Merge pull request ARMmbed#10219 from paul-szczepanek-arm/fix-legacy-scan-timeout

BLE: fix scan timeout being called from interrupt

Author: Cruz Monrreal II

features/FEATURE_BLE/ble/generic/GenericGap.h

@@ -782,7 +782,7 @@ class GenericGap :
     );
 
     void on_scan_timeout_();
-
+    void process_legacy_scan_timeout();
 
 private:
     pal::EventQueue &_event_queue;

features/FEATURE_BLE/source/generic/GenericGap.tpp

@@ -1605,21 +1605,36 @@ void GenericGap<PalGapImpl, PalSecurityManager, ConnectionEventMonitorEventHandl
         return;
     }
 
-    /* if timeout happened on a 4.2 chip we need to stop the scan manually */
+    _scan_enabled = false;
+
     if (!is_extended_advertising_available()) {
-        _pal_gap.scan_enable(false, false);
-#if BLE_FEATURE_PRIVACY
-        set_random_address_rotation(false);
-#endif
+        /* if timeout happened on a 4.2 chip this means legacy scanning and a timer timeout
+         * but we need to handle the event from user context - use the event queue to handle it */
+        _event_queue.post(
+            mbed::callback(
+                this,
+                &GenericGap::process_legacy_scan_timeout
+            )
+        );
+    } else {
+        if (_eventHandler) {
+            _eventHandler->onScanTimeout(ScanTimeoutEvent());
+        }
     }
+}
 
-    _scan_enabled = false;
+template <template<class> class PalGapImpl, class PalSecurityManager, class ConnectionEventMonitorEventHandler>
+void GenericGap<PalGapImpl, PalSecurityManager, ConnectionEventMonitorEventHandler>::process_legacy_scan_timeout()
+{
+    /* legacy scanning timed out is based on timer so we need to stop the scan manually */
+    _pal_gap.scan_enable(false, false);
+#if BLE_FEATURE_PRIVACY
+    set_random_address_rotation(false);
+#endif
 
-    if (!_eventHandler) {
-        return;
+    if (_eventHandler) {
+        _eventHandler->onScanTimeout(ScanTimeoutEvent());
     }
-
-    _eventHandler->onScanTimeout(ScanTimeoutEvent());
 }
 
 template <template<class> class PalGapImpl, class PalSecurityManager, class ConnectionEventMonitorEventHandler>