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linux/net/irda/wrapper.c

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/*********************************************************************
*
* Filename: wrapper.c
* Version: 1.2
* Description: IrDA SIR async wrapper layer
* Status: Stable
* Author: Dag Brattli <dagb@cs.uit.no>
* Created at: Mon Aug 4 20:40:53 1997
* Modified at: Fri Jan 28 13:21:09 2000
* Modified by: Dag Brattli <dagb@cs.uit.no>
* Modified at: Fri May 28 3:11 CST 1999
* Modified by: Horst von Brand <vonbrand@sleipnir.valparaiso.cl>
*
* Copyright (c) 1998-2000 Dag Brattli <dagb@cs.uit.no>,
* All Rights Reserved.
* Copyright (c) 2000-2002 Jean Tourrilhes <jt@hpl.hp.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* Neither Dag Brattli nor University of Tromsø admit liability nor
* provide warranty for any of this software. This material is
* provided "AS-IS" and at no charge.
*
********************************************************************/
#include <linux/skbuff.h>
#include <linux/string.h>
#include <linux/module.h>
#include <asm/byteorder.h>
#include <net/irda/irda.h>
#include <net/irda/wrapper.h>
#include <net/irda/crc.h>
#include <net/irda/irlap.h>
#include <net/irda/irlap_frame.h>
#include <net/irda/irda_device.h>
/************************** FRAME WRAPPING **************************/
/*
* Unwrap and unstuff SIR frames
*
* Note : at FIR and MIR, HDLC framing is used and usually handled
* by the controller, so we come here only for SIR... Jean II
*/
/*
* Function stuff_byte (byte, buf)
*
* Byte stuff one single byte and put the result in buffer pointed to by
* buf. The buffer must at all times be able to have two bytes inserted.
*
* This is in a tight loop, better inline it, so need to be prior to callers.
* (2000 bytes on P6 200MHz, non-inlined ~370us, inline ~170us) - Jean II
*/
static inline int stuff_byte(__u8 byte, __u8 *buf)
{
switch (byte) {
case BOF: /* FALLTHROUGH */
case EOF: /* FALLTHROUGH */
case CE:
/* Insert transparently coded */
buf[0] = CE; /* Send link escape */
buf[1] = byte^IRDA_TRANS; /* Complement bit 5 */
return 2;
/* break; */
default:
/* Non-special value, no transparency required */
buf[0] = byte;
return 1;
/* break; */
}
}
/*
* Function async_wrap (skb, *tx_buff, buffsize)
*
* Makes a new buffer with wrapping and stuffing, should check that
* we don't get tx buffer overflow.
*/
int async_wrap_skb(struct sk_buff *skb, __u8 *tx_buff, int buffsize)
{
struct irda_skb_cb *cb = (struct irda_skb_cb *) skb->cb;
int xbofs;
int i;
int n;
union {
__u16 value;
__u8 bytes[2];
} fcs;
/* Initialize variables */
fcs.value = INIT_FCS;
n = 0;
/*
* Send XBOF's for required min. turn time and for the negotiated
* additional XBOFS
*/
if (cb->magic != LAP_MAGIC) {
/*
* This will happen for all frames sent from user-space.
* Nothing to worry about, but we set the default number of
* BOF's
*/
IRDA_DEBUG(1, "%s(), wrong magic in skb!\n", __FUNCTION__);
xbofs = 10;
} else
xbofs = cb->xbofs + cb->xbofs_delay;
IRDA_DEBUG(4, "%s(), xbofs=%d\n", __FUNCTION__, xbofs);
/* Check that we never use more than 115 + 48 xbofs */
if (xbofs > 163) {
IRDA_DEBUG(0, "%s(), too many xbofs (%d)\n", __FUNCTION__,
xbofs);
xbofs = 163;
}
memset(tx_buff + n, XBOF, xbofs);
n += xbofs;
/* Start of packet character BOF */
tx_buff[n++] = BOF;
/* Insert frame and calc CRC */
for (i=0; i < skb->len; i++) {
/*
* Check for the possibility of tx buffer overflow. We use
* bufsize-5 since the maximum number of bytes that can be
* transmitted after this point is 5.
