drivers/net/plip.c

/* Plip.c: A parallel port "network" driver for linux. */
/*
    Written 1993 by Donald Becker and TANABE Hiroyasu.
    This code is distributed under the GPL.
    
    The current author is reached as hiro@sanpo.t.u-tokyo.ac.jp .
    For more information do 'whois -h whois.nic.ad.jp HT043JP'

    The original author may be reached as becker@super.org or
    C/O Supercomputing Research Ctr., 17100 Science Dr., Bowie MD 20715

    This is parallel port packet pusher.  It's actually more general
    than the "IP" in its name suggests -- but 'plip' is just such a
    great name!

    This driver was first developed by D. Becker, when he was inspired by
    Russ Nelson's parallel port packet driver.  He also did the update
    to 0.99.10.

    It was further developed by Tommy Thorn (tthorn@daimi.aau.dk).

    Recent versions were debugged and maintained by TANABE Hiroyasu.

    Updated for 0.99pl12 by Donald Becker.
    
    Changes even more Alan Cox <iiitac@pyr.swan.ac.uk>
    Fixed: sets skb->arp=1, always claims success like ethernet, doesn't
    free skb and then claim fail. Incorrect brackets causing reset problem
    Attempting to make it work (works for me - email me if it does work)
    
    Bugs:
    	Should be timer oriented state machine. 
    	Should never use jiffies for timeouts.
    	Protocol is buggy when broadcasts occur (Must ask Russ Nelson)
    	Can hang forever on collisions (tough - you fix it!).
    	I get 15K/second NFS throughput (about 20-25K second IP).
    	Change the protocol back.
    	
*/

static char *version =
    "Net2Debugged PLIP 1.01 (from plip.c:v0.15 for 0.99pl12+, 8/11/93)\n";

#include <linux/config.h>

/*
  Sources:
	Ideas and protocols came from Russ Nelson's (nelson@crynwr.com)
	"parallel.asm" parallel port packet driver.
	TANABE Hiroyasu changes the protocol.
  The "Crynwr" parallel port standard specifies the following protocol:
   send header nibble '8'
   type octet '0xfd' or '0xfc'
   count-low octet
   count-high octet
   ... data octets
   checksum octet
Each octet is sent as <wait for rx. '0x1?'> <send 0x10+(octet&0x0F)>
			<wait for rx. '0x0?'> <send 0x00+((octet>>4)&0x0F)>

The cable used is a de facto standard parallel null cable -- sold as
a "LapLink" cable by various places.  You'll need a 10-conductor cable to
make one yourself.  The wiring is:
    INIT	16 - 16		SLCTIN	17 - 17
    GROUND	25 - 25
    D0->ERROR	2 - 15		15 - 2
    D1->SLCT	3 - 13		13 - 3
    D2->PAPOUT	4 - 12		12 - 4
    D3->ACK	5 - 10		10 - 5
    D4->BUSY	6 - 11		11 - 6
  Do not connect the other pins.  They are
    D5,D6,D7 are 7,8,9
    STROBE is 1, FEED is 14
    extra grounds are 18,19,20,21,22,23,24
*/

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/interrupt.h>
#include <linux/string.h>
#include <linux/ptrace.h>
#include <linux/if_ether.h>
#include <asm/system.h>
#include <asm/io.h>
#include <netinet/in.h>
#include <errno.h>

#include "dev.h"
#include "eth.h"
#include "ip.h"
#include "protocol.h"
#include "tcp.h"
#include "skbuff.h"
#include "sock.h"
#include "arp.h"

#ifdef PRINTK
#undef PRINTK
#endif
#ifdef PRINTK2
#undef PRINTK2
#endif

#define PLIP_DEBUG	/* debugging */
#undef  PLIP_DEBUG2	/* debugging with more varbose report */

#ifdef PLIP_DEBUG
#define PRINTK(x) printk x
#else
#define PRINTK(x) /**/
#endif
#ifdef PLIP_DEBUG2
#define PRINTK2(x) printk x
#else
#define PRINTK2(x) /**/
#endif

