hdlcdrv.c

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/*****************************************************************************/

/*
 *  hdlcdrv.c  -- HDLC packet radio network driver.
 *
 *  Copyright (C) 1996-2000  Thomas Sailer ([email protected])
 *
 *  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.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *  Please note that the GPL allows you to use the driver, NOT the radio.
 *  In order to use the radio, you need a license from the communications
 *  authority of your country.
 *
 *  The driver was derived from Donald Beckers skeleton.c
 *  Written 1993-94 by Donald Becker.
 *
 *  History:
 *   0.1  21.09.1996  Started
 *        18.10.1996  Changed to new user space access routines 
 *                    (copy_{to,from}_user)
 *   0.2  21.11.1996  various small changes
 *   0.3  03.03.1997  fixed (hopefully) IP not working with ax.25 as a module
 *   0.4  16.04.1997  init code/data tagged
 *   0.5  30.07.1997  made HDLC buffers bigger (solves a problem with the
 *                    soundmodem driver)
 *   0.6  05.04.1998  add spinlocks
 *   0.7  03.08.1999  removed some old compatibility cruft
 *   0.8  12.02.2000  adapted to softnet driver interface
 */

/*****************************************************************************/

#include <linux/capability.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/net.h>
#include <linux/in.h>
#include <linux/if.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/bitops.h>

#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/hdlcdrv.h>
#include <linux/random.h>
#include <net/ax25.h> 
#include <asm/uaccess.h>

#include <linux/crc-ccitt.h>

/* --------------------------------------------------------------------- */

#define KISS_VERBOSE

/* --------------------------------------------------------------------- */

#define PARAM_TXDELAY   1
#define PARAM_PERSIST   2
#define PARAM_SLOTTIME  3
#define PARAM_TXTAIL    4
#define PARAM_FULLDUP   5
#define PARAM_HARDWARE  6
#define PARAM_RETURN    255

/* --------------------------------------------------------------------- */
/*
 * the CRC routines are stolen from WAMPES
 * by Dieter Deyke
 */


/*---------------------------------------------------------------------------*/

static inline void append_crc_ccitt(unsigned char *buffer, int len)
{
    unsigned int crc = crc_ccitt(0xffff, buffer, len) ^ 0xffff;
    buffer += len;
    *buffer++ = crc;
    *buffer++ = crc >> 8;
}

/*---------------------------------------------------------------------------*/

static inline int check_crc_ccitt(const unsigned char *buf, int cnt)
{
    return (crc_ccitt(0xffff, buf, cnt) & 0xffff) == 0xf0b8;
}

/*---------------------------------------------------------------------------*/

#if 0
static int calc_crc_ccitt(const unsigned char *buf, int cnt)
{
    unsigned int crc = 0xffff;

    for (; cnt > 0; cnt--)
        crc = (crc >> 8) ^ crc_ccitt_table[(crc ^ *buf++) & 0xff];
    crc ^= 0xffff;
    return crc & 0xffff;
}
#endif

/* ---------------------------------------------------------------------- */

#define tenms_to_2flags(s,tenms) ((tenms * s->par.bitrate) / 100 / 16)

/* ---------------------------------------------------------------------- */
/*
 * The HDLC routines
 */

static int hdlc_rx_add_bytes(struct hdlcdrv_state *s, unsigned int bits, 
                 int num)
{
    int added = 0;
    
    while (s->hdlcrx.rx_state && num >= 8) {
        if (s->hdlcrx.len >= sizeof(s->hdlcrx.buffer)) {
            s->hdlcrx.rx_state = 0;
            return 0;
        }
        *s->hdlcrx.bp++ = bits >> (32-num);
        s->hdlcrx.len++;
        num -= 8;
        added += 8;
    }
    return added;
}

static void hdlc_rx_flag(struct net_device *dev, struct hdlcdrv_state *s)
{
    struct sk_buff *skb;
    int pkt_len;
    unsigned char *cp;

