initial commit with v2.6.9

[linux-2.6.9-moxart.git] / drivers / net / arcnet / arcnet.c

/*
 * Linux ARCnet driver - device-independent routines
 * 
 * Written 1997 by David Woodhouse.
 * Written 1994-1999 by Avery Pennarun.
 * Written 1999-2000 by Martin Mares <mj@ucw.cz>.
 * Derived from skeleton.c by Donald Becker.
 *
 * Special thanks to Contemporary Controls, Inc. (www.ccontrols.com)
 *  for sponsoring the further development of this driver.
 *
 * **********************
 *
 * The original copyright was as follows:
 *
 * skeleton.c Written 1993 by Donald Becker.
 * Copyright 1993 United States Government as represented by the
 * Director, National Security Agency.  This software may only be used
 * and distributed according to the terms of the GNU General Public License as
 * modified by SRC, incorporated herein by reference.
 *
 * **********************
 * 
 * The change log is now in a file called ChangeLog in this directory.
 *
 * Sources:
 *  - Crynwr arcnet.com/arcether.com packet drivers.
 *  - arcnet.c v0.00 dated 1/1/94 and apparently by 
 *     Donald Becker - it didn't work :)
 *  - skeleton.c v0.05 dated 11/16/93 by Donald Becker
 *     (from Linux Kernel 1.1.45)
 *  - RFC's 1201 and 1051 - re: TCP/IP over ARCnet
 *  - The official ARCnet COM9026 data sheets (!) thanks to
 *     Ken Cornetet <kcornete@nyx10.cs.du.edu>
 *  - The official ARCnet COM20020 data sheets.
 *  - Information on some more obscure ARCnet controller chips, thanks
 *     to the nice people at SMSC.
 *  - net/inet/eth.c (from kernel 1.1.50) for header-building info.
 *  - Alternate Linux ARCnet source by V.Shergin <vsher@sao.stavropol.su>
 *  - Textual information and more alternate source from Joachim Koenig
 *     <jojo@repas.de>
 */

#define VERSION "arcnet: v3.93 BETA 2000/04/29 - by Avery Pennarun et al.\n"

#include <linux/module.h>
#include <linux/config.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <net/arp.h>
#include <linux/init.h>
#include <linux/arcdevice.h>


/* "do nothing" functions for protocol drivers */
static void null_rx(struct net_device *dev, int bufnum,
                    struct archdr *pkthdr, int length);
static int null_build_header(struct sk_buff *skb, struct net_device *dev,
                             unsigned short type, uint8_t daddr);
static int null_prepare_tx(struct net_device *dev, struct archdr *pkt,
                           int length, int bufnum);


/*
 * one ArcProto per possible proto ID.  None of the elements of
 * arc_proto_map are allowed to be NULL; they will get set to
 * arc_proto_default instead.  It also must not be NULL; if you would like
 * to set it to NULL, set it to &arc_proto_null instead.
 */
struct ArcProto *arc_proto_map[256], *arc_proto_default, *arc_bcast_proto;

struct ArcProto arc_proto_null =
{
        .suffix         = '?',
        .mtu            = XMTU,
        .rx             = null_rx,
        .build_header   = null_build_header,
        .prepare_tx     = null_prepare_tx,
};

static spinlock_t arcnet_lock = SPIN_LOCK_UNLOCKED;

/* Exported function prototypes */
int arcnet_debug = ARCNET_DEBUG;

EXPORT_SYMBOL(arc_proto_map);
EXPORT_SYMBOL(arc_proto_default);
EXPORT_SYMBOL(arc_bcast_proto);
EXPORT_SYMBOL(arc_proto_null);
EXPORT_SYMBOL(arcnet_unregister_proto);
EXPORT_SYMBOL(arcnet_debug);
EXPORT_SYMBOL(arcdev_setup);
EXPORT_SYMBOL(alloc_arcdev);
EXPORT_SYMBOL(arcnet_interrupt);

/* Internal function prototypes */
static int arcnet_open(struct net_device *dev);
static int arcnet_close(struct net_device *dev);
static int arcnet_send_packet(struct sk_buff *skb, struct net_device *dev);
static void arcnet_timeout(struct net_device *dev);
static int arcnet_header(struct sk_buff *skb, struct net_device *dev,
                         unsigned short type, void *daddr, void *saddr,
                         unsigned len);
static int arcnet_rebuild_header(struct sk_buff *skb);
static struct net_device_stats *arcnet_get_stats(struct net_device *dev);
static int go_tx(struct net_device *dev);

static int debug = ARCNET_DEBUG;
MODULE_PARM(debug, "i");
MODULE_LICENSE("GPL");

static int __init arcnet_init(void)
{
        int count;

        arcnet_debug = debug;

        printk(VERSION);

