/*
 * Dynamic Span Interface for Zaptel (Multi-Span Ethernet Interface)
 *
 * Modifications by Brett Carrington <brettcar@gmail.com>
 * Copyright (C) 2007-2008, Redfone Communications, LLC.
 *
 * Written by Joseph Benden <joe@thrallingpenguin.com>
 * Copyright (C) 2007, Thralling Penguin LLC
 *
 * Based on code written by Mark Spencer <markster@digium.com>
 * Copyright (C) 2001, Linux Support Services, Inc.
 *
 * All rights reserved.
 *
 * 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. 
 *
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/netdevice.h>
#include <linux/notifier.h>
#include <linux/crc32.h>

#if 0
#ifdef CONFIG_DEVFS_FS
#include <linux/devfs_fs_kernel.h>
#endif
#endif
#ifdef STANDALONE_ZAPATA
#include "zaptel.h"
#else
#include <zaptel/zaptel.h>
#endif

#define ETH_P_ZTDETH	0xd00d

#define ETHMF_FLAG_IGNORE_CHAN0 (1 << 3)

struct ztdeth_header {
	unsigned short subaddr;
};

/* Timer for enabling spans - used to combat a Zaptel lock problem */
static struct timer_list timer;
/* Variable used by the timer to correctly deduce the amount of time passed */
static int timer_counter;

/* We take the raw message, put it in an ethernet frame, and add a
   two byte addressing header at the top for future use */
#ifdef DEFINE_SPINLOCK
static DEFINE_SPINLOCK(zlock);
#else
static spinlock_t zlock = SPIN_LOCK_UNLOCKED;
#endif

static struct sk_buff_head skbs;

static struct ztdeth {
	unsigned char addr[ETH_ALEN];
	unsigned int addr_hash;

	unsigned short subaddr;	/* Network byte order */
	struct zt_span *span;
	char ethdev[IFNAMSIZ];
	struct net_device *dev;
	struct ztdeth *next;
	unsigned char *msgbuf;
	int msgbuf_len;
	int ready;

	int delay;

	unsigned char *rcvbuf;
	spinlock_t rblock;
	int real_channels;
	int no_front_padding;
} *zdevs = NULL;

/*
 * Return the ztdeth structure for a given MultiFrame zt_span
 */
struct ztdeth *ztdethmf_getz(struct zt_span *span)
{
	unsigned long flags;
	struct ztdeth *z = NULL, *found = NULL;

	spin_lock_irqsave(&zlock, flags);
	z = zdevs;
	while (z) {
		if (z->span == span)
			found = z;
		z = z->next;
	}
	spin_unlock_irqrestore(&zlock, flags);
	return found;
}

struct zt_span *ztdethmf_getspan(unsigned char *addr, unsigned short subaddr)
{
	unsigned long flags;
	struct ztdeth *z;
	struct zt_span *span = NULL;

	spin_lock_irqsave(&zlock, flags);
	z = zdevs;
	while (z) {
		if (!z->delay) {
			if (!memcmp(addr, z->addr, ETH_ALEN) && z->subaddr == subaddr)
				break;
		}
		z = z->next;
	}
	if (z)
		span = z->span;
	spin_unlock_irqrestore(&zlock, flags);
	return span;
}

#if defined(LINUX26) && LINUX_VERSION_CODE > KERNEL_VERSION(2,6,9)
static int ztdethmf_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
#else
static int ztdethmf_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt)
#endif
{
	int num_spans = 0, span_index = 0;
	struct ztdeth_header *zh;
	unsigned char *data;


#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
	zh = (struct ztdeth_header *) skb_network_header(skb);
#else
	zh = (struct ztdeth_header *) skb->nh.raw;
#endif

	/* The high order bit denotes that this is a multiframe span and not
	   a regular ztd-eth span. */
	if (unlikely(!(ntohs(zh->subaddr) & 0x8000))) {
		kfree_skb(skb);
		return 0;
	}

	/* got a multi-span frame */
	num_spans = ntohs(zh->subaddr) & 0xFF;

	/* Currently max of 4 spans supported */
	if (num_spans > 4) {
		kfree_skb(skb);
		return 0;
	}

	skb_pull(skb, sizeof(struct ztdeth_header));

	data = (unsigned char *) skb->data;
	do {
		struct zt_span *span;
		struct ztdeth *z;

		unsigned int samples, channels, rbslen, flags;
		unsigned int skip = 0;