*/
if(n >= (buffsize-5)) {
IRDA_ERROR("%s(), tx buffer overflow (n=%d)\n",
__FUNCTION__, n);
return n;
}
n += stuff_byte(skb->data[i], tx_buff+n);
fcs.value = irda_fcs(fcs.value, skb->data[i]);
}
/* Insert CRC in little endian format (LSB first) */
fcs.value = ~fcs.value;
#ifdef __LITTLE_ENDIAN
n += stuff_byte(fcs.bytes[0], tx_buff+n);
n += stuff_byte(fcs.bytes[1], tx_buff+n);
#else /* ifdef __BIG_ENDIAN */
n += stuff_byte(fcs.bytes[1], tx_buff+n);
n += stuff_byte(fcs.bytes[0], tx_buff+n);
#endif
tx_buff[n++] = EOF;
return n;
}
EXPORT_SYMBOL(async_wrap_skb);
/************************* FRAME UNWRAPPING *************************/
/*
* Unwrap and unstuff SIR frames
*
* Complete rewrite by Jean II :
* More inline, faster, more compact, more logical. Jean II
* (16 bytes on P6 200MHz, old 5 to 7 us, new 4 to 6 us)
* (24 bytes on P6 200MHz, old 9 to 10 us, new 7 to 8 us)
* (for reference, 115200 b/s is 1 byte every 69 us)
* And reduce wrapper.o by ~900B in the process ;-)
*
* Then, we have the addition of ZeroCopy, which is optional
* (i.e. the driver must initiate it) and improve final processing.
* (2005 B frame + EOF on P6 200MHz, without 30 to 50 us, with 10 to 25 us)
*
* Note : at FIR and MIR, HDLC framing is used and usually handled
* by the controller, so we come here only for SIR... Jean II
*/
/*
* We can also choose where we want to do the CRC calculation. We can
* do it "inline", as we receive the bytes, or "postponed", when
* receiving the End-Of-Frame.
* (16 bytes on P6 200MHz, inlined 4 to 6 us, postponed 4 to 5 us)
* (24 bytes on P6 200MHz, inlined 7 to 8 us, postponed 5 to 7 us)
* With ZeroCopy :
* (2005 B frame on P6 200MHz, inlined 10 to 25 us, postponed 140 to 180 us)
* Without ZeroCopy :
* (2005 B frame on P6 200MHz, inlined 30 to 50 us, postponed 150 to 180 us)
* (Note : numbers taken with irq disabled)
*
* From those numbers, it's not clear which is the best strategy, because
* we end up running through a lot of data one way or another (i.e. cache
* misses). I personally prefer to avoid the huge latency spike of the
* "postponed" solution, because it come just at the time when we have
* lot's of protocol processing to do and it will hurt our ability to
* reach low link turnaround times... Jean II
*/
//#define POSTPONE_RX_CRC
/*
* Function async_bump (buf, len, stats)
*
* Got a frame, make a copy of it, and pass it up the stack! We can try
* to inline it since it's only called from state_inside_frame
*/
static inline void
async_bump(struct net_device *dev,
struct net_device_stats *stats,
iobuff_t *rx_buff)
{
struct sk_buff *newskb;
struct sk_buff *dataskb;
int docopy;
/* Check if we need to copy the data to a new skb or not.
* If the driver doesn't use ZeroCopy Rx, we have to do it.
