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[PATCH v4] mac80211: Support on-channel scan option.

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From: Ben Greear <greearb@xxxxxxxxxxxxxxx>

This based on an idea posted by Stanislaw Gruszka,
though I accept full blame for the implementation!

This is compile-tested only at this point.

The idea is to let users scan on the current operating
channel without interrupting normal traffic more than
absolutely necessary (changing power level might reset
some hardware, for instance).

Signed-off-by: Ben Greear <greearb@xxxxxxxxxxxxxxx>
---

v4:  Add some newline whitespace in the scan-on-channel code.

:100644 100644 bd7a451... 1d07426... M	net/mac80211/ieee80211_i.h
:100644 100644 ac79d5e... b70f7f0... M	net/mac80211/main.c
:100644 100644 54a0491... dd2fbec... M	net/mac80211/rx.c
:100644 100644 45f5aa2... 8282284... M	net/mac80211/scan.c
 net/mac80211/ieee80211_i.h |    3 +
 net/mac80211/main.c        |    4 +-
 net/mac80211/rx.c          |    2 +
 net/mac80211/scan.c        |   95 ++++++++++++++++++++++++++++++++------------
 4 files changed, 77 insertions(+), 27 deletions(-)

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index bd7a451..1d07426 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -803,6 +803,8 @@ struct tpt_led_trigger {
  *	well be on the operating channel
  * @SCAN_HW_SCANNING: The hardware is scanning for us, we have no way to
  *	determine if we are on the operating channel or not
+ * @SCAN_ONCHANNEL_SCANNING:  Do a software scan on only the current operating
+ *	channel. This should not interrupt normal traffic.
  * @SCAN_COMPLETED: Set for our scan work function when the driver reported
  *	that the scan completed.
  * @SCAN_ABORTED: Set for our scan work function when the driver reported
@@ -811,6 +813,7 @@ struct tpt_led_trigger {
 enum {
 	SCAN_SW_SCANNING,
 	SCAN_HW_SCANNING,
+	SCAN_ONCHANNEL_SCANNING,
 	SCAN_COMPLETED,
 	SCAN_ABORTED,
 };
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index ac79d5e..b70f7f0 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -47,7 +47,8 @@ void ieee80211_configure_filter(struct ieee80211_local *local)
 	if (atomic_read(&local->iff_allmultis))
 		new_flags |= FIF_ALLMULTI;
 
-	if (local->monitors || test_bit(SCAN_SW_SCANNING, &local->scanning))
+	if (local->monitors || test_bit(SCAN_SW_SCANNING, &local->scanning) ||
+	    test_bit(SCAN_ONCHANNEL_SCANNING, &local->scanning))
 		new_flags |= FIF_BCN_PRBRESP_PROMISC;
 
 	if (local->fif_probe_req || local->probe_req_reg)
@@ -148,6 +149,7 @@ int ieee80211_hw_config(struct ieee80211_local *local, u32 changed)
 	}
 
 	if (test_bit(SCAN_SW_SCANNING, &local->scanning) ||
+	    test_bit(SCAN_ONCHANNEL_SCANNING, &local->scanning) ||
 	    test_bit(SCAN_HW_SCANNING, &local->scanning))
 		power = chan->max_power;
 	else
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 54a0491..dd2fbec 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -425,6 +425,7 @@ ieee80211_rx_h_passive_scan(struct ieee80211_rx_data *rx)
 
 	if (test_bit(SCAN_HW_SCANNING, &local->scanning) ||
 	    test_bit(SCAN_SW_SCANNING, &local->scanning) ||
+	    test_bit(SCAN_ONCHANNEL_SCANNING, &local->scanning) ||
 	    local->sched_scanning)
 		return ieee80211_scan_rx(rx->sdata, skb);
 
@@ -2915,6 +2916,7 @@ static void __ieee80211_rx_handle_packet(struct ieee80211_hw *hw,
 		local->dot11ReceivedFragmentCount++;
 
 	if (unlikely(test_bit(SCAN_HW_SCANNING, &local->scanning) ||
+		     test_bit(SCAN_ONCHANNEL_SCANNING, &local->scanning) ||
 		     test_bit(SCAN_SW_SCANNING, &local->scanning)))
 		status->rx_flags |= IEEE80211_RX_IN_SCAN;
 
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 45f5aa2..8282284 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -401,6 +401,30 @@ void ieee80211_run_deferred_scan(struct ieee80211_local *local)
 				     round_jiffies_relative(0));
 }
 