#ifdef ALPHA_WARNING
        BUGLVL(D_EXTRA) {
                printk("arcnet: ***\n"
                "arcnet: * Read arcnet.txt for important release notes!\n"
                       "arcnet: *\n"
                       "arcnet: * This is an ALPHA version! (Last stable release: v3.02)  E-mail\n"
                       "arcnet: * me if you have any questions, comments, or bug reports.\n"
                       "arcnet: ***\n");
        }
#endif

        /* initialize the protocol map */
        arc_proto_default = arc_bcast_proto = &arc_proto_null;
        for (count = 0; count < 256; count++)
                arc_proto_map[count] = arc_proto_default;

        BUGLVL(D_DURING)
            printk("arcnet: struct sizes: %Zd %Zd %Zd %Zd %Zd\n",
                 sizeof(struct arc_hardware), sizeof(struct arc_rfc1201),
                sizeof(struct arc_rfc1051), sizeof(struct arc_eth_encap),
                   sizeof(struct archdr));

        return 0;
}

static void __exit arcnet_exit(void)
{
}

module_init(arcnet_init);
module_exit(arcnet_exit);

/*
 * Dump the contents of an sk_buff
 */
#if ARCNET_DEBUG_MAX & D_SKB
void arcnet_dump_skb(struct net_device *dev, struct sk_buff *skb, char *desc)
{
        int i;

        printk(KERN_DEBUG "%6s: skb dump (%s) follows:", dev->name, desc);
        for (i = 0; i < skb->len; i++) {
                if (i % 16 == 0)
                        printk("\n" KERN_DEBUG "[%04X] ", i);
                printk("%02X ", ((u_char *) skb->data)[i]);
        }
        printk("\n");
}

EXPORT_SYMBOL(arcnet_dump_skb);
#endif


/*
 * Dump the contents of an ARCnet buffer
 */
#if (ARCNET_DEBUG_MAX & (D_RX | D_TX))
void arcnet_dump_packet(struct net_device *dev, int bufnum, char *desc)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;
        int i, length;
        unsigned long flags;
        static uint8_t buf[512];

        /* hw.copy_from_card expects IRQ context so take the IRQ lock
           to keep it single threaded */
        spin_lock_irqsave(&arcnet_lock, flags);
        lp->hw.copy_from_card(dev, bufnum, 0, buf, 512);
        spin_unlock_irqrestore(&arcnet_lock, flags);

        /* if the offset[0] byte is nonzero, this is a 256-byte packet */
        length = (buf[2] ? 256 : 512);

        printk(KERN_DEBUG "%6s: packet dump (%s) follows:", dev->name, desc);
        for (i = 0; i < length; i++) {
                if (i % 16 == 0)
                        printk("\n" KERN_DEBUG "[%04X] ", i);
                printk("%02X ", buf[i]);
        }
        printk("\n");

}

EXPORT_SYMBOL(arcnet_dump_packet);
#endif


/*
 * Unregister a protocol driver from the arc_proto_map.  Protocol drivers
 * are responsible for registering themselves, but the unregister routine
 * is pretty generic so we'll do it here.
 */
void arcnet_unregister_proto(struct ArcProto *proto)
{
        int count;

        if (arc_proto_default == proto)
                arc_proto_default = &arc_proto_null;
        if (arc_bcast_proto == proto)
                arc_bcast_proto = arc_proto_default;

        for (count = 0; count < 256; count++) {
                if (arc_proto_map[count] == proto)
                        arc_proto_map[count] = arc_proto_default;
        }
}


/*
 * Add a buffer to the queue.  Only the interrupt handler is allowed to do
 * this, unless interrupts are disabled.
 * 
 * Note: we don't check for a full queue, since there aren't enough buffers
 * to more than fill it.
 */
static void release_arcbuf(struct net_device *dev, int bufnum)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;
        int i;

        lp->buf_queue[lp->first_free_buf++] = bufnum;
        lp->first_free_buf %= 5;