* With ZeroCopy Rx, the rx_buff already point to a valid
* skb. But, if the frame is small, it is more efficient to
* copy it to save memory (copy will be fast anyway - that's
* called Rx-copy-break). Jean II */
docopy = ((rx_buff->skb == NULL) ||
(rx_buff->len < IRDA_RX_COPY_THRESHOLD));
/* Allocate a new skb */
newskb = dev_alloc_skb(docopy ? rx_buff->len + 1 : rx_buff->truesize);
if (!newskb) {
stats->rx_dropped++;
/* We could deliver the current skb if doing ZeroCopy Rx,
* but this would stall the Rx path. Better drop the
* packet... Jean II */
return;
}
/* Align IP header to 20 bytes (i.e. increase skb->data)
* Note this is only useful with IrLAN, as PPP has a variable
* header size (2 or 1 bytes) - Jean II */
skb_reserve(newskb, 1);
if(docopy) {
/* Copy data without CRC (lenght already checked) */
memcpy(newskb->data, rx_buff->data, rx_buff->len - 2);
/* Deliver this skb */
dataskb = newskb;
} else {
/* We are using ZeroCopy. Deliver old skb */
dataskb = rx_buff->skb;
/* And hook the new skb to the rx_buff */
rx_buff->skb = newskb;
rx_buff->head = newskb->data; /* NOT newskb->head */
//printk(KERN_DEBUG "ZeroCopy : len = %d, dataskb = %p, newskb = %p\n", rx_buff->len, dataskb, newskb);
}
/* Set proper length on skb (without CRC) */
skb_put(dataskb, rx_buff->len - 2);
/* Feed it to IrLAP layer */
dataskb->dev = dev;
dataskb->mac.raw = dataskb->data;
dataskb->protocol = htons(ETH_P_IRDA);
netif_rx(dataskb);
stats->rx_packets++;
stats->rx_bytes += rx_buff->len;
/* Clean up rx_buff (redundant with async_unwrap_bof() ???) */
rx_buff->data = rx_buff->head;
rx_buff->len = 0;
}
/*
* Function async_unwrap_bof(dev, byte)
*
* Handle Beginning Of Frame character received within a frame
*
*/
static inline void
async_unwrap_bof(struct net_device *dev,
struct net_device_stats *stats,
iobuff_t *rx_buff, __u8 byte)
{
switch(rx_buff->state) {
case LINK_ESCAPE:
case INSIDE_FRAME:
/* Not supposed to happen, the previous frame is not
* finished - Jean II */
IRDA_DEBUG(1, "%s(), Discarding incomplete frame\n",
__FUNCTION__);
stats->rx_errors++;
stats->rx_missed_errors++;
irda_device_set_media_busy(dev, TRUE);
break;
case OUTSIDE_FRAME:
case BEGIN_FRAME:
default:
/* We may receive multiple BOF at the start of frame */
break;
}
/* Now receiving frame */
rx_buff->state = BEGIN_FRAME;
rx_buff->in_frame = TRUE;
/* Time to initialize receive buffer */
rx_buff->data = rx_buff->head;
rx_buff->len = 0;
rx_buff->fcs = INIT_FCS;
}
/*
* Function async_unwrap_eof(dev, byte)
*
* Handle End Of Frame character received within a frame
*
*/
static inline void
async_unwrap_eof(struct net_device *dev,
struct net_device_stats *stats,
iobuff_t *rx_buff, __u8 byte)
{
#ifdef POSTPONE_RX_CRC
int i;
#endif
switch(rx_buff->state) {
case OUTSIDE_FRAME:
/* Probably missed the BOF */
stats->rx_errors++;
stats->rx_missed_errors++;
irda_device_set_media_busy(dev, TRUE);
break;
case BEGIN_FRAME:
case LINK_ESCAPE:
case INSIDE_FRAME:
default:
/* Note : in the case of BEGIN_FRAME and LINK_ESCAPE,
* the fcs will most likely not match and generate an
* error, as expected - Jean II */
rx_buff->state = OUTSIDE_FRAME;
