mac80211: Handle power constraint level advertised in 11d+h beacon

This patch uses power constraint level while determining the maximum
transmit power, there by it makes sure that any power mitigation
requirement for the channel in the current regulatory domain is met.
Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/ieee80211_i.h

@@ -715,6 +715,7 @@ struct ieee80211_local {
 	struct timer_list dynamic_ps_timer;
 
 	int user_power_level; /* in dBm */
+	int power_constr_level; /* in dBm */
 
 #ifdef CONFIG_MAC80211_DEBUGFS
 	struct local_debugfsdentries {
@@ -985,6 +986,9 @@ void ieee80211_chswitch_work(struct work_struct *work);
 void ieee80211_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 				  struct ieee80211_channel_sw_ie *sw_elem,
 				  struct ieee80211_bss *bss);
+void ieee80211_handle_pwr_constr(struct ieee80211_sub_if_data *sdata,
+				 u16 capab_info, u8 *pwr_constr_elem,
+				 u8 pwr_constr_elem_len);
 
 /* utility functions/constants */
 extern void *mac80211_wiphy_privid; /* for wiphy privid */

net/mac80211/main.c

@@ -214,10 +214,16 @@ int ieee80211_hw_config(struct ieee80211_local *local, u32 changed)
 		changed |= IEEE80211_CONF_CHANGE_CHANNEL;
 	}
 
-	if (!local->user_power_level)
+	if (local->sw_scanning)
 		power = chan->max_power;
 	else
-		power = min(chan->max_power, local->user_power_level);
+		power = local->power_constr_level ?
+			(chan->max_power - local->power_constr_level) :
+			chan->max_power;
+
+	if (local->user_power_level)
+		power = min(power, local->user_power_level);
+
 	if (local->hw.conf.power_level != power) {
 		changed |= IEEE80211_CONF_CHANGE_POWER;
 		local->hw.conf.power_level = power;

net/mac80211/mlme.c

@@ -905,6 +905,8 @@ static void ieee80211_set_disassoc(struct ieee80211_sub_if_data *sdata,
 	/* channel(_type) changes are handled by ieee80211_hw_config */
 	local->oper_channel_type = NL80211_CHAN_NO_HT;
 
+	local->power_constr_level = 0;
+
 	del_timer_sync(&local->dynamic_ps_timer);
 	cancel_work_sync(&local->dynamic_ps_enable_work);
 
@@ -1849,6 +1851,13 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 		 * for the BSSID we are associated to */
 		regulatory_hint_11d(local->hw.wiphy,
 			elems.country_elem, elems.country_elem_len);
+
+		/* TODO: IBSS also needs this */
+		if (elems.pwr_constr_elem)
+			ieee80211_handle_pwr_constr(sdata,
+				le16_to_cpu(mgmt->u.probe_resp.capab_info),
+				elems.pwr_constr_elem,
+				elems.pwr_constr_elem_len);
 	}
 
 	ieee80211_bss_info_change_notify(sdata, changed);

net/mac80211/spectmgmt.c

@@ -161,3 +161,24 @@ void ieee80211_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 			  jiffies + msecs_to_jiffies(sw_elem->count * bss->beacon_int));
 	}
 }
+
+void ieee80211_handle_pwr_constr(struct ieee80211_sub_if_data *sdata,
+				 u16 capab_info, u8 *pwr_constr_elem,
+				 u8 pwr_constr_elem_len)
+{
+	struct ieee80211_conf *conf = &sdata->local->hw.conf;
+
+	if (!(capab_info & WLAN_CAPABILITY_SPECTRUM_MGMT))
+		return;
+
+	/* Power constraint IE length should be 1 octet */
+	if (pwr_constr_elem_len != 1)
+		return;
+
+	if ((*pwr_constr_elem <= conf->channel->max_power) &&
+	    (*pwr_constr_elem != sdata->local->power_constr_level)) {
+		sdata->local->power_constr_level = *pwr_constr_elem;
+		ieee80211_hw_config(sdata->local, 0);
+	}
+}
+