        BUGLVL(D_DURING) {
                BUGMSG(D_DURING, "release_arcbuf: freed #%d; buffer queue is now: ",
                       bufnum);
                for (i = lp->next_buf; i != lp->first_free_buf; i = ++i % 5)
                        BUGMSG2(D_DURING, "#%d ", lp->buf_queue[i]);
                BUGMSG2(D_DURING, "\n");
        }
}


/*
 * Get a buffer from the queue.  If this returns -1, there are no buffers
 * available.
 */
static int get_arcbuf(struct net_device *dev)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;
        int buf = -1, i;

        if (!atomic_dec_and_test(&lp->buf_lock))        /* already in this function */
                BUGMSG(D_NORMAL, "get_arcbuf: overlap (%d)!\n", lp->buf_lock.counter);
        else {                  /* we can continue */
                if (lp->next_buf >= 5)
                        lp->next_buf -= 5;

                if (lp->next_buf == lp->first_free_buf)
                        BUGMSG(D_NORMAL, "get_arcbuf: BUG: no buffers are available??\n");
                else {
                        buf = lp->buf_queue[lp->next_buf++];
                        lp->next_buf %= 5;
                }
        }


        BUGLVL(D_DURING) {
                BUGMSG(D_DURING, "get_arcbuf: got #%d; buffer queue is now: ", buf);
                for (i = lp->next_buf; i != lp->first_free_buf; i = ++i % 5)
                        BUGMSG2(D_DURING, "#%d ", lp->buf_queue[i]);
                BUGMSG2(D_DURING, "\n");
        }

        atomic_inc(&lp->buf_lock);
        return buf;
}


static int choose_mtu(void)
{
        int count, mtu = 65535;

        /* choose the smallest MTU of all available encaps */
        for (count = 0; count < 256; count++) {
                if (arc_proto_map[count] != &arc_proto_null
                    && arc_proto_map[count]->mtu < mtu) {
                        mtu = arc_proto_map[count]->mtu;
                }
        }

        return mtu == 65535 ? XMTU : mtu;
}


/* Setup a struct device for ARCnet. */
void arcdev_setup(struct net_device *dev)
{
        dev->type = ARPHRD_ARCNET;
        dev->hard_header_len = sizeof(struct archdr);
        dev->mtu = choose_mtu();

        dev->addr_len = ARCNET_ALEN;
        dev->tx_queue_len = 30;
        dev->broadcast[0] = 0x00;       /* for us, broadcasts are address 0 */
        dev->watchdog_timeo = TX_TIMEOUT;

        /* New-style flags. */
        dev->flags = IFF_BROADCAST;

        /*
         * Put in this stuff here, so we don't have to export the symbols to
         * the chipset drivers.
         */
        dev->open = arcnet_open;
        dev->stop = arcnet_close;
        dev->hard_start_xmit = arcnet_send_packet;
        dev->tx_timeout = arcnet_timeout;
        dev->get_stats = arcnet_get_stats;
        dev->hard_header = arcnet_header;
        dev->rebuild_header = arcnet_rebuild_header;
}

struct net_device *alloc_arcdev(char *name)
{
        return alloc_netdev(sizeof(struct arcnet_local),
                            name && *name ? name : "arc%d", arcdev_setup);
}

/*
 * Open/initialize the board.  This is called sometime after booting when
 * the 'ifconfig' program is run.
 *
 * This routine should set everything up anew at each open, even registers
 * that "should" only need to be set once at boot, so that there is
 * non-reboot way to recover if something goes wrong.
 */
static int arcnet_open(struct net_device *dev)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;
        int count, newmtu, error;

        if (!try_module_get(lp->hw.owner))
                return -ENODEV;

        BUGLVL(D_PROTO) {
                int count;
                BUGMSG(D_PROTO, "protocol map (default is '%c'): ",
                       arc_proto_default->suffix);
                for (count = 0; count < 256; count++)
                        BUGMSG2(D_PROTO, "%c", arc_proto_map[count]->suffix);
                BUGMSG2(D_PROTO, "\n");
        }


        BUGMSG(D_INIT, "arcnet_open: resetting card.\n");

        /* try to put the card in a defined state - if it fails the first
         * time, actually reset it.
         */
        error = -ENODEV;
        if (ARCRESET(0) && ARCRESET(1))
                goto out_module_put;

        newmtu = choose_mtu();
        if (newmtu < dev->mtu)
                dev->mtu = newmtu;

