/*
 * cdc_ncm.c
 *
 * Copyright (C) ST-Ericsson 2010-2012
 * Contact: Alexey Orishko <alexey.orishko@stericsson.com>
 * Original author: Hans Petter Selasky <hans.petter.selasky@stericsson.com>
 *
 * USB Host Driver for Network Control Model (NCM)
 * http://www.usb.org/developers/docs/devclass_docs/NCM10_012011.zip
 *
 * The NCM encoding, decoding and initialization logic
 * derives from FreeBSD 8.x. if_cdce.c and if_cdcereg.h
 *
 * This software is available to you under a choice of one of two
 * licenses. You may choose this file to be licensed under the terms
 * of the GNU General Public License (GPL) Version 2 or the 2-clause
 * BSD license listed below:
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/ctype.h>
#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/kstrtox.h>
#include <linux/workqueue.h>
#include <linux/mii.h>
#include <linux/crc32.h>
#include <linux/usb.h>
#include <linux/hrtimer.h>
#include <linux/atomic.h>
#include <linux/usb/usbnet.h>
#include <linux/usb/cdc.h>
#include <linux/usb/cdc_ncm.h>

#if IS_ENABLED(CONFIG_USB_NET_CDC_MBIM)
static bool prefer_mbim = true;
#else
static bool prefer_mbim;
#endif
module_param(prefer_mbim, bool, 0644);
MODULE_PARM_DESC(prefer_mbim, "Prefer MBIM setting on dual NCM/MBIM functions");

static void cdc_ncm_txpath_bh(struct tasklet_struct *t);
static void cdc_ncm_tx_timeout_start(struct cdc_ncm_ctx *ctx);
static enum hrtimer_restart cdc_ncm_tx_timer_cb(struct hrtimer *hr_timer);
static struct usb_driver cdc_ncm_driver;

struct cdc_ncm_stats {
        char stat_string[ETH_GSTRING_LEN];
        int sizeof_stat;
        int stat_offset;
};

#define CDC_NCM_STAT(str, m) { \
                .stat_string = str, \
                .sizeof_stat = sizeof(((struct cdc_ncm_ctx *)0)->m), \
                .stat_offset = offsetof(struct cdc_ncm_ctx, m) }
#define CDC_NCM_SIMPLE_STAT(m)  CDC_NCM_STAT(__stringify(m), m)

static const struct cdc_ncm_stats cdc_ncm_gstrings_stats[] = {
        CDC_NCM_SIMPLE_STAT(tx_reason_ntb_full),
        CDC_NCM_SIMPLE_STAT(tx_reason_ndp_full),
        CDC_NCM_SIMPLE_STAT(tx_reason_timeout),
        CDC_NCM_SIMPLE_STAT(tx_reason_max_datagram),
        CDC_NCM_SIMPLE_STAT(tx_overhead),
        CDC_NCM_SIMPLE_STAT(tx_ntbs),
        CDC_NCM_SIMPLE_STAT(rx_overhead),
        CDC_NCM_SIMPLE_STAT(rx_ntbs),
};

#define CDC_NCM_LOW_MEM_MAX_CNT 10

static int cdc_ncm_get_sset_count(struct net_device __always_unused *netdev, int sset)
{
        switch (sset) {
        case ETH_SS_STATS:
                return ARRAY_SIZE(cdc_ncm_gstrings_stats);
        default:
                return -EOPNOTSUPP;
        }
}

static void cdc_ncm_get_ethtool_stats(struct net_device *netdev,
                                    struct ethtool_stats __always_unused *stats,
                                    u64 *data)
{
        struct usbnet *dev = netdev_priv(netdev);
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        int i;
        char *p = NULL;

        for (i = 0; i < ARRAY_SIZE(cdc_ncm_gstrings_stats); i++) {
                p = (char *)ctx + cdc_ncm_gstrings_stats[i].stat_offset;
                data[i] = (cdc_ncm_gstrings_stats[i].sizeof_stat == sizeof(u64)) ? *(u64 *)p : *(u32 *)p;
        }
}

static void cdc_ncm_get_strings(struct net_device __always_unused *netdev, u32 stringset, u8 *data)
{
        u8 *p = data;
        int i;

        switch (stringset) {
        case ETH_SS_STATS:
                for (i = 0; i < ARRAY_SIZE(cdc_ncm_gstrings_stats); i++) {
                        memcpy(p, cdc_ncm_gstrings_stats[i].stat_string, ETH_GSTRING_LEN);
                        p += ETH_GSTRING_LEN;
                }
        }
}

static void cdc_ncm_update_rxtx_max(struct usbnet *dev, u32 new_rx, u32 new_tx);

static const struct ethtool_ops cdc_ncm_ethtool_ops = {
        .get_link               = usbnet_get_link,
        .nway_reset             = usbnet_nway_reset,
        .get_drvinfo            = usbnet_get_drvinfo,
        .get_msglevel           = usbnet_get_msglevel,
        .set_msglevel           = usbnet_set_msglevel,
        .get_ts_info            = ethtool_op_get_ts_info,
        .get_sset_count         = cdc_ncm_get_sset_count,
        .get_strings            = cdc_ncm_get_strings,
        .get_ethtool_stats      = cdc_ncm_get_ethtool_stats,
        .get_link_ksettings     = usbnet_get_link_ksettings_internal,
        .set_link_ksettings     = NULL,
};

static u32 cdc_ncm_check_rx_max(struct usbnet *dev, u32 new_rx)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        u32 val, max, min;

        /* clamp new_rx to sane values */
        min = USB_CDC_NCM_NTB_MIN_IN_SIZE;
        max = min_t(u32, CDC_NCM_NTB_MAX_SIZE_RX, le32_to_cpu(ctx->ncm_parm.dwNtbInMaxSize));

        /* dwNtbInMaxSize spec violation? Use MIN size for both limits */
        if (max < min) {
                dev_warn(&dev->intf->dev, "dwNtbInMaxSize=%u is too small. Using %u\n",
                         le32_to_cpu(ctx->ncm_parm.dwNtbInMaxSize), min);
                max = min;
        }

        val = clamp_t(u32, new_rx, min, max);
        if (val != new_rx)
                dev_dbg(&dev->intf->dev, "rx_max must be in the [%u, %u] range\n", min, max);

        return val;
}

static u32 cdc_ncm_check_tx_max(struct usbnet *dev, u32 new_tx)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        u32 val, max, min;

