/*
   * CAIF Interface registration.
   * Copyright (C) ST-Ericsson AB 2010
   * Author:	Sjur Brendeland/sjur.brandeland@stericsson.com
   * License terms: GNU General Public License (GPL) version 2
   *
   * Borrowed heavily from file: pn_dev.c. Thanks to
   *  Remi Denis-Courmont <remi.denis-courmont@nokia.com>
   *  and Sakari Ailus <sakari.ailus@nokia.com>
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__

  #include <linux/kernel.h>
  #include <linux/if_arp.h>
  #include <linux/net.h>
  #include <linux/netdevice.h>

  #include <linux/mutex.h>

  #include <linux/module.h>

  #include <linux/spinlock.h>

  #include <net/netns/generic.h>
  #include <net/net_namespace.h>
  #include <net/pkt_sched.h>
  #include <net/caif/caif_device.h>

  #include <net/caif/caif_layer.h>
  #include <net/caif/cfpkt.h>
  #include <net/caif/cfcnfg.h>

  #include <net/caif/cfserl.h>

  
  MODULE_LICENSE("GPL");

  
  /* Used for local tracking of the CAIF net devices */
  struct caif_device_entry {
  	struct cflayer layer;
  	struct list_head list;

  	struct net_device *netdev;

  	int __percpu *pcpu_refcnt;

  	spinlock_t flow_lock;

  	struct sk_buff *xoff_skb;
  	void (*xoff_skb_dtor)(struct sk_buff *skb);

  	bool xoff;

  };
  
  struct caif_device_entry_list {
  	struct list_head list;
  	/* Protects simulanous deletes in list */

  	struct mutex lock;

  };
  
  struct caif_net {

  	struct cfcnfg *cfg;

  	struct caif_device_entry_list caifdevs;
  };
  
  static int caif_net_id;

  static int q_high = 50; /* Percent */

  
  struct cfcnfg *get_cfcnfg(struct net *net)
  {
  	struct caif_net *caifn;

  	caifn = net_generic(net, caif_net_id);

  	if (!caifn)
  		return NULL;

  	return caifn->cfg;
  }
  EXPORT_SYMBOL(get_cfcnfg);

  
  static struct caif_device_entry_list *caif_device_list(struct net *net)
  {
  	struct caif_net *caifn;

  	caifn = net_generic(net, caif_net_id);

  	if (!caifn)
  		return NULL;

  	return &caifn->caifdevs;
  }

  static void caifd_put(struct caif_device_entry *e)
  {

  	this_cpu_dec(*e->pcpu_refcnt);

  }
  
  static void caifd_hold(struct caif_device_entry *e)
  {

  	this_cpu_inc(*e->pcpu_refcnt);

  }
  
  static int caifd_refcnt_read(struct caif_device_entry *e)
  {
  	int i, refcnt = 0;
  	for_each_possible_cpu(i)
  		refcnt += *per_cpu_ptr(e->pcpu_refcnt, i);
  	return refcnt;
  }

  /* Allocate new CAIF device. */
  static struct caif_device_entry *caif_device_alloc(struct net_device *dev)
  {
  	struct caif_device_entry_list *caifdevs;
  	struct caif_device_entry *caifd;

  	caifdevs = caif_device_list(dev_net(dev));

  	if (!caifdevs)
  		return NULL;

  	caifd = kzalloc(sizeof(*caifd), GFP_KERNEL);

  	if (!caifd)
  		return NULL;

  	caifd->pcpu_refcnt = alloc_percpu(int);

  	if (!caifd->pcpu_refcnt) {
  		kfree(caifd);
  		return NULL;
  	}

  	caifd->netdev = dev;

  	dev_hold(dev);

  	return caifd;
  }
  
  static struct caif_device_entry *caif_get(struct net_device *dev)
  {
  	struct caif_device_entry_list *caifdevs =
  	    caif_device_list(dev_net(dev));
  	struct caif_device_entry *caifd;

  	if (!caifdevs)
  		return NULL;

  	list_for_each_entry_rcu(caifd, &caifdevs->list, list) {

  		if (caifd->netdev == dev)
  			return caifd;
  	}
  	return NULL;
  }

  void caif_flow_cb(struct sk_buff *skb)
  {
  	struct caif_device_entry *caifd;

  	void (*dtor)(struct sk_buff *skb) = NULL;

  	bool send_xoff;
  
