mac80211: introduce flush operation

We've long lacked a good confirmation that frames
have really gone out, e.g. before going off-channel
for a scan. Add a flush() operation that drivers
can implement to provide that confirmation, and use
it in a few places:
 * before scanning sends the nullfunc frames
 * after scanning sends the nullfunc frames, if any
 * when going idle, to send any pending frames

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

4 files changed, 41 insertions, 2 deletions

diff --git a/net/mac80211/driver-ops.h b/net/mac80211/driver-ops.h
index 727e4cf..cbe133b 100644
--- a/net/mac80211/driver-ops.h
+++ b/net/mac80211/driver-ops.h
@@ -259,4 +259,11 @@ static inline void drv_rfkill_poll(struct ieee80211_local *local)
 	if (local->ops->rfkill_poll)
 		local->ops->rfkill_poll(&local->hw);
 }
+
+static inline void drv_flush(struct ieee80211_local *local, bool drop)
+{
+	trace_drv_flush(local, drop);
+	if (local->ops->flush)
+		local->ops->flush(&local->hw, drop);
+}
 #endif /* __MAC80211_DRIVER_OPS */
diff --git a/net/mac80211/driver-trace.h b/net/mac80211/driver-trace.h
index 7a849b9..977cc75 100644
--- a/net/mac80211/driver-trace.h
+++ b/net/mac80211/driver-trace.h
@@ -690,6 +690,27 @@ TRACE_EVENT(drv_ampdu_action,
 		LOCAL_PR_ARG, VIF_PR_ARG, STA_PR_ARG, __entry->action, __entry->tid, __entry->ret
 	)
 );
+
+TRACE_EVENT(drv_flush,
+	TP_PROTO(struct ieee80211_local *local, bool drop),
+
+	TP_ARGS(local, drop),
+
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(bool, drop)
+	),
+
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->drop = drop;
+	),
+
+	TP_printk(
+		LOCAL_PR_FMT " drop:%d",
+		LOCAL_PR_ARG, __entry->drop
+	)
+);
 #endif /* !__MAC80211_DRIVER_TRACE || TRACE_HEADER_MULTI_READ */
 
 #undef TRACE_INCLUDE_PATH
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 1ceca14..389dc8d 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -917,6 +917,8 @@ static u32 ieee80211_idle_on(struct ieee80211_local *local)
 	       wiphy_name(local->hw.wiphy));
 #endif
 
+	drv_flush(local, false);
+
 	local->hw.conf.flags |= IEEE80211_CONF_IDLE;
 	return IEEE80211_CONF_CHANGE_IDLE;
 }
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index ae18300..d98c45e 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -418,9 +418,10 @@ static int ieee80211_start_sw_scan(struct ieee80211_local *local)
 	local->next_scan_state = SCAN_DECISION;
 	local->scan_channel_idx = 0;
 
+	drv_flush(local, false);
+
 	ieee80211_configure_filter(local);
 
-	/* TODO: start scan as soon as all nullfunc frames are ACKed */
 	ieee80211_queue_delayed_work(&local->hw,
 				     &local->scan_work,
 				     IEEE80211_CHANNEL_TIME);
@@ -584,8 +585,16 @@ static void ieee80211_scan_state_leave_oper_channel(struct ieee80211_local *loca
 
 	__set_bit(SCAN_OFF_CHANNEL, &local->scanning);
 
+	/*
+	 * What if the nullfunc frames didn't arrive?
+	 */
+	drv_flush(local, false);
+	if (local->ops->flush)
+		*next_delay = 0;
+	else
+		*next_delay = HZ / 10;
+
 	/* advance to the next channel to be scanned */
-	*next_delay = HZ / 10;
 	local->next_scan_state = SCAN_SET_CHANNEL;
 }