        /* clamp new_tx to sane values */
        if (ctx->is_ndp16)
                min = ctx->max_datagram_size + ctx->max_ndp_size + sizeof(struct usb_cdc_ncm_nth16);
        else
                min = ctx->max_datagram_size + ctx->max_ndp_size + sizeof(struct usb_cdc_ncm_nth32);

        if (le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize) == 0)
                max = CDC_NCM_NTB_MAX_SIZE_TX; /* dwNtbOutMaxSize not set */
        else
                max = clamp_t(u32, le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize),
                              USB_CDC_NCM_NTB_MIN_OUT_SIZE,
                              CDC_NCM_NTB_MAX_SIZE_TX);

        /* some devices set dwNtbOutMaxSize too low for the above default */
        min = min(min, max);

        val = clamp_t(u32, new_tx, min, max);
        if (val != new_tx)
                dev_dbg(&dev->intf->dev, "tx_max must be in the [%u, %u] range\n", min, max);

        return val;
}

static ssize_t min_tx_pkt_show(struct device *d,
                               struct device_attribute *attr, char *buf)
{
        struct usbnet *dev = netdev_priv(to_net_dev(d));
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];

        return sprintf(buf, "%u\n", ctx->min_tx_pkt);
}

static ssize_t rx_max_show(struct device *d,
                           struct device_attribute *attr, char *buf)
{
        struct usbnet *dev = netdev_priv(to_net_dev(d));
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];

        return sprintf(buf, "%u\n", ctx->rx_max);
}

static ssize_t tx_max_show(struct device *d,
                           struct device_attribute *attr, char *buf)
{
        struct usbnet *dev = netdev_priv(to_net_dev(d));
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];

        return sprintf(buf, "%u\n", ctx->tx_max);
}

static ssize_t tx_timer_usecs_show(struct device *d,
                                   struct device_attribute *attr, char *buf)
{
        struct usbnet *dev = netdev_priv(to_net_dev(d));
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];

        return sprintf(buf, "%u\n", ctx->timer_interval / (u32)NSEC_PER_USEC);
}

static ssize_t min_tx_pkt_store(struct device *d,
                                struct device_attribute *attr,
                                const char *buf, size_t len)
{
        struct usbnet *dev = netdev_priv(to_net_dev(d));
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        unsigned long val;

        /* no need to restrict values - anything from 0 to infinity is OK */
        if (kstrtoul(buf, 0, &val))
                return -EINVAL;

        ctx->min_tx_pkt = val;
        return len;
}

static ssize_t rx_max_store(struct device *d,
                            struct device_attribute *attr,
                            const char *buf, size_t len)
{
        struct usbnet *dev = netdev_priv(to_net_dev(d));
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        unsigned long val;

        if (kstrtoul(buf, 0, &val) || cdc_ncm_check_rx_max(dev, val) != val)
                return -EINVAL;

        cdc_ncm_update_rxtx_max(dev, val, ctx->tx_max);
        return len;
}

static ssize_t tx_max_store(struct device *d,
                            struct device_attribute *attr,
                            const char *buf, size_t len)
{
        struct usbnet *dev = netdev_priv(to_net_dev(d));
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        unsigned long val;

        if (kstrtoul(buf, 0, &val) || cdc_ncm_check_tx_max(dev, val) != val)
                return -EINVAL;

        cdc_ncm_update_rxtx_max(dev, ctx->rx_max, val);
        return len;
}

static ssize_t tx_timer_usecs_store(struct device *d,
                                    struct device_attribute *attr,
                                    const char *buf, size_t len)
{
        struct usbnet *dev = netdev_priv(to_net_dev(d));
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        ssize_t ret;
        unsigned long val;

        ret = kstrtoul(buf, 0, &val);
        if (ret)
                return ret;
        if (val && (val < CDC_NCM_TIMER_INTERVAL_MIN || val > CDC_NCM_TIMER_INTERVAL_MAX))
                return -EINVAL;

        spin_lock_bh(&ctx->mtx);
        ctx->timer_interval = val * NSEC_PER_USEC;
        if (!ctx->timer_interval)
                ctx->tx_timer_pending = 0;
        spin_unlock_bh(&ctx->mtx);
        return len;
}

static DEVICE_ATTR_RW(min_tx_pkt);
static DEVICE_ATTR_RW(rx_max);
static DEVICE_ATTR_RW(tx_max);
static DEVICE_ATTR_RW(tx_timer_usecs);

static ssize_t ndp_to_end_show(struct device *d, struct device_attribute *attr, char *buf)
{
        struct usbnet *dev = netdev_priv(to_net_dev(d));
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];

        return sprintf(buf, "%c\n", ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END ? 'Y' : 'N');
}

static ssize_t ndp_to_end_store(struct device *d,  struct device_attribute *attr, const char *buf, size_t len)
{
        struct usbnet *dev = netdev_priv(to_net_dev(d));
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        bool enable;

        if (kstrtobool(buf, &enable))
                return -EINVAL;

        /* no change? */
        if (enable == (ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END))
                return len;

        if (enable) {
                if (ctx->is_ndp16 && !ctx->delayed_ndp16) {
                        ctx->delayed_ndp16 = kzalloc(ctx->max_ndp_size, GFP_KERNEL);
                        if (!ctx->delayed_ndp16)
                                return -ENOMEM;
                }
                if (!ctx->is_ndp16 && !ctx->delayed_ndp32) {
                        ctx->delayed_ndp32 = kzalloc(ctx->max_ndp_size, GFP_KERNEL);
                        if (!ctx->delayed_ndp32)
                                return -ENOMEM;
                }
        }

        /* flush pending data before changing flag */
        netif_tx_lock_bh(dev->net);
        usbnet_start_xmit(NULL, dev->net);
        spin_lock_bh(&ctx->mtx);
        if (enable)
                ctx->drvflags |= CDC_NCM_FLAG_NDP_TO_END;
        else
                ctx->drvflags &= ~CDC_NCM_FLAG_NDP_TO_END;
        spin_unlock_bh(&ctx->mtx);
        netif_tx_unlock_bh(dev->net);

        return len;
}
static DEVICE_ATTR_RW(ndp_to_end);

#define NCM_PARM_ATTR(name, format, tocpu)                              \
static ssize_t cdc_ncm_show_##name(struct device *d, struct device_attribute *attr, char *buf) \
{ \
        struct usbnet *dev = netdev_priv(to_net_dev(d)); \
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0]; \
        return sprintf(buf, format "\n", tocpu(ctx->ncm_parm.name));    \
} \
static DEVICE_ATTR(name, 0444, cdc_ncm_show_##name, NULL)

