// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * USB-to-WWAN Driver for Sierra Wireless modems
 *
 * Copyright (C) 2008, 2009, 2010 Paxton Smith, Matthew Safar, Rory Filer
 *                          <linux@sierrawireless.com>
 *
 * Portions of this based on the cdc_ether driver by David Brownell (2003-2005)
 * and Ole Andre Vadla Ravnas (ActiveSync) (2006).
 *
 * IMPORTANT DISCLAIMER: This driver is not commercially supported by
 * Sierra Wireless. Use at your own risk.
 */

#define DRIVER_AUTHOR "Paxton Smith, Matthew Safar, Rory Filer"
#define DRIVER_DESC "USB-to-WWAN Driver for Sierra Wireless modems"

/* if defined debug messages enabled */
/*#define       DEBUG*/

#include <linux/module.h>
#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/mii.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/usb.h>
#include <linux/usb/cdc.h>
#include <net/ip.h>
#include <net/udp.h>
#include <linux/unaligned.h>
#include <linux/usb/usbnet.h>

#define SWI_USB_REQUEST_GET_FW_ATTR     0x06
#define SWI_GET_FW_ATTR_MASK            0x08

/* atomic counter partially included in MAC address to make sure 2 devices
 * do not end up with the same MAC - concept breaks in case of > 255 ifaces
 */
static  atomic_t iface_counter = ATOMIC_INIT(0);

/*
 * SYNC Timer Delay definition used to set the expiry time
 */
#define SIERRA_NET_SYNCDELAY (2*HZ)

/* Max. MTU supported. The modem buffers are limited to 1500 */
#define SIERRA_NET_MAX_SUPPORTED_MTU    1500

/* The SIERRA_NET_USBCTL_BUF_LEN defines a buffer size allocated for control
 * message reception ... and thus the max. received packet.
 * (May be the cause for parse_hip returning -EINVAL)
 */
#define SIERRA_NET_USBCTL_BUF_LEN       1024

/* Overriding the default usbnet rx_urb_size */
#define SIERRA_NET_RX_URB_SIZE          (8 * 1024)

/* Private data structure */
struct sierra_net_data {

        u16 link_up;            /* air link up or down */
        u8 tx_hdr_template[4];  /* part of HIP hdr for tx'd packets */

        u8 sync_msg[4];         /* SYNC message */
        u8 shdwn_msg[4];        /* Shutdown message */

        /* Backpointer to the container */
        struct usbnet *usbnet;

        u8 ifnum;       /* interface number */

/* Bit masks, must be a power of 2 */
#define SIERRA_NET_EVENT_RESP_AVAIL    0x01
#define SIERRA_NET_TIMER_EXPIRY        0x02
        unsigned long kevent_flags;
        struct work_struct sierra_net_kevent;
        struct timer_list sync_timer; /* For retrying SYNC sequence */
};

struct param {
        int is_present;
        union {
                void  *ptr;
                u32    dword;
                u16    word;
                u8     byte;
        };
};

/* HIP message type */
#define SIERRA_NET_HIP_EXTENDEDID       0x7F
#define SIERRA_NET_HIP_HSYNC_ID         0x60    /* Modem -> host */
#define SIERRA_NET_HIP_RESTART_ID       0x62    /* Modem -> host */
#define SIERRA_NET_HIP_MSYNC_ID         0x20    /* Host -> modem */
#define SIERRA_NET_HIP_SHUTD_ID         0x26    /* Host -> modem */

#define SIERRA_NET_HIP_EXT_IP_IN_ID   0x0202
#define SIERRA_NET_HIP_EXT_IP_OUT_ID  0x0002

/* 3G UMTS Link Sense Indication definitions */
#define SIERRA_NET_HIP_LSI_UMTSID       0x78

/* Reverse Channel Grant Indication HIP message */
#define SIERRA_NET_HIP_RCGI             0x64

/* LSI Protocol types */
#define SIERRA_NET_PROTOCOL_UMTS      0x01
#define SIERRA_NET_PROTOCOL_UMTS_DS   0x04
/* LSI Coverage */
#define SIERRA_NET_COVERAGE_NONE      0x00
#define SIERRA_NET_COVERAGE_NOPACKET  0x01