    if (s->hdlcrx.len < 4) 
        return;
    if (!check_crc_ccitt(s->hdlcrx.buffer, s->hdlcrx.len)) 
        return;
    pkt_len = s->hdlcrx.len - 2 + 1; /* KISS kludge */
    if (!(skb = dev_alloc_skb(pkt_len))) {
        printk("%s: memory squeeze, dropping packet\n", dev->name);
        dev->stats.rx_dropped++;
        return;
    }
    cp = skb_put(skb, pkt_len);
    *cp++ = 0; /* KISS kludge */
    memcpy(cp, s->hdlcrx.buffer, pkt_len - 1);
    skb->protocol = ax25_type_trans(skb, dev);
    netif_rx(skb);
    dev->stats.rx_packets++;
}

void hdlcdrv_receiver(struct net_device *dev, struct hdlcdrv_state *s)
{
    int i;
    unsigned int mask1, mask2, mask3, mask4, mask5, mask6, word;
    
    if (!s || s->magic != HDLCDRV_MAGIC) 
        return;
    if (test_and_set_bit(0, &s->hdlcrx.in_hdlc_rx))
        return;

    while (!hdlcdrv_hbuf_empty(&s->hdlcrx.hbuf)) {
        word = hdlcdrv_hbuf_get(&s->hdlcrx.hbuf);   

#ifdef HDLCDRV_DEBUG
        hdlcdrv_add_bitbuffer_word(&s->bitbuf_hdlc, word);
#endif /* HDLCDRV_DEBUG */
            s->hdlcrx.bitstream >>= 16;
        s->hdlcrx.bitstream |= word << 16;
        s->hdlcrx.bitbuf >>= 16;
        s->hdlcrx.bitbuf |= word << 16;
        s->hdlcrx.numbits += 16;
        for(i = 15, mask1 = 0x1fc00, mask2 = 0x1fe00, mask3 = 0x0fc00,
            mask4 = 0x1f800, mask5 = 0xf800, mask6 = 0xffff; 
            i >= 0; 
            i--, mask1 <<= 1, mask2 <<= 1, mask3 <<= 1, mask4 <<= 1, 
            mask5 <<= 1, mask6 = (mask6 << 1) | 1) {
            if ((s->hdlcrx.bitstream & mask1) == mask1)
                s->hdlcrx.rx_state = 0; /* abort received */
            else if ((s->hdlcrx.bitstream & mask2) == mask3) {
                /* flag received */
                if (s->hdlcrx.rx_state) {
                    hdlc_rx_add_bytes(s, s->hdlcrx.bitbuf 
                              << (8+i),
                              s->hdlcrx.numbits
                              -8-i);
                    hdlc_rx_flag(dev, s);
                }
                s->hdlcrx.len = 0;
                s->hdlcrx.bp = s->hdlcrx.buffer;
                s->hdlcrx.rx_state = 1;
                s->hdlcrx.numbits = i;
            } else if ((s->hdlcrx.bitstream & mask4) == mask5) {
                /* stuffed bit */
                s->hdlcrx.numbits--;
                s->hdlcrx.bitbuf = (s->hdlcrx.bitbuf & (~mask6)) |
                    ((s->hdlcrx.bitbuf & mask6) << 1);
            }
        }
        s->hdlcrx.numbits -= hdlc_rx_add_bytes(s, s->hdlcrx.bitbuf,
                               s->hdlcrx.numbits);
    }
    clear_bit(0, &s->hdlcrx.in_hdlc_rx);
}

/* ---------------------------------------------------------------------- */

static inline void do_kiss_params(struct hdlcdrv_state *s,
                  unsigned char *data, unsigned long len)
{