NCM_PARM_ATTR(bmNtbFormatsSupported, "0x%04x", le16_to_cpu);
NCM_PARM_ATTR(dwNtbInMaxSize, "%u", le32_to_cpu);
NCM_PARM_ATTR(wNdpInDivisor, "%u", le16_to_cpu);
NCM_PARM_ATTR(wNdpInPayloadRemainder, "%u", le16_to_cpu);
NCM_PARM_ATTR(wNdpInAlignment, "%u", le16_to_cpu);
NCM_PARM_ATTR(dwNtbOutMaxSize, "%u", le32_to_cpu);
NCM_PARM_ATTR(wNdpOutDivisor, "%u", le16_to_cpu);
NCM_PARM_ATTR(wNdpOutPayloadRemainder, "%u", le16_to_cpu);
NCM_PARM_ATTR(wNdpOutAlignment, "%u", le16_to_cpu);
NCM_PARM_ATTR(wNtbOutMaxDatagrams, "%u", le16_to_cpu);

static struct attribute *cdc_ncm_sysfs_attrs[] = {
        &dev_attr_min_tx_pkt.attr,
        &dev_attr_ndp_to_end.attr,
        &dev_attr_rx_max.attr,
        &dev_attr_tx_max.attr,
        &dev_attr_tx_timer_usecs.attr,
        &dev_attr_bmNtbFormatsSupported.attr,
        &dev_attr_dwNtbInMaxSize.attr,
        &dev_attr_wNdpInDivisor.attr,
        &dev_attr_wNdpInPayloadRemainder.attr,
        &dev_attr_wNdpInAlignment.attr,
        &dev_attr_dwNtbOutMaxSize.attr,
        &dev_attr_wNdpOutDivisor.attr,
        &dev_attr_wNdpOutPayloadRemainder.attr,
        &dev_attr_wNdpOutAlignment.attr,
        &dev_attr_wNtbOutMaxDatagrams.attr,
        NULL,
};

static const struct attribute_group cdc_ncm_sysfs_attr_group = {
        .name = "cdc_ncm",
        .attrs = cdc_ncm_sysfs_attrs,
};

/* handle rx_max and tx_max changes */
static void cdc_ncm_update_rxtx_max(struct usbnet *dev, u32 new_rx, u32 new_tx)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        u8 iface_no = ctx->control->cur_altsetting->desc.bInterfaceNumber;
        u32 val;

        val = cdc_ncm_check_rx_max(dev, new_rx);

        /* inform device about NTB input size changes */
        if (val != ctx->rx_max) {
                __le32 dwNtbInMaxSize = cpu_to_le32(val);

                dev_info(&dev->intf->dev, "setting rx_max = %u\n", val);

                /* tell device to use new size */
                if (usbnet_write_cmd(dev, USB_CDC_SET_NTB_INPUT_SIZE,
                                     USB_TYPE_CLASS | USB_DIR_OUT
                                     | USB_RECIP_INTERFACE,
                                     0, iface_no, &dwNtbInMaxSize, 4) < 0)
                        dev_dbg(&dev->intf->dev, "Setting NTB Input Size failed\n");
                else
                        ctx->rx_max = val;
        }

        /* usbnet use these values for sizing rx queues */
        if (dev->rx_urb_size != ctx->rx_max) {
                dev->rx_urb_size = ctx->rx_max;
                if (netif_running(dev->net))
                        usbnet_unlink_rx_urbs(dev);
        }

        val = cdc_ncm_check_tx_max(dev, new_tx);
        if (val != ctx->tx_max)
                dev_info(&dev->intf->dev, "setting tx_max = %u\n", val);

        /* Adding a pad byte here if necessary simplifies the handling
         * in cdc_ncm_fill_tx_frame, making tx_max always represent
         * the real skb max size.
         *
         * We cannot use dev->maxpacket here because this is called from
         * .bind which is called before usbnet sets up dev->maxpacket
         */
        if (val != le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize) &&
            val % usb_maxpacket(dev->udev, dev->out) == 0)
                val++;

        /* we might need to flush any pending tx buffers if running */
        if (netif_running(dev->net) && val > ctx->tx_max) {
                netif_tx_lock_bh(dev->net);
                usbnet_start_xmit(NULL, dev->net);
                /* make sure tx_curr_skb is reallocated if it was empty */
                if (ctx->tx_curr_skb) {
                        dev_kfree_skb_any(ctx->tx_curr_skb);
                        ctx->tx_curr_skb = NULL;
                }
                ctx->tx_max = val;
                netif_tx_unlock_bh(dev->net);
        } else {
                ctx->tx_max = val;
        }

        dev->hard_mtu = ctx->tx_max;

        /* max qlen depend on hard_mtu and rx_urb_size */
        usbnet_update_max_qlen(dev);

        /* never pad more than 3 full USB packets per transfer */
        ctx->min_tx_pkt = clamp_t(u16, ctx->tx_max - 3 * usb_maxpacket(dev->udev, dev->out),
                                  CDC_NCM_MIN_TX_PKT, ctx->tx_max);
}

/* helpers for NCM and MBIM differences */
static u8 cdc_ncm_flags(struct usbnet *dev)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];

        if (cdc_ncm_comm_intf_is_mbim(dev->intf->cur_altsetting) && ctx->mbim_desc)
                return ctx->mbim_desc->bmNetworkCapabilities;
        if (ctx->func_desc)
                return ctx->func_desc->bmNetworkCapabilities;
        return 0;
}

static int cdc_ncm_eth_hlen(struct usbnet *dev)
{
        if (cdc_ncm_comm_intf_is_mbim(dev->intf->cur_altsetting))
                return 0;
        return ETH_HLEN;
}

static u32 cdc_ncm_min_dgram_size(struct usbnet *dev)
{
        if (cdc_ncm_comm_intf_is_mbim(dev->intf->cur_altsetting))
                return CDC_MBIM_MIN_DATAGRAM_SIZE;
        return CDC_NCM_MIN_DATAGRAM_SIZE;
}

static u32 cdc_ncm_max_dgram_size(struct usbnet *dev)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];

        if (cdc_ncm_comm_intf_is_mbim(dev->intf->cur_altsetting) && ctx->mbim_desc)
                return le16_to_cpu(ctx->mbim_desc->wMaxSegmentSize);
        if (ctx->ether_desc)
                return le16_to_cpu(ctx->ether_desc->wMaxSegmentSize);
        return CDC_NCM_MAX_DATAGRAM_SIZE;
}