/* The map from IRQ number (as passed to the interrupt handler) to
   'struct device'. */
extern struct device *irq2dev_map[16];

/* Network statistics, with the same names as 'struct enet_statistics'. */
#define netstats enet_statistics

/* constants */
#define PAR_DATA	0
#define PAR_STATUS	1
#define PAR_CONTROL	2
#define PLIP_MTU 1600
#define PLIP_HEADER_TYPE1 0xfd
#define PLIP_HEADER_TYPE2 0xfc

/* Index to functions, as function prototypes. */
extern int plip_probe(int ioaddr, struct device *dev);
static int plip_open(struct device *dev);
static int plip_close(struct device *dev);
static int plip_tx_packet(struct sk_buff *skb, struct device *dev);
static int plip_header (unsigned char *buff, struct device *dev,
		 unsigned short type, unsigned long h_dest,
		 unsigned long h_source, unsigned len);

/* variables used internally. */
#define INITIALTIMEOUTFACTOR 4
#define MAXTIMEOUTFACTOR 20
static int timeoutfactor = INITIALTIMEOUTFACTOR;

/* Routines used internally. */
static void plip_device_clear(struct device *dev);
static void plip_receiver_error(struct device *dev);
static void plip_set_physicaladdr(struct device *dev, unsigned long ipaddr);
static int plip_addrcmp(struct ethhdr *eth);
static int plip_send_enethdr(struct device *dev, struct ethhdr *eth);
static int plip_rebuild_enethdr(struct device *dev, struct ethhdr *eth,
				unsigned char h_dest, unsigned char h_source,
				unsigned short type);
static void cold_sleep(int tics);
static void plip_interrupt(int reg_ptr); /* Dispatch from interrupts. */
static int plip_receive_packet(struct device *dev);
static int plip_send_packet(struct device *dev, unsigned char *buf, int length);
static int plip_send_start(struct device *dev, struct ethhdr *eth);
static void double_timeoutfactor(void);
static struct enet_statistics *plip_get_stats(struct device *dev);

int
plip_init(struct device *dev)
{
    int port_base = dev->base_addr;
    int i;

    /* Check that there is something at base_addr. */
    outb(0x00, port_base + PAR_CONTROL);
    outb(0x55, port_base + PAR_DATA);
    if (inb(port_base + PAR_DATA) != 0x55)
	return -ENODEV;

    /* Alpha testers must have the version number to report bugs. */
#ifdef PLIP_DEBUG
    {
	static int version_shown = 0;
	if (! version_shown)
	    printk(version), version_shown++;
    }
#endif

    /* Initialize the device structure. */
    dev->priv = kmalloc(sizeof(struct netstats), GFP_KERNEL);
    memset(dev->priv, 0, sizeof(struct netstats));

    for (i = 0; i < DEV_NUMBUFFS; i++)
	dev->buffs[i] = NULL;
    dev->hard_header = &plip_header;
    dev->add_arp = eth_add_arp;
    dev->queue_xmit = dev_queue_xmit;
    dev->rebuild_header = eth_rebuild_header;
    dev->type_trans = eth_type_trans;

    dev->open = &plip_open;
    dev->stop = &plip_close;
    dev->hard_start_xmit = &plip_tx_packet;
    dev->get_stats = &plip_get_stats;

    /* These are ethernet specific. */
    dev->type = ARPHRD_ETHER;
    dev->hard_header_len = ETH_HLEN;
    dev->mtu = PLIP_MTU;	/* PLIP may later negotiate max pkt size */
    dev->addr_len = ETH_ALEN;
    for (i = 0; i < dev->addr_len; i++) {
	dev->broadcast[i]=0xff;
	dev->dev_addr[i] = 0;
    }
    printk("%s: configured for parallel port at %#3x, IRQ %d.\n",
	   dev->name, dev->base_addr, dev->irq);

    /* initialize internal value */
    timeoutfactor = INITIALTIMEOUTFACTOR;
    return 0;
}

/* Open/initialize the board.  This is called (in the current kernel)
   sometime after booting when the 'config <dev->name>' program is
   run.

