// SPDX-License-Identifier: GPL-2.0-or-later
/*****************************************************************************/

/*
 *      hdlcdrv.c  -- HDLC packet radio network driver.
 *
 *      Copyright (C) 1996-2000  Thomas Sailer (sailer@ife.ee.ethz.ch)
 *
 *  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/compat.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 <linux/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 (get_random_u8() > 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->protocol == htons(ETH_P_IP))
                return ax25_ip_xmit(skb);

        if (skb->data[0] != 0) {
                do_kiss_params(sm, skb->data, skb->len);
                dev_kfree_skb(skb);
                return NETDEV_TX_OK;
        }
        if (sm->skb) {
                dev_kfree_skb(skb);
                return NETDEV_TX_OK;
        }
        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 */
        dev_addr_set(dev, sa->sa_data);
        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);
        dev_kfree_skb(s->skb);
        s->skb = NULL;
        s->opened = 0;
        return i;
}

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

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

        if (cmd != SIOCDEVPRIVATE)
                return -ENOIOCTLCMD;

        if (in_compat_syscall()) /* to be implemented */
                return -ENOIOCTLCMD;

        if (copy_from_user(&bi, data, sizeof(bi)))
                return -EFAULT;

        switch (bi.cmd) {
        default:
                if (s->ops && s->ops->ioctl)
                        return s->ops->ioctl(dev, data, &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;
                if (s->par.bitrate <= 0)
                        return -EINVAL;
                if (bi.data.calibrate > INT_MAX / s->par.bitrate)
                        return -EINVAL;
                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) {
                        strscpy(bi.data.drivername, s->ops->drvname,
                                sizeof(bi.data.drivername));
                        break;
                }
                bi.data.drivername[0] = '\0';
                break;
                
        }
        if (copy_to_user(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_siocdevprivate  = hdlcdrv_siocdevprivate,
        .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);
        dev_addr_set(dev, (u8 *)&ax25_defaddr);
        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;

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

        dev = alloc_netdev(privsize, ifname, NET_NAME_UNKNOWN, 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);

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

MODULE_AUTHOR("Thomas M. Sailer, sailer@ife.ee.ethz.ch, hb9jnx@hb9w.che.eu");
MODULE_DESCRIPTION("Packet Radio network interface HDLC encoder/decoder");
MODULE_LICENSE("GPL");