/*
 * Linux ARCnet driver - "raw mode" packet encapsulation (no soft headers)
 * 
 * Written 1994-1999 by Avery Pennarun.
 * 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 of skeleton.c 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.
 *
 * **********************
 *
 * For more details, see drivers/net/arcnet.c
 *
 * **********************
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/if_arp.h>
#include <net/arp.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/arcdevice.h>

#define VERSION "arcnet: raw mode (`r') encapsulation support loaded.\n"


static void rx(struct net_device *dev, int bufnum,
               struct archdr *pkthdr, int length);
static int build_header(struct sk_buff *skb, struct net_device *dev,
                        unsigned short type, uint8_t daddr);
static int prepare_tx(struct net_device *dev, struct archdr *pkt, int length,
                      int bufnum);

static struct ArcProto rawmode_proto =
{
        .suffix         = 'r',
        .mtu            = XMTU,
        .rx             = rx,
        .build_header   = build_header,
        .prepare_tx     = prepare_tx,
        .continue_tx    = NULL,
        .ack_tx         = NULL
};


static int __init arcnet_raw_init(void)
{
        int count;

        printk(VERSION);

        for (count = 0; count < 256; count++)
                if (arc_proto_map[count] == arc_proto_default)
                        arc_proto_map[count] = &rawmode_proto;

        /* for raw mode, we only set the bcast proto if there's no better one */
        if (arc_bcast_proto == arc_proto_default)
                arc_bcast_proto = &rawmode_proto;

        arc_proto_default = &rawmode_proto;
        return 0;
}

static void __exit arcnet_raw_exit(void)
{
        arcnet_unregister_proto(&rawmode_proto);
}

module_init(arcnet_raw_init);
module_exit(arcnet_raw_exit);

MODULE_LICENSE("GPL");


/* packet receiver */
static void rx(struct net_device *dev, int bufnum,
               struct archdr *pkthdr, int length)
{
        struct arcnet_local *lp = netdev_priv(dev);
        struct sk_buff *skb;
        struct archdr *pkt = pkthdr;
        int ofs;

        BUGMSG(D_DURING, "it's a raw packet (length=%d)\n", length);

        if (length > MTU)
                ofs = 512 - length;
        else
                ofs = 256 - length;

        skb = alloc_skb(length + ARC_HDR_SIZE, GFP_ATOMIC);
        if (skb == NULL) {
                BUGMSG(D_NORMAL, "Memory squeeze, dropping packet.\n");
                dev->stats.rx_dropped++;
                return;
        }
        skb_put(skb, length + ARC_HDR_SIZE);
        skb->dev = dev;

        pkt = (struct archdr *) skb->data;

        skb_reset_mac_header(skb);
        skb_pull(skb, ARC_HDR_SIZE);

        /* up to sizeof(pkt->soft) has already been copied from the card */
        memcpy(pkt, pkthdr, sizeof(struct archdr));
        if (length > sizeof(pkt->soft))
                lp->hw.copy_from_card(dev, bufnum, ofs + sizeof(pkt->soft),
                                      pkt->soft.raw + sizeof(pkt->soft),
                                      length - sizeof(pkt->soft));

        BUGLVL(D_SKB) arcnet_dump_skb(dev, skb, "rx");

        skb->protocol = cpu_to_be16(ETH_P_ARCNET);
        netif_rx(skb);
}


/*
 * Create the ARCnet hard/soft headers for raw mode.
 * There aren't any soft headers in raw mode - not even the protocol id.
 */
static int build_header(struct sk_buff *skb, struct net_device *dev,
                        unsigned short type, uint8_t daddr)
{
        int hdr_size = ARC_HDR_SIZE;
        struct archdr *pkt = (struct archdr *) skb_push(skb, hdr_size);

        /*
         * Set the source hardware address.
         *
         * This is pretty pointless for most purposes, but it can help in
         * debugging.  ARCnet does not allow us to change the source address in
         * the actual packet sent)
         */
        pkt->hard.source = *dev->dev_addr;

        /* see linux/net/ethernet/eth.c to see where I got the following */

        if (dev->flags & (IFF_LOOPBACK | IFF_NOARP)) {
                /* 
                 * FIXME: fill in the last byte of the dest ipaddr here to better
                 * comply with RFC1051 in "noarp" mode.
                 */
                pkt->hard.dest = 0;
                return hdr_size;
        }
        /* otherwise, just fill it in and go! */
        pkt->hard.dest = daddr;

        return hdr_size;        /* success */
}


static int prepare_tx(struct net_device *dev, struct archdr *pkt, int length,
                      int bufnum)
{
        struct arcnet_local *lp = netdev_priv(dev);
        struct arc_hardware *hard = &pkt->hard;
        int ofs;

        BUGMSG(D_DURING, "prepare_tx: txbufs=%d/%d/%d\n",
               lp->next_tx, lp->cur_tx, bufnum);

        length -= ARC_HDR_SIZE; /* hard header is not included in packet length */

        if (length > XMTU) {
                /* should never happen! other people already check for this. */
                BUGMSG(D_NORMAL, "Bug!  prepare_tx with size %d (> %d)\n",
                       length, XMTU);
                length = XMTU;
        }
        if (length >= MinTU) {
                hard->offset[0] = 0;
                hard->offset[1] = ofs = 512 - length;
        } else if (length > MTU) {
                hard->offset[0] = 0;
                hard->offset[1] = ofs = 512 - length - 3;
        } else
                hard->offset[0] = ofs = 256 - length;

        BUGMSG(D_DURING, "prepare_tx: length=%d ofs=%d\n",
               length,ofs);

        lp->hw.copy_to_card(dev, bufnum, 0, hard, ARC_HDR_SIZE);
        lp->hw.copy_to_card(dev, bufnum, ofs, &pkt->soft, length);

        lp->lastload_dest = hard->dest;

        return 1;               /* done */
}