/* initial one-time device setup.  MUST be called with the data interface
 * in altsetting 0
 */
static int cdc_ncm_init(struct usbnet *dev)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        u8 iface_no = ctx->control->cur_altsetting->desc.bInterfaceNumber;
        int err;

        err = usbnet_read_cmd(dev, USB_CDC_GET_NTB_PARAMETERS,
                              USB_TYPE_CLASS | USB_DIR_IN
                              |USB_RECIP_INTERFACE,
                              0, iface_no, &ctx->ncm_parm,
                              sizeof(ctx->ncm_parm));
        if (err < 0) {
                dev_err(&dev->intf->dev, "failed GET_NTB_PARAMETERS\n");
                return err; /* GET_NTB_PARAMETERS is required */
        }

        /* set CRC Mode */
        if (cdc_ncm_flags(dev) & USB_CDC_NCM_NCAP_CRC_MODE) {
                dev_dbg(&dev->intf->dev, "Setting CRC mode off\n");
                err = usbnet_write_cmd(dev, USB_CDC_SET_CRC_MODE,
                                       USB_TYPE_CLASS | USB_DIR_OUT
                                       | USB_RECIP_INTERFACE,
                                       USB_CDC_NCM_CRC_NOT_APPENDED,
                                       iface_no, NULL, 0);
                if (err < 0)
                        dev_err(&dev->intf->dev, "SET_CRC_MODE failed\n");
        }

        /* use ndp16 by default */
        ctx->is_ndp16 = 1;

        /* set NTB format, if both formats are supported.
         *
         * "The host shall only send this command while the NCM Data
         *  Interface is in alternate setting 0."
         */
        if (le16_to_cpu(ctx->ncm_parm.bmNtbFormatsSupported) &
                                                USB_CDC_NCM_NTB32_SUPPORTED) {
                if (ctx->drvflags & CDC_NCM_FLAG_PREFER_NTB32) {
                        ctx->is_ndp16 = 0;
                        dev_dbg(&dev->intf->dev, "Setting NTB format to 32-bit\n");
                        err = usbnet_write_cmd(dev, USB_CDC_SET_NTB_FORMAT,
                                               USB_TYPE_CLASS | USB_DIR_OUT
                                               | USB_RECIP_INTERFACE,
                                               USB_CDC_NCM_NTB32_FORMAT,
                                               iface_no, NULL, 0);
                } else {
                        ctx->is_ndp16 = 1;
                        dev_dbg(&dev->intf->dev, "Setting NTB format to 16-bit\n");
                        err = usbnet_write_cmd(dev, USB_CDC_SET_NTB_FORMAT,
                                               USB_TYPE_CLASS | USB_DIR_OUT
                                               | USB_RECIP_INTERFACE,
                                               USB_CDC_NCM_NTB16_FORMAT,
                                               iface_no, NULL, 0);
                }
                if (err < 0) {
                        ctx->is_ndp16 = 1;
                        dev_err(&dev->intf->dev, "SET_NTB_FORMAT failed\n");
                }
        }

        /* set initial device values */
        ctx->rx_max = le32_to_cpu(ctx->ncm_parm.dwNtbInMaxSize);
        ctx->tx_max = le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize);
        ctx->tx_remainder = le16_to_cpu(ctx->ncm_parm.wNdpOutPayloadRemainder);
        ctx->tx_modulus = le16_to_cpu(ctx->ncm_parm.wNdpOutDivisor);
        ctx->tx_ndp_modulus = le16_to_cpu(ctx->ncm_parm.wNdpOutAlignment);
        /* devices prior to NCM Errata shall set this field to zero */
        ctx->tx_max_datagrams = le16_to_cpu(ctx->ncm_parm.wNtbOutMaxDatagrams);

        dev_dbg(&dev->intf->dev,
                "dwNtbInMaxSize=%u dwNtbOutMaxSize=%u wNdpOutPayloadRemainder=%u wNdpOutDivisor=%u wNdpOutAlignment=%u wNtbOutMaxDatagrams=%u flags=0x%x\n",
                ctx->rx_max, ctx->tx_max, ctx->tx_remainder, ctx->tx_modulus,
                ctx->tx_ndp_modulus, ctx->tx_max_datagrams, cdc_ncm_flags(dev));

        /* max count of tx datagrams */
        if ((ctx->tx_max_datagrams == 0) ||
                        (ctx->tx_max_datagrams > CDC_NCM_DPT_DATAGRAMS_MAX))
                ctx->tx_max_datagrams = CDC_NCM_DPT_DATAGRAMS_MAX;

        /* set up maximum NDP size */
        if (ctx->is_ndp16)
                ctx->max_ndp_size = sizeof(struct usb_cdc_ncm_ndp16) + (ctx->tx_max_datagrams + 1) * sizeof(struct usb_cdc_ncm_dpe16);
        else
                ctx->max_ndp_size = sizeof(struct usb_cdc_ncm_ndp32) + (ctx->tx_max_datagrams + 1) * sizeof(struct usb_cdc_ncm_dpe32);

        /* initial coalescing timer interval */
        ctx->timer_interval = CDC_NCM_TIMER_INTERVAL_USEC * NSEC_PER_USEC;

        return 0;
}

/* set a new max datagram size */
static void cdc_ncm_set_dgram_size(struct usbnet *dev, int new_size)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        u8 iface_no = ctx->control->cur_altsetting->desc.bInterfaceNumber;
        __le16 max_datagram_size;
        u16 mbim_mtu;
        int err;

        /* set default based on descriptors */
        ctx->max_datagram_size = clamp_t(u32, new_size,
                                         cdc_ncm_min_dgram_size(dev),
                                         CDC_NCM_MAX_DATAGRAM_SIZE);

        /* inform the device about the selected Max Datagram Size? */
        if (!(cdc_ncm_flags(dev) & USB_CDC_NCM_NCAP_MAX_DATAGRAM_SIZE))
                goto out;

        /* read current mtu value from device */
        err = usbnet_read_cmd(dev, USB_CDC_GET_MAX_DATAGRAM_SIZE,
                              USB_TYPE_CLASS | USB_DIR_IN | USB_RECIP_INTERFACE,
                              0, iface_no, &max_datagram_size, sizeof(max_datagram_size));
        if (err != sizeof(max_datagram_size)) {
                dev_dbg(&dev->intf->dev, "GET_MAX_DATAGRAM_SIZE failed\n");
                goto out;
        }

        if (le16_to_cpu(max_datagram_size) == ctx->max_datagram_size)
                goto out;

        max_datagram_size = cpu_to_le16(ctx->max_datagram_size);
        err = usbnet_write_cmd(dev, USB_CDC_SET_MAX_DATAGRAM_SIZE,
                               USB_TYPE_CLASS | USB_DIR_OUT | USB_RECIP_INTERFACE,
                               0, iface_no, &max_datagram_size, sizeof(max_datagram_size));
        if (err < 0)
                dev_dbg(&dev->intf->dev, "SET_MAX_DATAGRAM_SIZE failed\n");

out:
        /* set MTU to max supported by the device if necessary */
        dev->net->mtu = min_t(int, dev->net->mtu, ctx->max_datagram_size - cdc_ncm_eth_hlen(dev));