  	WARN_ON(skb->dev == NULL);
  
  	rcu_read_lock();
  	caifd = caif_get(skb->dev);
  	caifd_hold(caifd);
  	rcu_read_unlock();
  
  	spin_lock_bh(&caifd->flow_lock);
  	send_xoff = caifd->xoff;
  	caifd->xoff = 0;

  	if (!WARN_ON(caifd->xoff_skb_dtor == NULL)) {
  		WARN_ON(caifd->xoff_skb != skb);
  		dtor = caifd->xoff_skb_dtor;
  		caifd->xoff_skb = NULL;
  		caifd->xoff_skb_dtor = NULL;
  	}

  	spin_unlock_bh(&caifd->flow_lock);

  	if (dtor)
  		dtor(skb);

  	if (send_xoff)
  		caifd->layer.up->
  			ctrlcmd(caifd->layer.up,
  				_CAIF_CTRLCMD_PHYIF_FLOW_ON_IND,
  				caifd->layer.id);
  	caifd_put(caifd);
  }

  static int transmit(struct cflayer *layer, struct cfpkt *pkt)
  {

  	int err, high = 0, qlen = 0;
  	struct caif_dev_common *caifdev;

  	struct caif_device_entry *caifd =
  	    container_of(layer, struct caif_device_entry, layer);

  	struct sk_buff *skb;

  	struct netdev_queue *txq;
  
  	rcu_read_lock_bh();

  	skb = cfpkt_tonative(pkt);
  	skb->dev = caifd->netdev;

  	skb_reset_network_header(skb);
  	skb->protocol = htons(ETH_P_CAIF);

  	caifdev = netdev_priv(caifd->netdev);
  
  	/* Check if we need to handle xoff */
  	if (likely(caifd->netdev->tx_queue_len == 0))
  		goto noxoff;
  
  	if (unlikely(caifd->xoff))
  		goto noxoff;
  
  	if (likely(!netif_queue_stopped(caifd->netdev))) {
  		/* If we run with a TX queue, check if the queue is too long*/
  		txq = netdev_get_tx_queue(skb->dev, 0);
  		qlen = qdisc_qlen(rcu_dereference_bh(txq->qdisc));
  
  		if (likely(qlen == 0))
  			goto noxoff;
  
  		high = (caifd->netdev->tx_queue_len * q_high) / 100;
  		if (likely(qlen < high))
  			goto noxoff;
  	}
  
  	/* Hold lock while accessing xoff */
  	spin_lock_bh(&caifd->flow_lock);
  	if (caifd->xoff) {
  		spin_unlock_bh(&caifd->flow_lock);
  		goto noxoff;
  	}
  
  	/*
  	 * Handle flow off, we do this by temporary hi-jacking this
  	 * skb's destructor function, and replace it with our own
  	 * flow-on callback. The callback will set flow-on and call
  	 * the original destructor.
  	 */
  
  	pr_debug("queue has stopped(%d) or is full (%d > %d)
  ",
  			netif_queue_stopped(caifd->netdev),
  			qlen, high);
  	caifd->xoff = 1;

  	caifd->xoff_skb = skb;
  	caifd->xoff_skb_dtor = skb->destructor;
  	skb->destructor = caif_flow_cb;

  	spin_unlock_bh(&caifd->flow_lock);

  
  	caifd->layer.up->ctrlcmd(caifd->layer.up,
  					_CAIF_CTRLCMD_PHYIF_FLOW_OFF_IND,
  					caifd->layer.id);
  noxoff:
  	rcu_read_unlock_bh();

  	err = dev_queue_xmit(skb);
  	if (err > 0)
  		err = -EIO;

  	return err;

  }

  /*

   * Stuff received packets into the CAIF stack.

