/*
 * 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 <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>

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;
};

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;

struct cfcnfg *get_cfcnfg(struct net *net)
{
        struct caif_net *caifn;
        BUG_ON(!net);
        caifn = net_generic(net, caif_net_id);
        BUG_ON(!caifn);
        return caifn->cfg;
}
EXPORT_SYMBOL(get_cfcnfg);

static struct caif_device_entry_list *caif_device_list(struct net *net)
{
        struct caif_net *caifn;
        BUG_ON(!net);
        caifn = net_generic(net, caif_net_id);
        BUG_ON(!caifn);
        return &caifn->caifdevs;
}

static void caifd_put(struct caif_device_entry *e)
{
        irqsafe_cpu_dec(*e->pcpu_refcnt);
}

static void caifd_hold(struct caif_device_entry *e)
{
        irqsafe_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));
        BUG_ON(!caifdevs);

        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;
        BUG_ON(!caifdevs);
        list_for_each_entry_rcu(caifd, &caifdevs->list, list) {
                if (caifd->netdev == dev)
                        return caifd;
        }
        return NULL;
}

static int transmit(struct cflayer *layer, struct cfpkt *pkt)
{
        int err;
        struct caif_device_entry *caifd =
            container_of(layer, struct caif_device_entry, layer);
        struct sk_buff *skb;

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

        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);
        return 0;
}

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);
}

/* 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;
        enum cfcnfg_phy_preference pref;
        enum cfcnfg_phy_type phy_type;
        struct cfcnfg *cfg;
        struct caif_device_entry_list *caifdevs =
            caif_device_list(dev_net(dev));

        if (dev->type != ARPHRD_CAIF)
                return 0;

        cfg = get_cfcnfg(dev_net(dev));
        if (cfg == NULL)
                return 0;

        switch (what) {
        case NETDEV_REGISTER:
                caifd = caif_device_alloc(dev);
                if (!caifd)
                        return 0;

                caifdev = netdev_priv(dev);
                caifdev->flowctrl = dev_flowctrl;

                caifd->layer.transmit = transmit;

                if (caifdev->use_frag)
                        phy_type = CFPHYTYPE_FRAG;
                else
                        phy_type = CFPHYTYPE_CAIF;

                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;
                }
                strncpy(caifd->layer.name, dev->name,
                        sizeof(caifd->layer.name) - 1);
                caifd->layer.name[sizeof(caifd->layer.name) - 1] = 0;

                mutex_lock(&caifdevs->lock);
                list_add_rcu(&caifd->list, &caifdevs->list);

                cfcnfg_add_phy_layer(cfg,
                                     phy_type,
                                     dev,
                                     &caifd->layer,
                                     pref,
                                     caifdev->use_fcs,
                                     caifdev->use_stx);
                mutex_unlock(&caifdevs->lock);
                break;

        case NETDEV_UP:
                rcu_read_lock();

                caifd = caif_get(dev);
                if (caifd == NULL) {
                        rcu_read_unlock();
                        break;
                }

                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);
                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\n");
                        /* 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);
        BUG_ON(!caifn);
        INIT_LIST_HEAD(&caifn->caifdevs.list);
        mutex_init(&caifn->caifdevs.lock);

        caifn->cfg = cfcnfg_create();
        if (!caifn->cfg) {
                pr_warn("can't create cfcnfg\n");
                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;

        rtnl_lock();
        mutex_lock(&caifdevs->lock);

        cfg = get_cfcnfg(net);
        if (cfg == NULL) {
                mutex_unlock(&caifdevs->lock);
                return;
        }

        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\n");
                        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);