        /* do not exceed operator preferred MTU */
        if (ctx->mbim_extended_desc) {
                mbim_mtu = le16_to_cpu(ctx->mbim_extended_desc->wMTU);
                if (mbim_mtu != 0 && mbim_mtu < dev->net->mtu)
                        dev->net->mtu = mbim_mtu;
        }
}

static void cdc_ncm_fix_modulus(struct usbnet *dev)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        u32 val;

        /*
         * verify that the structure alignment is:
         * - power of two
         * - not greater than the maximum transmit length
         * - not less than four bytes
         */
        val = ctx->tx_ndp_modulus;

        if ((val < USB_CDC_NCM_NDP_ALIGN_MIN_SIZE) ||
            (val != ((-val) & val)) || (val >= ctx->tx_max)) {
                dev_dbg(&dev->intf->dev, "Using default alignment: 4 bytes\n");
                ctx->tx_ndp_modulus = USB_CDC_NCM_NDP_ALIGN_MIN_SIZE;
        }

        /*
         * verify that the payload alignment is:
         * - power of two
         * - not greater than the maximum transmit length
         * - not less than four bytes
         */
        val = ctx->tx_modulus;

        if ((val < USB_CDC_NCM_NDP_ALIGN_MIN_SIZE) ||
            (val != ((-val) & val)) || (val >= ctx->tx_max)) {
                dev_dbg(&dev->intf->dev, "Using default transmit modulus: 4 bytes\n");
                ctx->tx_modulus = USB_CDC_NCM_NDP_ALIGN_MIN_SIZE;
        }

        /* verify the payload remainder */
        if (ctx->tx_remainder >= ctx->tx_modulus) {
                dev_dbg(&dev->intf->dev, "Using default transmit remainder: 0 bytes\n");
                ctx->tx_remainder = 0;
        }

        /* adjust TX-remainder according to NCM specification. */
        ctx->tx_remainder = ((ctx->tx_remainder - cdc_ncm_eth_hlen(dev)) &
                             (ctx->tx_modulus - 1));
}

static int cdc_ncm_setup(struct usbnet *dev)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        u32 def_rx, def_tx;

        /* be conservative when selecting initial buffer size to
         * increase the number of hosts this will work for
         */
        def_rx = min_t(u32, CDC_NCM_NTB_DEF_SIZE_RX,
                       le32_to_cpu(ctx->ncm_parm.dwNtbInMaxSize));
        def_tx = min_t(u32, CDC_NCM_NTB_DEF_SIZE_TX,
                       le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize));

        /* clamp rx_max and tx_max and inform device */
        cdc_ncm_update_rxtx_max(dev, def_rx, def_tx);

        /* sanitize the modulus and remainder values */
        cdc_ncm_fix_modulus(dev);

        /* set max datagram size */
        cdc_ncm_set_dgram_size(dev, cdc_ncm_max_dgram_size(dev));
        return 0;
}

static void
cdc_ncm_find_endpoints(struct usbnet *dev, struct usb_interface *intf)
{
        struct usb_host_endpoint *e, *in = NULL, *out = NULL;
        u8 ep;

        for (ep = 0; ep < intf->cur_altsetting->desc.bNumEndpoints; ep++) {
                e = intf->cur_altsetting->endpoint + ep;

                /* ignore endpoints which cannot transfer data */
                if (!usb_endpoint_maxp(&e->desc))
                        continue;

                switch (e->desc.bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) {
                case USB_ENDPOINT_XFER_INT:
                        if (usb_endpoint_dir_in(&e->desc)) {
                                if (!dev->status)
                                        dev->status = e;
                        }
                        break;

                case USB_ENDPOINT_XFER_BULK:
                        if (usb_endpoint_dir_in(&e->desc)) {
                                if (!in)
                                        in = e;
                        } else {
                                if (!out)
                                        out = e;
                        }
                        break;

                default:
                        break;
                }
        }
        if (in && !dev->in)
                dev->in = usb_rcvbulkpipe(dev->udev,
                                          in->desc.bEndpointAddress &
                                          USB_ENDPOINT_NUMBER_MASK);
        if (out && !dev->out)
                dev->out = usb_sndbulkpipe(dev->udev,
                                           out->desc.bEndpointAddress &
                                           USB_ENDPOINT_NUMBER_MASK);
}

static void cdc_ncm_free(struct cdc_ncm_ctx *ctx)
{
        if (ctx == NULL)
                return;

        if (ctx->tx_rem_skb != NULL) {
                dev_kfree_skb_any(ctx->tx_rem_skb);
                ctx->tx_rem_skb = NULL;
        }

        if (ctx->tx_curr_skb != NULL) {
                dev_kfree_skb_any(ctx->tx_curr_skb);
                ctx->tx_curr_skb = NULL;
        }

        if (ctx->is_ndp16)
                kfree(ctx->delayed_ndp16);
        else
                kfree(ctx->delayed_ndp32);

        kfree(ctx);
}

/* we need to override the usbnet change_mtu ndo for two reasons:
 *  - respect the negotiated maximum datagram size
 *  - avoid unwanted changes to rx and tx buffers
 */
int cdc_ncm_change_mtu(struct net_device *net, int new_mtu)
{
        struct usbnet *dev = netdev_priv(net);

