softdevice: return an error on a connection timeout

This makes sure an error is reported on a connection timeout. Previously
it would just block forever.

adapter_nrf528xx-full.go

@@ -115,6 +115,21 @@ func handleEvent() {
 			C.sd_ble_gap_phy_update(gapEvent.conn_handle, &phyUpdateRequest.peer_preferred_phys)
 		case C.BLE_GAP_EVT_PHY_UPDATE:
 			// ignore confirmation of phy successfully updated
+		case C.BLE_GAP_EVT_TIMEOUT:
+			timeoutEvt := gapEvent.params.unionfield_timeout()
+			switch timeoutEvt.src {
+			case C.BLE_GAP_TIMEOUT_SRC_CONN:
+				// Failed to connect to a peripheral.
+				if debug {
+					println("gap timeout: conn")
+				}
+				connectionAttempt.state.Set(3) // connection timed out
+			default:
+				// For example a scan timeout.
+				if debug {
+					println("gap timeout: other")
+				}
+			}
 		default:
 			if debug {
 				println("unknown GAP event:", id)

gap_nrf528xx-central.go

@@ -16,6 +16,7 @@ import (
 import "C"
 
 var errAlreadyConnecting = errors.New("bluetooth: already in a connection attempt")
+var errConnectionTimeout = errors.New("bluetooth: timeout while connecting")
 
 // Memory buffers needed by sd_ble_gap_scan_start.
 var (
@@ -94,7 +95,7 @@ func (a *Adapter) StopScan() error {
 
 // In-progress connection attempt.
 var connectionAttempt struct {
-	state            volatile.Register8 // 0 means unused, 1 means connecting, 2 means ready (connected or timeout)
+	state            volatile.Register8 // 0 means unused, 1 means connecting, 2 means connected, 3 means timeout
 	connectionHandle C.uint16_t
 }
 
@@ -165,18 +166,25 @@ func (a *Adapter) Connect(address Address, params ConnectionParams) (Device, err
 	}
 
 	// Wait until the connection is established.
-	// TODO: use some sort of condition variable once the scheduler supports
-	// them.
-	for connectionAttempt.state.Get() != 2 {
-		arm.Asm("wfe")
-	}
-	connectionHandle := connectionAttempt.connectionHandle
+	for {
+		state := connectionAttempt.state.Get()
+		if state == 2 {
+			// Successfully connected.
 			connectionAttempt.state.Set(0)
-
-	// Connection has been established.
+			connectionHandle := connectionAttempt.connectionHandle
 			return Device{
 				connectionHandle: connectionHandle,
 			}, nil
+		} else if state == 3 {
+			// Timeout while connecting.
+			connectionAttempt.state.Set(0)
+			return Device{}, errConnectionTimeout
+		} else {
+			// TODO: use some sort of condition variable once the scheduler
+			// supports them.
+			arm.Asm("wfe")
+		}
+	}
 }
 
 // Disconnect from the BLE device.