HT_AMPDU_PARM_DENSITY)
+                        >> IEEE80211_HT_AMPDU_PARM_DENSITY_SHIFT;
+                if (n > ht_cap->ampdu_density)
+                        ht_cap->ampdu_density = n;
+        }
+}
+
+
+void ieee80211_ht_cap_ie_to_sta_ht_cap(struct ieee80211_sub_if_data *sdata,
+                                       struct ieee80211_supported_band *sband,
                                        struct ieee80211_ht_cap *ht_cap_ie,
                                        struct ieee80211_sta_ht_cap *ht_cap)
 {
@@ -102,6 +177,12 @@ void ieee80211_ht_cap_ie_to_sta_ht_cap(struct ieee80211_supported_band *sband,
         /* handle MCS rate 32 too */
         if (sband->ht_cap.mcs.rx_mask[32/8] & ht_cap_ie->mcs.rx_mask[32/8] & 1)
                 ht_cap->mcs.rx_mask[32/8] |= 1;
+
+        /*
+         * If user has specified capability over-rides, take care
+         * of that here.
+         */
+        ieee80211_apply_htcap_overrides(sdata, ht_cap);
 }
 
 void ieee80211_sta_tear_down_BA_sessions(struct sta_info *sta, bool tx)