mac80211: allow releasing driver-buffered frames

If there are frames for a station buffered in
the driver, mac80211 announces those in the TIM
IE but there's no way to release them. Add new
API to release such frames and use it when the
station polls for a frame.

Since the API will soon also be used for uAPSD
it is easily extensible.

Note that before this change drivers announcing
driver-buffered frames in the TIM bit actually
will respond to a PS-Poll with a potentially
lower priority frame (if there are any frames
buffered in mac80211), after this patch a driver
that hasn't been changed will no longer respond
at all. This only affects ath9k, which will need
to be fixed to implement the new API.

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

3 files changed, 116 insertions, 16 deletions

diff --git a/net/mac80211/driver-ops.h b/net/mac80211/driver-ops.h
index 4f845c0845ee..8fa0d2edf54c 100644
--- a/net/mac80211/driver-ops.h
+++ b/net/mac80211/driver-ops.h
@@ -670,4 +670,19 @@ static inline void drv_rssi_callback(struct ieee80211_local *local,
                 local->ops->rssi_callback(&local->hw, event);
         trace_drv_return_void(local);
 }
+
+static inline void
+drv_release_buffered_frames(struct ieee80211_local *local,
+                            struct sta_info *sta, u16 tids, int num_frames,
+                            enum ieee80211_frame_release_type reason,
+                            bool more_data)
+{
+        trace_drv_release_buffered_frames(local, &sta->sta, tids, num_frames,
+                                          reason, more_data);
+        if (local->ops->release_buffered_frames)
+                local->ops->release_buffered_frames(&local->hw, &sta->sta, tids,
+                                                    num_frames, reason,
+                                                    more_data);
+        trace_drv_return_void(local);
+}
 #endif /* __MAC80211_DRIVER_OPS */
diff --git a/net/mac80211/driver-trace.h b/net/mac80211/driver-trace.h
index a46b279bbbe4..531fbd086794 100644
--- a/net/mac80211/driver-trace.h
+++ b/net/mac80211/driver-trace.h
@@ -1129,6 +1129,41 @@ TRACE_EVENT(drv_rssi_callback,
         )
 );
 
+TRACE_EVENT(drv_release_buffered_frames,
+        TP_PROTO(struct ieee80211_local *local,
+                 struct ieee80211_sta *sta,
+                 u16 tids, int num_frames,
+                 enum ieee80211_frame_release_type reason,
+                 bool more_data),
+
+        TP_ARGS(local, sta, tids, num_frames, reason, more_data),
+
+        TP_STRUCT__entry(
+                LOCAL_ENTRY
+                STA_ENTRY
+                __field(u16, tids)
+                __field(int, num_frames)
+                __field(int, reason)
+                __field(bool, more_data)
+        ),
+
+        TP_fast_assign(
+                LOCAL_ASSIGN;
+                STA_ASSIGN;
+                __entry->tids = tids;
+                __entry->num_frames = num_frames;
+                __entry->reason = reason;
+                __entry->more_data = more_data;
+        ),
+
+        TP_printk(
+                LOCAL_PR_FMT STA_PR_FMT
+                " TIDs:0x%.4x frames:%d reason:%d more:%d",
+                LOCAL_PR_ARG, STA_PR_ARG, __entry->tids, __entry->num_frames,
+                __entry->reason, __entry->more_data
+        )
+);
+
 /*
  * Tracing for API calls that drivers call.
  */
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 4d85672f0b8f..b3f841948c09 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -1157,8 +1157,10 @@ void ieee80211_sta_ps_deliver_poll_response(struct sta_info *sta)
         struct ieee80211_sub_if_data *sdata = sta->sdata;
         struct ieee80211_local *local = sdata->local;
         struct sk_buff *skb = NULL;
+        bool found = false;
         bool more_data = false;
         int ac;
+        unsigned long driver_release_tids = 0;
         u8 ignore_for_response = sta->sta.uapsd_queues;
 