   This routine gets exclusive access to the parallel port by allocating
   its IRQ line.
   */
static int
plip_open(struct device *dev)
{
    if (dev->irq == 0)
	dev->irq = 7;
    cli();
    if (request_irq(dev->irq , &plip_interrupt) != 0) {
    	sti();
	PRINTK(("%s: couldn't get IRQ %d.\n", dev->name, dev->irq));
	return -EAGAIN;
    }

    irq2dev_map[dev->irq] = dev;
    sti();
    plip_device_clear(dev);
    dev->tbusy = 0;
    dev->interrupt = 0;
    dev->start = 1;
    return 0;
}

/* The inverse routine to plip_open(). */
static int
plip_close(struct device *dev)
{
    dev->tbusy = 1;
    dev->start = 0;
    cli();
    free_irq(dev->irq);
    irq2dev_map[dev->irq] = NULL;
    sti();
    outb(0x00, dev->base_addr);		/* Release the interrupt. */
    return 0;
}

static int
plip_tx_packet(struct sk_buff *skb, struct device *dev)
{
    int ret_val;

    if (dev->tbusy || dev->interrupt) {	/* Do timeouts, to avoid hangs. */
	int tickssofar = jiffies - dev->trans_start;
	if (tickssofar < 50)
	    return 1;
	printk("%s: transmit timed out\n", dev->name);
	/* Try to restart the adaptor. */
	plip_device_clear(dev);
	return 0;
    }

    /* If some higher layer thinks we've missed an tx-done interrupt
       we are passed NULL. Caution: dev_tint() handles the cli()/sti()
       itself. */
    if (skb == NULL) {
	dev_tint(dev);
	return 0;
    }

    /* Pretend we are an ethernet and fill in the header.  This could use
       a simplified routine someday. */
    if (!skb->arp  &&  dev->rebuild_header(skb->data, dev)) {
	skb->dev = dev;
	arp_queue (skb);
	return 0;
    }
    skb->arp=1;

    dev->trans_start = jiffies;
    ret_val = plip_send_packet(dev, skb->data, skb->len);
    if (skb->free)
	kfree_skb (skb, FREE_WRITE);
    dev->tbusy = 0;
    mark_bh (INET_BH);
    return 0/*ret_val*/;
}

static int
plip_header (unsigned char *buff, struct device *dev,
	     unsigned short type, unsigned long h_dest,
	     unsigned long h_source, unsigned len)
{
    if (dev->dev_addr[0] == 0) {
	/* set physical address */
	plip_set_physicaladdr(dev, h_source);
    }
    return eth_header(buff, dev, type, h_dest, h_source, len);
}

static void
  plip_device_clear(struct device *dev)
{
    dev->interrupt = 0;
    dev->tbusy = 0;
    outb(0x00, dev->base_addr + PAR_DATA);
    outb(0x10, dev->base_addr + PAR_CONTROL);		/* Enable the rx interrupt. */
}

static void
  plip_receiver_error(struct device *dev)
{
    dev->interrupt = 0;
    dev->tbusy = 0;
    outb(0x02, dev->base_addr + PAR_DATA);
    outb(0x10, dev->base_addr + PAR_CONTROL);		/* Enable the rx interrupt. */
}

