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From:   Alain Michaud <alainm@chromium.org>
To:     linux-bluetooth@vger.kernel.org
Cc:     Alain Michaud <alainm@chromium.org>,
        Abhishek Pandit-Subedi <abhishekpandit@chromium.org>,
        Yu Liu <yudilu@google.com>
Subject: [PATCH] Bluetooth: use the proper scan params when conn is pending
Date:   Fri, 31 Jul 2020 01:03:41 +0000
Message-Id: <20200731010341.1421926-1-alainm@chromium.org>
MIME-Version: 1.0
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Sender: linux-bluetooth-owner@vger.kernel.org
Precedence: bulk

When an LE connection is requested and an RPA update is needed via
hci_connect_le_scan, the default scanning parameters are used rather
than the connect parameters.  This leads to significant delays in the
connection establishment process when using lower duty cycle scanning
parameters.

The patch simply looks at the pended connection list when trying to
determine which scanning parameters should be used.

Before:
< HCI Command: LE Set Extended Scan Parameters (0x08|0x0041) plen 8
                            #378 [hci0] 1659.247156
        Own address type: Public (0x00)
        Filter policy: Ignore not in white list (0x01)
        PHYs: 0x01
        Entry 0: LE 1M
          Type: Passive (0x00)
          Interval: 367.500 msec (0x024c)
          Window: 37.500 msec (0x003c)

After:
< HCI Command: LE Set Extended Scan Parameters (0x08|0x0041) plen 8
                               #39 [hci0] 7.422109
        Own address type: Public (0x00)
        Filter policy: Ignore not in white list (0x01)
        PHYs: 0x01
        Entry 0: LE 1M
          Type: Passive (0x00)
          Interval: 60.000 msec (0x0060)
          Window: 60.000 msec (0x0060)

Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Reviewed-by: Yu Liu <yudilu@google.com>
Signed-off-by: Alain Michaud <alainm@chromium.org>

---

 net/bluetooth/hci_request.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c
index 435400a43a78..e0269192f2e5 100644
--- a/net/bluetooth/hci_request.c
+++ b/net/bluetooth/hci_request.c
@@ -953,6 +953,27 @@ static void hci_req_start_scan(struct hci_request *req, u8 type, u16 interval,
 	}
 }
 
+/* Returns true if an le connection is in the scanning state */
+static inline bool hci_is_le_conn_scanning(struct hci_dev *hdev)
+{
+	struct hci_conn_hash *h = &hdev->conn_hash;
+	struct hci_conn  *c;
+
+	rcu_read_lock();
+
+	list_for_each_entry_rcu(c, &h->list, list) {
+		if (c->type == LE_LINK && c->state == BT_CONNECT &&
+		    test_bit(HCI_CONN_SCANNING, &c->flags)) {
+			rcu_read_unlock();
+			return true;
+		}
+	}
+
+	rcu_read_unlock();
+
+	return false;
+}
+
 /* Ensure to call hci_req_add_le_scan_disable() first to disable the
  * controller based address resolution to be able to reconfigure
  * resolving list.
@@ -1003,6 +1024,9 @@ void hci_req_add_le_passive_scan(struct hci_request *req)
 	if (hdev->suspended) {
 		window = hdev->le_scan_window_suspend;
 		interval = hdev->le_scan_int_suspend;
+	} else if (hci_is_le_conn_scanning(hdev)) {
+		window = hdev->le_scan_window_connect;
+		interval = hdev->le_scan_int_connect;
 	} else {
 		window = hdev->le_scan_window;
 		interval = hdev->le_scan_interval;
-- 
2.28.0.163.g6104cc2f0b6-goog