+static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
+					    unsigned long *next_delay)
+{
+	int i;
+	struct ieee80211_sub_if_data *sdata = local->scan_sdata;
+	enum ieee80211_band band = local->hw.conf.channel->band;
+
+	for (i = 0; i < local->scan_req->n_ssids; i++)
+		ieee80211_send_probe_req(
+			sdata, NULL,
+			local->scan_req->ssids[i].ssid,
+			local->scan_req->ssids[i].ssid_len,
+			local->scan_req->ie, local->scan_req->ie_len,
+			local->scan_req->rates[band], false,
+			local->scan_req->no_cck);
+
+	/*
+	 * After sending probe requests, wait for probe responses
+	 * on the channel.
+	 */
+	*next_delay = IEEE80211_CHANNEL_TIME;
+	local->next_scan_state = SCAN_DECISION;
+}
+
 static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
 				  struct cfg80211_scan_request *req)
 {
@@ -451,10 +475,47 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
 	local->scan_req = req;
 	local->scan_sdata = sdata;
 
-	if (local->ops->hw_scan)
+	if (local->ops->hw_scan) {
 		__set_bit(SCAN_HW_SCANNING, &local->scanning);
-	else
+	} else if ((req->n_channels == 1) &&
+		   (req->channels[0]->center_freq ==
+		    local->hw.conf.channel->center_freq)) {
+
+		/* If we are scanning only on the current channel, then
+		 * we do not need to stop normal activities
+		 */
+		unsigned long next_delay;
+
+		__set_bit(SCAN_ONCHANNEL_SCANNING, &local->scanning);
+
+		ieee80211_recalc_idle(local);
+
+		/* Notify driver scan is starting, keep order of operations
+		 * same as normal software scan, in case that matters. */
+		drv_sw_scan_start(local);
+
+		ieee80211_configure_filter(local); /* accept probe-responses */
+
+		/* We need to ensure power level is at max for scanning. */
+		ieee80211_hw_config(local, 0);
+
+		if ((req->channels[0]->flags &
+		     IEEE80211_CHAN_PASSIVE_SCAN) ||
+		    !local->scan_req->n_ssids) {
+			next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
+		} else {
+			ieee80211_scan_state_send_probe(local, &next_delay);
+			next_delay = IEEE80211_CHANNEL_TIME;
+		}
+
+		/* Now, just wait a bit and we are all done! */
+		ieee80211_queue_delayed_work(&local->hw, &local->scan_work,
+					     next_delay);
+		return 0;
+	} else {
+		/* Do normal software scan */
 		__set_bit(SCAN_SW_SCANNING, &local->scanning);
+	}
 
 	ieee80211_recalc_idle(local);
 
@@ -611,30 +672,6 @@ static void ieee80211_scan_state_set_channel(struct ieee80211_local *local,
 	local->next_scan_state = SCAN_SEND_PROBE;
 }
 
-static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
-					    unsigned long *next_delay)
-{
-	int i;
-	struct ieee80211_sub_if_data *sdata = local->scan_sdata;
-	enum ieee80211_band band = local->hw.conf.channel->band;
-
-	for (i = 0; i < local->scan_req->n_ssids; i++)
-		ieee80211_send_probe_req(
-			sdata, NULL,
-			local->scan_req->ssids[i].ssid,
-			local->scan_req->ssids[i].ssid_len,
-			local->scan_req->ie, local->scan_req->ie_len,
-			local->scan_req->rates[band], false,
-			local->scan_req->no_cck);
-
-	/*
-	 * After sending probe requests, wait for probe responses
-	 * on the channel.
-	 */
-	*next_delay = IEEE80211_CHANNEL_TIME;
-	local->next_scan_state = SCAN_DECISION;
-}
-
 static void ieee80211_scan_state_suspend(struct ieee80211_local *local,
 					 unsigned long *next_delay)
 {
@@ -685,6 +722,12 @@ void ieee80211_scan_work(struct work_struct *work)
 
 	sdata = local->scan_sdata;
 
+	/* When scanning on-channel, the first-callback means completed. */
+	if (test_bit(SCAN_ONCHANNEL_SCANNING, &local->scanning)) {
+		aborted = test_and_clear_bit(SCAN_ABORTED, &local->scanning);
+		goto out_complete;
+	}
+
 	if (test_and_clear_bit(SCAN_COMPLETED, &local->scanning)) {
 		aborted = test_and_clear_bit(SCAN_ABORTED, &local->scanning);
 		goto out_complete;
-- 
1.7.3.4

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