diff --git a/src/drivers/net/ncm.c b/src/drivers/net/ncm.c
index e05559bb..02b4cc36 100644
--- a/src/drivers/net/ncm.c
+++ b/src/drivers/net/ncm.c
@@ -35,10 +35,6 @@ FILE_LICENCE ( GPL2_OR_LATER );
  *
  */
 
-/** Ring refill profiler */
-static struct profiler ncm_refill_profiler __profiler =
-	{ .name = "ncm.refill" };
-
 /** Interrupt completion profiler */
 static struct profiler ncm_intr_profiler __profiler =
 	{ .name = "ncm.intr" };
@@ -55,144 +51,6 @@ static struct profiler ncm_in_datagram_profiler __profiler =
 static struct profiler ncm_out_profiler __profiler =
 	{ .name = "ncm.out" };
 
-/******************************************************************************
- *
- * Ring management
- *
- ******************************************************************************
- */
-
-/**
- * Transcribe receive ring name (for debugging)
- *
- * @v ncm		CDC-NCM device
- * @v ring		Receive ring
- * @ret name		Receive ring name
- */
-static inline const char * ncm_rx_name ( struct ncm_device *ncm,
-					 struct ncm_rx_ring *ring ) {
-	if ( ring == &ncm->intr ) {
-		return "interrupt";
-	} else if ( ring == &ncm->in ) {
-		return "bulk IN";
-	} else {
-		return "UNKNOWN";
-	}
-}
-
-/**
- * Allocate receive ring buffers
- *
- * @v ncm		CDC-NCM device
- * @v ring		Receive ring
- * @v mtu		I/O buffer size
- * @v count		Number of I/O buffers
- * @ret rc		Return status code
- */
-static int ncm_rx_alloc ( struct ncm_device *ncm, struct ncm_rx_ring *ring,
-			  size_t mtu, unsigned int count ) {
-	struct io_buffer *iobuf;
-	struct io_buffer *tmp;
-	unsigned int i;
-	int rc;
-
-	/* Initialise ring */
-	ring->mtu = mtu;
-	INIT_LIST_HEAD ( &ring->list );
-
-	/* Allocate I/O buffers */
-	for ( i = 0 ; i < count ; i++ ) {
-		iobuf = alloc_iob ( mtu );
-		if ( ! iobuf ) {
-			DBGC ( ncm, "NCM %p could not allocate %dx %zd-byte "
-			       "buffers for %s\n", ncm, count, mtu,
-			       ncm_rx_name ( ncm, ring ) );
-			rc = -ENOMEM;
-			goto err_alloc;
-		}
-		list_add ( &iobuf->list, &ring->list );
-	}
-
-	return 0;
-
- err_alloc:
-	list_for_each_entry_safe ( iobuf, tmp, &ring->list, list ) {
-		list_del ( &iobuf->list );
-		free_iob ( iobuf );
-	}
-	return rc;
-}
-
-/**
- * Refill receive ring
- *
- * @v ncm		CDC-NCM device
- * @v ring		Receive ring
- * @ret rc		Return status code
- */
-static int ncm_rx_refill ( struct ncm_device *ncm, struct ncm_rx_ring *ring ) {
-	struct io_buffer *iobuf;
-	int rc;
-
-	/* Enqueue any recycled I/O buffers */
-	while ( ( iobuf = list_first_entry ( &ring->list, struct io_buffer,
-					     list ) ) ) {
-
-		/* Profile refill */
-		profile_start ( &ncm_refill_profiler );
-
-		/* Reset size */
-		iob_put ( iobuf, ( ring->mtu - iob_len ( iobuf ) ) );
-
-		/* Enqueue I/O buffer */
-		if ( ( rc = usb_stream ( &ring->ep, iobuf, 0 ) ) != 0 ) {
-			DBGC ( ncm, "NCM %p could not enqueue %s: %s\n", ncm,
-			       ncm_rx_name ( ncm, ring ), strerror ( rc ) );
-			/* Leave in recycled list and wait for next refill */
-			return rc;
-		}
-
-		/* Remove from recycled list */
-		list_del ( &iobuf->list );
-		profile_stop ( &ncm_refill_profiler );
-	}
-
-	return 0;
-}
-
-/**
- * Recycle receive buffer
- *
- * @v ncm		CDC-NCM device
- * @v ring		Receive ring
- * @v iobuf		I/O buffer
- */
-static inline void ncm_rx_recycle ( struct ncm_device *ncm __unused,
-				    struct ncm_rx_ring *ring,
-				    struct io_buffer *iobuf ) {
-
-	/* Add to recycled list */
-	list_add_tail ( &iobuf->list, &ring->list );
-}
-
-/**
- * Free receive ring
- *
- * @v ncm		CDC-NCM device
- * @v ring		Receive ring
- */
-static void ncm_rx_free ( struct ncm_device *ncm __unused,
-			  struct ncm_rx_ring *ring ) {
-	struct io_buffer *iobuf;
-	struct io_buffer *tmp;
-
-	/* Free I/O buffers */
-	list_for_each_entry_safe ( iobuf, tmp, &ring->list, list ) {
-		list_del ( &iobuf->list );
-		free_iob ( iobuf );
-	}
-}
-
 /******************************************************************************
  *
  * CDC-NCM communications interface
@@ -209,7 +67,7 @@ static void ncm_rx_free ( struct ncm_device *ncm __unused,
  */
 static void ncm_intr_complete ( struct usb_endpoint *ep,
 				struct io_buffer *iobuf, int rc ) {
-	struct ncm_device *ncm = container_of ( ep, struct ncm_device, intr.ep);
+	struct ncm_device *ncm = container_of ( ep, struct ncm_device, intr );
 	struct net_device *netdev = ncm->netdev;
 	struct usb_setup_packet *message;
 	size_t len = iob_len ( iobuf );
@@ -219,21 +77,22 @@ static void ncm_intr_complete ( struct usb_endpoint *ep,
 