         /*
@@ -1173,19 +1175,40 @@ void ieee80211_sta_ps_deliver_poll_response(struct sta_info *sta)
          * Get response frame and more data bit for it.
          */
         for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
+                unsigned long tids;
+
                 if (ignore_for_response & BIT(ac))
                         continue;
 
-                if (!skb) {
-                        skb = skb_dequeue(&sta->tx_filtered[ac]);
-                        if (!skb) {
-                                skb = skb_dequeue(&sta->ps_tx_buf[ac]);
+                tids = ieee80211_tids_for_ac(ac);
+
+                if (!found) {
+                        driver_release_tids = sta->driver_buffered_tids & tids;
+                        if (driver_release_tids) {
+                                found = true;
+                        } else {
+                                skb = skb_dequeue(&sta->tx_filtered[ac]);
+                                if (!skb) {
+                                        skb = skb_dequeue(&sta->ps_tx_buf[ac]);
+                                        if (skb)
+                                                local->total_ps_buffered--;
+                                }
                                 if (skb)
-                                        local->total_ps_buffered--;
+                                        found = true;
                         }
-                }
 
-                /* FIXME: take into account driver-buffered frames */
+                        /*
+                         * If the driver has data on more than one TID then
+                         * certainly there's more data if we release just a
+                         * single frame now (from a single TID).
+                         */
+                        if (hweight16(driver_release_tids) > 1) {
+                                more_data = true;
+                                driver_release_tids =
+                                        BIT(ffs(driver_release_tids) - 1);
+                                break;
+                        }
+                }
 
                 if (!skb_queue_empty(&sta->tx_filtered[ac]) ||
                     !skb_queue_empty(&sta->ps_tx_buf[ac])) {
@@ -1194,6 +1217,22 @@ void ieee80211_sta_ps_deliver_poll_response(struct sta_info *sta)
                 }
         }
 
+        if (!found) {
+#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
+                /*
+                 * FIXME: This can be the result of a race condition between
+                 *        us expiring a frame and the station polling for it.
+                 *        Should we send it a null-func frame indicating we
+                 *        have nothing buffered for it?
+                 */
+                printk(KERN_DEBUG "%s: STA %pM sent PS Poll even "
+                       "though there are no buffered frames for it\n",
+                       sdata->name, sta->sta.addr);
+#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
+
+                return;
+        }
+
         if (skb) {
                 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
                 struct ieee80211_hdr *hdr =
@@ -1220,18 +1259,29 @@ void ieee80211_sta_ps_deliver_poll_response(struct sta_info *sta)
                 ieee80211_add_pending_skb(local, skb);
 
                 sta_info_recalc_tim(sta);
-#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
         } else {
                 /*
-                 * FIXME: This can be the result of a race condition between
-                 *        us expiring a frame and the station polling for it.
-                 *        Should we send it a null-func frame indicating we
-                 *        have nothing buffered for it?
+                 * We need to release a frame that is buffered somewhere in the
+                 * driver ... it'll have to handle that.
+                 * Note that, as per the comment above, it'll also have to see
+                 * if there is more than just one frame on the specific TID that
+                 * we're releasing from, and it needs to set the more-data bit
+                 * accordingly if we tell it that there's no more data. If we do
+                 * tell it there's more data, then of course the more-data bit
+                 * needs to be set anyway.
+                 */
+                drv_release_buffered_frames(local, sta, driver_release_tids,
+                                            1, IEEE80211_FRAME_RELEASE_PSPOLL,
+                                            more_data);
+
+                /*
+                 * Note that we don't recalculate the TIM bit here as it would
+                 * most likely have no effect at all unless the driver told us
+                 * that the TID became empty before returning here from the
+                 * release function.
+                 * Either way, however, when the driver tells us that the TID
+                 * became empty we'll do the TIM recalculation.
                  */
-                printk(KERN_DEBUG "%s: STA %pM sent PS Poll even "
-                       "though there are no buffered frames for it\n",
-                       sdata->name, sta->sta.addr);
-#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
         }
 }