1 files changed, 31 insertions, 23 deletions

diff --git a/src/interface/efi/efi_snp.c b/src/interface/efi/efi_snp.c
index 67fba342..c21af33d 100644
--- a/src/interface/efi/efi_snp.c
+++ b/src/interface/efi/efi_snp.c
@@ -68,6 +68,14 @@ static void efi_snp_set_state ( struct efi_snp_device *snpdev ) {
 		 */
 		mode->State = EfiSimpleNetworkInitialized;
 	}
+
+	if (mode->State != EfiSimpleNetworkInitialized) {
+		/* Zero the number of recycled buffers when moving to any other
+		 * state than Initialized. Transmit() and GetStatus() are only
+		 * valid in Initialized.
+		 */
+		snpdev->tx_count_txbufs = 0;
+	}
 }
 
 /**
@@ -446,12 +454,12 @@ efi_snp_nvdata ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, BOOLEAN read,
  *
  * @v snp		SNP interface
  * @v interrupts	Interrupt status, or NULL
- * @v txbufs		Recycled transmit buffer address, or NULL
+ * @v txbuf		Recycled transmit buffer address, or NULL
  * @ret efirc		EFI status code
  */
 static EFI_STATUS EFIAPI
 efi_snp_get_status ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
-		     UINT32 *interrupts, VOID **txbufs ) {
+		     UINT32 *interrupts, VOID **txbuf ) {
 	struct efi_snp_device *snpdev =
 		container_of ( snp, struct efi_snp_device, snp );
 
@@ -485,30 +493,22 @@ efi_snp_get_status ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 		DBGC2 ( snpdev, " INTS:%02x", *interrupts );
 	}
 
-	/* TX completions.  It would be possible to design a more
-	 * idiotic scheme for this, but it would be a challenge.
-	 * According to the UEFI header file, txbufs will be filled in
-	 * with a list of "recycled transmit buffers" (i.e. completed
-	 * TX buffers).  Observant readers may care to note that
-	 * *txbufs is a void pointer.  Precisely how a list of
-	 * completed transmit buffers is meant to be represented as an
-	 * array of voids is left as an exercise for the reader.
-	 *
-	 * The only users of this interface (MnpDxe/MnpIo.c and
-	 * PxeBcDxe/Bc.c within the EFI dev kit) both just poll until
-	 * seeing a non-NULL result return in txbufs.  This is valid
-	 * provided that they do not ever attempt to transmit more
-	 * than one packet concurrently (and that TX never times out).
+	/* In efi_snp_transmit() we enqueue packets by copying them (not by
+	 * linking them), hence we can recycle them immediately to the SNP
+	 * client.
 	 */
-	if ( txbufs ) {
-		if ( snpdev->tx_count_txbufs &&
-		     list_empty ( &snpdev->netdev->tx_queue ) ) {
-			*txbufs = "Which idiot designed this API?";
+	if ( txbuf ) {
+		if ( snpdev->tx_count_txbufs ) {
+			unsigned first;
+
+			first = snpdev->tx_first_txbuf++;
+			snpdev->tx_first_txbuf %= MAX_RECYCLED_TXBUFS;
+			*txbuf = snpdev->tx_recycled_txbufs[first];
 			snpdev->tx_count_txbufs--;
 		} else {
-			*txbufs = NULL;
+			*txbuf = NULL;
 		}
-		DBGC2 ( snpdev, " TX:%s", ( *txbufs ? "some" : "none" ) );
+		DBGC2 ( snpdev, " TX:%p", *txbuf );
 	}
 
 	DBGC2 ( snpdev, "\n" );
@@ -560,6 +560,12 @@ efi_snp_transmit ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 	if ( efi_snp_claimed )
 		return EFI_NOT_READY;
 
+	assert ( snpdev->tx_count_txbufs <= MAX_RECYCLED_TXBUFS );
+	if ( snpdev->tx_count_txbufs == MAX_RECYCLED_TXBUFS ) {
+		/* No room to recycle another buffer. */
+		return EFI_NOT_READY;
+	}
+
 	/* Sanity checks */
 	if ( ll_header_len ) {
 		if ( ll_header_len != ll_protocol->ll_header_len ) {
@@ -626,7 +632,9 @@ efi_snp_transmit ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 
 	/* Record transmission as outstanding */
 	snpdev->tx_count_interrupts++;
-	snpdev->tx_count_txbufs++;
+	snpdev->tx_recycled_txbufs[(snpdev->tx_first_txbuf +
+				    snpdev->tx_count_txbufs++
+				   ) % MAX_RECYCLED_TXBUFS] = data;
 
 	return 0;