#ifdef KISS_VERBOSE
#define PKP(a,b) printk(KERN_INFO "hdlcdrv.c: channel params: " a "\n", b)
#else /* KISS_VERBOSE */          
#define PKP(a,b) 
#endif /* KISS_VERBOSE */         

    if (len < 2)
        return;
    switch(data[0]) {
    case PARAM_TXDELAY:
        s->ch_params.tx_delay = data[1];
        PKP("TX delay = %ums", 10 * s->ch_params.tx_delay);
        break;
    case PARAM_PERSIST:   
        s->ch_params.ppersist = data[1];
        PKP("p persistence = %u", s->ch_params.ppersist);
        break;
    case PARAM_SLOTTIME:  
        s->ch_params.slottime = data[1];
        PKP("slot time = %ums", s->ch_params.slottime);
        break;
    case PARAM_TXTAIL:    
        s->ch_params.tx_tail = data[1];
        PKP("TX tail = %ums", s->ch_params.tx_tail);
        break;
    case PARAM_FULLDUP:   
        s->ch_params.fulldup = !!data[1];
        PKP("%s duplex", s->ch_params.fulldup ? "full" : "half");
        break;
    default:
        break;
    }
#undef PKP
}

/* ---------------------------------------------------------------------- */

void hdlcdrv_transmitter(struct net_device *dev, struct hdlcdrv_state *s)
{
    unsigned int mask1, mask2, mask3;
    int i;
    struct sk_buff *skb;
    int pkt_len;

    if (!s || s->magic != HDLCDRV_MAGIC) 
        return;
    if (test_and_set_bit(0, &s->hdlctx.in_hdlc_tx))
        return;
    for (;;) {
        if (s->hdlctx.numbits >= 16) {
            if (hdlcdrv_hbuf_full(&s->hdlctx.hbuf)) {
                clear_bit(0, &s->hdlctx.in_hdlc_tx);
                return;
            }
            hdlcdrv_hbuf_put(&s->hdlctx.hbuf, s->hdlctx.bitbuf);
            s->hdlctx.bitbuf >>= 16;
            s->hdlctx.numbits -= 16;
        }
        switch (s->hdlctx.tx_state) {
        default:
            clear_bit(0, &s->hdlctx.in_hdlc_tx);
            return;
        case 0:
        case 1:
            if (s->hdlctx.numflags) {
                s->hdlctx.numflags--;
                s->hdlctx.bitbuf |= 
                    0x7e7e << s->hdlctx.numbits;
                s->hdlctx.numbits += 16;
                break;
            }
            if (s->hdlctx.tx_state == 1) {
                clear_bit(0, &s->hdlctx.in_hdlc_tx);
                return;
            }
            if (!(skb = s->skb)) {
                int flgs = tenms_to_2flags(s, s->ch_params.tx_tail);
                if (flgs < 2)
                    flgs = 2;
                s->hdlctx.tx_state = 1;
                s->hdlctx.numflags = flgs;
                break;
            }
            s->skb = NULL;
            netif_wake_queue(dev);
            pkt_len = skb->len-1; /* strip KISS byte */
            if (pkt_len >= HDLCDRV_MAXFLEN || pkt_len < 2) {
                s->hdlctx.tx_state = 0;
                s->hdlctx.numflags = 1;
                dev_kfree_skb_irq(skb);
                break;
            }
            skb_copy_from_linear_data_offset(skb, 1,
                             s->hdlctx.buffer,
                             pkt_len);
            dev_kfree_skb_irq(skb);
            s->hdlctx.bp = s->hdlctx.buffer;
            append_crc_ccitt(s->hdlctx.buffer, pkt_len);
            s->hdlctx.len = pkt_len+2; /* the appended CRC */
            s->hdlctx.tx_state = 2;
            s->hdlctx.bitstream = 0;
            dev->stats.tx_packets++;
            break;
        case 2:
            if (!s->hdlctx.len) {
                s->hdlctx.tx_state = 0;
                s->hdlctx.numflags = 1;
                break;
            }
            s->hdlctx.len--;
            s->hdlctx.bitbuf |= *s->hdlctx.bp <<
                s->hdlctx.numbits;
            s->hdlctx.bitstream >>= 8;
            s->hdlctx.bitstream |= (*s->hdlctx.bp++) << 16;
            mask1 = 0x1f000;
            mask2 = 0x10000;
            mask3 = 0xffffffff >> (31-s->hdlctx.numbits);
            s->hdlctx.numbits += 8;
            for(i = 0; i < 8; i++, mask1 <<= 1, mask2 <<= 1, 
                mask3 = (mask3 << 1) | 1) {
                if ((s->hdlctx.bitstream & mask1) != mask1) 
                    continue;
                s->hdlctx.bitstream &= ~mask2;
                s->hdlctx.bitbuf = 
                    (s->hdlctx.bitbuf & mask3) |
                        ((s->hdlctx.bitbuf & 
                         (~mask3)) << 1);
                s->hdlctx.numbits++;
                mask3 = (mask3 << 1) | 1;
            }
            break;
        }
    }
}

