mac80211: rename bss_conf timestamp to last_tsf

This value is not really very useful by itself,
yet some drivers (including iwlwifi until I can
figure out what it should do) use it. At least
rename it to "last_tsf" to indicate the meaning
and add a note that it may be really old.

I suspect the value may become useful combined
with the rx_status->mactime, but we don't (yet)
store that value and pass it to the driver.

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

drivers/net/wireless/iwlegacy/common.c

@@ -5355,7 +5355,7 @@ il_mac_bss_info_changed(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	if (changes & BSS_CHANGED_ASSOC) {
 		D_MAC80211("ASSOC %d\n", bss_conf->assoc);
 		if (bss_conf->assoc) {
-			il->timestamp = bss_conf->timestamp;
+			il->timestamp = bss_conf->last_tsf;
 
 			if (!il_is_rfkill(il))
 				il->ops->post_associate(il);

drivers/net/wireless/iwlwifi/iwl-agn-rxon.c

@@ -822,7 +822,7 @@ void iwlagn_bss_info_changed(struct ieee80211_hw *hw,
 
 	if (changes & BSS_CHANGED_ASSOC) {
 		if (bss_conf->assoc) {
-			priv->timestamp = bss_conf->timestamp;
+			priv->timestamp = bss_conf->last_tsf;
 			ctx->staging.filter_flags |= RXON_FILTER_ASSOC_MSK;
 		} else {
 			/*

drivers/net/wireless/rt2x00/rt2x00config.c

@@ -102,7 +102,7 @@ void rt2x00lib_config_erp(struct rt2x00_dev *rt2x00dev,
 
 	/* Update the AID, this is needed for dynamic PS support */
 	rt2x00dev->aid = bss_conf->assoc ? bss_conf->aid : 0;
-	rt2x00dev->last_beacon = bss_conf->timestamp;
+	rt2x00dev->last_beacon = bss_conf->last_tsf;
 
 	/* Update global beacon interval time, this is needed for PS support */
 	rt2x00dev->beacon_int = bss_conf->beacon_int;

include/net/mac80211.h

@@ -229,7 +229,8 @@ enum ieee80211_rssi_event {
  *	valid in station mode only while @assoc is true and if also
  *	requested by %IEEE80211_HW_NEED_DTIM_PERIOD (cf. also hw conf
  *	@ps_dtim_period)
- * @timestamp: beacon timestamp
+ * @last_tsf: last beacon's/probe response's TSF timestamp (could be old
+ *	as it may have been received during scanning long ago)
  * @beacon_int: beacon interval
  * @assoc_capability: capabilities taken from assoc resp
  * @basic_rates: bitmap of basic rates, each bit stands for an
@@ -276,7 +277,7 @@ struct ieee80211_bss_conf {
 	u8 dtim_period;
 	u16 beacon_int;
 	u16 assoc_capability;
-	u64 timestamp;
+	u64 last_tsf;
 	u32 basic_rates;
 	int mcast_rate[IEEE80211_NUM_BANDS];
 	u16 ht_operation_mode;

net/mac80211/driver-trace.h

@@ -296,7 +296,7 @@ TRACE_EVENT(drv_bss_info_changed,
 		__entry->dtimper = info->dtim_period;
 		__entry->bcnint = info->beacon_int;
 		__entry->assoc_cap = info->assoc_capability;
-		__entry->timestamp = info->timestamp;
+		__entry->timestamp = info->last_tsf;
 		__entry->basic_rates = info->basic_rates;
 		__entry->enable_beacon = info->enable_beacon;
 		__entry->ht_operation_mode = info->ht_operation_mode;

net/mac80211/mlme.c

@@ -1318,7 +1318,7 @@ static void ieee80211_set_associated(struct ieee80211_sub_if_data *sdata,
 	bss_info_changed |= BSS_CHANGED_ASSOC;
 	/* set timing information */
 	bss_conf->beacon_int = cbss->beacon_interval;
-	bss_conf->timestamp = cbss->tsf;
+	bss_conf->last_tsf = cbss->tsf;
 
 	bss_info_changed |= BSS_CHANGED_BEACON_INT;
 	bss_info_changed |= ieee80211_handle_bss_capability(sdata,