        WRITE_ONCE(net->mtu, new_mtu);
        cdc_ncm_set_dgram_size(dev, new_mtu + cdc_ncm_eth_hlen(dev));

        return 0;
}
EXPORT_SYMBOL_GPL(cdc_ncm_change_mtu);

static const struct net_device_ops cdc_ncm_netdev_ops = {
        .ndo_open            = usbnet_open,
        .ndo_stop            = usbnet_stop,
        .ndo_start_xmit      = usbnet_start_xmit,
        .ndo_tx_timeout      = usbnet_tx_timeout,
        .ndo_set_rx_mode     = usbnet_set_rx_mode,
        .ndo_get_stats64     = dev_get_tstats64,
        .ndo_change_mtu      = cdc_ncm_change_mtu,
        .ndo_set_mac_address = eth_mac_addr,
        .ndo_validate_addr   = eth_validate_addr,
};

int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_altsetting, int drvflags)
{
        struct cdc_ncm_ctx *ctx;
        struct usb_driver *driver;
        u8 *buf;
        int len;
        int temp;
        u8 iface_no;
        struct usb_cdc_parsed_header hdr;

        ctx = kzalloc_obj(*ctx);
        if (!ctx)
                return -ENOMEM;

        ctx->dev = dev;

        hrtimer_setup(&ctx->tx_timer, &cdc_ncm_tx_timer_cb, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        tasklet_setup(&ctx->bh, cdc_ncm_txpath_bh);
        atomic_set(&ctx->stop, 0);
        spin_lock_init(&ctx->mtx);

        /* store ctx pointer in device data field */
        dev->data[0] = (unsigned long)ctx;

        /* only the control interface can be successfully probed */
        ctx->control = intf;

        /* get some pointers */
        driver = driver_of(intf);
        buf = intf->cur_altsetting->extra;
        len = intf->cur_altsetting->extralen;

        /* parse through descriptors associated with control interface */
        cdc_parse_cdc_header(&hdr, intf, buf, len);

        if (hdr.usb_cdc_union_desc)
                ctx->data = usb_ifnum_to_if(dev->udev,
                                            hdr.usb_cdc_union_desc->bSlaveInterface0);
        ctx->ether_desc = hdr.usb_cdc_ether_desc;
        ctx->func_desc = hdr.usb_cdc_ncm_desc;
        ctx->mbim_desc = hdr.usb_cdc_mbim_desc;
        ctx->mbim_extended_desc = hdr.usb_cdc_mbim_extended_desc;

        /* some buggy devices have an IAD but no CDC Union */
        if (!hdr.usb_cdc_union_desc && intf->intf_assoc && intf->intf_assoc->bInterfaceCount == 2) {
                ctx->data = usb_ifnum_to_if(dev->udev, intf->cur_altsetting->desc.bInterfaceNumber + 1);
                dev_dbg(&intf->dev, "CDC Union missing - got slave from IAD\n");
        }

        /* check if we got everything */
        if (!ctx->data) {
                dev_err(&intf->dev, "CDC Union missing and no IAD found\n");
                goto error;
        }
        if (cdc_ncm_comm_intf_is_mbim(intf->cur_altsetting)) {
                if (!ctx->mbim_desc) {
                        dev_err(&intf->dev, "MBIM functional descriptor missing\n");
                        goto error;
                }
        } else {
                if (!ctx->ether_desc || !ctx->func_desc) {
                        dev_err(&intf->dev, "NCM or ECM functional descriptors missing\n");
                        goto error;
                }
        }

        /* claim data interface, if different from control */
        if (ctx->data != ctx->control) {
                temp = usb_driver_claim_interface(driver, ctx->data, dev);
                if (temp) {
                        dev_err(&intf->dev, "failed to claim data intf\n");
                        goto error;
                }
        }

        if (ctx->func_desc)
                ctx->filtering_supported = !!(ctx->func_desc->bmNetworkCapabilities
                        & USB_CDC_NCM_NCAP_ETH_FILTER);

        iface_no = ctx->data->cur_altsetting->desc.bInterfaceNumber;

        /* Device-specific flags */
        ctx->drvflags = drvflags;

        /* Reset data interface. Some devices will not reset properly
         * unless they are configured first.  Toggle the altsetting to
         * force a reset.
         * Some other devices do not work properly with this procedure
         * that can be avoided using quirk CDC_MBIM_FLAG_AVOID_ALTSETTING_TOGGLE
         */
        if (!(ctx->drvflags & CDC_MBIM_FLAG_AVOID_ALTSETTING_TOGGLE))
                usb_set_interface(dev->udev, iface_no, data_altsetting);

        temp = usb_set_interface(dev->udev, iface_no, 0);
        if (temp) {
                dev_dbg(&intf->dev, "set interface failed\n");
                goto error2;
        }

        /* initialize basic device settings */
        if (cdc_ncm_init(dev))
                goto error2;

        /* Some firmwares need a pause here or they will silently fail
         * to set up the interface properly.  This value was decided
         * empirically on a Sierra Wireless MC7455 running 02.08.02.00
         * firmware.
         */
        usleep_range(10000, 20000);

        /* configure data interface */
        temp = usb_set_interface(dev->udev, iface_no, data_altsetting);
        if (temp) {
                dev_dbg(&intf->dev, "set interface failed\n");
                goto error2;
        }

        cdc_ncm_find_endpoints(dev, ctx->data);
        cdc_ncm_find_endpoints(dev, ctx->control);
        if (!dev->in || !dev->out ||
            (!dev->status && dev->driver_info->flags & FLAG_LINK_INTR)) {
                dev_dbg(&intf->dev, "failed to collect endpoints\n");
                goto error2;
        }

        usb_set_intfdata(ctx->control, dev);

        if (ctx->ether_desc) {
                temp = usbnet_get_ethernet_addr(dev, ctx->ether_desc->iMACAddress);
                if (temp) {
                        dev_err(&intf->dev, "failed to get mac address\n");
                        goto error2;
                }
                dev_info(&intf->dev, "MAC-Address: %pM\n", dev->net->dev_addr);
        }

        /* finish setting up the device specific data */
        cdc_ncm_setup(dev);

        /* Allocate the delayed NDP if needed. */
        if (ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END) {
                if (ctx->is_ndp16) {
                        ctx->delayed_ndp16 = kzalloc(ctx->max_ndp_size, GFP_KERNEL);
                        if (!ctx->delayed_ndp16)
                                goto error2;
                } else {
                        ctx->delayed_ndp32 = kzalloc(ctx->max_ndp_size, GFP_KERNEL);
                        if (!ctx->delayed_ndp32)
                                goto error2;
                }
                dev_info(&intf->dev, "NDP will be placed at end of frame for this device.");
        }

        /* override ethtool_ops */
        dev->net->ethtool_ops = &cdc_ncm_ethtool_ops;

        /* add our sysfs attrs */
        dev->net->sysfs_groups[0] = &cdc_ncm_sysfs_attr_group;