rx_buff->in_frame = FALSE;
#ifdef POSTPONE_RX_CRC
/* If we haven't done the CRC as we receive bytes, we
* must do it now... Jean II */
for(i = 0; i < rx_buff->len; i++)
rx_buff->fcs = irda_fcs(rx_buff->fcs,
rx_buff->data[i]);
#endif
/* Test FCS and signal success if the frame is good */
if (rx_buff->fcs == GOOD_FCS) {
/* Deliver frame */
async_bump(dev, stats, rx_buff);
break;
} else {
/* Wrong CRC, discard frame! */
irda_device_set_media_busy(dev, TRUE);
IRDA_DEBUG(1, "%s(), crc error\n", __FUNCTION__);
stats->rx_errors++;
stats->rx_crc_errors++;
}
break;
}
}
/*
* Function async_unwrap_ce(dev, byte)
*
* Handle Character Escape character received within a frame
*
*/
static inline void
async_unwrap_ce(struct net_device *dev,
struct net_device_stats *stats,
iobuff_t *rx_buff, __u8 byte)
{
switch(rx_buff->state) {
case OUTSIDE_FRAME:
/* Activate carrier sense */
irda_device_set_media_busy(dev, TRUE);
break;
case LINK_ESCAPE:
IRDA_WARNING("%s: state not defined\n", __FUNCTION__);
break;
case BEGIN_FRAME:
case INSIDE_FRAME:
default:
/* Stuffed byte coming */
rx_buff->state = LINK_ESCAPE;
break;
}
}
/*
* Function async_unwrap_other(dev, byte)
*
* Handle other characters received within a frame
*
*/
static inline void
async_unwrap_other(struct net_device *dev,
struct net_device_stats *stats,
iobuff_t *rx_buff, __u8 byte)
{
switch(rx_buff->state) {
/* This is on the critical path, case are ordered by
* probability (most frequent first) - Jean II */
case INSIDE_FRAME:
/* Must be the next byte of the frame */
if (rx_buff->len < rx_buff->truesize) {
rx_buff->data[rx_buff->len++] = byte;
#ifndef POSTPONE_RX_CRC
rx_buff->fcs = irda_fcs(rx_buff->fcs, byte);
#endif
} else {
IRDA_DEBUG(1, "%s(), Rx buffer overflow, aborting\n",
__FUNCTION__);
rx_buff->state = OUTSIDE_FRAME;
}
break;
case LINK_ESCAPE:
/*
* Stuffed char, complement bit 5 of byte
* following CE, IrLAP p.114
*/
byte ^= IRDA_TRANS;
if (rx_buff->len < rx_buff->truesize) {
rx_buff->data[rx_buff->len++] = byte;
#ifndef POSTPONE_RX_CRC
rx_buff->fcs = irda_fcs(rx_buff->fcs, byte);
#endif
rx_buff->state = INSIDE_FRAME;
} else {
IRDA_DEBUG(1, "%s(), Rx buffer overflow, aborting\n",
__FUNCTION__);
rx_buff->state = OUTSIDE_FRAME;
}
break;
case OUTSIDE_FRAME:
/* Activate carrier sense */
if(byte != XBOF)
irda_device_set_media_busy(dev, TRUE);
break;
case BEGIN_FRAME:
default:
rx_buff->data[rx_buff->len++] = byte;
#ifndef POSTPONE_RX_CRC
rx_buff->fcs = irda_fcs(rx_buff->fcs, byte);
#endif
rx_buff->state = INSIDE_FRAME;
break;
}
}
/*
* Function async_unwrap_char (dev, rx_buff, byte)
*
* Parse and de-stuff frame received from the IrDA-port
*
* This is the main entry point for SIR drivers.
*/
void async_unwrap_char(struct net_device *dev,
struct net_device_stats *stats,
iobuff_t *rx_buff, __u8 byte)
{
switch(byte) {
case CE:
async_unwrap_ce(dev, stats, rx_buff, byte);
break;
case BOF:
async_unwrap_bof(dev, stats, rx_buff, byte);
break;
case EOF:
async_unwrap_eof(dev, stats, rx_buff, byte);
break;
default:
async_unwrap_other(dev, stats, rx_buff, byte);
break;
}
}
EXPORT_SYMBOL(async_unwrap_char);
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