 	/* Ignore packets cancelled when the endpoint closes */
 	if ( ! ep->open )
-		goto done;
+		goto ignore;
 
 	/* Ignore packets with errors */
 	if ( rc != 0 ) {
 		DBGC ( ncm, "NCM %p interrupt failed: %s\n",
 		       ncm, strerror ( rc ) );
 		DBGC_HDA ( ncm, 0, iobuf->data, iob_len ( iobuf ) );
-		goto done;
+		goto error;
 	}
 
 	/* Extract message header */
 	if ( len < sizeof ( *message ) ) {
 		DBGC ( ncm, "NCM %p underlength interrupt:\n", ncm );
 		DBGC_HDA ( ncm, 0, iobuf->data, iob_len ( iobuf ) );
-		goto done;
+		rc = -EINVAL;
+		goto error;
 	}
 	message = iobuf->data;
 
@@ -257,13 +116,20 @@ static void ncm_intr_complete ( struct usb_endpoint *ep,
 	default:
 		DBGC ( ncm, "NCM %p unrecognised interrupt:\n", ncm );
 		DBGC_HDA ( ncm, 0, iobuf->data, iob_len ( iobuf ) );
-		break;
+		goto error;
 	}
 
- done:
-	/* Recycle buffer */
-	ncm_rx_recycle ( ncm, &ncm->intr, iobuf );
+	/* Free I/O buffer */
+	free_iob ( iobuf );
 	profile_stop ( &ncm_intr_profiler );
+
+	return;
+
+ error:
+	netdev_rx_err ( netdev, iob_disown ( iobuf ), rc );
+ ignore:
+	free_iob ( iobuf );
+	return;
 }
 
 /** Interrupt endpoint operations */
@@ -280,27 +146,20 @@ static struct usb_endpoint_driver_operations ncm_intr_operations = {
 static int ncm_comms_open ( struct ncm_device *ncm ) {
 	int rc;
 
-	/* Allocate I/O buffers */
-	if ( ( rc = ncm_rx_alloc ( ncm, &ncm->intr, ncm->intr.ep.mtu,
-				   NCM_INTR_COUNT ) ) != 0 ) {
-		DBGC ( ncm, "NCM %p could not allocate RX buffers: %s\n",
-		       ncm, strerror ( rc ) );
-		goto err_alloc;
-	}
-
 	/* Open interrupt endpoint */
-	if ( ( rc = usb_endpoint_open ( &ncm->intr.ep ) ) != 0 ) {
+	if ( ( rc = usb_endpoint_open ( &ncm->intr ) ) != 0 ) {
 		DBGC ( ncm, "NCM %p could not open interrupt: %s\n",
 		       ncm, strerror ( rc ) );
 		goto err_open;
 	}
 