/* LSI Session */
#define SIERRA_NET_SESSION_IDLE       0x00
/* LSI Link types */
#define SIERRA_NET_AS_LINK_TYPE_IPV4  0x00
#define SIERRA_NET_AS_LINK_TYPE_IPV6  0x02

struct lsi_umts {
        u8 protocol;
        u8 unused1;
        __be16 length;
        /* eventually use a union for the rest - assume umts for now */
        u8 coverage;
        u8 network_len; /* network name len */
        u8 network[40]; /* network name (UCS2, bigendian) */
        u8 session_state;
        u8 unused3[33];
} __packed;

struct lsi_umts_single {
        struct lsi_umts lsi;
        u8 link_type;
        u8 pdp_addr_len; /* NW-supplied PDP address len */
        u8 pdp_addr[16]; /* NW-supplied PDP address (bigendian)) */
        u8 unused4[23];
        u8 dns1_addr_len; /* NW-supplied 1st DNS address len (bigendian) */
        u8 dns1_addr[16]; /* NW-supplied 1st DNS address */
        u8 dns2_addr_len; /* NW-supplied 2nd DNS address len */
        u8 dns2_addr[16]; /* NW-supplied 2nd DNS address (bigendian)*/
        u8 wins1_addr_len; /* NW-supplied 1st Wins address len */
        u8 wins1_addr[16]; /* NW-supplied 1st Wins address (bigendian)*/
        u8 wins2_addr_len; /* NW-supplied 2nd Wins address len */
        u8 wins2_addr[16]; /* NW-supplied 2nd Wins address (bigendian) */
        u8 unused5[4];
        u8 gw_addr_len; /* NW-supplied GW address len */
        u8 gw_addr[16]; /* NW-supplied GW address (bigendian) */
        u8 reserved[8];
} __packed;

struct lsi_umts_dual {
        struct lsi_umts lsi;
        u8 pdp_addr4_len; /* NW-supplied PDP IPv4 address len */
        u8 pdp_addr4[4];  /* NW-supplied PDP IPv4 address (bigendian)) */
        u8 pdp_addr6_len; /* NW-supplied PDP IPv6 address len */
        u8 pdp_addr6[16]; /* NW-supplied PDP IPv6 address (bigendian)) */
        u8 unused4[23];
        u8 dns1_addr4_len; /* NW-supplied 1st DNS v4 address len (bigendian) */
        u8 dns1_addr4[4];  /* NW-supplied 1st DNS v4 address */
        u8 dns1_addr6_len; /* NW-supplied 1st DNS v6 address len */
        u8 dns1_addr6[16]; /* NW-supplied 1st DNS v6 address (bigendian)*/
        u8 dns2_addr4_len; /* NW-supplied 2nd DNS v4 address len (bigendian) */
        u8 dns2_addr4[4];  /* NW-supplied 2nd DNS v4 address */
        u8 dns2_addr6_len; /* NW-supplied 2nd DNS v6 address len */
        u8 dns2_addr6[16]; /* NW-supplied 2nd DNS v6 address (bigendian)*/
        u8 unused5[68];
} __packed;

#define SIERRA_NET_LSI_COMMON_LEN      4
#define SIERRA_NET_LSI_UMTS_LEN        (sizeof(struct lsi_umts_single))
#define SIERRA_NET_LSI_UMTS_STATUS_LEN \
        (SIERRA_NET_LSI_UMTS_LEN - SIERRA_NET_LSI_COMMON_LEN)
#define SIERRA_NET_LSI_UMTS_DS_LEN     (sizeof(struct lsi_umts_dual))
#define SIERRA_NET_LSI_UMTS_DS_STATUS_LEN \
        (SIERRA_NET_LSI_UMTS_DS_LEN - SIERRA_NET_LSI_COMMON_LEN)

/* Our own net device operations structure */
static const struct net_device_ops sierra_net_device_ops = {
        .ndo_open               = usbnet_open,
        .ndo_stop               = usbnet_stop,
        .ndo_start_xmit         = usbnet_start_xmit,
        .ndo_tx_timeout         = usbnet_tx_timeout,
        .ndo_change_mtu         = usbnet_change_mtu,
        .ndo_get_stats64        = dev_get_tstats64,
        .ndo_set_mac_address    = eth_mac_addr,
        .ndo_validate_addr      = eth_validate_addr,
};

/* get private data associated with passed in usbnet device */
static inline struct sierra_net_data *sierra_net_get_private(struct usbnet *dev)
{
        return (struct sierra_net_data *)dev->data[0];
}

/* set private data associated with passed in usbnet device */
static inline void sierra_net_set_private(struct usbnet *dev,
                        struct sierra_net_data *priv)
{
        dev->data[0] = (unsigned long)priv;
}

/* is packet IPv4/IPv6 */
static inline int is_ip(struct sk_buff *skb)
{
        return skb->protocol == cpu_to_be16(ETH_P_IP) ||
               skb->protocol == cpu_to_be16(ETH_P_IPV6);
}

