Index: uspace/srv/fs/devfs/devfs_ops.c
===================================================================
--- uspace/srv/fs/devfs/devfs_ops.c	(revision cfd630afac68c4e32746bbb4631110e5a2b386e8)
+++ uspace/srv/fs/devfs/devfs_ops.c	(revision 1affcdf3220abde47fe1219335c44e6763d27fd6)
@@ -59,8 +59,8 @@
 typedef struct {
 	devmap_handle_t handle;
-	int phone;		/**< When < 0, the structure is incomplete. */
+	async_sess_t *sess;       /**< If NULL, the structure is incomplete. */
 	size_t refcount;
 	link_t link;
-	fibril_condvar_t cv;	/**< Broadcast when completed. */
+	fibril_condvar_t cv;      /**< Broadcast when completed. */
 } device_t;
 
@@ -232,5 +232,5 @@
 		};
 		link_t *lnk;
-
+		
 		fibril_mutex_lock(&devices_mutex);
 restart:
@@ -244,8 +244,10 @@
 			
 			dev->handle = node->handle;
-			dev->phone = -1;	/* mark as incomplete */
+			
+			/* Mark as incomplete */
+			dev->sess = NULL;
 			dev->refcount = 1;
 			fibril_condvar_initialize(&dev->cv);
-
+			
 			/*
 			 * Insert the incomplete device structure so that other
@@ -254,14 +256,15 @@
 			 */
 			hash_table_insert(&devices, key, &dev->link);
-
+			
 			/*
 			 * Drop the mutex to allow recursive devfs requests.
 			 */
 			fibril_mutex_unlock(&devices_mutex);
-
-			int phone = devmap_device_connect(node->handle, 0);
-
+			
+			async_sess_t *sess = devmap_device_connect(EXCHANGE_SERIALIZE,
+			    node->handle, 0);
+			
 			fibril_mutex_lock(&devices_mutex);
-
+			
 			/*
 			 * Notify possible waiters about this device structure
@@ -269,6 +272,6 @@
 			 */
 			fibril_condvar_broadcast(&dev->cv);
-
-			if (phone < 0) {
+			
+			if (!sess) {
 				/*
 				 * Connecting failed, need to remove the
@@ -277,14 +280,14 @@
 				hash_table_remove(&devices, key, DEVICES_KEYS);
 				fibril_mutex_unlock(&devices_mutex);
-
+				
 				return ENOENT;
 			}
 			
-			/* Set the correct phone. */
-			dev->phone = phone;
+			/* Set the correct session. */
+			dev->sess = sess;
 		} else {
 			device_t *dev = hash_table_get_instance(lnk, device_t, link);
-
-			if (dev->phone < 0) {
+			
+			if (!dev->sess) {
 				/*
 				 * Wait until the device structure is completed
@@ -608,5 +611,5 @@
 		
 		device_t *dev = hash_table_get_instance(lnk, device_t, link);
-		assert(dev->phone >= 0);
+		assert(dev->sess);
 		
 		ipc_callid_t callid;
@@ -619,11 +622,16 @@
 		
 		/* Make a request at the driver */
+		async_exch_t *exch = async_exchange_begin(dev->sess);
+		
 		ipc_call_t answer;
-		aid_t msg = async_send_3(dev->phone, IPC_GET_IMETHOD(*request),
+		aid_t msg = async_send_3(exch, IPC_GET_IMETHOD(*request),
 		    IPC_GET_ARG1(*request), IPC_GET_ARG2(*request),
 		    IPC_GET_ARG3(*request), &answer);
 		
 		/* Forward the IPC_M_DATA_READ request to the driver */
-		async_forward_fast(callid, dev->phone, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);
+		async_forward_fast(callid, exch, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);
+		
+		async_exchange_end(exch);
+		
 		fibril_mutex_unlock(&devices_mutex);
 		
@@ -672,5 +680,5 @@
 		
 		device_t *dev = hash_table_get_instance(lnk, device_t, link);
-		assert(dev->phone >= 0);
+		assert(dev->sess);
 		
 		ipc_callid_t callid;
@@ -683,11 +691,15 @@
 		
 		/* Make a request at the driver */
+		async_exch_t *exch = async_exchange_begin(dev->sess);
+		
 		ipc_call_t answer;
-		aid_t msg = async_send_3(dev->phone, IPC_GET_IMETHOD(*request),
+		aid_t msg = async_send_3(exch, IPC_GET_IMETHOD(*request),
 		    IPC_GET_ARG1(*request), IPC_GET_ARG2(*request),
 		    IPC_GET_ARG3(*request), &answer);
 		
 		/* Forward the IPC_M_DATA_WRITE request to the driver */
-		async_forward_fast(callid, dev->phone, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);
+		async_forward_fast(callid, exch, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);
+		
+		async_exchange_end(exch);
 		
 		fibril_mutex_unlock(&devices_mutex);
@@ -742,9 +754,9 @@
 		
 		device_t *dev = hash_table_get_instance(lnk, device_t, link);
-		assert(dev->phone >= 0);
+		assert(dev->sess);
 		dev->refcount--;
 		
 		if (dev->refcount == 0) {
-			async_hangup(dev->phone);
+			async_hangup(dev->sess);
 			hash_table_remove(&devices, key, DEVICES_KEYS);
 		}
@@ -790,10 +802,14 @@
 		
 		device_t *dev = hash_table_get_instance(lnk, device_t, link);
-		assert(dev->phone >= 0);
+		assert(dev->sess);
 		
 		/* Make a request at the driver */
+		async_exch_t *exch = async_exchange_begin(dev->sess);
+		
 		ipc_call_t answer;
-		aid_t msg = async_send_2(dev->phone, IPC_GET_IMETHOD(*request),
+		aid_t msg = async_send_2(exch, IPC_GET_IMETHOD(*request),
 		    IPC_GET_ARG1(*request), IPC_GET_ARG2(*request), &answer);
+		
+		async_exchange_end(exch);
 		
 		fibril_mutex_unlock(&devices_mutex);