+	/* Refill interrupt endpoint */
+	usb_refill ( &ncm->intr );
+
 	return 0;
 
-	usb_endpoint_close ( &ncm->intr.ep );
+	usb_endpoint_close ( &ncm->intr );
  err_open:
-	ncm_rx_free ( ncm, &ncm->intr );
- err_alloc:
 	return rc;
 }
 
@@ -312,10 +171,7 @@ static int ncm_comms_open ( struct ncm_device *ncm ) {
 static void ncm_comms_close ( struct ncm_device *ncm ) {
 
 	/* Close interrupt endpoint */
-	usb_endpoint_close ( &ncm->intr.ep );
-
-	/* Free I/O buffers */
-	ncm_rx_free ( ncm, &ncm->intr );
+	usb_endpoint_close ( &ncm->intr );
 }
 
 /******************************************************************************
@@ -326,12 +182,12 @@ static void ncm_comms_close ( struct ncm_device *ncm ) {
  */
 
 /**
- * Allocate bulk IN receive ring buffers
+ * Prefill bulk IN endpoint
  *
  * @v ncm		CDC-NCM device
  * @ret rc		Return status code
  */
-static int ncm_in_alloc ( struct ncm_device *ncm ) {
+static int ncm_in_prefill ( struct ncm_device *ncm ) {
 	size_t mtu;
 	unsigned int count;
 	int rc;
@@ -358,15 +214,19 @@ static int ncm_in_alloc ( struct ncm_device *ncm ) {
 			count = NCM_IN_MIN_COUNT;
 		if ( ( count * mtu ) > NCM_IN_MAX_SIZE )
 			continue;
-		if ( ( rc = ncm_rx_alloc ( ncm, &ncm->in, mtu, count ) ) != 0 )
+		usb_refill_init ( &ncm->in, mtu, count );
+		if ( ( rc = usb_prefill ( &ncm->in ) ) != 0 ) {
+			DBGC ( ncm, "NCM %p could not prefill %dx %zd-byte "
+			       "buffers for bulk IN\n", ncm, count, mtu );
 			continue;
+		}
 
 		DBGC ( ncm, "NCM %p using %dx %zd-byte buffers for bulk IN\n",
 		       ncm, count, mtu );
 		return 0;
 	}
 
-	DBGC ( ncm, "NCM %p could not allocate bulk IN buffers\n", ncm );
+	DBGC ( ncm, "NCM %p could not prefill bulk IN endpoint\n", ncm );
 	return -ENOMEM;
 }
 
@@ -379,7 +239,7 @@ static int ncm_in_alloc ( struct ncm_device *ncm ) {
  */
 static void ncm_in_complete ( struct usb_endpoint *ep, struct io_buffer *iobuf,
 			      int rc ) {
-	struct ncm_device *ncm = container_of ( ep, struct ncm_device, in.ep );
+	struct ncm_device *ncm = container_of ( ep, struct ncm_device, in );
 	struct net_device *netdev = ncm->netdev;
 	struct ncm_transfer_header *nth;
 	struct ncm_datagram_pointer *ndp;
@@ -404,13 +264,14 @@ static void ncm_in_complete ( struct usb_endpoint *ep, struct io_buffer *iobuf,
 	if ( rc != 0 ) {
 		DBGC ( ncm, "NCM %p bulk IN failed: %s\n",
 		       ncm, strerror ( rc ) );
-		goto drop;
+		goto error;
 	}
 
