mac80211: add cancel_hw_scan() callback

When suspending, __ieee80211_suspend() calls ieee80211_scan_cancel(),
which will only cancel sw scan. In order to cancel hw scan, the
low-level driver has to cancel it in the suspend() callback. however,
this is too late, as a new scan_work will be enqueued (while the driver
is going into suspend).

Add a new cancel_hw_scan() callback, asking the driver to cancel an
active hw scan, and call it in ieee80211_scan_cancel().
Signed-off-by: Eliad Peller <eliad@wizery.com>
Reviewed-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/mac80211.h

@@ -1708,6 +1708,14 @@ enum ieee80211_ampdu_mlme_action {
  *	any error unless this callback returned a negative error code.
  *	The callback can sleep.
  *
+ * @cancel_hw_scan: Ask the low-level tp cancel the active hw scan.
+ *	The driver should ask the hardware to cancel the scan (if possible),
+ *	but the scan will be completed only after the driver will call
+ *	ieee80211_scan_completed().
+ *	This callback is needed for wowlan, to prevent enqueueing a new
+ *	scan_work after the low-level driver was already suspended.
+ *	The callback can sleep.
+ *
  * @sched_scan_start: Ask the hardware to start scanning repeatedly at
  *	specific intervals.  The driver must call the
  *	ieee80211_sched_scan_results() function whenever it finds results.
@@ -1900,6 +1908,8 @@ struct ieee80211_ops {
 				u32 iv32, u16 *phase1key);
 	int (*hw_scan)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 		       struct cfg80211_scan_request *req);
+	void (*cancel_hw_scan)(struct ieee80211_hw *hw,
+			       struct ieee80211_vif *vif);
 	int (*sched_scan_start)(struct ieee80211_hw *hw,
 				struct ieee80211_vif *vif,
 				struct cfg80211_sched_scan_request *req,

net/mac80211/driver-ops.h

@@ -218,6 +218,16 @@ static inline int drv_hw_scan(struct ieee80211_local *local,
 	return ret;
 }
 
+static inline void drv_cancel_hw_scan(struct ieee80211_local *local,
+				      struct ieee80211_sub_if_data *sdata)
+{
+	might_sleep();
+
+	trace_drv_cancel_hw_scan(local, sdata);
+	local->ops->cancel_hw_scan(&local->hw, &sdata->vif);
+	trace_drv_return_void(local);
+}
+
 static inline int
 drv_sched_scan_start(struct ieee80211_local *local,
 		     struct ieee80211_sub_if_data *sdata,

net/mac80211/driver-trace.h

@@ -460,6 +460,12 @@ DEFINE_EVENT(local_sdata_evt, drv_hw_scan,
 	TP_ARGS(local, sdata)
 );
 
+DEFINE_EVENT(local_sdata_evt, drv_cancel_hw_scan,
+	TP_PROTO(struct ieee80211_local *local,
+		 struct ieee80211_sub_if_data *sdata),
+	TP_ARGS(local, sdata)
+);
+
 DEFINE_EVENT(local_sdata_evt, drv_sched_scan_start,
 	TP_PROTO(struct ieee80211_local *local,
 		 struct ieee80211_sub_if_data *sdata),

net/mac80211/scan.c

@@ -821,10 +821,8 @@ int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
  */
 void ieee80211_scan_cancel(struct ieee80211_local *local)
 {
-	bool abortscan;
-
 	/*
-	 * We are only canceling software scan, or deferred scan that was not
+	 * We are canceling software scan, or deferred scan that was not
 	 * yet really started (see __ieee80211_start_scan ).
 	 *
 	 * Regarding hardware scan:
@@ -836,15 +834,22 @@ void ieee80211_scan_cancel(struct ieee80211_local *local)
 	 * - we can not cancel scan_work since driver can schedule it
 	 *   by ieee80211_scan_completed(..., true) to finish scan
 	 *
-	 * Hence low lever driver is responsible for canceling HW scan.
+	 * Hence we only call the cancel_hw_scan() callback, but the low-level
+	 * driver is still responsible for calling ieee80211_scan_completed()
+	 * after the scan was completed/aborted.
 	 */
 
 	mutex_lock(&local->mtx);
-	abortscan = local->scan_req && !test_bit(SCAN_HW_SCANNING, &local->scanning);
-	if (abortscan) {
+	if (!local->scan_req)
+		goto out;
+
+	if (test_bit(SCAN_HW_SCANNING, &local->scanning)) {
+		if (local->ops->cancel_hw_scan)
+			drv_cancel_hw_scan(local, local->scan_sdata);
+		goto out;
+	}
+
 	/*
-		 * The scan is canceled, but stop work from being pending.
-		 *
 	 * If the work is currently running, it must be blocked on
 	 * the mutex, but we'll set scan_sdata = NULL and it'll
 	 * simply exit once it acquires the mutex.
@@ -852,7 +857,7 @@ void ieee80211_scan_cancel(struct ieee80211_local *local)
 	cancel_delayed_work(&local->scan_work);
 	/* and clean up */
 	__ieee80211_scan_completed(&local->hw, true, false);
-	}
+out:
 	mutex_unlock(&local->mtx);
 }