/*
 * check passed in packet and make sure that:
 *  - it is linear (no scatter/gather)
 *  - it is ethernet (mac_header properly set)
 */
static int check_ethip_packet(struct sk_buff *skb, struct usbnet *dev)
{
        skb_reset_mac_header(skb); /* ethernet header */

        if (skb_is_nonlinear(skb)) {
                netdev_err(dev->net, "Non linear buffer-dropping\n");
                return 0;
        }

        if (!pskb_may_pull(skb, ETH_HLEN))
                return 0;
        skb->protocol = eth_hdr(skb)->h_proto;

        return 1;
}

static const u8 *save16bit(struct param *p, const u8 *datap)
{
        p->is_present = 1;
        p->word = get_unaligned_be16(datap);
        return datap + sizeof(p->word);
}

static const u8 *save8bit(struct param *p, const u8 *datap)
{
        p->is_present = 1;
        p->byte = *datap;
        return datap + sizeof(p->byte);
}

/*----------------------------------------------------------------------------*
 *                              BEGIN HIP                                     *
 *----------------------------------------------------------------------------*/
/* HIP header */
#define SIERRA_NET_HIP_HDR_LEN 4
/* Extended HIP header */
#define SIERRA_NET_HIP_EXT_HDR_LEN 6

struct hip_hdr {
        int    hdrlen;
        struct param payload_len;
        struct param msgid;
        struct param msgspecific;
        struct param extmsgid;
};

static int parse_hip(const u8 *buf, const u32 buflen, struct hip_hdr *hh)
{
        const u8 *curp = buf;
        int    padded;

        if (buflen < SIERRA_NET_HIP_HDR_LEN)
                return -EPROTO;

        curp = save16bit(&hh->payload_len, curp);
        curp = save8bit(&hh->msgid, curp);
        curp = save8bit(&hh->msgspecific, curp);

        padded = hh->msgid.byte & 0x80;
        hh->msgid.byte &= 0x7F;                 /* 7 bits */

        hh->extmsgid.is_present = (hh->msgid.byte == SIERRA_NET_HIP_EXTENDEDID);
        if (hh->extmsgid.is_present) {
                if (buflen < SIERRA_NET_HIP_EXT_HDR_LEN)
                        return -EPROTO;

                hh->payload_len.word &= 0x3FFF; /* 14 bits */

                curp = save16bit(&hh->extmsgid, curp);
                hh->extmsgid.word &= 0x03FF;    /* 10 bits */

                hh->hdrlen = SIERRA_NET_HIP_EXT_HDR_LEN;
        } else {
                hh->payload_len.word &= 0x07FF; /* 11 bits */
                hh->hdrlen = SIERRA_NET_HIP_HDR_LEN;
        }

        if (padded) {
                hh->hdrlen++;
                hh->payload_len.word--;
        }

        /* if real packet shorter than the claimed length */
        if (buflen < (hh->hdrlen + hh->payload_len.word))
                return -EINVAL;

        return 0;
}

static void build_hip(u8 *buf, const u16 payloadlen,
                struct sierra_net_data *priv)
{
        /* the following doesn't have the full functionality. We
         * currently build only one kind of header, so it is faster this way
         */
        put_unaligned_be16(payloadlen, buf);
        memcpy(buf+2, priv->tx_hdr_template, sizeof(priv->tx_hdr_template));
}
/*----------------------------------------------------------------------------*
 *                              END HIP                                       *
 *----------------------------------------------------------------------------*/

static int sierra_net_send_cmd(struct usbnet *dev,
                u8 *cmd, int cmdlen, const char * cmd_name)
{
        struct sierra_net_data *priv = sierra_net_get_private(dev);
        int  status;

        status = usbnet_write_cmd(dev, USB_CDC_SEND_ENCAPSULATED_COMMAND,
                                  USB_DIR_OUT|USB_TYPE_CLASS|USB_RECIP_INTERFACE,
                                  0, priv->ifnum, cmd, cmdlen);

        if (status != cmdlen && status != -ENODEV)
                netdev_err(dev->net, "Submit %s failed %d\n", cmd_name, status);

        return status;
}

static int sierra_net_send_sync(struct usbnet *dev)
{
        int  status;
        struct sierra_net_data *priv = sierra_net_get_private(dev);

        dev_dbg(&dev->udev->dev, "%s", __func__);

        status = sierra_net_send_cmd(dev, priv->sync_msg,
                        sizeof(priv->sync_msg), "SYNC");

        return status;
}

static void sierra_net_set_ctx_index(struct sierra_net_data *priv, u8 ctx_ix)
{
        dev_dbg(&(priv->usbnet->udev->dev), "%s %d", __func__, ctx_ix);
        priv->tx_hdr_template[0] = 0x3F;
        priv->tx_hdr_template[1] = ctx_ix;
        *((__be16 *)&priv->tx_hdr_template[2]) =
                cpu_to_be16(SIERRA_NET_HIP_EXT_IP_OUT_ID);
}

static int sierra_net_parse_lsi(struct usbnet *dev, char *data, int datalen)
{
        struct lsi_umts *lsi = (struct lsi_umts *)data;
        u32 expected_length;

        if (datalen < sizeof(struct lsi_umts_single)) {
                netdev_err(dev->net, "%s: Data length %d, exp >= %zu\n",
                           __func__, datalen, sizeof(struct lsi_umts_single));
                return -1;
        }