#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,9)
		span = ztdethmf_getspan(eth_hdr(skb)->h_source, htons(span_index));
#else
		span = ztdethmf_getspan(skb->mac.ethernet->h_source, htons(span_index));
#endif

		if (!span) {
			kfree_skb(skb);
			return 0;
		}

		samples = data[span_index * 6] & 0xFF;
		flags = data[span_index * 6 + 1] & 0xFF;
		channels = data[span_index * 6 + 5] & 0xFF;

		/* Precomputed defaults for most typical values */
		if (channels == 24) {
			rbslen = 12;
		} else if (channels == 31) {
			rbslen = 16;
		} else {
			rbslen = ((channels + 3) / 4) * 2;
		}

		if (unlikely(!(samples == 8 && channels < 32))) {
			kfree_skb(skb);
			return 0;
		}

		/* Find the correct ethmf span */
		z = ztdethmf_getz(span);
		if (!z) {
			kfree_skb(skb);
			return 0;
		}

		spin_lock(&z->rblock);

		/* TDM Header */
		memcpy(z->rcvbuf, data + 6 * span_index, 6);

		/* 
		 * If we ignore channel zero we must skip the first eight bytes
		 * and ensure that ztdynamic doesn't get confused by this new
		 * flag
		 */

		if (flags & ETHMF_FLAG_IGNORE_CHAN0) {
			skip = 8;
			/* Remove this flag since ztdynamic may not understand it */
			z->rcvbuf[1] = flags & ~(ETHMF_FLAG_IGNORE_CHAN0);
			/* Additionally, now we will transmit with front padding */
			z->no_front_padding = 0;
		} else {
			/* Disable front padding if we recv'd a packet without it */
			z->no_front_padding = 1;
		}

		/* RBS Header */
		memcpy(z->rcvbuf + 6, data + 6 * num_spans + 16 * span_index, rbslen);

		/* Payload: 256 == 32*8 -- if padding lengths change, this must be modified */
		memcpy(z->rcvbuf + 6 + rbslen, data + 6 * num_spans + 16 * num_spans + (256) * span_index + skip, channels * 8);

		zt_dynamic_receive(span, z->rcvbuf, 6 + rbslen + channels * 8);

		spin_unlock(&z->rblock);
		span_index++;
	}
	while (span_index < num_spans);

	kfree_skb(skb);
	return 0;
}

static int ztdethmf_notifier(struct notifier_block *block, unsigned long event, void *ptr)
{
	struct net_device *dev = ptr;
	struct ztdeth *z;
	unsigned long flags;

	switch (event) {
	case NETDEV_GOING_DOWN:
	case NETDEV_DOWN:
		spin_lock_irqsave(&zlock, flags);
		z = zdevs;
		while (z) {
			/* Note that the device no longer exists */
			if (z->dev == dev)
				z->dev = NULL;
			z = z->next;
		}
		spin_unlock_irqrestore(&zlock, flags);
		break;
	case NETDEV_UP:
		spin_lock_irqsave(&zlock, flags);
		z = zdevs;
		while (z) {
			/* Now that the device exists again, use it */
			if (!strcmp(z->ethdev, dev->name))
				z->dev = dev;
			z = z->next;
		}
		spin_unlock_irqrestore(&zlock, flags);
		break;
	}
	return 0;
}

static int ztdethmf_transmit(void *pvt, unsigned char *msg, int msglen)
{
	struct ztdeth *z, *t, *ready_spans[8];
	struct sk_buff *skb;
	struct ztdeth_header *zh;
	unsigned long flags;
	struct net_device *dev;
	unsigned char addr[ETH_ALEN];
	unsigned short tmp_subaddr;
	unsigned short span_count = 0, spans_ready = 0, index = 0;

	spin_lock_irqsave(&zlock, flags);

	z = pvt;
	if (unlikely(!z->dev)) {
		spin_unlock_irqrestore(&zlock, flags);
		return 0;
	}

	/* Store the present data in the buffers */
	memcpy(z->msgbuf, msg, msglen);
	z->msgbuf_len = msglen;
	z->ready = 1;

	/* Are all available spans ready for transmit? */
	t = zdevs;
	while (t) {
		if (!t->delay) {
			/* 
			 * A profiling showed that this hash method was faster than
			 * the previous memcmp
			 */
			if (t->addr_hash == z->addr_hash) {
				++span_count;
				if (t->ready) {
					ready_spans[ntohs(t->subaddr)] = t;
					++spans_ready;
				}
			}
		}
		t = t->next;
	}