        /* autodetect the encapsulation for each host. */
        memset(lp->default_proto, 0, sizeof(lp->default_proto));

        /* the broadcast address is special - use the 'bcast' protocol */
        for (count = 0; count < 256; count++) {
                if (arc_proto_map[count] == arc_bcast_proto) {
                        lp->default_proto[0] = count;
                        break;
                }
        }

        /* initialize buffers */
        atomic_set(&lp->buf_lock, 1);
        lp->next_buf = lp->first_free_buf = 0;
        release_arcbuf(dev, 0);
        release_arcbuf(dev, 1);
        release_arcbuf(dev, 2);
        release_arcbuf(dev, 3);
        lp->cur_tx = lp->next_tx = -1;
        lp->cur_rx = -1;

        lp->rfc1201.sequence = 1;

        /* bring up the hardware driver */
        if (lp->hw.open)
                lp->hw.open(dev);

        if (dev->dev_addr[0] == 0)
                BUGMSG(D_NORMAL, "WARNING!  Station address 00 is reserved "
                       "for broadcasts!\n");
        else if (dev->dev_addr[0] == 255)
                BUGMSG(D_NORMAL, "WARNING!  Station address FF may confuse "
                       "DOS networking programs!\n");

        if (ASTATUS() & RESETflag)
                ACOMMAND(CFLAGScmd | RESETclear);

        /* make sure we're ready to receive IRQ's. */
        AINTMASK(0);
        udelay(1);              /* give it time to set the mask before
                                 * we reset it again. (may not even be
                                 * necessary)
                                 */
        lp->intmask = NORXflag | RECONflag;
        AINTMASK(lp->intmask);

        netif_start_queue(dev);

        return 0;

 out_module_put:
        module_put(lp->hw.owner);
        return error;
}


/* The inverse routine to arcnet_open - shuts down the card. */
static int arcnet_close(struct net_device *dev)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;

        netif_stop_queue(dev);

        /* flush TX and disable RX */
        AINTMASK(0);
        ACOMMAND(NOTXcmd);      /* stop transmit */
        ACOMMAND(NORXcmd);      /* disable receive */
        mdelay(1);

        /* shut down the card */
        lp->hw.close(dev);
        module_put(lp->hw.owner);
        return 0;
}


static int arcnet_header(struct sk_buff *skb, struct net_device *dev,
                         unsigned short type, void *daddr, void *saddr,
                         unsigned len)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;
        uint8_t _daddr, proto_num;
        struct ArcProto *proto;

        BUGMSG(D_DURING,
            "create header from %d to %d; protocol %d (%Xh); size %u.\n",
               saddr ? *(uint8_t *) saddr : -1,
               daddr ? *(uint8_t *) daddr : -1,
               type, type, len);

        if (len != skb->len)
                BUGMSG(D_NORMAL, "arcnet_header: Yikes!  skb->len(%d) != len(%d)!\n",
                       skb->len, len);

        /*
         * if the dest addr isn't provided, we can't choose an encapsulation!
         * Store the packet type (eg. ETH_P_IP) for now, and we'll push on a
         * real header when we do rebuild_header. 
         */
        if (!daddr) {
                *(uint16_t *) skb_push(skb, 2) = type;
                if (skb->nh.raw - skb->mac.raw != 2)
                        BUGMSG(D_NORMAL, "arcnet_header: Yikes!  diff (%d) is not 2!\n",
                               (int)(skb->nh.raw - skb->mac.raw));
                return -2;      /* return error -- can't transmit yet! */
        }
        /* otherwise, we can just add the header as usual. */
        _daddr = *(uint8_t *) daddr;
        proto_num = lp->default_proto[_daddr];
        proto = arc_proto_map[proto_num];
        BUGMSG(D_DURING, "building header for %02Xh using protocol '%c'\n",
               proto_num, proto->suffix);
        if (proto == &arc_proto_null && arc_bcast_proto != proto) {
                BUGMSG(D_DURING, "actually, let's use '%c' instead.\n",
                       arc_bcast_proto->suffix);
                proto = arc_bcast_proto;
        }
        return proto->build_header(skb, dev, type, _daddr);
}