static int
  get_byte(struct device *dev)
{
    unsigned char val, oldval;
    unsigned char low_nibble;
    int timeout;
    int error = 0;
    val = inb(dev->base_addr + PAR_STATUS);
    timeout = jiffies + timeoutfactor * 2;
    do {
	oldval = val;
	val = inb(dev->base_addr + PAR_STATUS);
	if ( oldval != val ) continue; /* it's unstable */
	if ( timeout < jiffies ) {
	    error++;
	    break;
	}
    } while ( (val & 0x80) );
    val = inb(dev->base_addr + PAR_STATUS);
    low_nibble = (val >> 3) & 0x0f;
    outb(0x11, dev->base_addr + PAR_DATA);
    timeout = jiffies + timeoutfactor * 2;
    do {
	oldval = val;
	val = inb(dev->base_addr + PAR_STATUS);
	if (oldval != val) continue; /* it's unstable */
	if ( timeout < jiffies ) {
	    error++;
	    break;
	}
    } while ( !(val & 0x80) );
    val = inb(dev->base_addr + PAR_STATUS);
    PRINTK2(("%02x %s ", low_nibble | ((val << 1) & 0xf0),
	       error ? "t":""));
    outb(0x01, dev->base_addr + PAR_DATA);
    if (error) {
	/* timeout error */
	double_timeoutfactor();
	return -1;
    }
    return low_nibble | ((val << 1) & 0xf0);
}

/* The typical workload of the driver:
   Handle the parallel port interrupts. */
static void
  plip_interrupt(int reg_ptr)
{
    int irq = -(((struct pt_regs *)reg_ptr)->orig_eax+2);
    struct device *dev = irq2dev_map[irq];
    struct netstats *localstats;

    if (dev == NULL) {
	PRINTK(("plip_interrupt(): irq %d for unknown device.\n", irq));
	return;
    }
    localstats = (struct netstats*) dev->priv;
    if (dev->tbusy || dev->interrupt) return;
    dev->interrupt = 1;
    outb(0x00, dev->base_addr + PAR_CONTROL);  /* Disable the rx interrupt. */
    sti(); /* Allow other interrupts. */
    PRINTK2(("%s: interrupt.  ", dev->name));

    {
	/* check whether the interrupt is valid or not.*/
	int timeout = jiffies + timeoutfactor;
	while ((inb(dev->base_addr + PAR_STATUS) & 0xf8) != 0xc0) {
	    if ( timeout < jiffies ) {
		PRINTK2(("%s: No interrupt (status=%#02x)!\n",
			 dev->name, inb(dev->base_addr + PAR_STATUS)));
		plip_device_clear(dev);
		return;
	    }
	}
    }
    if (plip_receive_packet(dev)) {
	/* get some error while receiving data */
	localstats->rx_errors++;
	plip_receiver_error(dev);
    } else {
	plip_device_clear(dev);
    }
}

static int
plip_receive_packet(struct device *dev)
{
    int plip_type;
    unsigned length;
    int checksum = 0;
    struct sk_buff *skb;
    struct netstats *localstats;
    struct ethhdr eth;

    localstats = (struct netstats*) dev->priv;
    
