Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
[linux-2.6.git] / net / mac80211 / scan.c
index 85507bd..1ce4ce8 100644 (file)
@@ -14,6 +14,8 @@
 
 #include <linux/if_arp.h>
 #include <linux/rtnetlink.h>
+#include <linux/pm_qos_params.h>
+#include <net/sch_generic.h>
 #include <linux/slab.h>
 #include <net/mac80211.h>
 
@@ -322,6 +324,7 @@ static int ieee80211_start_sw_scan(struct ieee80211_local *local)
 
        ieee80211_offchannel_stop_beaconing(local);
 
+       local->leave_oper_channel_time = 0;
        local->next_scan_state = SCAN_DECISION;
        local->scan_channel_idx = 0;
 
@@ -426,11 +429,28 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
        return rc;
 }
 
+static unsigned long
+ieee80211_scan_get_channel_time(struct ieee80211_channel *chan)
+{
+       /*
+        * TODO: channel switching also consumes quite some time,
+        * add that delay as well to get a better estimation
+        */
+       if (chan->flags & IEEE80211_CHAN_PASSIVE_SCAN)
+               return IEEE80211_PASSIVE_CHANNEL_TIME;
+       return IEEE80211_PROBE_DELAY + IEEE80211_CHANNEL_TIME;
+}
+
 static int ieee80211_scan_state_decision(struct ieee80211_local *local,
                                         unsigned long *next_delay)
 {
        bool associated = false;
+       bool tx_empty = true;
+       bool bad_latency;
+       bool listen_int_exceeded;
+       unsigned long min_beacon_int = 0;
        struct ieee80211_sub_if_data *sdata;
+       struct ieee80211_channel *next_chan;
 
        /* if no more bands/channels left, complete scan and advance to the idle state */
        if (local->scan_channel_idx >= local->scan_req->n_channels) {
@@ -438,7 +458,11 @@ static int ieee80211_scan_state_decision(struct ieee80211_local *local,
                return 1;
        }
 
-       /* check if at least one STA interface is associated */
+       /*
+        * check if at least one STA interface is associated,
+        * check if at least one STA interface has pending tx frames
+        * and grab the lowest used beacon interval
+        */
        mutex_lock(&local->iflist_mtx);
        list_for_each_entry(sdata, &local->interfaces, list) {
                if (!ieee80211_sdata_running(sdata))
@@ -447,7 +471,16 @@ static int ieee80211_scan_state_decision(struct ieee80211_local *local,
                if (sdata->vif.type == NL80211_IFTYPE_STATION) {
                        if (sdata->u.mgd.associated) {
                                associated = true;
-                               break;
+
+                               if (sdata->vif.bss_conf.beacon_int <
+                                   min_beacon_int || min_beacon_int == 0)
+                                       min_beacon_int =
+                                               sdata->vif.bss_conf.beacon_int;
+
+                               if (!qdisc_all_tx_empty(sdata->dev)) {
+                                       tx_empty = false;
+                                       break;
+                               }
                        }
                }
        }
@@ -456,11 +489,34 @@ static int ieee80211_scan_state_decision(struct ieee80211_local *local,
        if (local->scan_channel) {
                /*
                 * we're currently scanning a different channel, let's
-                * switch back to the operating channel now if at least
-                * one interface is associated. Otherwise just scan the
-                * next channel
+                * see if we can scan another channel without interfering
+                * with the current traffic situation.
+                *
+                * Since we don't know if the AP has pending frames for us
+                * we can only check for our tx queues and use the current
+                * pm_qos requirements for rx. Hence, if no tx traffic occurs
+                * at all we will scan as many channels in a row as the pm_qos
+                * latency allows us to. Additionally we also check for the
+                * currently negotiated listen interval to prevent losing
+                * frames unnecessarily.
+                *
+                * Otherwise switch back to the operating channel.
                 */
-               if (associated)
+               next_chan = local->scan_req->channels[local->scan_channel_idx];
+
+               bad_latency = time_after(jiffies +
+                               ieee80211_scan_get_channel_time(next_chan),
+                               local->leave_oper_channel_time +
+                               usecs_to_jiffies(pm_qos_requirement(PM_QOS_NETWORK_LATENCY)));
+
+               listen_int_exceeded = time_after(jiffies +
+                               ieee80211_scan_get_channel_time(next_chan),
+                               local->leave_oper_channel_time +
+                               usecs_to_jiffies(min_beacon_int * 1024) *
+                               local->hw.conf.listen_interval);
+
+               if (associated && ( !tx_empty || bad_latency ||
+                   listen_int_exceeded))
                        local->next_scan_state = SCAN_ENTER_OPER_CHANNEL;
                else
                        local->next_scan_state = SCAN_SET_CHANNEL;
@@ -492,6 +548,9 @@ static void ieee80211_scan_state_leave_oper_channel(struct ieee80211_local *loca
        else
                *next_delay = HZ / 10;
 
+       /* remember when we left the operating channel */
+       local->leave_oper_channel_time = jiffies;
+
        /* advance to the next channel to be scanned */
        local->next_scan_state = SCAN_SET_CHANNEL;
 }