/* 
 * Rebuild the ARCnet hard header. This is called after an ARP (or in the
 * future other address resolution) has completed on this sk_buff. We now
 * let ARP fill in the destination field.
 */
static int arcnet_rebuild_header(struct sk_buff *skb)
{
        struct net_device *dev = skb->dev;
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;
        int status = 0;         /* default is failure */
        unsigned short type;
        uint8_t daddr=0;
        struct ArcProto *proto;

        if (skb->nh.raw - skb->mac.raw != 2) {
                BUGMSG(D_NORMAL,
                     "rebuild_header: shouldn't be here! (hdrsize=%d)\n",
                     (int)(skb->nh.raw - skb->mac.raw));
                return 0;
        }
        type = *(uint16_t *) skb_pull(skb, 2);

        if (type == ETH_P_IP) {
#ifdef CONFIG_INET
                BUGMSG(D_DURING, "rebuild header for ethernet protocol %Xh\n", type);
                status = arp_find(&daddr, skb) ? 1 : 0;
                BUGMSG(D_DURING, " rebuilt: dest is %d; protocol %Xh\n",
                       daddr, type);
#endif
        } else {
                BUGMSG(D_NORMAL,
                       "I don't understand ethernet protocol %Xh addresses!\n", type);
                lp->stats.tx_errors++;
                lp->stats.tx_aborted_errors++;
        }

        /* if we couldn't resolve the address... give up. */
        if (!status)
                return 0;

        /* add the _real_ header this time! */
        proto = arc_proto_map[lp->default_proto[daddr]];
        proto->build_header(skb, dev, type, daddr);

        return 1;               /* success */
}



/* Called by the kernel in order to transmit a packet. */
static int arcnet_send_packet(struct sk_buff *skb, struct net_device *dev)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;
        struct archdr *pkt;
        struct arc_rfc1201 *soft;
        struct ArcProto *proto;
        int txbuf;

        BUGMSG(D_DURING,
               "transmit requested (status=%Xh, txbufs=%d/%d, len=%d)\n",
               ASTATUS(), lp->cur_tx, lp->next_tx, skb->len);

        pkt = (struct archdr *) skb->data;
        soft = &pkt->soft.rfc1201;
        proto = arc_proto_map[soft->proto];

        BUGMSG(D_SKB_SIZE, "skb: transmitting %d bytes to %02X\n",
                skb->len, pkt->hard.dest);
        BUGLVL(D_SKB) arcnet_dump_skb(dev, skb, "tx");

        /* fits in one packet? */
        if (skb->len - ARC_HDR_SIZE > XMTU && !proto->continue_tx) {
                BUGMSG(D_NORMAL, "fixme: packet too large: compensating badly!\n");
                dev_kfree_skb(skb);
                return 0;       /* don't try again */
        }

        /* We're busy transmitting a packet... */
        netif_stop_queue(dev);

        AINTMASK(0);

        txbuf = get_arcbuf(dev);
        if (txbuf != -1) {
                if (proto->prepare_tx(dev, pkt, skb->len, txbuf)) {
                        /* done right away */
                        lp->stats.tx_bytes += skb->len;
                        dev_kfree_skb(skb);
                } else {
                        /* do it the 'split' way */
                        lp->outgoing.proto = proto;
                        lp->outgoing.skb = skb;
                        lp->outgoing.pkt = pkt;

                        if (!proto->continue_tx)
                                BUGMSG(D_NORMAL, "bug! prep_tx==0, but no continue_tx!\n");
                        else if (proto->continue_tx(dev, txbuf)) {
                                BUGMSG(D_NORMAL,
                                       "bug! continue_tx finished the first time! "
                                       "(proto='%c')\n", proto->suffix);
                        }
                }

                lp->next_tx = txbuf;
        } else
                dev_kfree_skb(skb);

        /* make sure we didn't ignore a TX IRQ while we were in here */
        AINTMASK(0);
        lp->intmask |= TXFREEflag;
        AINTMASK(lp->intmask);

        return 0;               /* no need to try again */
}


/*
 * Actually start transmitting a packet that was loaded into a buffer
 * by prepare_tx.  This should _only_ be called by the interrupt handler.
 */
static int go_tx(struct net_device *dev)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;

        BUGMSG(D_DURING, "go_tx: status=%Xh, intmask=%Xh, next_tx=%d, cur_tx=%d\n",
               ASTATUS(), lp->intmask, lp->next_tx, lp->cur_tx);

        if (lp->cur_tx != -1 || lp->next_tx == -1)
                return 0;

