[PATCH] USB speedtouch: add a new speedtouch encoding function

  speedtouch: add a new encoding function, atmsar_encode.  Calling it amounts to doing
  atmsar_encode_aal5 followed by atmsar_encode_rawcell in one fell swoop.  It eliminates
  the need for intermediate buffers and reduces memory movement.  The following patches
  use it to simplify the send logic (and get rid of those annoying little oopsen).

drivers/usb/misc/atmsar.c

@@ -381,6 +381,83 @@ void atmsar_close (struct atmsar_vcc_data **list, struct atmsar_vcc_data *vcc)
  **
  ***********************/
 
+/* encapsulate in an AAL5 frame, which is then split into ATM cells */
+unsigned int atmsar_encode (struct atmsar_vcc_data *ctx, char *source, char *target, unsigned int pdu_length)
+{
+	unsigned int num_cells = (pdu_length + ATM_AAL5_TRAILER + ATM_CELL_PAYLOAD - 1) / ATM_CELL_PAYLOAD;
+	unsigned int num_pdu_cells = pdu_length / ATM_CELL_PAYLOAD + 1;
+	unsigned int aal5_length = num_cells * ATM_CELL_PAYLOAD;
+	unsigned int zero_padding = aal5_length - pdu_length - ATM_AAL5_TRAILER;
+	unsigned int final_length = num_cells * ATM_CELL_SIZE;
+	unsigned char aal5_trailer [ATM_AAL5_TRAILER];
+	unsigned char cell_header [ATM_CELL_HEADER];
+	u32 crc;
+	int i;
+
+	PDEBUG ("atmsar_encode entered\n");
+
+	PDEBUG ("pdu_length %d, num_cells %d, num_pdu_cells %d, aal5_length %d, zero_padding %d, final_length %d\n", pdu_length, num_cells, num_pdu_cells, aal5_length, zero_padding, final_length);
+
+	PDEBUG ("source 0x=%p, target 0x%p\n", source, target);
+
+	aal5_trailer [0] = 0; /* UU = 0 */
+	aal5_trailer [1] = 0; /* CPI = 0 */
+	aal5_trailer [2] = pdu_length >> 8;
+	aal5_trailer [3] = pdu_length;
+
+	crc = crc32 (~0, source, pdu_length);
+	for (i = 0; i < zero_padding; i++)
+		crc = CRC32 (0, crc);
+	crc = crc32 (crc, aal5_trailer, 4);
+	crc = ~crc;
+
+	aal5_trailer [4] = crc >> 24;
+	aal5_trailer [5] = crc >> 16;
+	aal5_trailer [6] = crc >> 8;
+	aal5_trailer [7] = crc;
+
+	cell_header [0] = ctx->atmHeader >> 24;
+	cell_header [1] = ctx->atmHeader >> 16;
+	cell_header [2] = ctx->atmHeader >> 8;
+	cell_header [3] = ctx->atmHeader;
+	cell_header [4] = 0xec;
+
+	for (i = 1; i < num_pdu_cells; i++) {
+		memcpy (target, cell_header, ATM_CELL_HEADER);
+		target += ATM_CELL_HEADER;
+		memcpy (target, source, ATM_CELL_PAYLOAD);
+		target += ATM_CELL_PAYLOAD;
+		source += ATM_CELL_PAYLOAD;
+		PDEBUG ("source 0x=%p, target 0x%p\n", source, target);
+	}
+	memcpy (target, cell_header, ATM_CELL_HEADER);
+	target += ATM_CELL_HEADER;
+	memcpy (target, source, pdu_length % ATM_CELL_PAYLOAD);
+	target += pdu_length % ATM_CELL_PAYLOAD;
+	if (num_pdu_cells < num_cells) {
+		memset (target, 0, zero_padding + ATM_AAL5_TRAILER - ATM_CELL_PAYLOAD);
+		target += zero_padding + ATM_AAL5_TRAILER - ATM_CELL_PAYLOAD;
+		memcpy (target, cell_header, ATM_CELL_HEADER);
+		target += ATM_CELL_HEADER;
+		zero_padding = ATM_CELL_PAYLOAD - ATM_AAL5_TRAILER;
+	}
+	memset (target, 0, zero_padding);
+	target += zero_padding;
+	memcpy (target, aal5_trailer, ATM_AAL5_TRAILER);
+
+	/* set pti bit in last cell */
+	*(target + ATM_AAL5_TRAILER + 3 - ATM_CELL_SIZE) |= 0x2;
+
+	/* update stats */
+	if (ctx->stats)
+		atomic_inc (&ctx->stats->tx);
+
+	if (ctx->stats && (ctx->type <= ATMSAR_TYPE_AAL1))
+		atomic_add (num_cells, &(ctx->stats->tx));
+
+	return final_length;
+}
+
 struct sk_buff *atmsar_encode_rawcell (struct atmsar_vcc_data *ctx, struct sk_buff *skb)
 {
 	int number_of_cells = (skb->len) / 48;

drivers/usb/misc/atmsar.h

@@ -33,6 +33,7 @@
 #define ATMSAR_USE_53BYTE_CELL  0x1L
 #define ATMSAR_SET_PTI          0x2L
 
+#define ATM_CELL_HEADER		(ATM_CELL_SIZE - ATM_CELL_PAYLOAD)
 
 /* types */
 #define ATMSAR_TYPE_AAL0        ATM_AAL0
@@ -89,4 +90,6 @@ struct sk_buff *atmsar_decode_aal5 (struct atmsar_vcc_data *ctx, struct sk_buff
 
 struct sk_buff *atmsar_alloc_tx (struct atmsar_vcc_data *vcc, unsigned int size);
 
+unsigned int atmsar_encode (struct atmsar_vcc_data *ctx, char *source, char *target, unsigned int pdu_length);
+
 #endif				/* _ATMSAR_H_ */