/*
 * Linux ARCnet driver - "cap mode" packet encapsulation.
 * It adds sequence numbers to packets for communicating between a user space
 * application and the driver. After a transmit it sends a packet with protocol
 * byte 0 back up to the userspace containing the sequence number of the packet
 * plus the transmit-status on the ArcNet.
 *
 * Written 2002-4 by Esben Nielsen, Vestas Wind Systems A/S
 * Derived from arc-rawmode.c by Avery Pennarun.
 * arc-rawmode was in turned based on skeleton.c, see below.
 *
 * **********************
 *
 * 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"

/* 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;
	char *pktbuf, *pkthdrbuf;
	int ofs;

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

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

	skb = alloc_skb(length + ARC_HDR_SIZE + sizeof(int), GFP_ATOMIC);
	if (!skb) {
		dev->stats.rx_dropped++;
		return;
	}
	skb_put(skb, length + ARC_HDR_SIZE + sizeof(int));
	skb->dev = dev;
	skb_reset_mac_header(skb);
	pkt = (struct archdr *)skb_mac_header(skb);
	skb_pull(skb, ARC_HDR_SIZE);

	/* up to sizeof(pkt->soft) has already been copied from the card
	 * squeeze in an int for the cap encapsulation
	 * use these variables to be sure we count in bytes, not in
	 * sizeof(struct archdr)
	 */
	pktbuf = (char *)pkt;
	pkthdrbuf = (char *)pkthdr;
	memcpy(pktbuf, pkthdrbuf, ARC_HDR_SIZE + sizeof(pkt->soft.cap.proto));
	memcpy(pktbuf + ARC_HDR_SIZE + sizeof(pkt->soft.cap.proto) + sizeof(int),
	       pkthdrbuf + ARC_HDR_SIZE + sizeof(pkt->soft.cap.proto),
	       sizeof(struct archdr) - ARC_HDR_SIZE - sizeof(pkt->soft.cap.proto));

	if (length > sizeof(pkt->soft))
		lp->hw.copy_from_card(dev, bufnum, ofs + sizeof(pkt->soft),
				      pkt->soft.raw + sizeof(pkt->soft)
				      + sizeof(int),
				      length - sizeof(pkt->soft));

	if (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 cap mode.
 * There aren't any soft headers in cap 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 = skb_push(skb, hdr_size);

	arc_printk(D_PROTO, dev, "Preparing header for cap packet %x.\n",
		   *((int *)&pkt->soft.cap.cookie[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;

	/* hard header is not included in packet length */
	length -= ARC_HDR_SIZE;
	/* And neither is the cookie field */
	length -= sizeof(int);

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

	arc_printk(D_PROTO, dev, "Sending for cap packet %x.\n",
		   *((int *)&pkt->soft.cap.cookie[0]));

	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;
	}

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

	/* Copy the arcnet-header + the protocol byte down: */
	lp->hw.copy_to_card(dev, bufnum, 0, hard, ARC_HDR_SIZE);
	lp->hw.copy_to_card(dev, bufnum, ofs, &pkt->soft.cap.proto,
			    sizeof(pkt->soft.cap.proto));

	/* Skip the extra integer we have written into it as a cookie
	 * but write the rest of the message:
	 */
	lp->hw.copy_to_card(dev, bufnum, ofs + 1,
			    ((unsigned char *)&pkt->soft.cap.mes), length - 1);

	lp->lastload_dest = hard->dest;

	return 1;	/* done */
}

static int ack_tx(struct net_device *dev, int acked)
{
	struct arcnet_local *lp = netdev_priv(dev);
	struct sk_buff *ackskb;
	struct archdr *ackpkt;
	int length = sizeof(struct arc_cap);

	arc_printk(D_DURING, dev, "capmode: ack_tx: protocol: %x: result: %d\n",
		   lp->outgoing.skb->protocol, acked);

	if (BUGLVL(D_SKB))
		arcnet_dump_skb(dev, lp->outgoing.skb, "ack_tx");

	/* Now alloc a skb to send back up through the layers: */
	ackskb = alloc_skb(length + ARC_HDR_SIZE, GFP_ATOMIC);
	if (!ackskb)
		goto free_outskb;

	skb_put(ackskb, length + ARC_HDR_SIZE);
	ackskb->dev = dev;

	skb_reset_mac_header(ackskb);
	ackpkt = (struct archdr *)skb_mac_header(ackskb);
	/* skb_pull(ackskb, ARC_HDR_SIZE); */

	skb_copy_from_linear_data(lp->outgoing.skb, ackpkt,
				  ARC_HDR_SIZE + sizeof(struct arc_cap));
	ackpkt->soft.cap.proto = 0; /* using protocol 0 for acknowledge */
	ackpkt->soft.cap.mes.ack = acked;

	arc_printk(D_PROTO, dev, "Acknowledge for cap packet %x.\n",
		   *((int *)&ackpkt->soft.cap.cookie[0]));

	ackskb->protocol = cpu_to_be16(ETH_P_ARCNET);

	if (BUGLVL(D_SKB))
		arcnet_dump_skb(dev, ackskb, "ack_tx_recv");
	netif_rx(ackskb);

free_outskb:
	dev_kfree_skb_irq(lp->outgoing.skb);
	lp->outgoing.proto = NULL;
			/* We are always finished when in this protocol */

	return 0;
}

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

static int __init capmode_module_init(void)
{
	int count;

	pr_info("cap mode (`c') encapsulation support loaded\n");

	for (count = 1; count <= 8; count++)
		if (arc_proto_map[count] == arc_proto_default)
			arc_proto_map[count] = &capmode_proto;

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

	arc_proto_default = &capmode_proto;
	arc_raw_proto = &capmode_proto;

	return 0;
}

static void __exit capmode_module_exit(void)
{
	arcnet_unregister_proto(&capmode_proto);
}
module_init(capmode_module_init);
module_exit(capmode_module_exit);

MODULE_LICENSE("GPL");