        BUGLVL(D_TX) arcnet_dump_packet(dev, lp->next_tx, "go_tx");

        lp->cur_tx = lp->next_tx;
        lp->next_tx = -1;

        /* start sending */
        ACOMMAND(TXcmd | (lp->cur_tx << 3));

        dev->trans_start = jiffies;
        lp->stats.tx_packets++;
        lp->lasttrans_dest = lp->lastload_dest;
        lp->lastload_dest = 0;
        lp->intmask |= TXFREEflag;

        return 1;
}


/* Called by the kernel when transmit times out */
static void arcnet_timeout(struct net_device *dev)
{
        unsigned long flags;
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;
        int status = ASTATUS();
        char *msg;

        spin_lock_irqsave(&arcnet_lock, flags);
        if (status & TXFREEflag) {      /* transmit _DID_ finish */
                msg = " - missed IRQ?";
        } else {
                msg = "";
                lp->stats.tx_aborted_errors++;
                lp->timed_out = 1;
                ACOMMAND(NOTXcmd | (lp->cur_tx << 3));
        }
        lp->stats.tx_errors++;

        /* make sure we didn't miss a TX IRQ */
        AINTMASK(0);
        lp->intmask |= TXFREEflag;
        AINTMASK(lp->intmask);
        
        spin_unlock_irqrestore(&arcnet_lock, flags);

        if (jiffies - lp->last_timeout > 10*HZ) {
                BUGMSG(D_EXTRA, "tx timed out%s (status=%Xh, intmask=%Xh, dest=%02Xh)\n",
                       msg, status, lp->intmask, lp->lasttrans_dest);
                lp->last_timeout = jiffies;
        }

        if (lp->cur_tx == -1)
                netif_wake_queue(dev);
}


/*
 * The typical workload of the driver: Handle the network interface
 * interrupts. Establish which device needs attention, and call the correct
 * chipset interrupt handler.
 */
irqreturn_t arcnet_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
        struct net_device *dev = dev_id;
        struct arcnet_local *lp;
        int recbuf, status, didsomething, boguscount;

        BUGMSG(D_DURING, "\n");

        BUGMSG(D_DURING, "in arcnet_interrupt\n");

        spin_lock(&arcnet_lock);
        
        lp = (struct arcnet_local *) dev->priv;
        if (!lp)
                BUG();
                
        /*
         * RESET flag was enabled - if device is not running, we must clear it right
         * away (but nothing else).
         */
        if (!netif_running(dev)) {
                if (ASTATUS() & RESETflag)
                        ACOMMAND(CFLAGScmd | RESETclear);
                AINTMASK(0);
                spin_unlock(&arcnet_lock);
                return IRQ_HANDLED;
        }

        BUGMSG(D_DURING, "in arcnet_inthandler (status=%Xh, intmask=%Xh)\n",
               ASTATUS(), lp->intmask);

        boguscount = 5;
        do {
                status = ASTATUS();
                didsomething = 0;

                /*
                 * RESET flag was enabled - card is resetting and if RX is
                 * disabled, it's NOT because we just got a packet.
                 * 
                 * The card is in an undefined state.  Clear it out and start over.
                 */
                if (status & RESETflag) {
                        BUGMSG(D_NORMAL, "spurious reset (status=%Xh)\n", status);
                        arcnet_close(dev);
                        arcnet_open(dev);

                        /* get out of the interrupt handler! */
                        break;
                }
                /* 
                 * RX is inhibited - we must have received something. Prepare to
                 * receive into the next buffer.
                 * 
                 * We don't actually copy the received packet from the card until
                 * after the transmit handler runs (and possibly launches the next
                 * tx); this should improve latency slightly if we get both types
                 * of interrupts at once. 
                 */
                recbuf = -1;
                if (status & lp->intmask & NORXflag) {
                        recbuf = lp->cur_rx;
                        BUGMSG(D_DURING, "Buffer #%d: receive irq (status=%Xh)\n",
                               recbuf, status);

                        lp->cur_rx = get_arcbuf(dev);
                        if (lp->cur_rx != -1) {
                                BUGMSG(D_DURING, "enabling receive to buffer #%d\n",
                                       lp->cur_rx);
                                ACOMMAND(RXcmd | (lp->cur_rx << 3) | RXbcasts);
                        }
                        didsomething++;
                }
                /* a transmit finished, and we're interested in it. */
                if ((status & lp->intmask & TXFREEflag) || lp->timed_out) {
                        lp->intmask &= ~TXFREEflag;