/* ---------------------------------------------------------------------- */

static void start_tx(struct net_device *dev, struct hdlcdrv_state *s)
{
    s->hdlctx.tx_state = 0;
    s->hdlctx.numflags = tenms_to_2flags(s, s->ch_params.tx_delay);
    s->hdlctx.bitbuf = s->hdlctx.bitstream = s->hdlctx.numbits = 0;
    hdlcdrv_transmitter(dev, s);
    s->hdlctx.ptt = 1;
    s->ptt_keyed++;
}

/* ---------------------------------------------------------------------- */

void hdlcdrv_arbitrate(struct net_device *dev, struct hdlcdrv_state *s)
{
    if (!s || s->magic != HDLCDRV_MAGIC || s->hdlctx.ptt || !s->skb) 
        return;
    if (s->ch_params.fulldup) {
        start_tx(dev, s);
        return;
    }
    if (s->hdlcrx.dcd) {
        s->hdlctx.slotcnt = s->ch_params.slottime;
        return;
    }
    if ((--s->hdlctx.slotcnt) > 0)
        return;
    s->hdlctx.slotcnt = s->ch_params.slottime;
    if ((random32() % 256) > s->ch_params.ppersist)
        return;
    start_tx(dev, s);
}

/* --------------------------------------------------------------------- */
/*
 * ===================== network driver interface =========================
 */

static netdev_tx_t hdlcdrv_send_packet(struct sk_buff *skb,
                       struct net_device *dev)
{
    struct hdlcdrv_state *sm = netdev_priv(dev);

    if (skb->data[0] != 0) {
        do_kiss_params(sm, skb->data, skb->len);
        dev_kfree_skb(skb);
        return NETDEV_TX_OK;
    }
    if (sm->skb)
        return NETDEV_TX_LOCKED;
    netif_stop_queue(dev);
    sm->skb = skb;
    return NETDEV_TX_OK;
}

/* --------------------------------------------------------------------- */

static int hdlcdrv_set_mac_address(struct net_device *dev, void *addr)
{
    struct sockaddr *sa = (struct sockaddr *)addr;

    /* addr is an AX.25 shifted ASCII mac address */
    memcpy(dev->dev_addr, sa->sa_data, dev->addr_len); 
    return 0;                                         
}

/* --------------------------------------------------------------------- */
/*
 * Open/initialize the board. This is called (in the current kernel)
 * 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 hdlcdrv_open(struct net_device *dev)
{
    struct hdlcdrv_state *s = netdev_priv(dev);
    int i;

    if (!s->ops || !s->ops->open)
        return -ENODEV;

    /*
     * initialise some variables
     */
    s->opened = 1;
    s->hdlcrx.hbuf.rd = s->hdlcrx.hbuf.wr = 0;
    s->hdlcrx.in_hdlc_rx = 0;
    s->hdlcrx.rx_state = 0;
    
    s->hdlctx.hbuf.rd = s->hdlctx.hbuf.wr = 0;
    s->hdlctx.in_hdlc_tx = 0;
    s->hdlctx.tx_state = 1;
    s->hdlctx.numflags = 0;
    s->hdlctx.bitstream = s->hdlctx.bitbuf = s->hdlctx.numbits = 0;
    s->hdlctx.ptt = 0;
    s->hdlctx.slotcnt = s->ch_params.slottime;
    s->hdlctx.calibrate = 0;

    i = s->ops->open(dev);
    if (i)
        return i;
    netif_start_queue(dev);
    return 0;
}