    outb(1, dev->base_addr + PAR_DATA);		/* Ack: 'Ready' */

    {
	/* get header octet and length of packet */
	plip_type = get_byte(dev);
	if (plip_type < 0) return 1; /* probably wrong interrupt */
	length = get_byte(dev) << 8;
	length |= get_byte(dev);
	switch ( plip_type ) {
	  case PLIP_HEADER_TYPE1:
	    {
		int i;
		unsigned char *eth_p = (unsigned char*)&eth;
		for ( i = 0; i < sizeof(eth); i++, eth_p++) {
		    *eth_p = get_byte(dev);
		}
	    }
	    break;
	  case PLIP_HEADER_TYPE2:
	    {
		unsigned char h_dest, h_source;
		unsigned short type;
		h_dest = get_byte(dev);
		h_source = get_byte(dev);
		type = get_byte(dev) << 8;
		type |= get_byte(dev);
		plip_rebuild_enethdr(dev, &eth, h_dest, h_source, type);
	    }
	    break;
	  default:
	    PRINTK(("%s: wrong header octet\n", dev->name));
	}
	PRINTK2(("length = %d\n", length));
	if (length > dev->mtu || length < 8) {
	    PRINTK2(("%s: bogus packet size %d.\n", dev->name, length));
	    return 1;
	}
    }
    {
	/* get skb area from kernel and 
	 * set appropriate values to skb
	 */
	int sksize;
	sksize = sizeof(struct sk_buff) + length;
	skb = alloc_skb(sksize, GFP_ATOMIC);
	if (skb == NULL) {
	    PRINTK(("%s: Couldn't allocate a sk_buff of size %d.\n",
		    dev->name, sksize));
	    return 1;
	}
	skb->lock = 0;
	skb->mem_len = sksize;
	skb->mem_addr = skb;
    }
    {
	/* phase of receiving the data */
	/* 'skb->data' points to the start of sk_buff data area. */
	unsigned char *buf = skb->data;
	unsigned char *eth_p = (unsigned char *)&eth;
	int i;
	for ( i = 0; i < sizeof(eth); i++) {
	    checksum += *eth_p;
	    *buf++ = *eth_p++;
	}
	for ( i = 0; i < length - sizeof(eth); i++) {
	    unsigned char new_byte = get_byte(dev);
	    checksum += new_byte;
	    *buf++ = new_byte;
	}
	checksum &= 0xff;
	if (checksum != get_byte(dev)) {
	    localstats->rx_crc_errors++;
	    PRINTK(("checksum error\n"));
	    return 1;
	} else if(dev_rint((unsigned char *)skb, length, IN_SKBUFF, dev)) {
	    printk("%s: rcv buff full.\n", dev->name);
	    localstats->rx_dropped++;
	    return 1;
	}
    }
    {
	/* phase of terminating this connection */
	int timeout;

	timeout = jiffies + length * timeoutfactor / 16;
	outb(0x00, dev->base_addr + PAR_DATA);
	/* Wait for the remote end to reset. */
	while ( (inb(dev->base_addr + PAR_STATUS) & 0xf8) != 0x80 ) {
	    if (timeout < jiffies ) {
		double_timeoutfactor();
		PRINTK(("Remote has not reset.\n"));
		break;
	    }
	}
    }
    localstats->rx_packets++;
    return 0;
}


static int send_byte(struct device *dev, unsigned char val)
{
    int timeout;
    int error = 0;
    if (!(inb(dev->base_addr+PAR_STATUS) & 0x08)) {
	PRINTK(("remote end become unready while sending\n"));
	return -1;
    }
    PRINTK2((" S%02x", val));
    outb(val, dev->base_addr); /* this makes data bits more stable */
    outb(0x10 | val, dev->base_addr);
    timeout = jiffies + timeoutfactor;
    while( inb(dev->base_addr+PAR_STATUS) & 0x80 )
	if ( timeout < jiffies ) {
	    error++;
	    break;
	}
    outb(0x10 | (val >> 4), dev->base_addr);
    outb(val >> 4, dev->base_addr);
    timeout = jiffies + timeoutfactor;
    while( (inb(dev->base_addr+PAR_STATUS) & 0x80) == 0 )
	if ( timeout < jiffies ) {
	    error++;
	    break;
	}
    if (error) {
	/* timeout error */
	double_timeoutfactor();
	PRINTK2(("t"));
	return -1;
    }
    return 0;
}
/*
 * plip_send_start
 * trigger remoto rx interrupt and establish a connection.
 * 
 * return value
 * 0 : establish the connection
 * -1 : connection failed.
 */
static int
plip_send_start(struct device *dev, struct ethhdr *eth)
{	
    int timeout;
    int status;
    int lasttrigger;
    struct netstats *localstats = (struct netstats*) dev->priv;