        /* Validate the session state */
        if (lsi->session_state == SIERRA_NET_SESSION_IDLE) {
                netdev_err(dev->net, "Session idle, 0x%02x\n",
                           lsi->session_state);
                return 0;
        }

        /* Validate the protocol  - only support UMTS for now */
        if (lsi->protocol == SIERRA_NET_PROTOCOL_UMTS) {
                struct lsi_umts_single *single = (struct lsi_umts_single *)lsi;

                /* Validate the link type */
                if (single->link_type != SIERRA_NET_AS_LINK_TYPE_IPV4 &&
                    single->link_type != SIERRA_NET_AS_LINK_TYPE_IPV6) {
                        netdev_err(dev->net, "Link type unsupported: 0x%02x\n",
                                   single->link_type);
                        return -1;
                }
                expected_length = SIERRA_NET_LSI_UMTS_STATUS_LEN;
        } else if (lsi->protocol == SIERRA_NET_PROTOCOL_UMTS_DS) {
                expected_length = SIERRA_NET_LSI_UMTS_DS_STATUS_LEN;
        } else {
                netdev_err(dev->net, "Protocol unsupported, 0x%02x\n",
                           lsi->protocol);
                return -1;
        }

        if (be16_to_cpu(lsi->length) != expected_length) {
                netdev_err(dev->net, "%s: LSI_UMTS_STATUS_LEN %d, exp %u\n",
                           __func__, be16_to_cpu(lsi->length), expected_length);
                return -1;
        }

        /* Validate the coverage */
        if (lsi->coverage == SIERRA_NET_COVERAGE_NONE ||
            lsi->coverage == SIERRA_NET_COVERAGE_NOPACKET) {
                netdev_err(dev->net, "No coverage, 0x%02x\n", lsi->coverage);
                return 0;
        }

        /* Set link_sense true */
        return 1;
}

static void sierra_net_handle_lsi(struct usbnet *dev, char *data,
                struct hip_hdr  *hh)
{
        struct sierra_net_data *priv = sierra_net_get_private(dev);
        int link_up;

        link_up = sierra_net_parse_lsi(dev, data + hh->hdrlen,
                                        hh->payload_len.word);
        if (link_up < 0) {
                netdev_err(dev->net, "Invalid LSI\n");
                return;
        }
        if (link_up) {
                sierra_net_set_ctx_index(priv, hh->msgspecific.byte);
                priv->link_up = 1;
        } else {
                priv->link_up = 0;
        }
        usbnet_link_change(dev, link_up, 0);
}

static void sierra_net_dosync(struct usbnet *dev)
{
        int status;
        struct sierra_net_data *priv = sierra_net_get_private(dev);

        dev_dbg(&dev->udev->dev, "%s", __func__);

        /* The SIERRA_NET_HIP_MSYNC_ID command appears to request that the
         * firmware restart itself.  After restarting, the modem will respond
         * with the SIERRA_NET_HIP_RESTART_ID indication.  The driver continues
         * sending MSYNC commands every few seconds until it receives the
         * RESTART event from the firmware
         */

        /* tell modem we are ready */
        status = sierra_net_send_sync(dev);
        if (status < 0)
                netdev_err(dev->net,
                        "Send SYNC failed, status %d\n", status);
        status = sierra_net_send_sync(dev);
        if (status < 0)
                netdev_err(dev->net,
                        "Send SYNC failed, status %d\n", status);

        /* Now, start a timer and make sure we get the Restart Indication */
        priv->sync_timer.expires = jiffies + SIERRA_NET_SYNCDELAY;
        add_timer(&priv->sync_timer);
}

static void sierra_net_kevent(struct work_struct *work)
{
        struct sierra_net_data *priv =
                container_of(work, struct sierra_net_data, sierra_net_kevent);
        struct usbnet *dev = priv->usbnet;
        int  len;
        int  err;
        u8  *buf;
        u8   ifnum;

        if (test_bit(SIERRA_NET_EVENT_RESP_AVAIL, &priv->kevent_flags)) {
                clear_bit(SIERRA_NET_EVENT_RESP_AVAIL, &priv->kevent_flags);

