// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 * arch/xtensa/platforms/iss/network.c
 *
 * Platform specific initialization.
 *
 * Authors: Chris Zankel <chris@zankel.net>
 * Based on work form the UML team.
 *
 * Copyright 2005 Tensilica Inc.
 */

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

#include <linux/hex.h>
#include <linux/list.h>
#include <linux/irq.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/timer.h>
#include <linux/if_ether.h>
#include <linux/inetdevice.h>
#include <linux/init.h>
#include <linux/if_tun.h>
#include <linux/etherdevice.h>
#include <linux/interrupt.h>
#include <linux/ioctl.h>
#include <linux/memblock.h>
#include <linux/ethtool.h>
#include <linux/rtnetlink.h>
#include <linux/platform_device.h>

#include <platform/simcall.h>

#define DRIVER_NAME "iss-netdev"
#define ETH_MAX_PACKET 1500
#define ETH_HEADER_OTHER 14
#define ISS_NET_TIMER_VALUE (HZ / 10)

/* ------------------------------------------------------------------------- */

/* We currently only support the TUNTAP transport protocol. */

#define TRANSPORT_TUNTAP_NAME "tuntap"
#define TRANSPORT_TUNTAP_MTU ETH_MAX_PACKET

struct tuntap_info {
        char dev_name[IFNAMSIZ];
        int fd;
};

/* ------------------------------------------------------------------------- */


struct iss_net_private;

struct iss_net_ops {
        int (*open)(struct iss_net_private *lp);
        void (*close)(struct iss_net_private *lp);
        int (*read)(struct iss_net_private *lp, struct sk_buff **skb);
        int (*write)(struct iss_net_private *lp, struct sk_buff **skb);
        unsigned short (*protocol)(struct sk_buff *skb);
        int (*poll)(struct iss_net_private *lp);
};

/* This structure contains out private information for the driver. */

struct iss_net_private {
        spinlock_t lock;
        struct net_device *dev;
        struct platform_device pdev;
        struct timer_list tl;
        struct rtnl_link_stats64 stats;

        struct timer_list timer;
        unsigned int timer_val;

        int index;
        int mtu;

        struct {
                union {
                        struct tuntap_info tuntap;
                } info;

                const struct iss_net_ops *net_ops;
        } tp;

};

/* ================================ HELPERS ================================ */


static char *split_if_spec(char *str, ...)
{
        char **arg, *end;
        va_list ap;

        va_start(ap, str);
        while ((arg = va_arg(ap, char**)) != NULL) {
                if (*str == '\0') {
                        va_end(ap);
                        return NULL;
                }
                end = strchr(str, ',');
                if (end != str)
                        *arg = str;
                if (end == NULL) {
                        va_end(ap);
                        return NULL;
                }
                *end++ = '\0';
                str = end;
        }
        va_end(ap);
        return str;
}

/* Set Ethernet address of the specified device. */

static void setup_etheraddr(struct net_device *dev, char *str)
{
        u8 addr[ETH_ALEN];

        if (str == NULL)
                goto random;

        if (!mac_pton(str, addr)) {
                pr_err("%s: failed to parse '%s' as an ethernet address\n",
                       dev->name, str);
                goto random;
        }
        if (is_multicast_ether_addr(addr)) {
                pr_err("%s: attempt to assign a multicast ethernet address\n",
                       dev->name);
                goto random;
        }
        if (!is_valid_ether_addr(addr)) {
                pr_err("%s: attempt to assign an invalid ethernet address\n",
                       dev->name);
                goto random;
        }
        if (!is_local_ether_addr(addr))
                pr_warn("%s: assigning a globally valid ethernet address\n",
                        dev->name);
        eth_hw_addr_set(dev, addr);
        return;

random:
        pr_info("%s: choosing a random ethernet address\n",
                dev->name);
        eth_hw_addr_random(dev);
}