/* --------------------------------------------------------------------- */
/* 
 * The inverse routine to hdlcdrv_open(). 
 */

static int hdlcdrv_close(struct net_device *dev)
{
    struct hdlcdrv_state *s = netdev_priv(dev);
    int i = 0;

    netif_stop_queue(dev);

    if (s->ops && s->ops->close)
        i = s->ops->close(dev);
    if (s->skb)
        dev_kfree_skb(s->skb);
    s->skb = NULL;
    s->opened = 0;
    return i;
}

/* --------------------------------------------------------------------- */

static int hdlcdrv_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
    struct hdlcdrv_state *s = netdev_priv(dev);
    struct hdlcdrv_ioctl bi;

    if (cmd != SIOCDEVPRIVATE) {
        if (s->ops && s->ops->ioctl)
            return s->ops->ioctl(dev, ifr, &bi, cmd);
        return -ENOIOCTLCMD;
    }
    if (copy_from_user(&bi, ifr->ifr_data, sizeof(bi)))
        return -EFAULT;

    switch (bi.cmd) {
    default:
        if (s->ops && s->ops->ioctl)
            return s->ops->ioctl(dev, ifr, &bi, cmd);
        return -ENOIOCTLCMD;

    case HDLCDRVCTL_GETCHANNELPAR:
        bi.data.cp.tx_delay = s->ch_params.tx_delay;
        bi.data.cp.tx_tail = s->ch_params.tx_tail;
        bi.data.cp.slottime = s->ch_params.slottime;
        bi.data.cp.ppersist = s->ch_params.ppersist;
        bi.data.cp.fulldup = s->ch_params.fulldup;
        break;

    case HDLCDRVCTL_SETCHANNELPAR:
        if (!capable(CAP_NET_ADMIN))
            return -EACCES;
        s->ch_params.tx_delay = bi.data.cp.tx_delay;
        s->ch_params.tx_tail = bi.data.cp.tx_tail;
        s->ch_params.slottime = bi.data.cp.slottime;
        s->ch_params.ppersist = bi.data.cp.ppersist;
        s->ch_params.fulldup = bi.data.cp.fulldup;
        s->hdlctx.slotcnt = 1;
        return 0;
        
    case HDLCDRVCTL_GETMODEMPAR:
        bi.data.mp.iobase = dev->base_addr;
        bi.data.mp.irq = dev->irq;
        bi.data.mp.dma = dev->dma;
        bi.data.mp.dma2 = s->ptt_out.dma2;
        bi.data.mp.seriobase = s->ptt_out.seriobase;
        bi.data.mp.pariobase = s->ptt_out.pariobase;
        bi.data.mp.midiiobase = s->ptt_out.midiiobase;
        break;

    case HDLCDRVCTL_SETMODEMPAR:
        if ((!capable(CAP_SYS_RAWIO)) || netif_running(dev))
            return -EACCES;
        dev->base_addr = bi.data.mp.iobase;
        dev->irq = bi.data.mp.irq;
        dev->dma = bi.data.mp.dma;
        s->ptt_out.dma2 = bi.data.mp.dma2;
        s->ptt_out.seriobase = bi.data.mp.seriobase;
        s->ptt_out.pariobase = bi.data.mp.pariobase;
        s->ptt_out.midiiobase = bi.data.mp.midiiobase;
        return 0;   
    
    case HDLCDRVCTL_GETSTAT:
        bi.data.cs.ptt = hdlcdrv_ptt(s);
        bi.data.cs.dcd = s->hdlcrx.dcd;
        bi.data.cs.ptt_keyed = s->ptt_keyed;
        bi.data.cs.tx_packets = dev->stats.tx_packets;
        bi.data.cs.tx_errors = dev->stats.tx_errors;
        bi.data.cs.rx_packets = dev->stats.rx_packets;
        bi.data.cs.rx_errors = dev->stats.rx_errors;
        break;      