	/* Copy fields to local variables to remove spinlock ASAP */
	dev = z->dev;
	memcpy(addr, z->addr, sizeof(z->addr));
	spin_unlock_irqrestore(&zlock, flags);

	/* ready_spans[8] forces us to check spans_ready < 8 */
	if (span_count && spans_ready && span_count == spans_ready && spans_ready < 8) {
		int pad[spans_ready], rbs[spans_ready];

		for (index = 0; index < spans_ready; index++) {
			int chan = ready_spans[index]->real_channels;
			/* By default we pad to 32 channels, but if no_front_padding
			 * is false then we have a pad in the front of 8 bytes, so
			 * this implies one less channel */
			if (ready_spans[index]->no_front_padding)
				pad[index] = (32 - chan) * 8;
			else
				pad[index] = (31 - chan) * 8;

			if (chan == 24) {
				rbs[index] = 12;
			} else if (chan == 31) {
				rbs[index] = 16;
			} else {
				rbs[spans_ready] = ((chan + 3) / 4) * 2;
			}
		}

		/* Standard size for 32-chan frame */
		skb = dev_alloc_skb(1112 + dev->hard_header_len + sizeof(struct ztdeth_header) + 32);
		if (!skb) {
			if (printk_ratelimit())
				printk(KERN_WARNING "ztd-ethmf: Unable to allocate memory for transmission!\n");
			return 0;
		}

		/* Reserve header space */
		skb_reserve(skb, dev->hard_header_len + sizeof(struct ztdeth_header));
		for (index = 0; index < spans_ready; index++) {
			if (!ready_spans[index]->no_front_padding) {
				ready_spans[index]->msgbuf[1] |= ETHMF_FLAG_IGNORE_CHAN0;
			}

			memcpy(skb_put(skb, 6), ready_spans[index]->msgbuf, 6);
		}

		for (index = 0; index < spans_ready; index++) {
			memcpy(skb_put(skb, 16), ready_spans[index]->msgbuf + 6, rbs[index]);
		}
		for (index = 0; index < spans_ready; index++) {
			int chan = ready_spans[index]->real_channels;
			if (!ready_spans[index]->no_front_padding) {
				/* This adds an additional (padded) channel */
				memset(skb_put(skb, 8), 0xA5, 8);	/* ETHMF_IGNORE_CHAN0 */
			}
			memcpy(skb_put(skb, chan * 8), ready_spans[index]->msgbuf + (6 + rbs[index]), chan * 8);
			if (pad[index] > 0) {
				memset(skb_put(skb, pad[index]), 0xDD, pad[index]);
			}
			/* We're done with this span */
			ready_spans[index]->ready = 0;
		}

		/* Throw on header */
		zh = (struct ztdeth_header *) skb_push(skb, sizeof(struct ztdeth_header));
		tmp_subaddr = (0x8000 | (span_count & 0xFF));
		zh->subaddr = htons(tmp_subaddr);

		/* Setup protocol and such */
		skb->protocol = __constant_htons(ETH_P_ZTDETH);

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
		skb_set_network_header(skb, 0);
#else
		skb->nh.raw = skb->data;
#endif
		skb->dev = dev;

#if  LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,24)
		dev_hard_header(skb, dev, ETH_P_ZTDETH, addr, dev->dev_addr, skb->len);
#else
		if (dev->hard_header)
			dev->hard_header(skb, dev, ETH_P_ZTDETH, addr, dev->dev_addr, skb->len);
#endif
		skb_queue_tail(&skbs, skb);
	}
	return 0;
}


static int ztdethmf_flush(void)
{
	struct sk_buff *skb;
	/* Handle all transmissions now */
	while ((skb = skb_dequeue(&skbs))) {
		dev_queue_xmit(skb);
	}
	return 0;
}

static struct packet_type ztdethmf_ptype = {
      type:__constant_htons(ETH_P_ZTDETH),
	/* Protocol */
      dev:NULL,		/* Device (NULL = wildcard) */
      func:ztdethmf_rcv	/* Recv func */
};

static int digit2int(char d)
{
	switch (d) {
	case 'F':
	case 'E':
	case 'D':
	case 'C':
	case 'B':
	case 'A':
		return d - 'A' + 10;
	case 'f':
	case 'e':
	case 'd':
	case 'c':
	case 'b':
	case 'a':
		return d - 'a' + 10;
	case '9':
	case '8':
	case '7':
	case '6':
	case '5':
	case '4':
	case '3':
	case '2':
	case '1':
	case '0':
		return d - '0';
	}
	return -1;
}