                /* Query the modem for the LSI message */
                buf = kzalloc(SIERRA_NET_USBCTL_BUF_LEN, GFP_KERNEL);
                if (!buf)
                        return;

                ifnum = priv->ifnum;
                len = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0),
                                USB_CDC_GET_ENCAPSULATED_RESPONSE,
                                USB_DIR_IN|USB_TYPE_CLASS|USB_RECIP_INTERFACE,
                                0, ifnum, buf, SIERRA_NET_USBCTL_BUF_LEN,
                                USB_CTRL_SET_TIMEOUT);

                if (len < 0) {
                        netdev_err(dev->net,
                                "usb_control_msg failed, status %d\n", len);
                } else {
                        struct hip_hdr  hh;

                        dev_dbg(&dev->udev->dev, "%s: Received status message,"
                                " %04x bytes", __func__, len);

                        err = parse_hip(buf, len, &hh);
                        if (err) {
                                netdev_err(dev->net, "%s: Bad packet,"
                                        " parse result %d\n", __func__, err);
                                kfree(buf);
                                return;
                        }

                        /* Validate packet length */
                        if (len != hh.hdrlen + hh.payload_len.word) {
                                netdev_err(dev->net, "%s: Bad packet, received"
                                        " %d, expected %d\n",   __func__, len,
                                        hh.hdrlen + hh.payload_len.word);
                                kfree(buf);
                                return;
                        }

                        /* Switch on received message types */
                        switch (hh.msgid.byte) {
                        case SIERRA_NET_HIP_LSI_UMTSID:
                                dev_dbg(&dev->udev->dev, "LSI for ctx:%d",
                                        hh.msgspecific.byte);
                                sierra_net_handle_lsi(dev, buf, &hh);
                                break;
                        case SIERRA_NET_HIP_RESTART_ID:
                                dev_dbg(&dev->udev->dev, "Restart reported: %d,"
                                                " stopping sync timer",
                                                hh.msgspecific.byte);
                                /* Got sync resp - stop timer & clear mask */
                                timer_delete_sync(&priv->sync_timer);
                                clear_bit(SIERRA_NET_TIMER_EXPIRY,
                                          &priv->kevent_flags);
                                break;
                        case SIERRA_NET_HIP_HSYNC_ID:
                                dev_dbg(&dev->udev->dev, "SYNC received");
                                err = sierra_net_send_sync(dev);
                                if (err < 0)
                                        netdev_err(dev->net,
                                                "Send SYNC failed %d\n", err);
                                break;
                        case SIERRA_NET_HIP_EXTENDEDID:
                                netdev_err(dev->net, "Unrecognized HIP msg, "
                                        "extmsgid 0x%04x\n", hh.extmsgid.word);
                                break;
                        case SIERRA_NET_HIP_RCGI:
                                /* Ignored */
                                break;
                        default:
                                netdev_err(dev->net, "Unrecognized HIP msg, "
                                        "msgid 0x%02x\n", hh.msgid.byte);
                                break;
                        }
                }
                kfree(buf);
        }
        /* The sync timer bit might be set */
        if (test_bit(SIERRA_NET_TIMER_EXPIRY, &priv->kevent_flags)) {
                clear_bit(SIERRA_NET_TIMER_EXPIRY, &priv->kevent_flags);
                dev_dbg(&dev->udev->dev, "Deferred sync timer expiry");
                sierra_net_dosync(priv->usbnet);
        }

        if (priv->kevent_flags)
                dev_dbg(&dev->udev->dev, "sierra_net_kevent done, "
                        "kevent_flags = 0x%lx", priv->kevent_flags);
}

static void sierra_net_defer_kevent(struct usbnet *dev, int work)
{
        struct sierra_net_data *priv = sierra_net_get_private(dev);

        set_bit(work, &priv->kevent_flags);
        schedule_work(&priv->sierra_net_kevent);
}

/*
 * Sync Retransmit Timer Handler. On expiry, kick the work queue
 */
static void sierra_sync_timer(struct timer_list *t)
{
        struct sierra_net_data *priv = timer_container_of(priv, t, sync_timer);
        struct usbnet *dev = priv->usbnet;

        dev_dbg(&dev->udev->dev, "%s", __func__);
        /* Kick the tasklet */
        sierra_net_defer_kevent(dev, SIERRA_NET_TIMER_EXPIRY);
}

static void sierra_net_status(struct usbnet *dev, struct urb *urb)
{
        struct usb_cdc_notification *event;

        dev_dbg(&dev->udev->dev, "%s", __func__);

        if (urb->actual_length < sizeof *event)
                return;