    case HDLCDRVCTL_OLDGETSTAT:
        bi.data.ocs.ptt = hdlcdrv_ptt(s);
        bi.data.ocs.dcd = s->hdlcrx.dcd;
        bi.data.ocs.ptt_keyed = s->ptt_keyed;
        break;      

    case HDLCDRVCTL_CALIBRATE:
        if(!capable(CAP_SYS_RAWIO))
            return -EPERM;
        s->hdlctx.calibrate = bi.data.calibrate * s->par.bitrate / 16;
        return 0;

    case HDLCDRVCTL_GETSAMPLES:
#ifndef HDLCDRV_DEBUG
        return -EPERM;
#else /* HDLCDRV_DEBUG */
        if (s->bitbuf_channel.rd == s->bitbuf_channel.wr) 
            return -EAGAIN;
        bi.data.bits = 
            s->bitbuf_channel.buffer[s->bitbuf_channel.rd];
        s->bitbuf_channel.rd = (s->bitbuf_channel.rd+1) %
            sizeof(s->bitbuf_channel.buffer);
        break;
#endif /* HDLCDRV_DEBUG */
                
    case HDLCDRVCTL_GETBITS:
#ifndef HDLCDRV_DEBUG
        return -EPERM;
#else /* HDLCDRV_DEBUG */
        if (s->bitbuf_hdlc.rd == s->bitbuf_hdlc.wr) 
            return -EAGAIN;
        bi.data.bits = 
            s->bitbuf_hdlc.buffer[s->bitbuf_hdlc.rd];
        s->bitbuf_hdlc.rd = (s->bitbuf_hdlc.rd+1) %
            sizeof(s->bitbuf_hdlc.buffer);
        break;      
#endif /* HDLCDRV_DEBUG */

    case HDLCDRVCTL_DRIVERNAME:
        if (s->ops && s->ops->drvname) {
            strncpy(bi.data.drivername, s->ops->drvname, 
                sizeof(bi.data.drivername));
            break;
        }
        bi.data.drivername[0] = '\0';
        break;
        
    }
    if (copy_to_user(ifr->ifr_data, &bi, sizeof(bi)))
        return -EFAULT;
    return 0;

}

/* --------------------------------------------------------------------- */

static const struct net_device_ops hdlcdrv_netdev = {
    .ndo_open   = hdlcdrv_open,
    .ndo_stop   = hdlcdrv_close,
    .ndo_start_xmit = hdlcdrv_send_packet,
    .ndo_do_ioctl   = hdlcdrv_ioctl,
    .ndo_set_mac_address = hdlcdrv_set_mac_address,
};

/*
 * Initialize fields in hdlcdrv
 */
static void hdlcdrv_setup(struct net_device *dev)
{
    static const struct hdlcdrv_channel_params dflt_ch_params = { 
        20, 2, 10, 40, 0 
    };
    struct hdlcdrv_state *s = netdev_priv(dev);

    /*
     * initialize the hdlcdrv_state struct
     */
    s->ch_params = dflt_ch_params;
    s->ptt_keyed = 0;

    spin_lock_init(&s->hdlcrx.hbuf.lock);
    s->hdlcrx.hbuf.rd = s->hdlcrx.hbuf.wr = 0;
    s->hdlcrx.in_hdlc_rx = 0;
    s->hdlcrx.rx_state = 0;
    
    spin_lock_init(&s->hdlctx.hbuf.lock);
    s->hdlctx.hbuf.rd = s->hdlctx.hbuf.wr = 0;
    s->hdlctx.in_hdlc_tx = 0;
    s->hdlctx.tx_state = 1;
    s->hdlctx.numflags = 0;
    s->hdlctx.bitstream = s->hdlctx.bitbuf = s->hdlctx.numbits = 0;
    s->hdlctx.ptt = 0;
    s->hdlctx.slotcnt = s->ch_params.slottime;
    s->hdlctx.calibrate = 0;