 	/* Locate transfer header */
 	len = iob_len ( iobuf );
 	if ( sizeof ( *nth ) > len ) {
 		DBGC ( ncm, "NCM %p packet too short for NTH:\n", ncm );
+		rc = -EINVAL;
 		goto error;
 	}
 	nth = iobuf->data;
@@ -419,16 +280,19 @@ static void ncm_in_complete ( struct usb_endpoint *ep, struct io_buffer *iobuf,
 	ndp_offset = le16_to_cpu ( nth->offset );
 	if ( ( ndp_offset + sizeof ( *ndp ) ) > len ) {
 		DBGC ( ncm, "NCM %p packet too short for NDP:\n", ncm );
+		rc = -EINVAL;
 		goto error;
 	}
 	ndp = ( iobuf->data + ndp_offset );
 	ndp_len = le16_to_cpu ( ndp->header_len );
 	if ( ndp_len < offsetof ( typeof ( *ndp ), desc ) ) {
 		DBGC ( ncm, "NCM %p NDP header length too short:\n", ncm );
+		rc = -EINVAL;
 		goto error;
 	}
 	if ( ( ndp_offset + ndp_len ) > len ) {
 		DBGC ( ncm, "NCM %p packet too short for NDP:\n", ncm );
+		rc = -EINVAL;
 		goto error;
 	}
 
@@ -445,10 +309,12 @@ static void ncm_in_complete ( struct usb_endpoint *ep, struct io_buffer *iobuf,
 		pkt_len = le16_to_cpu ( desc->len );
 		if ( pkt_len < ETH_HLEN ) {
 			DBGC ( ncm, "NCM %p underlength datagram:\n", ncm );
+			rc = -EINVAL;
 			goto error;
 		}
 		if ( ( pkt_offset + pkt_len ) > len ) {
 			DBGC ( ncm, "NCM %p datagram exceeds packet:\n", ncm );
+			rc = -EINVAL;
 			goto error;
 		}
 
@@ -468,8 +334,7 @@ static void ncm_in_complete ( struct usb_endpoint *ep, struct io_buffer *iobuf,
 		 * received packet and reuse the same I/O buffer for
 		 * transmission.
 		 */
-		headroom = ( sizeof ( struct ncm_ntb_header ) +
-			     ncm->out.padding );
+		headroom = ( sizeof ( struct ncm_ntb_header ) + ncm->padding );
 		pkt = alloc_iob ( headroom + pkt_len );
 		if ( ! pkt ) {
 			/* Record error and continue */
@@ -490,19 +355,17 @@ static void ncm_in_complete ( struct usb_endpoint *ep, struct io_buffer *iobuf,
 	}
 
 	/* Recycle I/O buffer */
-	ncm_rx_recycle ( ncm, &ncm->in, iobuf );
+	usb_recycle ( &ncm->in, iobuf );
 	profile_stop ( &ncm_in_profiler );
 
 	return;
 
  error:
-	rc = -EIO;
- drop:
 	/* Record error against network device */
 	DBGC_HDA ( ncm, 0, iobuf->data, iob_len ( iobuf ) );
 	netdev_rx_err ( netdev, NULL, rc );
  ignore:
-	ncm_rx_recycle ( ncm, &ncm->in, iobuf );
+	usb_recycle ( &ncm->in, iobuf );
 }
 
 /** Bulk IN endpoint operations */
@@ -521,7 +384,7 @@ static int ncm_out_transmit ( struct ncm_device *ncm,
 			      struct io_buffer *iobuf ) {
 	struct ncm_ntb_header *header;
 	size_t len = iob_len ( iobuf );
-	size_t header_len = ( sizeof ( *header ) + ncm->out.padding );
+	size_t header_len = ( sizeof ( *header ) + ncm->padding );
 	int rc;
 
 	/* Profile transmissions */
@@ -535,7 +398,7 @@ static int ncm_out_transmit ( struct ncm_device *ncm,
 	/* Populate header */
 	header->nth.magic = cpu_to_le32 ( NCM_TRANSFER_HEADER_MAGIC );
 	header->nth.header_len = cpu_to_le16 ( sizeof ( header->nth ) );
-	header->nth.sequence = cpu_to_le16 ( ncm->out.sequence );
+	header->nth.sequence = cpu_to_le16 ( ncm->sequence );
 	header->nth.len = cpu_to_le16 ( iob_len ( iobuf ) );
 	header->nth.offset =
 		cpu_to_le16 ( offsetof ( typeof ( *header ), ndp ) );
@@ -548,11 +411,11 @@ static int ncm_out_transmit ( struct ncm_device *ncm,
 	memset ( &header->desc[1], 0, sizeof ( header->desc[1] ) );
 
