Commit 210e817e authored by Duncan Sands's avatar Duncan Sands Committed by Greg Kroah-Hartman

[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.
parent 3a16d1e5
......@@ -242,6 +242,86 @@ static struct usb_driver udsl_usb_driver = {
};
/*************
** 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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