/* ======================= TUNTAP TRANSPORT INTERFACE ====================== */

static int tuntap_open(struct iss_net_private *lp)
{
        struct ifreq ifr;
        char *dev_name = lp->tp.info.tuntap.dev_name;
        int err = -EINVAL;
        int fd;

        fd = simc_open("/dev/net/tun", 02, 0); /* O_RDWR */
        if (fd < 0) {
                pr_err("%s: failed to open /dev/net/tun, returned %d (errno = %d)\n",
                       lp->dev->name, fd, errno);
                return fd;
        }

        memset(&ifr, 0, sizeof(ifr));
        ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
        strscpy(ifr.ifr_name, dev_name, sizeof(ifr.ifr_name));

        err = simc_ioctl(fd, TUNSETIFF, &ifr);
        if (err < 0) {
                pr_err("%s: failed to set interface %s, returned %d (errno = %d)\n",
                       lp->dev->name, dev_name, err, errno);
                simc_close(fd);
                return err;
        }

        lp->tp.info.tuntap.fd = fd;
        return err;
}

static void tuntap_close(struct iss_net_private *lp)
{
        simc_close(lp->tp.info.tuntap.fd);
        lp->tp.info.tuntap.fd = -1;
}

static int tuntap_read(struct iss_net_private *lp, struct sk_buff **skb)
{
        return simc_read(lp->tp.info.tuntap.fd,
                        (*skb)->data, (*skb)->dev->mtu + ETH_HEADER_OTHER);
}

static int tuntap_write(struct iss_net_private *lp, struct sk_buff **skb)
{
        return simc_write(lp->tp.info.tuntap.fd, (*skb)->data, (*skb)->len);
}

static unsigned short tuntap_protocol(struct sk_buff *skb)
{
        return eth_type_trans(skb, skb->dev);
}

static int tuntap_poll(struct iss_net_private *lp)
{
        return simc_poll(lp->tp.info.tuntap.fd);
}

static const struct iss_net_ops tuntap_ops = {
        .open           = tuntap_open,
        .close          = tuntap_close,
        .read           = tuntap_read,
        .write          = tuntap_write,
        .protocol       = tuntap_protocol,
        .poll           = tuntap_poll,
};

/*
 * ethX=tuntap,[mac address],device name
 */

static int tuntap_probe(struct iss_net_private *lp, int index, char *init)
{
        struct net_device *dev = lp->dev;
        char *dev_name = NULL, *mac_str = NULL, *rem = NULL;

        /* Transport should be 'tuntap': ethX=tuntap,mac,dev_name */

        if (strncmp(init, TRANSPORT_TUNTAP_NAME,
                    sizeof(TRANSPORT_TUNTAP_NAME) - 1))
                return 0;

        init += sizeof(TRANSPORT_TUNTAP_NAME) - 1;
        if (*init == ',') {
                rem = split_if_spec(init + 1, &mac_str, &dev_name, NULL);
                if (rem != NULL) {
                        pr_err("%s: extra garbage on specification : '%s'\n",
                               dev->name, rem);
                        return 0;
                }
        } else if (*init != '\0') {
                pr_err("%s: invalid argument: %s. Skipping device!\n",
                       dev->name, init);
                return 0;
        }

        if (!dev_name) {
                pr_err("%s: missing tuntap device name\n", dev->name);
                return 0;
        }

        strscpy(lp->tp.info.tuntap.dev_name, dev_name,
                sizeof(lp->tp.info.tuntap.dev_name));

        setup_etheraddr(dev, mac_str);

        lp->mtu = TRANSPORT_TUNTAP_MTU;

        lp->tp.info.tuntap.fd = -1;
        lp->tp.net_ops = &tuntap_ops;

        return 1;
}

/* ================================ ISS NET ================================ */

static int iss_net_rx(struct net_device *dev)
{
        struct iss_net_private *lp = netdev_priv(dev);
        int pkt_len;
        struct sk_buff *skb;

        /* Check if there is any new data. */

        if (lp->tp.net_ops->poll(lp) == 0)
                return 0;

        /* Try to allocate memory, if it fails, try again next round. */

        skb = dev_alloc_skb(dev->mtu + 2 + ETH_HEADER_OTHER);
        if (skb == NULL) {
                spin_lock_bh(&lp->lock);
                lp->stats.rx_dropped++;
                spin_unlock_bh(&lp->lock);
                return 0;
        }

        skb_reserve(skb, 2);