 	/* Enqueue I/O buffer */
-	if ( ( rc = usb_stream ( &ncm->out.ep, iobuf, 0 ) ) != 0 )
+	if ( ( rc = usb_stream ( &ncm->out, iobuf, 0 ) ) != 0 )
 		return rc;
 
 	/* Increment sequence number */
-	ncm->out.sequence++;
+	ncm->sequence++;
 
 	profile_stop ( &ncm_out_profiler );
 	return 0;
@@ -567,7 +430,7 @@ static int ncm_out_transmit ( struct ncm_device *ncm,
  */
 static void ncm_out_complete ( struct usb_endpoint *ep, struct io_buffer *iobuf,
 			       int rc ) {
-	struct ncm_device *ncm = container_of ( ep, struct ncm_device, out.ep );
+	struct ncm_device *ncm = container_of ( ep, struct ncm_device, out );
 	struct net_device *netdev = ncm->netdev;
 
 	/* Report TX completion */
@@ -590,13 +453,13 @@ static int ncm_data_open ( struct ncm_device *ncm ) {
 	struct ncm_set_ntb_input_size size;
 	int rc;
 
-	/* Allocate I/O buffers */
-	if ( ( rc = ncm_in_alloc ( ncm ) ) != 0 )
-		goto err_alloc;
+	/* Prefill I/O buffers */
+	if ( ( rc = ncm_in_prefill ( ncm ) ) != 0 )
+		goto err_prefill;
 
 	/* Set maximum input size */
 	memset ( &size, 0, sizeof ( size ) );
-	size.mtu = cpu_to_le32 ( ncm->in.mtu );
+	size.mtu = cpu_to_le32 ( ncm->in.len );
 	if ( ( rc = usb_control ( usb, NCM_SET_NTB_INPUT_SIZE, 0, ncm->comms,
 				  &size, sizeof ( size ) ) ) != 0 ) {
 		DBGC ( ncm, "NCM %p could not set input size to %zd: %s\n",
@@ -613,33 +476,38 @@ static int ncm_data_open ( struct ncm_device *ncm ) {
 	}
 
 	/* Open bulk IN endpoint */
-	if ( ( rc = usb_endpoint_open ( &ncm->in.ep ) ) != 0 ) {
+	if ( ( rc = usb_endpoint_open ( &ncm->in ) ) != 0 ) {
 		DBGC ( ncm, "NCM %p could not open bulk IN: %s\n",
 		       ncm, strerror ( rc ) );
 		goto err_open_in;
 	}
 
 	/* Open bulk OUT endpoint */
-	if ( ( rc = usb_endpoint_open ( &ncm->out.ep ) ) != 0 ) {
+	if ( ( rc = usb_endpoint_open ( &ncm->out ) ) != 0 ) {
 		DBGC ( ncm, "NCM %p could not open bulk OUT: %s\n",
 		       ncm, strerror ( rc ) );
 		goto err_open_out;
 	}
 
-	/* Reset transmit sequence number */
-	ncm->out.sequence = 0;
+	/* Refill bulk IN endpoint */
+	if ( ( rc = usb_refill ( &ncm->in ) ) != 0 ) {
+		DBGC ( ncm, "NCM %p could not refill bulk IN: %s\n",
+		       ncm, strerror ( rc ) );
+		goto err_refill;
+	}
 
 	return 0;
 
-	usb_endpoint_close ( &ncm->out.ep );
+ err_refill:
+	usb_endpoint_close ( &ncm->out );
  err_open_out:
-	usb_endpoint_close ( &ncm->in.ep );
+	usb_endpoint_close ( &ncm->in );
  err_open_in:
 	usb_set_interface ( usb, ncm->data, 0 );
  err_set_interface:
  err_set_ntb_input_size:
-	ncm_rx_free ( ncm, &ncm->in );
- err_alloc:
+	usb_flush ( &ncm->in );
+ err_prefill:
 	return rc;
 }
 
