ChangeSet 1.1043.1.7, 2003/02/16 09:39:17-08:00, [EMAIL PROTECTED]
[PATCH] USB speedtouch: on-the-fly AAL5/ATM encoding for speedtouch
Add a new encoding routine, udsl_write_cell, which extracts one ATM cell from a skb
and writes it, doing the AAL5/ATM encoding on the fly. To make this possible, various
bits of info about the AAL5/ATM structure need to be stored beforehand in the skb.
This is done by udsl_groom_skb using the udsl_control structure introduced in the
previous patch.
diff -Nru a/drivers/usb/misc/speedtouch.c b/drivers/usb/misc/speedtouch.c
--- a/drivers/usb/misc/speedtouch.c Tue Feb 18 16:42:23 2003
+++ b/drivers/usb/misc/speedtouch.c Tue Feb 18 16:42:23 2003
@@ -242,6 +242,86 @@
};
+/*************
+** encode **
+*************/
+
+static void udsl_groom_skb (struct atm_vcc *vcc, struct sk_buff *skb) {
+ struct udsl_control *ctrl = UDSL_SKB (skb);
+ unsigned int zero_padding;
+ int i;
+ u32 crc;
+
+ ctrl->atm_data.vcc = vcc;
+ ctrl->cell_header [0] = vcc->vpi >> 4;
+ ctrl->cell_header [1] = (vcc->vpi << 4) | (vcc->vci >> 12);
+ ctrl->cell_header [2] = vcc->vci >> 4;
+ ctrl->cell_header [3] = vcc->vci << 4;
+ ctrl->cell_header [4] = 0xec;
+
+ ctrl->num_cells = (skb->len + ATM_AAL5_TRAILER + ATM_CELL_PAYLOAD - 1) /
+ATM_CELL_PAYLOAD;
+ ctrl->num_entire = skb->len / ATM_CELL_PAYLOAD;
+
+ zero_padding = ctrl->num_cells * ATM_CELL_PAYLOAD - skb->len -
+ATM_AAL5_TRAILER;
+
+ if (ctrl->num_entire + 1 < ctrl->num_cells)
+ ctrl->pdu_padding = zero_padding - (ATM_CELL_PAYLOAD -
+ATM_AAL5_TRAILER);
+ else
+ ctrl->pdu_padding = zero_padding;
+
+ ctrl->aal5_trailer [0] = 0; /* UU = 0 */
+ ctrl->aal5_trailer [1] = 0; /* CPI = 0 */
+ ctrl->aal5_trailer [2] = skb->len >> 8;
+ ctrl->aal5_trailer [3] = skb->len;
+
+ crc = crc32 (~0, skb->data, skb->len);
+ for (i = 0; i < zero_padding; i++)
+ crc = CRC32 (0, crc);
+ crc = crc32 (crc, ctrl->aal5_trailer, 4);
+ crc = ~crc;
+
+ ctrl->aal5_trailer [4] = crc >> 24;
+ ctrl->aal5_trailer [5] = crc >> 16;
+ ctrl->aal5_trailer [6] = crc >> 8;
+ ctrl->aal5_trailer [7] = crc;
+}
+
+static char *udsl_write_cell (struct sk_buff *skb, char *target) {
+ struct udsl_control *ctrl = UDSL_SKB (skb);
+
+ ctrl->num_cells--;
+
+ memcpy (target, ctrl->cell_header, ATM_CELL_HEADER);
+ target += ATM_CELL_HEADER;
+
+ if (ctrl->num_entire) {
+ ctrl->num_entire--;
+ memcpy (target, skb->data, ATM_CELL_PAYLOAD);
+ target += ATM_CELL_PAYLOAD;
+ __skb_pull (skb, ATM_CELL_PAYLOAD);
+ return target;
+ }
+
+ memcpy (target, skb->data, skb->len);
+ target += skb->len;
+ __skb_pull (skb, skb->len);
+
+ memset (target, 0, ctrl->pdu_padding);
+ target += ctrl->pdu_padding;
+
+ if (ctrl->num_cells) {
+ ctrl->pdu_padding = ATM_CELL_PAYLOAD - ATM_AAL5_TRAILER;
+ } else {
+ memcpy (target, ctrl->aal5_trailer, ATM_AAL5_TRAILER);
+ target += ATM_AAL5_TRAILER;
+ /* set pti bit in last cell */
+ *(target + 3 - ATM_CELL_SIZE) |= 0x2;
+ }
+
+ return target;
+}
+
+
/**************
** receive **
**************/
-------------------------------------------------------
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