        /* Setup skb */

        skb->dev = dev;
        skb_reset_mac_header(skb);
        pkt_len = lp->tp.net_ops->read(lp, &skb);
        skb_put(skb, pkt_len);

        if (pkt_len > 0) {
                skb_trim(skb, pkt_len);
                skb->protocol = lp->tp.net_ops->protocol(skb);

                spin_lock_bh(&lp->lock);
                lp->stats.rx_bytes += skb->len;
                lp->stats.rx_packets++;
                spin_unlock_bh(&lp->lock);
                netif_rx(skb);
                return pkt_len;
        }
        kfree_skb(skb);
        return pkt_len;
}

static int iss_net_poll(struct iss_net_private *lp)
{
        int err, ret = 0;

        if (!netif_running(lp->dev))
                return 0;

        while ((err = iss_net_rx(lp->dev)) > 0)
                ret++;

        if (err < 0) {
                pr_err("Device '%s' read returned %d, shutting it down\n",
                       lp->dev->name, err);
                dev_close(lp->dev);
        } else {
                /* FIXME reactivate_fd(lp->fd, ISS_ETH_IRQ); */
        }

        return ret;
}


static void iss_net_timer(struct timer_list *t)
{
        struct iss_net_private *lp = timer_container_of(lp, t, timer);

        iss_net_poll(lp);
        mod_timer(&lp->timer, jiffies + lp->timer_val);
}


static int iss_net_open(struct net_device *dev)
{
        struct iss_net_private *lp = netdev_priv(dev);
        int err;

        err = lp->tp.net_ops->open(lp);
        if (err < 0)
                return err;

        netif_start_queue(dev);

        /* clear buffer - it can happen that the host side of the interface
         * is full when we get here. In this case, new data is never queued,
         * SIGIOs never arrive, and the net never works.
         */
        while ((err = iss_net_rx(dev)) > 0)
                ;

        timer_setup(&lp->timer, iss_net_timer, 0);
        lp->timer_val = ISS_NET_TIMER_VALUE;
        mod_timer(&lp->timer, jiffies + lp->timer_val);

        return err;
}

static int iss_net_close(struct net_device *dev)
{
        struct iss_net_private *lp = netdev_priv(dev);

        netif_stop_queue(dev);
        timer_delete_sync(&lp->timer);
        lp->tp.net_ops->close(lp);

        return 0;
}

static int iss_net_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct iss_net_private *lp = netdev_priv(dev);
        int len;

        netif_stop_queue(dev);

        len = lp->tp.net_ops->write(lp, &skb);

        if (len == skb->len) {
                spin_lock_bh(&lp->lock);
                lp->stats.tx_packets++;
                lp->stats.tx_bytes += skb->len;
                spin_unlock_bh(&lp->lock);
                netif_trans_update(dev);
                netif_start_queue(dev);

                /* this is normally done in the interrupt when tx finishes */
                netif_wake_queue(dev);

        } else if (len == 0) {
                netif_start_queue(dev);
                spin_lock_bh(&lp->lock);
                lp->stats.tx_dropped++;
                spin_unlock_bh(&lp->lock);

        } else {
                netif_start_queue(dev);
                pr_err("%s: %s failed(%d)\n", dev->name, __func__, len);
        }


        dev_kfree_skb(skb);
        return NETDEV_TX_OK;
}


static void iss_net_get_stats64(struct net_device *dev,
                                struct rtnl_link_stats64 *stats)
{
        struct iss_net_private *lp = netdev_priv(dev);

        spin_lock_bh(&lp->lock);
        *stats = lp->stats;
        spin_unlock_bh(&lp->lock);
}

static void iss_net_set_multicast_list(struct net_device *dev)
{
}

static void iss_net_tx_timeout(struct net_device *dev, unsigned int txqueue)
{
}

static int iss_net_change_mtu(struct net_device *dev, int new_mtu)
{
        return -EINVAL;
}

static void iss_net_user_timer_expire(struct timer_list *unused)
{
}


static struct platform_driver iss_net_driver = {
        .driver = {
                .name  = DRIVER_NAME,
        },
};

static int driver_registered;

static const struct net_device_ops iss_netdev_ops = {
        .ndo_open               = iss_net_open,
        .ndo_stop               = iss_net_close,
        .ndo_get_stats64        = iss_net_get_stats64,
        .ndo_start_xmit         = iss_net_start_xmit,
        .ndo_validate_addr      = eth_validate_addr,
        .ndo_change_mtu         = iss_net_change_mtu,
        .ndo_set_mac_address    = eth_mac_addr,
        .ndo_tx_timeout         = iss_net_tx_timeout,
        .ndo_set_rx_mode        = iss_net_set_multicast_list,
};

static void iss_net_pdev_release(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct iss_net_private *lp =
                container_of(pdev, struct iss_net_private, pdev);

        free_netdev(lp->dev);
}

static void iss_net_configure(int index, char *init)
{
        struct net_device *dev;
        struct iss_net_private *lp;

        dev = alloc_etherdev(sizeof(*lp));
        if (dev == NULL) {
                pr_err("eth_configure: failed to allocate device\n");
                return;
        }

