[snpnet] Give up entirely on the transmit queue

Practically speaking, it seems the convention is to only have one
packet pending and not rely upon any mechanism to associate returned
txbuf with txqueue.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/net/efi/snpnet.c

 	struct snpnet_device *snpnetdev = netdev->priv;
 	EFI_SIMPLE_NETWORK_PROTOCOL *snp = snpnetdev->snp;
 	EFI_STATUS efirc;
+	void *txbuf=NULL;
 	size_t len = iob_len ( iobuf );
 
 	efirc = snp->Transmit ( snp, 0, len, iobuf->data, NULL, NULL, NULL );
-	return EFIRC_TO_RC ( efirc );
-}
-
-/**
- * Find a I/O buffer on the list of outstanding Tx buffers and complete it.
- *
- * @v snpnetdev		SNP network device
- * @v txbuf		Buffer address
- */
-static void snpnet_complete ( struct net_device *netdev, void *txbuf ) {
-	struct io_buffer *tmp;
-	struct io_buffer *iobuf;
-
-	list_for_each_entry_safe ( iobuf, tmp, &netdev->tx_queue, list ) {
-		if ( iobuf->data == txbuf ) {
-			netdev_tx_complete ( netdev, iobuf );
+	if (efirc) {
+		return EFIRC_TO_RC ( efirc );
+	}
+	/* since GetStatus is so inconsistent, don't try more than one outstanding transmit at a time */
+	while ( txbuf == NULL ) {
+		efirc = snp->GetStatus ( snp, NULL, &txbuf );
+		if ( efirc ) {
+			DBGC ( snp, "SNP %p could not get status %s\n", snp,
+			       efi_strerror ( efirc ) );
 			break;
 		}
+
 	}
+	netdev_tx_complete ( netdev, iobuf );
+	return 0;
 }
 
 /**
 	EFI_STATUS efirc;
 	struct io_buffer *iobuf = NULL;
 	UINTN len;
-	void *txbuf;
-
-	/* Process Tx completions */
-	while ( 1 ) {
-		efirc = snp->GetStatus ( snp, NULL, &txbuf );
-		if ( efirc ) {
-			DBGC ( snp, "SNP %p could not get status %s\n", snp,
-			       efi_strerror ( efirc ) );
-			break;
-		}
-
-		if ( txbuf == NULL )
-			break;
-
-		snpnet_complete ( netdev, txbuf );
-	}
 
 	/* Process received packets */
 	while ( 1 ) {