1 files changed, 75 insertions, 2 deletions

diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 5030a3c87509..3bf9839f5916 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -214,6 +214,66 @@ void ieee80211_scan_failed(struct ieee80211_local *local)
         local->scan_req = NULL;
 }
 
+/*
+ * inform AP that we will go to sleep so that it will buffer the frames
+ * while we scan
+ */
+static void ieee80211_scan_ps_enable(struct ieee80211_sub_if_data *sdata)
+{
+        struct ieee80211_local *local = sdata->local;
+        bool ps = false;
+
+        /* FIXME: what to do when local->pspolling is true? */
+
+        del_timer_sync(&local->dynamic_ps_timer);
+        cancel_work_sync(&local->dynamic_ps_enable_work);
+
+        if (local->hw.conf.flags & IEEE80211_CONF_PS) {
+                ps = true;
+                local->hw.conf.flags &= ~IEEE80211_CONF_PS;
+                ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
+        }
+
+        if (!ps || !(local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK))
+                /*
+                 * If power save was enabled, no need to send a nullfunc
+                 * frame because AP knows that we are sleeping. But if the
+                 * hardware is creating the nullfunc frame for power save
+                 * status (ie. IEEE80211_HW_PS_NULLFUNC_STACK is not
+                 * enabled) and power save was enabled, the firmware just
+                 * sent a null frame with power save disabled. So we need
+                 * to send a new nullfunc frame to inform the AP that we
+                 * are again sleeping.
+                 */
+                ieee80211_send_nullfunc(local, sdata, 1);
+}
+
+/* inform AP that we are awake again, unless power save is enabled */
+static void ieee80211_scan_ps_disable(struct ieee80211_sub_if_data *sdata)
+{
+        struct ieee80211_local *local = sdata->local;
+
+        if (!local->powersave)
+                ieee80211_send_nullfunc(local, sdata, 0);
+        else {
+                /*
+                 * In !IEEE80211_HW_PS_NULLFUNC_STACK case the hardware
+                 * will send a nullfunc frame with the powersave bit set
+                 * even though the AP already knows that we are sleeping.
+                 * This could be avoided by sending a null frame with power
+                 * save bit disabled before enabling the power save, but
+                 * this doesn't gain anything.
+                 *
+                 * When IEEE80211_HW_PS_NULLFUNC_STACK is enabled, no need
+                 * to send a nullfunc frame because AP already knows that
+                 * we are sleeping, let's just enable power save mode in
+                 * hardware.
+                 */
+                local->hw.conf.flags |= IEEE80211_CONF_PS;
+                ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
+        }
+}
+
 void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
 {
         struct ieee80211_local *local = hw_to_local(hw);
@@ -268,7 +328,7 @@ void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
                 /* Tell AP we're back */
                 if (sdata->vif.type == NL80211_IFTYPE_STATION) {
                         if (sdata->u.mgd.flags & IEEE80211_STA_ASSOCIATED) {
-                                ieee80211_send_nullfunc(local, sdata, 0);
+                                ieee80211_scan_ps_disable(sdata);
                                 netif_tx_wake_all_queues(sdata->dev);
                         }
                 } else
@@ -409,6 +469,19 @@ int ieee80211_start_scan(struct ieee80211_sub_if_data *scan_sdata,
                 return 0;
         }
 
+        /*
+         * Hardware/driver doesn't support hw_scan, so use software
+         * scanning instead. First send a nullfunc frame with power save
+         * bit on so that AP will buffer the frames for us while we are not
+         * listening, then send probe requests to each channel and wait for
+         * the responses. After all channels are scanned, tune back to the
+         * original channel and send a nullfunc frame with power save bit
+         * off to trigger the AP to send us all the buffered frames.
+         *
+         * Note that while local->sw_scanning is true everything else but
+         * nullfunc frames and probe requests will be dropped in
+         * ieee80211_tx_h_check_assoc().
+         */
         local->sw_scanning = true;
         if (local->ops->sw_scan_start)
                 local->ops->sw_scan_start(local_to_hw(local));
@@ -428,7 +501,7 @@ int ieee80211_start_scan(struct ieee80211_sub_if_data *scan_sdata,
                 if (sdata->vif.type == NL80211_IFTYPE_STATION) {
                         if (sdata->u.mgd.flags & IEEE80211_STA_ASSOCIATED) {
                                 netif_tx_stop_all_queues(sdata->dev);
-                                ieee80211_send_nullfunc(local, sdata, 1);
+                                ieee80211_scan_ps_enable(sdata);
                         }
                 } else
                         netif_tx_stop_all_queues(sdata->dev);