        /* Initialize private element. */

        lp = netdev_priv(dev);
        *lp = (struct iss_net_private) {
                .dev                    = dev,
                .index                  = index,
        };

        spin_lock_init(&lp->lock);
        /*
         * If this name ends up conflicting with an existing registered
         * netdevice, that is OK, register_netdev{,ice}() will notice this
         * and fail.
         */
        snprintf(dev->name, sizeof(dev->name), "eth%d", index);

        /*
         * Try all transport protocols.
         * Note: more protocols can be added by adding '&& !X_init(lp, eth)'.
         */

        if (!tuntap_probe(lp, index, init)) {
                pr_err("%s: invalid arguments. Skipping device!\n",
                       dev->name);
                goto err_free_netdev;
        }

        pr_info("Netdevice %d (%pM)\n", index, dev->dev_addr);

        /* sysfs register */

        if (!driver_registered) {
                if (platform_driver_register(&iss_net_driver))
                        goto err_free_netdev;
                driver_registered = 1;
        }

        lp->pdev.id = index;
        lp->pdev.name = DRIVER_NAME;
        lp->pdev.dev.release = iss_net_pdev_release;
        if (platform_device_register(&lp->pdev))
                goto err_free_netdev;
        SET_NETDEV_DEV(dev, &lp->pdev.dev);

        dev->netdev_ops = &iss_netdev_ops;
        dev->mtu = lp->mtu;
        dev->watchdog_timeo = (HZ >> 1);
        dev->irq = -1;

        rtnl_lock();
        if (register_netdevice(dev)) {
                rtnl_unlock();
                pr_err("%s: error registering net device!\n", dev->name);
                platform_device_unregister(&lp->pdev);
                /* dev is freed by the iss_net_pdev_release callback */
                return;
        }
        rtnl_unlock();

        timer_setup(&lp->tl, iss_net_user_timer_expire, 0);

        return;

err_free_netdev:
        free_netdev(dev);
}

/* ------------------------------------------------------------------------- */

/* Filled in during early boot */

struct list_head eth_cmd_line = LIST_HEAD_INIT(eth_cmd_line);

struct iss_net_init {
        struct list_head list;
        char *init;             /* init string */
        int index;
};

/*
 * Parse the command line and look for 'ethX=...' fields, and register all
 * those fields. They will be later initialized in iss_net_init.
 */

static int __init iss_net_setup(char *str)
{
        struct iss_net_init *device = NULL;
        struct iss_net_init *new;
        struct list_head *ele;
        char *end;
        int rc;
        unsigned n;

        end = strchr(str, '=');
        if (!end) {
                pr_err("Expected '=' after device number\n");
                return 1;
        }
        *end = 0;
        rc = kstrtouint(str, 0, &n);
        *end = '=';
        if (rc < 0) {
                pr_err("Failed to parse '%s'\n", str);
                return 1;
        }
        str = end;

        list_for_each(ele, &eth_cmd_line) {
                device = list_entry(ele, struct iss_net_init, list);
                if (device->index == n)
                        break;
        }

        if (device && device->index == n) {
                pr_err("Device %u already configured\n", n);
                return 1;
        }

        new = memblock_alloc(sizeof(*new), SMP_CACHE_BYTES);
        if (new == NULL) {
                pr_err("Alloc_bootmem failed\n");
                return 1;
        }

        INIT_LIST_HEAD(&new->list);
        new->index = n;
        new->init = str + 1;

        list_add_tail(&new->list, &eth_cmd_line);
        return 1;
}

__setup("eth", iss_net_setup);

/*
 * Initialize all ISS Ethernet devices previously registered in iss_net_setup.
 */

static int iss_net_init(void)
{
        struct list_head *ele, *next;

        /* Walk through all Ethernet devices specified in the command line. */

        list_for_each_safe(ele, next, &eth_cmd_line) {
                struct iss_net_init *eth;
                eth = list_entry(ele, struct iss_net_init, list);
                iss_net_configure(eth->index, eth->init);
        }

        return 1;
}
device_initcall(iss_net_init);