Bluetooth: Add dynamic le scan listener interface

Adds a way to register listeners for incoming scanner packets, in
addition to the callback passed in bt_le_scan_enable.

This allows application modules to add multiple scan packet listeners
without owning the scanner life cycle API, enabling use cases like
beacon scanning alongside Bluetooth Mesh.

Signed-off-by: Trond Einar Snekvik <Trond.Einar.Snekvik@nordicsemi.no>

include/bluetooth/bluetooth.h

@@ -443,6 +443,32 @@ struct bt_le_scan_param {
 	u16_t window;
 };
 
+/** LE advertisement packet information */
+struct bt_le_adv_info {
+	/** Advertiser LE address and type */
+	const bt_addr_le_t *addr;
+
+	/** Strength of advertiser signal */
+	s8_t rssi;
+
+	/** Advertising packet type */
+	u8_t adv_type;
+};
+
+/** Listener context for (LE) scanning. */
+struct bt_le_scan_cb {
+
+	/** @brief Advertisement packet received callback.
+	 *
+	 *  @param info Advertiser packet information.
+	 *  @param buf  Buffer containing advertiser data.
+	 */
+	void (*recv)(const struct bt_le_adv_info *info,
+		     struct net_buf_simple *buf);
+
+	sys_snode_t node;
+};
+
 /** Helper to declare scan parameters inline
   *
   * @param _type     Scan Type, BT_LE_SCAN_TYPE_ACTIVE or
@@ -481,7 +507,8 @@ struct bt_le_scan_param {
  *  the specified callback.
  *
  *  @param param Scan parameters.
- *  @param cb Callback to notify scan results.
+ *  @param cb Callback to notify scan results. May be NULL if callback
+ *            registration through @ref bt_le_scan_cb_register is preferred.
  *
  *  @return Zero on success or error code otherwise, positive in case
  *  of protocol error or negative (POSIX) in case of stack internal error
@@ -497,6 +524,18 @@ int bt_le_scan_start(const struct bt_le_scan_param *param, bt_le_scan_cb_t cb);
  */
 int bt_le_scan_stop(void);
 
+/** @brief Register scanner packet callbacks.
+ *
+ *  Adds the callback structure to the list of callback structures that monitors
+ *  scanner activity.
+ *
+ *  This callback will be called for all scanner activity, regardless of what
+ *  API was used to start the scanner.
+ *
+ *  @param cb Callback struct. Must point to static memory.
+ */
+void bt_le_scan_cb_register(struct bt_le_scan_cb *cb);
+
 /** @brief Add device (LE) to whitelist.
  *
  *  Add peer device LE address to the whitelist.

subsys/bluetooth/host/hci_core.c

@@ -83,6 +83,10 @@ static bt_ready_cb_t ready_cb;
 
 static bt_le_scan_cb_t *scan_dev_found_cb;
 
+#if defined(CONFIG_BT_OBSERVER)
+static sys_slist_t scan_cbs = SYS_SLIST_STATIC_INIT(&scan_cbs);
+#endif
+
 #if defined(CONFIG_BT_HCI_VS_EVT_USER)
 static bt_hci_vnd_evt_cb_t *hci_vnd_evt_cb;
 #endif /* CONFIG_BT_HCI_VS_EVT_USER */
@@ -3662,6 +3666,9 @@ static void le_adv_report(struct net_buf *buf)
 	BT_DBG("Adv number of reports %u",  num_reports);
 
 	while (num_reports--) {
+		struct bt_le_scan_cb *cb;
+		struct net_buf_simple_state state;
+		struct bt_le_adv_info adv_info;
 		bt_addr_le_t id_addr;
 		s8_t rssi;
 
@@ -3687,9 +3694,11 @@ static void le_adv_report(struct net_buf *buf)
 							  &info->addr));
 		}
 
-		if (scan_dev_found_cb) {
+		adv_info.addr = &id_addr;
-			struct net_buf_simple_state state;
+		adv_info.adv_type = info->evt_type;
+		adv_info.rssi = rssi;
 
+		if (scan_dev_found_cb) {
 			net_buf_simple_save(&buf->b, &state);
 
 			buf->len = info->length;
@@ -3699,6 +3708,15 @@ static void le_adv_report(struct net_buf *buf)
 			net_buf_simple_restore(&buf->b, &state);
 		}
 
+		SYS_SLIST_FOR_EACH_CONTAINER(&scan_cbs, cb, node) {
+			net_buf_simple_save(&buf->b, &state);
+
+			buf->len = info->length;
+			cb->recv(&adv_info, &buf->b);
+
+			net_buf_simple_restore(&buf->b, &state);
+		}
+
 #if defined(CONFIG_BT_CENTRAL)
 		check_pending_conn(&id_addr, &info->addr, info->evt_type);
 #endif /* CONFIG_BT_CENTRAL */
@@ -6064,6 +6082,11 @@ int bt_le_scan_stop(void)
 
 	return bt_le_scan_update(false);
 }
+
+void bt_le_scan_cb_register(struct bt_le_scan_cb *cb)
+{
+	sys_slist_append(&scan_cbs, &cb->node);
+}
 #endif /* CONFIG_BT_OBSERVER */
 
 #if defined(CONFIG_BT_WHITELIST)