                        BUGMSG(D_DURING, "TX IRQ (stat=%Xh)\n", status);

                        if (lp->cur_tx != -1 && !(status & TXACKflag) && !lp->timed_out) {
                                if (lp->lasttrans_dest != 0) {
                                        BUGMSG(D_EXTRA, "transmit was not acknowledged! "
                                            "(status=%Xh, dest=%02Xh)\n",
                                             status, lp->lasttrans_dest);
                                        lp->stats.tx_errors++;
                                        lp->stats.tx_carrier_errors++;
                                } else {
                                        BUGMSG(D_DURING,
                                               "broadcast was not acknowledged; that's normal "
                                            "(status=%Xh, dest=%02Xh)\n",
                                             status, lp->lasttrans_dest);
                                }
                        }
                        if (lp->cur_tx != -1)
                                release_arcbuf(dev, lp->cur_tx);

                        lp->cur_tx = -1;
                        lp->timed_out = 0;
                        didsomething++;

                        /* send another packet if there is one */
                        go_tx(dev);

                        /* continue a split packet, if any */
                        if (lp->outgoing.proto && lp->outgoing.proto->continue_tx) {
                                int txbuf = get_arcbuf(dev);
                                if (txbuf != -1) {
                                        if (lp->outgoing.proto->continue_tx(dev, txbuf)) {
                                                /* that was the last segment */
                                                lp->stats.tx_bytes += lp->outgoing.skb->len;
                                                dev_kfree_skb_irq(lp->outgoing.skb);
                                                lp->outgoing.proto = NULL;
                                        }
                                        lp->next_tx = txbuf;
                                }
                        }
                        /* inform upper layers of idleness, if necessary */
                        if (lp->cur_tx == -1)
                                netif_wake_queue(dev);
                }
                /* now process the received packet, if any */
                if (recbuf != -1) {
                        BUGLVL(D_RX) arcnet_dump_packet(dev, recbuf, "rx irq");

                        arcnet_rx(dev, recbuf);
                        release_arcbuf(dev, recbuf);

                        didsomething++;
                }
                if (status & lp->intmask & RECONflag) {
                        ACOMMAND(CFLAGScmd | CONFIGclear);
                        lp->stats.tx_carrier_errors++;

                        BUGMSG(D_RECON, "Network reconfiguration detected (status=%Xh)\n",
                               status);

                        /* is the RECON info empty or old? */
                        if (!lp->first_recon || !lp->last_recon ||
                            jiffies - lp->last_recon > HZ * 10) {
                                if (lp->network_down)
                                        BUGMSG(D_NORMAL, "reconfiguration detected: cabling restored?\n");
                                lp->first_recon = lp->last_recon = jiffies;
                                lp->num_recons = lp->network_down = 0;

                                BUGMSG(D_DURING, "recon: clearing counters.\n");
                        } else {        /* add to current RECON counter */
                                lp->last_recon = jiffies;
                                lp->num_recons++;

                                BUGMSG(D_DURING, "recon: counter=%d, time=%lds, net=%d\n",
                                       lp->num_recons,
                                 (lp->last_recon - lp->first_recon) / HZ,
                                       lp->network_down);

                                /* if network is marked up;
                                 * and first_recon and last_recon are 60+ apart;
                                 * and the average no. of recons counted is
                                 *    > RECON_THRESHOLD/min;
                                 * then print a warning message.
                                 */
                                if (!lp->network_down
                                    && (lp->last_recon - lp->first_recon) <= HZ * 60
                                  && lp->num_recons >= RECON_THRESHOLD) {
                                        lp->network_down = 1;
                                        BUGMSG(D_NORMAL, "many reconfigurations detected: cabling problem?\n");
                                } else if (!lp->network_down
                                           && lp->last_recon - lp->first_recon > HZ * 60) {
                                        /* reset counters if we've gone for over a minute. */
                                        lp->first_recon = lp->last_recon;
                                        lp->num_recons = 1;
                                }
                        }
                } else if (lp->network_down && jiffies - lp->last_recon > HZ * 10) {
                        if (lp->network_down)
                                BUGMSG(D_NORMAL, "cabling restored?\n");
                        lp->first_recon = lp->last_recon = 0;
                        lp->num_recons = lp->network_down = 0;