    /* This starts the packet protocol by triggering a remote IRQ. */
    timeout = jiffies + timeoutfactor * 16;
    lasttrigger = jiffies;
    while ( ((status = inb(dev->base_addr+PAR_STATUS)) & 0x08) == 0 ) {
	dev->tbusy = 1;
	outb(0x00, dev->base_addr + PAR_CONTROL); /* Disable my rx intr. */
	outb(0x08, dev->base_addr + PAR_DATA); 	/* Trigger remote rx intr. */
	if (status & 0x40) {
	    /* The remote end is also trying to send a packet.
	     * Only one end may go to the receiving phase,
	     * so we use the "ethernet" address (set from the IP address)
	     * to determine which end dominates.
	     */
	    if ( plip_addrcmp(eth) > 0 ) {
		localstats->collisions++;
		PRINTK2(("both ends are trying to send a packet.\n"));
		if (plip_receive_packet(dev)) {
		    /* get some error while receiving data */
		    localstats->rx_errors++;
		    outb(0x02, dev->base_addr + PAR_DATA);
		} else {
		    outb(0x00, dev->base_addr + PAR_DATA);
		}
		cold_sleep(2); /* make sure that remote end is ready */
	    }
	    continue; /* restart send sequence */
	}
	if (lasttrigger != jiffies) {
	    /* trigger again */
	    outb(0x00, dev->base_addr + PAR_DATA);
	    cold_sleep(1);
	    lasttrigger = jiffies;
	}
	if (timeout < jiffies) {
	    double_timeoutfactor();
	    plip_device_clear(dev);
	    localstats->tx_errors++;
	    PRINTK(("%s: Connect failed in send_packet().\n",
		    dev->name));
	    /* We failed to send the packet.  To emulate the ethernet we
	       should pretent the send worked fine */
	    return -1;
	}
    }
    return 0;
}
static int
plip_send_packet(struct device *dev, unsigned char *buf, int length)
{
    int error = 0;
    int plip_type;
    struct netstats *localstats;

    PRINTK2(("%s: plip_send_packet(%d) %02x %02x %02x %02x %02x...",
	   dev->name, length, buf[0], buf[1], buf[2], buf[3], buf[4]));
    if (length > dev->mtu) {
	printk("%s: packet too big, %d.\n", dev->name, length);
	return 0;
    }
    localstats = (struct netstats*) dev->priv;

    {
	/* phase of checking remote status */
	int i;
	int timeout = jiffies + timeoutfactor * 8;
	while ( (i = (inb(dev->base_addr+PAR_STATUS) & 0xe8)) != 0x80 ) {
	    if (i == 0x78) {
		/* probably cable is not connected */
		/* Implementation Note:
		 * This status should result in 'Network unreachable'.
		 * but I don't know the way.
		 */
		return 0;
	    }
	    if (timeout < jiffies) {
		/* remote end is not ready */
		double_timeoutfactor();
		localstats->tx_errors++;
		PRINTK(("remote end is not ready.\n"));
		return 1; /* Failed to send the packet */
	    }
	}
    }
    /* phase of making a connection */
    if (plip_send_start(dev, (struct ethhdr *)buf) < 0)
	return 1;

    /* select plip type */
    {
	/* Use stripped ethernet header if each first 5 octet of eth
	 * address is same.
	 */
	int i;
	struct ethhdr *eth = (struct ethhdr *)buf;

	plip_type = PLIP_HEADER_TYPE2;	
	for ( i = 0; i < ETH_ALEN - 1; i++)
	    if (eth->h_dest[i] != eth->h_source[i])
		plip_type = PLIP_HEADER_TYPE1;
    }

    send_byte(dev, plip_type); /* send header octet */

    {
	/* send packet's length */
	/*
	 * in original plip (before v0.1), it was sent with little endian.
	 * but in internet, network byteorder is big endian,
	 * so changed to use big endian.
	 * maybe using 'ntos()' is better.
	 */
	send_byte(dev, length >> 8); send_byte(dev, length);
    }
    {
	/* phase of sending data */
	int i;
	int checksum = 0;

	if (plip_type == PLIP_HEADER_TYPE2) {
	    plip_send_enethdr(dev, (struct ethhdr*)buf);
	}
	for ( i = 0; i < sizeof(struct ethhdr); i++ ) {
	    if (plip_type == PLIP_HEADER_TYPE1) {
		send_byte(dev, *buf);
	    }
	    checksum += *buf++;
	}