#ifdef HDLCDRV_DEBUG
    s->bitbuf_channel.rd = s->bitbuf_channel.wr = 0;
    s->bitbuf_channel.shreg = 0x80;

    s->bitbuf_hdlc.rd = s->bitbuf_hdlc.wr = 0;
    s->bitbuf_hdlc.shreg = 0x80;
#endif /* HDLCDRV_DEBUG */


    /* Fill in the fields of the device structure */

    s->skb = NULL;
    
    dev->netdev_ops = &hdlcdrv_netdev;
    dev->header_ops = &ax25_header_ops;
    
    dev->type = ARPHRD_AX25;           /* AF_AX25 device */
    dev->hard_header_len = AX25_MAX_HEADER_LEN + AX25_BPQ_HEADER_LEN;
    dev->mtu = AX25_DEF_PACLEN;        /* eth_mtu is the default */
    dev->addr_len = AX25_ADDR_LEN;     /* sizeof an ax.25 address */
    memcpy(dev->broadcast, &ax25_bcast, AX25_ADDR_LEN);
    memcpy(dev->dev_addr, &ax25_defaddr, AX25_ADDR_LEN);
    dev->tx_queue_len = 16;
}

/* --------------------------------------------------------------------- */
struct net_device *hdlcdrv_register(const struct hdlcdrv_ops *ops,
                    unsigned int privsize, const char *ifname,
                    unsigned int baseaddr, unsigned int irq, 
                    unsigned int dma) 
{
    struct net_device *dev;
    struct hdlcdrv_state *s;
    int err;

    BUG_ON(ops == NULL);

    if (privsize < sizeof(struct hdlcdrv_state))
        privsize = sizeof(struct hdlcdrv_state);

    dev = alloc_netdev(privsize, ifname, hdlcdrv_setup);
    if (!dev)
        return ERR_PTR(-ENOMEM);

    /*
     * initialize part of the hdlcdrv_state struct
     */
    s = netdev_priv(dev);
    s->magic = HDLCDRV_MAGIC;
    s->ops = ops;
    dev->base_addr = baseaddr;
    dev->irq = irq;
    dev->dma = dma;

    err = register_netdev(dev);
    if (err < 0) {
        printk(KERN_WARNING "hdlcdrv: cannot register net "
               "device %s\n", dev->name);
        free_netdev(dev);
        dev = ERR_PTR(err);
    }
    return dev;
}

/* --------------------------------------------------------------------- */

void hdlcdrv_unregister(struct net_device *dev) 
{
    struct hdlcdrv_state *s = netdev_priv(dev);

    BUG_ON(s->magic != HDLCDRV_MAGIC);

    if (s->opened && s->ops->close)
        s->ops->close(dev);
    unregister_netdev(dev);
    
    free_netdev(dev);
}

/* --------------------------------------------------------------------- */

EXPORT_SYMBOL(hdlcdrv_receiver);
EXPORT_SYMBOL(hdlcdrv_transmitter);
EXPORT_SYMBOL(hdlcdrv_arbitrate);
EXPORT_SYMBOL(hdlcdrv_register);
EXPORT_SYMBOL(hdlcdrv_unregister);

/* --------------------------------------------------------------------- */

static int __init hdlcdrv_init_driver(void)
{
    printk(KERN_INFO "hdlcdrv: (C) 1996-2000 Thomas Sailer HB9JNX/AE4WA\n");
    printk(KERN_INFO "hdlcdrv: version 0.8\n");
    return 0;
}

/* --------------------------------------------------------------------- */

static void __exit hdlcdrv_cleanup_driver(void)
{
    printk(KERN_INFO "hdlcdrv: cleanup\n");
}

/* --------------------------------------------------------------------- */

MODULE_AUTHOR("Thomas M. Sailer, [email protected], [email protected]");
MODULE_DESCRIPTION("Packet Radio network interface HDLC encoder/decoder");
MODULE_LICENSE("GPL");
module_init(hdlcdrv_init_driver);
module_exit(hdlcdrv_cleanup_driver);

/* --------------------------------------------------------------------- */