                        BUGMSG(D_DURING, "not recon: clearing counters anyway.\n");
                }
        }
        while (--boguscount && didsomething);

        BUGMSG(D_DURING, "arcnet_interrupt complete (status=%Xh, count=%d)\n",
               ASTATUS(), boguscount);
        BUGMSG(D_DURING, "\n");


        AINTMASK(0);
        udelay(1);
        AINTMASK(lp->intmask);
        
        spin_unlock(&arcnet_lock);
        return IRQ_RETVAL(didsomething);
}


/*
 * This is a generic packet receiver that calls arcnet??_rx depending on the
 * protocol ID found.
 */
void arcnet_rx(struct net_device *dev, int bufnum)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;
        struct archdr pkt;
        struct arc_rfc1201 *soft;
        int length, ofs;

        soft = &pkt.soft.rfc1201;

        lp->hw.copy_from_card(dev, bufnum, 0, &pkt, sizeof(ARC_HDR_SIZE));
        if (pkt.hard.offset[0]) {
                ofs = pkt.hard.offset[0];
                length = 256 - ofs;
        } else {
                ofs = pkt.hard.offset[1];
                length = 512 - ofs;
        }

        /* get the full header, if possible */
        if (sizeof(pkt.soft) < length)
                lp->hw.copy_from_card(dev, bufnum, ofs, soft, sizeof(pkt.soft));
        else {
                memset(&pkt.soft, 0, sizeof(pkt.soft));
                lp->hw.copy_from_card(dev, bufnum, ofs, soft, length);
        }

        BUGMSG(D_DURING, "Buffer #%d: received packet from %02Xh to %02Xh "
               "(%d+4 bytes)\n",
               bufnum, pkt.hard.source, pkt.hard.dest, length);

        lp->stats.rx_packets++;
        lp->stats.rx_bytes += length + ARC_HDR_SIZE;

        /* call the right receiver for the protocol */
        if (arc_proto_map[soft->proto] != &arc_proto_null) {
                BUGLVL(D_PROTO) {
                        struct ArcProto
                        *oldp = arc_proto_map[lp->default_proto[pkt.hard.source]],
                        *newp = arc_proto_map[soft->proto];

                        if (oldp != newp) {
                                BUGMSG(D_PROTO,
                                       "got protocol %02Xh; encap for host %02Xh is now '%c'"
                                       " (was '%c')\n", soft->proto, pkt.hard.source,
                                       newp->suffix, oldp->suffix);
                        }
                }

                /* broadcasts will always be done with the last-used encap. */
                lp->default_proto[0] = soft->proto;

                /* in striking contrast, the following isn't a hack. */
                lp->default_proto[pkt.hard.source] = soft->proto;
        }
        /* call the protocol-specific receiver. */
        arc_proto_map[soft->proto]->rx(dev, bufnum, &pkt, length);
}



/* 
 * Get the current statistics.  This may be called with the card open or
 * closed.
 */
static struct net_device_stats *arcnet_get_stats(struct net_device *dev)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;
        return &lp->stats;
}


static void null_rx(struct net_device *dev, int bufnum,
                    struct archdr *pkthdr, int length)
{
        BUGMSG(D_PROTO,
        "rx: don't know how to deal with proto %02Xh from host %02Xh.\n",
               pkthdr->soft.rfc1201.proto, pkthdr->hard.source);
}


static int null_build_header(struct sk_buff *skb, struct net_device *dev,
                             unsigned short type, uint8_t daddr)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;

        BUGMSG(D_PROTO,
               "tx: can't build header for encap %02Xh; load a protocol driver.\n",
               lp->default_proto[daddr]);

        /* always fails */
        return 0;
}


/* the "do nothing" prepare_tx function warns that there's nothing to do. */
static int null_prepare_tx(struct net_device *dev, struct archdr *pkt,
                           int length, int bufnum)
{
        struct arcnet_local *lp = (struct arcnet_local *) dev->priv;
        struct arc_hardware newpkt;

        BUGMSG(D_PROTO, "tx: no encap for this host; load a protocol driver.\n");

        /* send a packet to myself -- will never get received, of course */
        newpkt.source = newpkt.dest = dev->dev_addr[0];

        /* only one byte of actual data (and it's random) */
        newpkt.offset[0] = 0xFF;

        lp->hw.copy_to_card(dev, bufnum, 0, &newpkt, ARC_HDR_SIZE);

        return 1;               /* done */
}