static int hex2int(char *s)
{
	int res;
	int tmp;
	/* Gotta be at least one digit */
	if (strlen(s) < 1)
		return -1;
	/* Can't be more than two */
	if (strlen(s) > 2)
		return -1;
	/* Grab the first digit */
	res = digit2int(s[0]);
	if (res < 0)
		return -1;
	tmp = res;
	/* Grab the next */
	if (strlen(s) > 1) {
		res = digit2int(s[1]);
		if (res < 0)
			return -1;
		tmp = tmp * 16 + res;
	}
	return tmp;
}

static void ztdethmf_destroy(void *pvt)
{
	struct ztdeth *z = pvt;
	unsigned long flags;
	struct ztdeth *prev = NULL, *cur;

	spin_lock_irqsave(&zlock, flags);
	cur = zdevs;
	while (cur) {
		if (cur == z) {
			if (prev)
				prev->next = cur->next;
			else
				zdevs = cur->next;
			break;
		}
		prev = cur;
		cur = cur->next;
	}

	spin_unlock_irqrestore(&zlock, flags);
	if (cur == z) {
		/* Successfully removed */
		printk(KERN_INFO "TDMoEmf: Removed interface for %s\n", z->span->name);
		kfree(z->msgbuf);
		kfree(z);
#ifndef LINUX26
		MOD_DEC_USE_COUNT;
#else
		module_put(THIS_MODULE);
#endif
	} else {
		if (z && z->span && z->span->name) {
			printk(KERN_INFO "TDMoEmf: Cannot find interface for %s\n", z->span->name);
		}
	}
}

static void *ztdethmf_create(struct zt_span *span, char *addr)
{
	struct ztdeth *z;
	char src[256];
	char tmp[256], *tmp2, *tmp3, *tmp4 = NULL;
	int res, x, bufsize;
	unsigned long flags;

	z = kmalloc(sizeof(struct ztdeth), GFP_KERNEL);
	if (!z) {
		printk(KERN_ERR "TDMoEmf: Unable to allocate memory for new span!\n");
		return z;
	}

	/* Zero it out */
	memset(z, 0, sizeof(struct ztdeth));

	/* set a delay for xmit/recv to workaround Zaptel problems */
	z->delay = 8;

	/* create a msg buffer */
	/* MAX OF 31 CHANNELS!!!! */
	bufsize = 31 * ZT_CHUNKSIZE + 31 / 4 + 48;
	z->msgbuf = kmalloc(bufsize, GFP_KERNEL);
	z->rcvbuf = kmalloc(bufsize, GFP_KERNEL);
	z->rblock = SPIN_LOCK_UNLOCKED;

	/* Address should be <dev>/<macaddr>[/subaddr] */
	zap_copy_string(tmp, addr, sizeof(tmp));
	tmp2 = strchr(tmp, '/');
	if (tmp2) {
		*tmp2 = '\0';
		tmp2++;
		zap_copy_string(z->ethdev, tmp, sizeof(z->ethdev));
	} else {
		printk(KERN_ERR "Invalid TDMoEmf address (no device) '%s'\n", addr);
		kfree(z);
		return NULL;
	}

	if (tmp2) {
		tmp4 = strchr(tmp2 + 1, '/');
		if (tmp4) {
			*tmp4 = '\0';
			tmp4++;
		}
		/* We don't have SSCANF :(  Gotta do this the hard way */
		tmp3 = strchr(tmp2, ':');
		for (x = 0; x < 6; x++) {
			if (tmp2) {
				if (tmp3) {
					*tmp3 = '\0';
					tmp3++;
				}
				res = hex2int(tmp2);
				if (res < 0)
					break;
				z->addr[x] = res & 0xff;
			} else
				break;
			if ((tmp2 = tmp3))
				tmp3 = strchr(tmp2, ':');
		}
		if (x != 6) {
			printk(KERN_ERR "TDMoEmf: Invalid MAC address in: %s\n", addr);
			kfree(z);
			return NULL;
		}
	} else {
		printk(KERN_ERR "TDMoEmf: Missing MAC address\n");
		kfree(z);
		return NULL;
	}

	if (tmp4) {
		int sub = 0;
		int mul = 1;

