// SPDX-License-Identifier: GPL-2.0-only
/*
 * CAIF Interface registration.
 * Copyright (C) ST-Ericsson AB 2010
 * Author:      Sjur Brendeland
 *
 * Borrowed heavily from file: pn_dev.c. Thanks to Remi Denis-Courmont
 *  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/caif_dev.h>
#include <net/caif/cfpkt.h>
#include <net/caif/cfcnfg.h>
#include <net/caif/cfserl.h>

MODULE_DESCRIPTION("ST-Ericsson CAIF modem protocol support");
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 unsigned 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);
        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);
        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 *caifd;

        caifd = kzalloc_obj(*caifd);
        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;

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

static 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);

        WARN_ON(caifd == NULL);
        if (!caifd) {
                rcu_read_unlock();
                return;
        }

        caifd_hold(caifd);
        rcu_read_unlock();

        spin_lock_bh(&caifd->flow_lock);
        send_xoff = caifd->xoff;
        caifd->xoff = false;
        dtor = caifd->xoff_skb_dtor;

        if (WARN_ON(caifd->xoff_skb != skb))
                skb = NULL;

        caifd->xoff_skb = NULL;
        caifd->xoff_skb_dtor = NULL;

        spin_unlock_bh(&caifd->flow_lock);

        if (dtor && skb)
                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_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);

        /* Check if we need to handle xoff */
        if (likely(caifd->netdev->priv_flags & IFF_NO_QUEUE))
                goto noxoff;

        if (unlikely(caifd->xoff))
                goto noxoff;

        if (likely(!netif_queue_stopped(caifd->netdev))) {
                struct Qdisc *sch;

                /* If we run with a TX queue, check if the queue is too long*/
                txq = netdev_get_tx_queue(skb->dev, 0);
                sch = rcu_dereference_bh(txq->qdisc);
                if (likely(qdisc_is_empty(sch)))
                        goto noxoff;

                /* can check for explicit qdisc len value only !NOLOCK,
                 * always set flow off otherwise
                 */
                high = (caifd->netdev->tx_queue_len * q_high) / 100;
                if (!(sch->flags & TCQ_F_NOLOCK) && likely(sch->q.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)\n",
                        netif_queue_stopped(caifd->netdev),
                        qlen, high);
        caifd->xoff = true;
        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 free 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);
}

int 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;
        int res;

        caifdevs = caif_device_list(dev_net(dev));
        caifd = caif_device_alloc(dev);
        if (!caifd)
                return -ENOMEM;
        *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);

        strscpy(caifd->layer.name, dev->name,
                sizeof(caifd->layer.name));
        caifd->layer.transmit = transmit;
        res = 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;
        return res;
}
EXPORT_SYMBOL(caif_enroll_dev);

/* notify Caif of device events */
static int caif_device_notify(struct notifier_block *me, unsigned long what,
                              void *ptr)
{
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);
        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;
        int res;

        cfg = get_cfcnfg(dev_net(dev));
        caifdevs = caif_device_list(dev_net(dev));

        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\n");
                                break;
                        }
                }
                res = caif_enroll_dev(dev, caifdev, link_support, head_room,
                                &layer, NULL);
                if (res)
                        cfserl_release(link_support);
                caifdev->flowctrl = dev_flowctrl;
                break;

        case NETDEV_UP:
                rcu_read_lock();

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

                caifd->xoff = false;
                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 = false;
                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\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);
        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);

        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\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_subsys(&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_netdevice_notifier(&caif_device_notifier);
        dev_remove_pack(&caif_packet_type);
        unregister_pernet_subsys(&caif_net_ops);
}

module_init(caif_device_init);
module_exit(caif_device_exit);