        /* must handle MTU changes */
        dev->net->netdev_ops = &cdc_ncm_netdev_ops;
        dev->net->max_mtu = cdc_ncm_max_dgram_size(dev) - cdc_ncm_eth_hlen(dev);

        return 0;

error2:
        usb_set_intfdata(ctx->control, NULL);
        usb_set_intfdata(ctx->data, NULL);
        if (ctx->data != ctx->control)
                usb_driver_release_interface(driver, ctx->data);
error:
        cdc_ncm_free((struct cdc_ncm_ctx *)dev->data[0]);
        dev->data[0] = 0;
        dev_info(&intf->dev, "bind() failure\n");
        return -ENODEV;
}
EXPORT_SYMBOL_GPL(cdc_ncm_bind_common);

void cdc_ncm_unbind(struct usbnet *dev, struct usb_interface *intf)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        struct usb_driver *driver = driver_of(intf);

        if (ctx == NULL)
                return;         /* no setup */

        atomic_set(&ctx->stop, 1);

        hrtimer_cancel(&ctx->tx_timer);

        tasklet_kill(&ctx->bh);

        /* handle devices with combined control and data interface */
        if (ctx->control == ctx->data)
                ctx->data = NULL;

        /* disconnect master --> disconnect slave */
        if (intf == ctx->control && ctx->data) {
                usb_set_intfdata(ctx->data, NULL);
                usb_driver_release_interface(driver, ctx->data);
                ctx->data = NULL;

        } else if (intf == ctx->data && ctx->control) {
                usb_set_intfdata(ctx->control, NULL);
                usb_driver_release_interface(driver, ctx->control);
                ctx->control = NULL;
        }

        usb_set_intfdata(intf, NULL);
        cdc_ncm_free(ctx);
}
EXPORT_SYMBOL_GPL(cdc_ncm_unbind);

/* Return the number of the MBIM control interface altsetting iff it
 * is preferred and available,
 */
u8 cdc_ncm_select_altsetting(struct usb_interface *intf)
{
        struct usb_host_interface *alt;

        /* The MBIM spec defines a NCM compatible default altsetting,
         * which we may have matched:
         *
         *  "Functions that implement both NCM 1.0 and MBIM (an
         *   “NCM/MBIM function”) according to this recommendation
         *   shall provide two alternate settings for the
         *   Communication Interface.  Alternate setting 0, and the
         *   associated class and endpoint descriptors, shall be
         *   constructed according to the rules given for the
         *   Communication Interface in section 5 of [USBNCM10].
         *   Alternate setting 1, and the associated class and
         *   endpoint descriptors, shall be constructed according to
         *   the rules given in section 6 (USB Device Model) of this
         *   specification."
         */
        if (intf->num_altsetting < 2)
                return intf->cur_altsetting->desc.bAlternateSetting;

        if (prefer_mbim) {
                alt = usb_altnum_to_altsetting(intf, CDC_NCM_COMM_ALTSETTING_MBIM);
                if (alt && cdc_ncm_comm_intf_is_mbim(alt))
                        return CDC_NCM_COMM_ALTSETTING_MBIM;
        }
        return CDC_NCM_COMM_ALTSETTING_NCM;
}
EXPORT_SYMBOL_GPL(cdc_ncm_select_altsetting);

static int cdc_ncm_bind(struct usbnet *dev, struct usb_interface *intf)
{
        /* MBIM backwards compatible function? */
        if (cdc_ncm_select_altsetting(intf) != CDC_NCM_COMM_ALTSETTING_NCM)
                return -ENODEV;

        /* The NCM data altsetting is fixed, so we hard-coded it.
         * Additionally, generic NCM devices are assumed to accept arbitrarily
         * placed NDP.
         */
        return cdc_ncm_bind_common(dev, intf, CDC_NCM_DATA_ALTSETTING_NCM, 0);
}

static void cdc_ncm_align_tail(struct sk_buff *skb, size_t modulus, size_t remainder, size_t max)
{
        size_t align = ALIGN(skb->len, modulus) - skb->len + remainder;

        if (skb->len + align > max)
                align = max - skb->len;
        if (align && skb_tailroom(skb) >= align)
                skb_put_zero(skb, align);
}

/* return a pointer to a valid struct usb_cdc_ncm_ndp16 of type sign, possibly
 * allocating a new one within skb
 */
static struct usb_cdc_ncm_ndp16 *cdc_ncm_ndp16(struct cdc_ncm_ctx *ctx, struct sk_buff *skb, __le32 sign, size_t reserve)
{
        struct usb_cdc_ncm_ndp16 *ndp16 = NULL;
        struct usb_cdc_ncm_nth16 *nth16 = (void *)skb->data;
        size_t ndpoffset = le16_to_cpu(nth16->wNdpIndex);

        /* If NDP should be moved to the end of the NCM package, we can't follow the
        * NTH16 header as we would normally do. NDP isn't written to the SKB yet, and
        * the wNdpIndex field in the header is actually not consistent with reality. It will be later.
        */
        if (ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END) {
                if (ctx->delayed_ndp16->dwSignature == sign)
                        return ctx->delayed_ndp16;

                /* We can only push a single NDP to the end. Return
                 * NULL to send what we've already got and queue this
                 * skb for later.
                 */
                else if (ctx->delayed_ndp16->dwSignature)
                        return NULL;
        }

        /* follow the chain of NDPs, looking for a match */
        while (ndpoffset) {
                ndp16 = (struct usb_cdc_ncm_ndp16 *)(skb->data + ndpoffset);
                if  (ndp16->dwSignature == sign)
                        return ndp16;
                ndpoffset = le16_to_cpu(ndp16->wNextNdpIndex);
        }

        /* align new NDP */
        if (!(ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END))
                cdc_ncm_align_tail(skb, ctx->tx_ndp_modulus, 0, ctx->tx_curr_size);

        /* verify that there is room for the NDP and the datagram (reserve) */
        if ((ctx->tx_curr_size - skb->len - reserve) < ctx->max_ndp_size)
                return NULL;

        /* link to it */
        if (ndp16)
                ndp16->wNextNdpIndex = cpu_to_le16(skb->len);
        else
                nth16->wNdpIndex = cpu_to_le16(skb->len);

        /* push a new empty NDP */
        if (!(ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END))
                ndp16 = skb_put_zero(skb, ctx->max_ndp_size);
        else
                ndp16 = ctx->delayed_ndp16;

        ndp16->dwSignature = sign;
        ndp16->wLength = cpu_to_le16(sizeof(struct usb_cdc_ncm_ndp16) + sizeof(struct usb_cdc_ncm_dpe16));
        return ndp16;
}

static struct usb_cdc_ncm_ndp32 *cdc_ncm_ndp32(struct cdc_ncm_ctx *ctx, struct sk_buff *skb, __le32 sign, size_t reserve)
{
        struct usb_cdc_ncm_ndp32 *ndp32 = NULL;
        struct usb_cdc_ncm_nth32 *nth32 = (void *)skb->data;
        size_t ndpoffset = le32_to_cpu(nth32->dwNdpIndex);