@@ -652,14 +520,11 @@ static void ncm_data_close ( struct ncm_device *ncm ) {
 	struct usb_device *usb = ncm->usb;
 
 	/* Close endpoints */
-	usb_endpoint_close ( &ncm->out.ep );
-	usb_endpoint_close ( &ncm->in.ep );
+	usb_endpoint_close ( &ncm->out );
+	usb_endpoint_close ( &ncm->in );
 
 	/* Reset data interface */
 	usb_set_interface ( usb, ncm->data, 0 );
-
-	/* Free I/O buffers */
-	ncm_rx_free ( ncm, &ncm->in );
 }
 
 /******************************************************************************
@@ -680,30 +545,20 @@ static int ncm_open ( struct net_device *netdev ) {
 	int rc;
 
 	/* Reset sequence number */
-	ncm->out.sequence = 0;
+	ncm->sequence = 0;
 
 	/* Open communications interface */
 	if ( ( rc = ncm_comms_open ( ncm ) ) != 0 )
 		goto err_comms_open;
 
-	/* Refill interrupt ring */
-	if ( ( rc = ncm_rx_refill ( ncm, &ncm->intr ) ) != 0 )
-		goto err_intr_refill;
-
 	/* Open data interface */
 	if ( ( rc = ncm_data_open ( ncm ) ) != 0 )
 		goto err_data_open;
 
-	/* Refill bulk IN ring */
-	if ( ( rc = ncm_rx_refill ( ncm, &ncm->in ) ) != 0 )
-		goto err_in_refill;
-
 	return 0;
 
- err_in_refill:
 	ncm_data_close ( ncm );
  err_data_open:
- err_intr_refill:
 	ncm_comms_close ( ncm );
  err_comms_open:
 	return rc;
@@ -755,12 +610,12 @@ static void ncm_poll ( struct net_device *netdev ) {
 	/* Poll USB bus */
 	usb_poll ( ncm->bus );
 
-	/* Refill interrupt ring */
-	if ( ( rc = ncm_rx_refill ( ncm, &ncm->intr ) ) != 0 )
+	/* Refill interrupt endpoint */
+	if ( ( rc = usb_refill ( &ncm->intr ) ) != 0 )
 		netdev_rx_err ( netdev, NULL, rc );
 
-	/* Refill bulk IN ring */
-	if ( ( rc = ncm_rx_refill ( ncm, &ncm->in ) ) != 0 )
+	/* Refill bulk IN endpoint */
+	if ( ( rc = usb_refill ( &ncm->in ) ) != 0 )
 		netdev_rx_err ( netdev, NULL, rc );
 }
 
@@ -810,9 +665,10 @@ static int ncm_probe ( struct usb_function *func,
 	ncm->usb = usb;
 	ncm->bus = usb->port->hub->bus;
 	ncm->netdev = netdev;
-	usb_endpoint_init ( &ncm->intr.ep, usb, &ncm_intr_operations );
-	usb_endpoint_init ( &ncm->in.ep, usb, &ncm_in_operations );
-	usb_endpoint_init ( &ncm->out.ep, usb, &ncm_out_operations );
+	usb_endpoint_init ( &ncm->intr, usb, &ncm_intr_operations );
+	usb_endpoint_init ( &ncm->in, usb, &ncm_in_operations );
+	usb_endpoint_init ( &ncm->out, usb, &ncm_out_operations );
+	usb_refill_init ( &ncm->intr, 0, NCM_INTR_COUNT );
 	DBGC ( ncm, "NCM %p on %s\n", ncm, func->name );
 
 	/* Identify interfaces */
@@ -843,7 +699,7 @@ static int ncm_probe ( struct usb_function *func,
 	}
 
 	/* Describe interrupt endpoint */
-	if ( ( rc = usb_endpoint_described ( &ncm->intr.ep, config, comms,
+	if ( ( rc = usb_endpoint_described ( &ncm->intr, config, comms,
 					     USB_INTERRUPT, 0 ) ) != 0 ) {
 		DBGC ( ncm, "NCM %p could not describe interrupt endpoint: "
 		       "%s\n", ncm, strerror ( rc ) );
@@ -851,7 +707,7 @@ static int ncm_probe ( struct usb_function *func,
 	}
 