   * On error, returns non-zero and releases the skb.
   */
  static int receive(struct sk_buff *skb, struct net_device *dev,
  		   struct packet_type *pkttype, struct net_device *orig_dev)
  {

  	struct cfpkt *pkt;
  	struct caif_device_entry *caifd;

  	int err;

  	pkt = cfpkt_fromnative(CAIF_DIR_IN, skb);

  
  	rcu_read_lock();

  	caifd = caif_get(dev);

  	if (!caifd || !caifd->layer.up || !caifd->layer.up->receive ||
  			!netif_oper_up(caifd->netdev)) {
  		rcu_read_unlock();
  		kfree_skb(skb);

  		return NET_RX_DROP;

  	}
  
  	/* Hold reference to netdevice while using CAIF stack */
  	caifd_hold(caifd);
  	rcu_read_unlock();

  	err = caifd->layer.up->receive(caifd->layer.up, pkt);
  
  	/* For -EILSEQ the packet is not freed so so it now */
  	if (err == -EILSEQ)
  		cfpkt_destroy(pkt);

  
  	/* Release reference to stack upwards */
  	caifd_put(caifd);

  
  	if (err != 0)
  		err = NET_RX_DROP;
  	return err;

  }
  
  static struct packet_type caif_packet_type __read_mostly = {
  	.type = cpu_to_be16(ETH_P_CAIF),
  	.func = receive,
  };
  
  static void dev_flowctrl(struct net_device *dev, int on)
  {

  	struct caif_device_entry *caifd;
  
  	rcu_read_lock();
  
  	caifd = caif_get(dev);
  	if (!caifd || !caifd->layer.up || !caifd->layer.up->ctrlcmd) {
  		rcu_read_unlock();

  		return;

  	}
  
  	caifd_hold(caifd);
  	rcu_read_unlock();

  
  	caifd->layer.up->ctrlcmd(caifd->layer.up,
  				 on ?
  				 _CAIF_CTRLCMD_PHYIF_FLOW_ON_IND :
  				 _CAIF_CTRLCMD_PHYIF_FLOW_OFF_IND,
  				 caifd->layer.id);

  	caifd_put(caifd);

  }

  void caif_enroll_dev(struct net_device *dev, struct caif_dev_common *caifdev,
  			struct cflayer *link_support, int head_room,
  			struct cflayer **layer, int (**rcv_func)(
  				struct sk_buff *, struct net_device *,
  				struct packet_type *, struct net_device *))
  {
  	struct caif_device_entry *caifd;
  	enum cfcnfg_phy_preference pref;
  	struct cfcnfg *cfg = get_cfcnfg(dev_net(dev));
  	struct caif_device_entry_list *caifdevs;
  
  	caifdevs = caif_device_list(dev_net(dev));
  	if (!cfg || !caifdevs)
  		return;
  	caifd = caif_device_alloc(dev);
  	if (!caifd)
  		return;
  	*layer = &caifd->layer;

  	spin_lock_init(&caifd->flow_lock);

  
  	switch (caifdev->link_select) {
  	case CAIF_LINK_HIGH_BANDW:
  		pref = CFPHYPREF_HIGH_BW;
  		break;
  	case CAIF_LINK_LOW_LATENCY:
  		pref = CFPHYPREF_LOW_LAT;
  		break;
  	default:
  		pref = CFPHYPREF_HIGH_BW;
  		break;
  	}
  	mutex_lock(&caifdevs->lock);
  	list_add_rcu(&caifd->list, &caifdevs->list);
  
  	strncpy(caifd->layer.name, dev->name,
  		sizeof(caifd->layer.name) - 1);
  	caifd->layer.name[sizeof(caifd->layer.name) - 1] = 0;
  	caifd->layer.transmit = transmit;
  	cfcnfg_add_phy_layer(cfg,
  				dev,
  				&caifd->layer,
  				pref,
  				link_support,
  				caifdev->use_fcs,
  				head_room);
  	mutex_unlock(&caifdevs->lock);
  	if (rcv_func)
  		*rcv_func = receive;
  }