        /* Add cases to handle other standard notifications. */
        event = urb->transfer_buffer;
        switch (event->bNotificationType) {
        case USB_CDC_NOTIFY_NETWORK_CONNECTION:
        case USB_CDC_NOTIFY_SPEED_CHANGE:
                /* USB 305 sends those */
                break;
        case USB_CDC_NOTIFY_RESPONSE_AVAILABLE:
                sierra_net_defer_kevent(dev, SIERRA_NET_EVENT_RESP_AVAIL);
                break;
        default:
                netdev_err(dev->net, ": unexpected notification %02x!\n",
                                event->bNotificationType);
                break;
        }
}

static u32 sierra_net_get_link(struct net_device *net)
{
        struct usbnet *dev = netdev_priv(net);
        /* Report link is down whenever the interface is down */
        return sierra_net_get_private(dev)->link_up && netif_running(net);
}

static const struct ethtool_ops sierra_net_ethtool_ops = {
        .get_drvinfo = usbnet_get_drvinfo,
        .get_link = sierra_net_get_link,
        .get_msglevel = usbnet_get_msglevel,
        .set_msglevel = usbnet_set_msglevel,
        .nway_reset = usbnet_nway_reset,
        .get_link_ksettings = usbnet_get_link_ksettings_mii,
        .set_link_ksettings = usbnet_set_link_ksettings_mii,
};

static int sierra_net_get_fw_attr(struct usbnet *dev, u16 *datap)
{
        int result = 0;
        __le16 attrdata;

        result = usbnet_read_cmd(dev,
                                /* _u8 vendor specific request */
                                SWI_USB_REQUEST_GET_FW_ATTR,
                                USB_DIR_IN | USB_TYPE_VENDOR,   /* __u8 request type */
                                0x0000,         /* __u16 value not used */
                                0x0000,         /* __u16 index  not used */
                                &attrdata,      /* char *data */
                                sizeof(attrdata)        /* __u16 size */
                                );

        if (result < 0)
                return -EIO;

        *datap = le16_to_cpu(attrdata);
        return result;
}

/*
 * collects the bulk endpoints, the status endpoint.
 */
static int sierra_net_bind(struct usbnet *dev, struct usb_interface *intf)
{
        u8      ifacenum;
        u8      numendpoints;
        u16     fwattr = 0;
        int     status;
        struct sierra_net_data *priv;
        static const u8 sync_tmplate[sizeof(priv->sync_msg)] = {
                0x00, 0x00, SIERRA_NET_HIP_MSYNC_ID, 0x00};
        static const u8 shdwn_tmplate[sizeof(priv->shdwn_msg)] = {
                0x00, 0x00, SIERRA_NET_HIP_SHUTD_ID, 0x00};
        u8 mod[2];

        dev_dbg(&dev->udev->dev, "%s", __func__);

        ifacenum = intf->cur_altsetting->desc.bInterfaceNumber;
        numendpoints = intf->cur_altsetting->desc.bNumEndpoints;
        /* We have three endpoints, bulk in and out, and a status */
        if (numendpoints != 3) {
                dev_err(&dev->udev->dev, "Expected 3 endpoints, found: %d",
                        numendpoints);
                return -ENODEV;
        }
        /* Status endpoint set in usbnet_get_endpoints() */
        dev->status = NULL;
        status = usbnet_get_endpoints(dev, intf);
        if (status < 0) {
                dev_err(&dev->udev->dev, "Error in usbnet_get_endpoints (%d)",
                        status);
                return -ENODEV;
        }
        if (!dev->status) {
                dev_err(&dev->udev->dev, "No status endpoint found");
                return -ENODEV;
        }
        /* Initialize sierra private data */
        priv = kzalloc_obj(*priv);
        if (!priv)
                return -ENOMEM;

        priv->usbnet = dev;
        priv->ifnum = ifacenum;
        dev->net->netdev_ops = &sierra_net_device_ops;

        /* change MAC addr to include, ifacenum, and to be unique */
        mod[0] = atomic_inc_return(&iface_counter);
        mod[1] = ifacenum;
        dev_addr_mod(dev->net, ETH_ALEN - 2, mod, 2);

        /* prepare shutdown message template */
        memcpy(priv->shdwn_msg, shdwn_tmplate, sizeof(priv->shdwn_msg));
        /* set context index initially to 0 - prepares tx hdr template */
        sierra_net_set_ctx_index(priv, 0);

        /* prepare sync message template */
        memcpy(priv->sync_msg, sync_tmplate, sizeof(priv->sync_msg));