	for (i = 0; i < length - sizeof(struct ethhdr); i++) {
	    checksum += buf[i];
	    if (send_byte(dev, buf[i]) < 0) {
		error++;
		break;
	    }
	}
	send_byte(dev, checksum & 0xff);
    }
    {
	/* phase of terminating this connection */
	int timeout;
	
	outb(0x00, dev->base_addr + PAR_DATA);
	/* Wait for the remote end to reset. */
	timeout = jiffies + ((length * timeoutfactor) >> 4);
	while ((inb(dev->base_addr + PAR_STATUS) & 0xe8) != 0x80) {
	    if (timeout < jiffies ) {	
		double_timeoutfactor();
		PRINTK(("Remote end has not reset.\n"));
		error++;
		break;
	    }
	}
	if (inb(dev->base_addr + PAR_STATUS) & 0x10) {
	    /* receiver reports error */
	    error++;
	}
    }
    plip_device_clear(dev);
    localstats->tx_packets++;
    PRINTK2(("plip_send_packet(%d) done.\n", length));
    return error?1:0;
}

/*
 * some trivial functions
 */
static void
plip_set_physicaladdr(struct device *dev, unsigned long ipaddr)
{
    /*
     * set physical address to
     *  0xfd.0xfd.ipaddr
     */

    unsigned char *addr = dev->dev_addr;
    int i;

    if ((ipaddr >> 24) == 0 || (ipaddr >> 24) == 0xff) return;
    PRINTK2(("%s: set physical address to %08x\n", dev->name, ipaddr));
    for (i=0; i < ETH_ALEN - sizeof(unsigned long); i++) {
	addr[i] = 0xfd;
    }
    memcpy(&(addr[i]), &ipaddr, sizeof(unsigned long));
}

static int
plip_addrcmp(struct ethhdr *eth)
{
    int i;
    for ( i = ETH_ALEN - 1; i >= 0; i-- ) {
	if (eth->h_dest[i] > eth->h_source[i]) return -1;
	if (eth->h_dest[i] < eth->h_source[i]) return 1;
    }
    PRINTK2(("h_dest = %08x%04x h_source = %08x%04x\n",
	    *(long*)&eth->h_dest[2],*(short*)&eth->h_dest[0],
	    *(long*)&eth->h_source[2],*(short*)&eth->h_source[0]));
    return 0;
}

static int
plip_send_enethdr(struct device *dev, struct ethhdr *eth)
{
    send_byte(dev, eth->h_dest[ETH_ALEN-1]);
    send_byte(dev, eth->h_source[ETH_ALEN-1]);
    send_byte(dev, eth->h_proto >> 8);
    send_byte(dev, eth->h_proto);
    return 0;
}

static int
plip_rebuild_enethdr(struct device *dev, struct ethhdr *eth,
		     unsigned char dest, unsigned char source,
		     unsigned short type)
{
    eth->h_proto = type;
    memcpy(eth->h_dest, dev->dev_addr, ETH_ALEN-1);
    eth->h_dest[ETH_ALEN-1] = dest;
    memcpy(eth->h_source, dev->dev_addr, ETH_ALEN-1);
    eth->h_source[ETH_ALEN-1] = source;
    return 0;
}

/* This function is evil, evil, evil.  This should be a
   _kernel_, rescheduling sleep!. */
static void
cold_sleep(int tics)
{
    int start = jiffies;
    while(jiffies < start + tics)
	; /* do nothing */
    return;
}

static void
  double_timeoutfactor()
{
    timeoutfactor *= 2;
    if (timeoutfactor >= MAXTIMEOUTFACTOR) {
	timeoutfactor = MAXTIMEOUTFACTOR;
    }
    return;
}

static struct enet_statistics *
plip_get_stats(struct device *dev)
{
    struct netstats *localstats = (struct netstats*) dev->priv;
    return localstats;
}

/*
 * Local variables:
 *  compile-command: "gcc -D__KERNEL__ -Wall -O6 -fomit-frame-pointer -x c++ -c plip.c"
 *  version-control: t
 *  kept-new-versions: 5
 * End:
 */