  EXPORT_SYMBOL(caif_enroll_dev);

  /* notify Caif of device events */
  static int caif_device_notify(struct notifier_block *me, unsigned long what,
  			      void *arg)
  {
  	struct net_device *dev = arg;
  	struct caif_device_entry *caifd = NULL;
  	struct caif_dev_common *caifdev;

  	struct cfcnfg *cfg;

  	struct cflayer *layer, *link_support;
  	int head_room = 0;

  	struct caif_device_entry_list *caifdevs;

  	cfg = get_cfcnfg(dev_net(dev));

  	caifdevs = caif_device_list(dev_net(dev));
  	if (!cfg || !caifdevs)

  		return 0;

  	caifd = caif_get(dev);
  	if (caifd == NULL && dev->type != ARPHRD_CAIF)
  		return 0;

  	switch (what) {
  	case NETDEV_REGISTER:

  		if (caifd != NULL)
  			break;

  		caifdev = netdev_priv(dev);

  		link_support = NULL;
  		if (caifdev->use_frag) {
  			head_room = 1;
  			link_support = cfserl_create(dev->ifindex,

  							caifdev->use_stx);

  			if (!link_support) {
  				pr_warn("Out of memory
  ");
  				break;
  			}

  		}

  		caif_enroll_dev(dev, caifdev, link_support, head_room,
  				&layer, NULL);
  		caifdev->flowctrl = dev_flowctrl;

  		break;

  	case NETDEV_UP:
  		rcu_read_lock();

  		caifd = caif_get(dev);

  		if (caifd == NULL) {
  			rcu_read_unlock();

  			break;

  		}

  		caifd->xoff = 0;

  		cfcnfg_set_phy_state(cfg, &caifd->layer, true);
  		rcu_read_unlock();

  		break;
  
  	case NETDEV_DOWN:

  		rcu_read_lock();

  		caifd = caif_get(dev);

  		if (!caifd || !caifd->layer.up || !caifd->layer.up->ctrlcmd) {
  			rcu_read_unlock();
  			return -EINVAL;
  		}
  
  		cfcnfg_set_phy_state(cfg, &caifd->layer, false);
  		caifd_hold(caifd);
  		rcu_read_unlock();
  
  		caifd->layer.up->ctrlcmd(caifd->layer.up,
  					 _CAIF_CTRLCMD_PHYIF_DOWN_IND,
  					 caifd->layer.id);

  
  		spin_lock_bh(&caifd->flow_lock);
  
  		/*
  		 * Replace our xoff-destructor with original destructor.
  		 * We trust that skb->destructor *always* is called before
  		 * the skb reference is invalid. The hijacked SKB destructor
  		 * takes the flow_lock so manipulating the skb->destructor here
  		 * should be safe.
  		*/
  		if (caifd->xoff_skb_dtor != NULL && caifd->xoff_skb != NULL)
  			caifd->xoff_skb->destructor = caifd->xoff_skb_dtor;
  
  		caifd->xoff = 0;
  		caifd->xoff_skb_dtor = NULL;
  		caifd->xoff_skb = NULL;
  
  		spin_unlock_bh(&caifd->flow_lock);

  		caifd_put(caifd);

  		break;
  
  	case NETDEV_UNREGISTER:

  		mutex_lock(&caifdevs->lock);

  		caifd = caif_get(dev);

  		if (caifd == NULL) {
  			mutex_unlock(&caifdevs->lock);

  			break;

  		}
  		list_del_rcu(&caifd->list);
  