        /* decrease the rx_urb_size and max_tx_size to 4k on USB 1.1 */
        dev->rx_urb_size  = SIERRA_NET_RX_URB_SIZE;
        if (dev->udev->speed != USB_SPEED_HIGH)
                dev->rx_urb_size  = min_t(size_t, 4096, SIERRA_NET_RX_URB_SIZE);

        dev->net->hard_header_len += SIERRA_NET_HIP_EXT_HDR_LEN;
        dev->hard_mtu = dev->net->mtu + dev->net->hard_header_len;
        dev->net->max_mtu = SIERRA_NET_MAX_SUPPORTED_MTU;

        /* Set up the netdev */
        dev->net->flags |= IFF_NOARP;
        dev->net->ethtool_ops = &sierra_net_ethtool_ops;
        netif_carrier_off(dev->net);

        sierra_net_set_private(dev, priv);

        priv->kevent_flags = 0;

        /* Use the shared workqueue */
        INIT_WORK(&priv->sierra_net_kevent, sierra_net_kevent);

        /* Only need to do this once */
        timer_setup(&priv->sync_timer, sierra_sync_timer, 0);

        /* verify fw attributes */
        status = sierra_net_get_fw_attr(dev, &fwattr);
        dev_dbg(&dev->udev->dev, "Fw attr: %x\n", fwattr);

        /* test whether firmware supports DHCP */
        if (!(status == sizeof(fwattr) && (fwattr & SWI_GET_FW_ATTR_MASK))) {
                /* found incompatible firmware version */
                dev_err(&dev->udev->dev, "Incompatible driver and firmware"
                        " versions\n");
                kfree(priv);
                return -ENODEV;
        }

        return 0;
}

static void sierra_net_unbind(struct usbnet *dev, struct usb_interface *intf)
{
        int status;
        struct sierra_net_data *priv = sierra_net_get_private(dev);

        dev_dbg(&dev->udev->dev, "%s", __func__);

        /* kill the timer and work */
        timer_shutdown_sync(&priv->sync_timer);
        cancel_work_sync(&priv->sierra_net_kevent);

        /* tell modem we are going away */
        status = sierra_net_send_cmd(dev, priv->shdwn_msg,
                        sizeof(priv->shdwn_msg), "Shutdown");
        if (status < 0)
                netdev_err(dev->net,
                        "usb_control_msg failed, status %d\n", status);

        usbnet_status_stop(dev);

        sierra_net_set_private(dev, NULL);
        kfree(priv);
}

static struct sk_buff *sierra_net_skb_clone(struct usbnet *dev,
                struct sk_buff *skb, int len)
{
        struct sk_buff *new_skb;

        /* clone skb */
        new_skb = skb_clone(skb, GFP_ATOMIC);

        /* remove len bytes from original */
        skb_pull(skb, len);

        /* trim next packet to it's length */
        if (new_skb) {
                skb_trim(new_skb, len);
        } else {
                if (netif_msg_rx_err(dev))
                        netdev_err(dev->net, "failed to get skb\n");
                dev->net->stats.rx_dropped++;
        }

        return new_skb;
}

/* ---------------------------- Receive data path ----------------------*/
static int sierra_net_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
{
        int err;
        struct hip_hdr  hh;
        struct sk_buff *new_skb;

        dev_dbg(&dev->udev->dev, "%s", __func__);

        /* could contain multiple packets */
        while (likely(skb->len)) {
                err = parse_hip(skb->data, skb->len, &hh);
                if (err) {
                        if (netif_msg_rx_err(dev))
                                netdev_err(dev->net, "Invalid HIP header %d\n",
                                        err);
                        /* dev->net->stats.rx_errors incremented by caller */
                        dev->net->stats.rx_length_errors++;
                        return 0;
                }

                /* Validate Extended HIP header */
                if (!hh.extmsgid.is_present
                    || hh.extmsgid.word != SIERRA_NET_HIP_EXT_IP_IN_ID) {
                        if (netif_msg_rx_err(dev))
                                netdev_err(dev->net, "HIP/ETH: Invalid pkt\n");

                        dev->net->stats.rx_frame_errors++;
                        /* dev->net->stats.rx_errors incremented by caller */
                        return 0;
                }

                skb_pull(skb, hh.hdrlen);

                /* We are going to accept this packet, prepare it.
                 * In case protocol is IPv6, keep it, otherwise force IPv4.
                 */
                skb_reset_mac_header(skb);
                if (eth_hdr(skb)->h_proto != cpu_to_be16(ETH_P_IPV6))
                        eth_hdr(skb)->h_proto = cpu_to_be16(ETH_P_IP);
                eth_zero_addr(eth_hdr(skb)->h_source);
                memcpy(eth_hdr(skb)->h_dest, dev->net->dev_addr, ETH_ALEN);

                /* Last packet in batch handled by usbnet */
                if (hh.payload_len.word == skb->len)
                        return 1;

                new_skb = sierra_net_skb_clone(dev, skb, hh.payload_len.word);
                if (new_skb)
                        usbnet_skb_return(dev, new_skb);

