/*
 * Linux ARCnet driver - RFC1051 ("simple" standard) packet encapsulation
 *
 * 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
 *
 * **********************
 */

#define pr_fmt(fmt) "arcnet:" KBUILD_MODNAME ": " fmt

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

#include "arcdevice.h"

static __be16 type_trans(struct sk_buff *skb, struct net_device *dev);
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 rfc1051_proto = {
        .suffix         = 's',
        .mtu            = XMTU - RFC1051_HDR_SIZE,
        .is_ip          = 1,
        .rx             = rx,
        .build_header   = build_header,
        .prepare_tx     = prepare_tx,
        .continue_tx    = NULL,
        .ack_tx         = NULL
};

static int __init arcnet_rfc1051_init(void)
{
        pr_info("%s\n", "RFC1051 \"simple standard\" (`s') encapsulation support loaded");

        arc_proto_map[ARC_P_IP_RFC1051]
            = arc_proto_map[ARC_P_ARP_RFC1051]
            = &rfc1051_proto;

        /* if someone else already owns the broadcast, we won't take it */
        if (arc_bcast_proto == arc_proto_default)
                arc_bcast_proto = &rfc1051_proto;

        return 0;
}

static void __exit arcnet_rfc1051_exit(void)
{
        arcnet_unregister_proto(&rfc1051_proto);
}

module_init(arcnet_rfc1051_init);
module_exit(arcnet_rfc1051_exit);

MODULE_LICENSE("GPL");

/* Determine a packet's protocol ID.
 *
 * With ARCnet we have to convert everything to Ethernet-style stuff.
 */
static __be16 type_trans(struct sk_buff *skb, struct net_device *dev)
{
        struct archdr *pkt = (struct archdr *)skb->data;
        struct arc_rfc1051 *soft = &pkt->soft.rfc1051;
        int hdr_size = ARC_HDR_SIZE + RFC1051_HDR_SIZE;

        /* Pull off the arcnet header. */
        skb_reset_mac_header(skb);
        skb_pull(skb, hdr_size);

        if (pkt->hard.dest == 0) {
                skb->pkt_type = PACKET_BROADCAST;
        } else if (dev->flags & IFF_PROMISC) {
                /* if we're not sending to ourselves :) */
                if (pkt->hard.dest != dev->dev_addr[0])
                        skb->pkt_type = PACKET_OTHERHOST;
        }
        /* now return the protocol number */
        switch (soft->proto) {
        case ARC_P_IP_RFC1051:
                return htons(ETH_P_IP);
        case ARC_P_ARP_RFC1051:
                return htons(ETH_P_ARP);

        default:
                dev->stats.rx_errors++;
                dev->stats.rx_crc_errors++;
                return 0;
        }

        return htons(ETH_P_IP);
}

/* 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;

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

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

        skb = alloc_skb(length + ARC_HDR_SIZE, GFP_ATOMIC);
        if (!skb) {
                dev->stats.rx_dropped++;
                return;
        }
        skb_put(skb, length + ARC_HDR_SIZE);
        skb->dev = dev;

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

        /* 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));

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

        skb->protocol = type_trans(skb, dev);
        netif_rx(skb);
}

/* Create the ARCnet hard/soft headers for RFC1051 */
static int build_header(struct sk_buff *skb, struct net_device *dev,
                        unsigned short type, uint8_t daddr)
{
        int hdr_size = ARC_HDR_SIZE + RFC1051_HDR_SIZE;
        struct archdr *pkt = skb_push(skb, hdr_size);
        struct arc_rfc1051 *soft = &pkt->soft.rfc1051;

        /* set the protocol ID according to RFC1051 */
        switch (type) {
        case ETH_P_IP:
                soft->proto = ARC_P_IP_RFC1051;
                break;
        case ETH_P_ARP:
                soft->proto = ARC_P_ARP_RFC1051;
                break;
        default:
                arc_printk(D_NORMAL, dev, "RFC1051: I don't understand protocol %d (%Xh)\n",
                           type, type);
                dev->stats.tx_errors++;
                dev->stats.tx_aborted_errors++;
                return 0;
        }

        /* 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;

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

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

        if (length > XMTU) {
                /* should never happen! other people already check for this. */
                arc_printk(D_NORMAL, dev, "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;
        }

        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 */
}