		/* We have a subaddr */
		tmp3 = tmp4 + strlen(tmp4) - 1;
		while (tmp3 >= tmp4) {
			if (*tmp3 >= '0' && *tmp3 <= '9') {
				sub += (*tmp3 - '0') * mul;
			} else {
				printk(KERN_ERR "TDMoEmf: Invalid subaddress\n");
				kfree(z);
				return NULL;
			}
			mul *= 10;
			tmp3--;
		}
		z->subaddr = htons(sub);
	}

	z->dev = dev_get_by_name(
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,24)
					&init_net,
#endif
					z->ethdev);
	if (!z->dev) {
		printk(KERN_ERR "TDMoEmf: Invalid device '%s'\n", z->ethdev);
		kfree(z);
		return NULL;
	}
	z->span = span;

	z->addr_hash = crc32_le(0, z->addr, ETH_ALEN);	/* Set up hashed MAC address */
	z->real_channels = span->channels;

	src[0] = '\0';
	for (x = 0; x < 5; x++)
		snprintf(src + strlen(src), 3, "%02x:", z->dev->dev_addr[x]);
	snprintf(src + strlen(src), 2, "%02x", z->dev->dev_addr[5]);
	printk(KERN_INFO "TDMoEmf: Added new interface for %s at %s (addr=%s, src=%s, subaddr=%d)\n", span->name, z->dev->name, addr, src, ntohs(z->subaddr));

	spin_lock_irqsave(&zlock, flags);
	z->next = zdevs;
	zdevs = z;
	spin_unlock_irqrestore(&zlock, flags);
#ifndef LINUX26
	MOD_INC_USE_COUNT;
#else
	if (!try_module_get(THIS_MODULE))
		printk(KERN_ERR "TDMoEmf: Unable to increment module use count\n");
#endif

	/* enable the timer for enabling the spans */
#if 0
	timer.expires = jiffies + 1;
	if (!timer_pending(&timer))
		add_timer(&timer);
#else
	mod_timer(&timer, jiffies + 1);
#endif
	return z;
}

static struct zt_dynamic_driver ztd_ethmf = {
	"ethmf",
	"Ethernet",
	ztdethmf_create,
	ztdethmf_destroy,
	ztdethmf_transmit,
	ztdethmf_flush
};

static struct notifier_block ztdethmf_nblock = {
      notifier_call:ztdethmf_notifier,
};

static void timer_callback(unsigned long param)
{
	unsigned long flags;
	struct ztdeth *z;
	int count_zero = 0, count_nonzero = 0;

	/* loop spans */
	++timer_counter;

	if (timer_counter >= HZ) {
		timer_counter -= HZ;
		spin_lock_irqsave(&zlock, flags);
		z = zdevs;
		while (z) {
			if (z->delay) {
				z->delay--;
				// ++count_nonzero;
				if (!z->delay) {
					printk(KERN_INFO "TDMoEmf: Span %s is ready for use.\n", z->span->name);
				} else {
					++count_nonzero;
				}
			} else {
				++count_zero;
			}
			z = z->next;
		}
		spin_unlock_irqrestore(&zlock, flags);

		if (count_nonzero
		    /* && count_zero && count_nonzero != count_zero */ ) {
			/* re-add the timer event */
			timer.expires = jiffies + 1;
			add_timer(&timer);
		} else {
			printk(KERN_INFO "TDMoEmf: All spans are active - removing delay timer.\n");
			del_timer(&timer);
		}

	} else {
		timer.expires = jiffies + 1;
		add_timer(&timer);
	}
}

static int __init ztdethmf_init(void)
{

	timer_counter = 0;

	init_timer(&timer);
	timer.expires = jiffies + 1;
	timer.function = &timer_callback;
	if (!timer_pending(&timer))
		add_timer(&timer);

	dev_add_pack(&ztdethmf_ptype);
	register_netdevice_notifier(&ztdethmf_nblock);
	zt_dynamic_register(&ztd_ethmf);

	skb_queue_head_init(&skbs);

	return 0;
}

static void __exit ztdethmf_exit(void)
{
	del_timer(&timer);

	dev_remove_pack(&ztdethmf_ptype);
	unregister_netdevice_notifier(&ztdethmf_nblock);
	zt_dynamic_unregister(&ztd_ethmf);
}

MODULE_DESCRIPTION("Zaptel Dynamic TDMoEmf Support");
MODULE_AUTHOR("Joseph Benden <joe@thrallingpenguin.com>");
#ifdef MODULE_LICENSE
MODULE_LICENSE("GPL");
#endif

module_init(ztdethmf_init);
module_exit(ztdethmf_exit);