        } /* while */

        return 0;
}

/* ---------------------------- Transmit data path ----------------------*/
static struct sk_buff *sierra_net_tx_fixup(struct usbnet *dev,
                                           struct sk_buff *skb, gfp_t flags)
{
        struct sierra_net_data *priv = sierra_net_get_private(dev);
        u16 len;
        bool need_tail;

        BUILD_BUG_ON(sizeof_field(struct usbnet, data)
                                < sizeof(struct cdc_state));

        dev_dbg(&dev->udev->dev, "%s", __func__);
        if (priv->link_up && check_ethip_packet(skb, dev) && is_ip(skb)) {
                /* enough head room as is? */
                if (SIERRA_NET_HIP_EXT_HDR_LEN <= skb_headroom(skb)) {
                        /* Save the Eth/IP length and set up HIP hdr */
                        len = skb->len;
                        skb_push(skb, SIERRA_NET_HIP_EXT_HDR_LEN);
                        /* Handle ZLP issue */
                        need_tail = ((len + SIERRA_NET_HIP_EXT_HDR_LEN)
                                % dev->maxpacket == 0);
                        if (need_tail) {
                                if (unlikely(skb_tailroom(skb) == 0)) {
                                        netdev_err(dev->net, "tx_fixup:"
                                                "no room for packet\n");
                                        dev_kfree_skb_any(skb);
                                        return NULL;
                                } else {
                                        skb->data[skb->len] = 0;
                                        __skb_put(skb, 1);
                                        len = len + 1;
                                }
                        }
                        build_hip(skb->data, len, priv);
                        return skb;
                } else {
                        /*
                         * compensate in the future if necessary
                         */
                        netdev_err(dev->net, "tx_fixup: no room for HIP\n");
                } /* headroom */
        }

        if (!priv->link_up)
                dev->net->stats.tx_carrier_errors++;

        /* tx_dropped incremented by usbnet */

        /* filter the packet out, release it  */
        dev_kfree_skb_any(skb);
        return NULL;
}

static const struct driver_info sierra_net_info_direct_ip = {
        .description = "Sierra Wireless USB-to-WWAN Modem",
        .flags = FLAG_WWAN | FLAG_SEND_ZLP,
        .bind = sierra_net_bind,
        .unbind = sierra_net_unbind,
        .status = sierra_net_status,
        .rx_fixup = sierra_net_rx_fixup,
        .tx_fixup = sierra_net_tx_fixup,
};

static int
sierra_net_probe(struct usb_interface *udev, const struct usb_device_id *prod)
{
        int ret;

        ret = usbnet_probe(udev, prod);
        if (ret == 0) {
                struct usbnet *dev = usb_get_intfdata(udev);

                ret = usbnet_status_start(dev, GFP_KERNEL);
                if (ret == 0) {
                        /* Interrupt URB now set up; initiate sync sequence */
                        sierra_net_dosync(dev);
                }
        }
        return ret;
}

#define DIRECT_IP_DEVICE(vend, prod) \
        {USB_DEVICE_INTERFACE_NUMBER(vend, prod, 7), \
        .driver_info = (unsigned long)&sierra_net_info_direct_ip}, \
        {USB_DEVICE_INTERFACE_NUMBER(vend, prod, 10), \
        .driver_info = (unsigned long)&sierra_net_info_direct_ip}, \
        {USB_DEVICE_INTERFACE_NUMBER(vend, prod, 11), \
        .driver_info = (unsigned long)&sierra_net_info_direct_ip}

static const struct usb_device_id products[] = {
        DIRECT_IP_DEVICE(0x1199, 0x68A3), /* Sierra Wireless USB-to-WWAN modem */
        DIRECT_IP_DEVICE(0x0F3D, 0x68A3), /* AT&T Direct IP modem */
        DIRECT_IP_DEVICE(0x1199, 0x68AA), /* Sierra Wireless Direct IP LTE modem */
        DIRECT_IP_DEVICE(0x0F3D, 0x68AA), /* AT&T Direct IP LTE modem */

        {}, /* last item */
};
MODULE_DEVICE_TABLE(usb, products);

/* We are based on usbnet, so let it handle the USB driver specifics */
static struct usb_driver sierra_net_driver = {
        .name = "sierra_net",
        .id_table = products,
        .probe = sierra_net_probe,
        .disconnect = usbnet_disconnect,
        .suspend = usbnet_suspend,
        .resume = usbnet_resume,
        .no_dynamic_id = 1,
        .disable_hub_initiated_lpm = 1,
};

module_usb_driver(sierra_net_driver);

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");