 	/* Describe bulk IN endpoint */
-	if ( ( rc = usb_endpoint_described ( &ncm->in.ep, config, data,
+	if ( ( rc = usb_endpoint_described ( &ncm->in, config, data,
 					     USB_BULK_IN, 0 ) ) != 0 ) {
 		DBGC ( ncm, "NCM %p could not describe bulk IN endpoint: "
 		       "%s\n", ncm, strerror ( rc ) );
@@ -859,7 +715,7 @@ static int ncm_probe ( struct usb_function *func,
 	}
 
 	/* Describe bulk OUT endpoint */
-	if ( ( rc = usb_endpoint_described ( &ncm->out.ep, config, data,
+	if ( ( rc = usb_endpoint_described ( &ncm->out, config, data,
 					     USB_BULK_OUT, 0 ) ) != 0 ) {
 		DBGC ( ncm, "NCM %p could not describe bulk OUT endpoint: "
 		       "%s\n", ncm, strerror ( rc ) );
@@ -894,12 +750,12 @@ static int ncm_probe ( struct usb_function *func,
 	DBGC2 ( ncm, "NCM %p maximum IN size is %zd bytes\n", ncm, ncm->mtu );
 
 	/* Calculate transmit padding */
-	ncm->out.padding = ( ( le16_to_cpu ( params.out.remainder ) -
-			       sizeof ( struct ncm_ntb_header ) - ETH_HLEN ) &
-			     ( le16_to_cpu ( params.out.divisor ) - 1 ) );
+	ncm->padding = ( ( le16_to_cpu ( params.out.remainder ) -
+			   sizeof ( struct ncm_ntb_header ) - ETH_HLEN ) &
+			 ( le16_to_cpu ( params.out.divisor ) - 1 ) );
 	DBGC2 ( ncm, "NCM %p using %zd-byte transmit padding\n",
-		ncm, ncm->out.padding );
-	assert ( ( ( sizeof ( struct ncm_ntb_header ) + ncm->out.padding +
+		ncm, ncm->padding );
+	assert ( ( ( sizeof ( struct ncm_ntb_header ) + ncm->padding +
 		     ETH_HLEN ) % le16_to_cpu ( params.out.divisor ) ) ==
 		 le16_to_cpu ( params.out.remainder ) );
 
diff --git a/src/drivers/net/ncm.h b/src/drivers/net/ncm.h
index b76902b9..a551f0d2 100644
--- a/src/drivers/net/ncm.h
+++ b/src/drivers/net/ncm.h
@@ -139,26 +139,6 @@ struct ncm_ntb_header {
 	struct ncm_datagram_descriptor desc[2];
 } __attribute__ (( packed ));
 
-/** A CDC-NCM receive ring */
-struct ncm_rx_ring {
-	/** USB endpoint */
-	struct usb_endpoint ep;
-	/** I/O buffer size */
-	size_t mtu;
-	/** Recycled buffer list */
-	struct list_head list;
-};
-
-/** A CDC-NCM transmit ring */
-struct ncm_tx_ring {
-	/** USB endpoint */
-	struct usb_endpoint ep;
-	/** Transmitted packet sequence number */
-	uint16_t sequence;
-	/** Alignment padding required on transmitted packets */
-	size_t padding;
-};
-
 /** A CDC-NCM network device */
 struct ncm_device {
 	/** USB device */
@@ -175,13 +155,17 @@ struct ncm_device {
 
 	/** Maximum supported NTB input size */
 	size_t mtu;
+	/** Transmitted packet sequence number */
+	uint16_t sequence;
+	/** Alignment padding required on transmitted packets */
+	size_t padding;
 
-	/** Interrupt ring */
-	struct ncm_rx_ring intr;
-	/** Bulk IN ring */
-	struct ncm_rx_ring in;
-	/** Bulk OUT ring */
-	struct ncm_tx_ring out;
+	/** Interrupt endpoint */
+	struct usb_endpoint intr;
+	/** Bulk IN endpoint */
+	struct usb_endpoint in;
+	/** Bulk OUT endpoint */
+	struct usb_endpoint out;
 };
 
 /** Bulk IN ring minimum buffer count