  		/*
  		 * NETDEV_UNREGISTER is called repeatedly until all reference
  		 * counts for the net-device are released. If references to
  		 * caifd is taken, simply ignore NETDEV_UNREGISTER and wait for
  		 * the next call to NETDEV_UNREGISTER.
  		 *
  		 * If any packets are in flight down the CAIF Stack,
  		 * cfcnfg_del_phy_layer will return nonzero.
  		 * If no packets are in flight, the CAIF Stack associated
  		 * with the net-device un-registering is freed.
  		 */
  
  		if (caifd_refcnt_read(caifd) != 0 ||
  			cfcnfg_del_phy_layer(cfg, &caifd->layer) != 0) {
  
  			pr_info("Wait for device inuse
  ");
  			/* Enrole device if CAIF Stack is still in use */
  			list_add_rcu(&caifd->list, &caifdevs->list);
  			mutex_unlock(&caifdevs->lock);
  			break;
  		}
  
  		synchronize_rcu();
  		dev_put(caifd->netdev);
  		free_percpu(caifd->pcpu_refcnt);
  		kfree(caifd);
  
  		mutex_unlock(&caifdevs->lock);

  		break;
  	}
  	return 0;
  }
  
  static struct notifier_block caif_device_notifier = {
  	.notifier_call = caif_device_notify,
  	.priority = 0,
  };

  /* Per-namespace Caif devices handling */
  static int caif_init_net(struct net *net)
  {
  	struct caif_net *caifn = net_generic(net, caif_net_id);

  	if (WARN_ON(!caifn))
  		return -EINVAL;

  	INIT_LIST_HEAD(&caifn->caifdevs.list);

  	mutex_init(&caifn->caifdevs.lock);

  
  	caifn->cfg = cfcnfg_create();

  	if (!caifn->cfg)

  		return -ENOMEM;

  	return 0;
  }
  
  static void caif_exit_net(struct net *net)
  {

  	struct caif_device_entry *caifd, *tmp;
  	struct caif_device_entry_list *caifdevs =
  	    caif_device_list(net);

  	struct cfcnfg *cfg =  get_cfcnfg(net);
  
  	if (!cfg || !caifdevs)
  		return;

  	rtnl_lock();

  	mutex_lock(&caifdevs->lock);
  
  	list_for_each_entry_safe(caifd, tmp, &caifdevs->list, list) {
  		int i = 0;
  		list_del_rcu(&caifd->list);
  		cfcnfg_set_phy_state(cfg, &caifd->layer, false);
  
  		while (i < 10 &&
  			(caifd_refcnt_read(caifd) != 0 ||
  			cfcnfg_del_phy_layer(cfg, &caifd->layer) != 0)) {
  
  			pr_info("Wait for device inuse
  ");
  			msleep(250);
  			i++;
  		}
  		synchronize_rcu();
  		dev_put(caifd->netdev);
  		free_percpu(caifd->pcpu_refcnt);
  		kfree(caifd);

  	}

  	cfcnfg_remove(cfg);

  
  	mutex_unlock(&caifdevs->lock);

  	rtnl_unlock();
  }
  
  static struct pernet_operations caif_net_ops = {
  	.init = caif_init_net,
  	.exit = caif_exit_net,
  	.id   = &caif_net_id,
  	.size = sizeof(struct caif_net),
  };
  
  /* Initialize Caif devices list */
  static int __init caif_device_init(void)
  {
  	int result;

  	result = register_pernet_device(&caif_net_ops);

  	if (result)

  		return result;

  	register_netdevice_notifier(&caif_device_notifier);

  	dev_add_pack(&caif_packet_type);

  
  	return result;

  }
  
  static void __exit caif_device_exit(void)
  {

  	unregister_pernet_device(&caif_net_ops);
  	unregister_netdevice_notifier(&caif_device_notifier);

  	dev_remove_pack(&caif_packet_type);

  }
  
  module_init(caif_device_init);
  module_exit(caif_device_exit);