        /* If NDP should be moved to the end of the NCM package, we can't follow the
         * NTH32 header as we would normally do. NDP isn't written to the SKB yet, and
         * the wNdpIndex field in the header is actually not consistent with reality. It will be later.
         */
        if (ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END) {
                if (ctx->delayed_ndp32->dwSignature == sign)
                        return ctx->delayed_ndp32;

                /* We can only push a single NDP to the end. Return
                 * NULL to send what we've already got and queue this
                 * skb for later.
                 */
                else if (ctx->delayed_ndp32->dwSignature)
                        return NULL;
        }

        /* follow the chain of NDPs, looking for a match */
        while (ndpoffset) {
                ndp32 = (struct usb_cdc_ncm_ndp32 *)(skb->data + ndpoffset);
                if  (ndp32->dwSignature == sign)
                        return ndp32;
                ndpoffset = le32_to_cpu(ndp32->dwNextNdpIndex);
        }

        /* align new NDP */
        if (!(ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END))
                cdc_ncm_align_tail(skb, ctx->tx_ndp_modulus, 0, ctx->tx_curr_size);

        /* verify that there is room for the NDP and the datagram (reserve) */
        if ((ctx->tx_curr_size - skb->len - reserve) < ctx->max_ndp_size)
                return NULL;

        /* link to it */
        if (ndp32)
                ndp32->dwNextNdpIndex = cpu_to_le32(skb->len);
        else
                nth32->dwNdpIndex = cpu_to_le32(skb->len);

        /* push a new empty NDP */
        if (!(ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END))
                ndp32 = skb_put_zero(skb, ctx->max_ndp_size);
        else
                ndp32 = ctx->delayed_ndp32;

        ndp32->dwSignature = sign;
        ndp32->wLength = cpu_to_le16(sizeof(struct usb_cdc_ncm_ndp32) + sizeof(struct usb_cdc_ncm_dpe32));
        return ndp32;
}

struct sk_buff *
cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        union {
                struct usb_cdc_ncm_nth16 *nth16;
                struct usb_cdc_ncm_nth32 *nth32;
        } nth;
        union {
                struct usb_cdc_ncm_ndp16 *ndp16;
                struct usb_cdc_ncm_ndp32 *ndp32;
        } ndp;
        struct sk_buff *skb_out;
        u16 n = 0, index, ndplen;
        u8 ready2send = 0;
        u32 delayed_ndp_size;
        size_t padding_count;

        /* When our NDP gets written in cdc_ncm_ndp(), then skb_out->len gets updated
         * accordingly. Otherwise, we should check here.
         */
        if (ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END)
                delayed_ndp_size = ctx->max_ndp_size +
                        max_t(u32,
                              ctx->tx_ndp_modulus,
                              ctx->tx_modulus + ctx->tx_remainder) - 1;
        else
                delayed_ndp_size = 0;

        /* if there is a remaining skb, it gets priority */
        if (skb != NULL) {
                swap(skb, ctx->tx_rem_skb);
                swap(sign, ctx->tx_rem_sign);
        } else {
                ready2send = 1;
        }

        /* check if we are resuming an OUT skb */
        skb_out = ctx->tx_curr_skb;

        /* allocate a new OUT skb */
        if (!skb_out) {
                if (ctx->tx_low_mem_val == 0) {
                        ctx->tx_curr_size = ctx->tx_max;
                        skb_out = alloc_skb(ctx->tx_curr_size, GFP_ATOMIC);
                        /* If the memory allocation fails we will wait longer
                         * each time before attempting another full size
                         * allocation again to not overload the system
                         * further.
                         */
                        if (skb_out == NULL) {
                                /* If even the smallest allocation fails, abort. */
                                if (ctx->tx_curr_size == USB_CDC_NCM_NTB_MIN_OUT_SIZE)
                                        goto alloc_failed;
                                ctx->tx_low_mem_max_cnt = min(ctx->tx_low_mem_max_cnt + 1,
                                                              (unsigned)CDC_NCM_LOW_MEM_MAX_CNT);
                                ctx->tx_low_mem_val = ctx->tx_low_mem_max_cnt;
                        }
                }
                if (skb_out == NULL) {
                        /* See if a very small allocation is possible.
                         * We will send this packet immediately and hope
                         * that there is more memory available later.
                         */
                        if (skb)
                                ctx->tx_curr_size = max(skb->len,
                                        (u32)USB_CDC_NCM_NTB_MIN_OUT_SIZE);
                        else
                                ctx->tx_curr_size = USB_CDC_NCM_NTB_MIN_OUT_SIZE;
                        skb_out = alloc_skb(ctx->tx_curr_size, GFP_ATOMIC);

                        /* No allocation possible so we will abort */
                        if (!skb_out)
                                goto alloc_failed;
                        ctx->tx_low_mem_val--;
                }
                if (ctx->is_ndp16) {
                        /* fill out the initial 16-bit NTB header */
                        nth.nth16 = skb_put_zero(skb_out, sizeof(struct usb_cdc_ncm_nth16));
                        nth.nth16->dwSignature = cpu_to_le32(USB_CDC_NCM_NTH16_SIGN);
                        nth.nth16->wHeaderLength = cpu_to_le16(sizeof(struct usb_cdc_ncm_nth16));
                        nth.nth16->wSequence = cpu_to_le16(ctx->tx_seq++);
                } else {
                        /* fill out the initial 32-bit NTB header */
                        nth.nth32 = skb_put_zero(skb_out, sizeof(struct usb_cdc_ncm_nth32));
                        nth.nth32->dwSignature = cpu_to_le32(USB_CDC_NCM_NTH32_SIGN);
                        nth.nth32->wHeaderLength = cpu_to_le16(sizeof(struct usb_cdc_ncm_nth32));
                        nth.nth32->wSequence = cpu_to_le16(ctx->tx_seq++);
                }

                /* count total number of frames in this NTB */
                ctx->tx_curr_frame_num = 0;

                /* recent payload counter for this skb_out */
                ctx->tx_curr_frame_payload = 0;
        }

        for (n = ctx->tx_curr_frame_num; n < ctx->tx_max_datagrams; n++) {
                /* send any remaining skb first */
                if (skb == NULL) {
                        skb = ctx->tx_rem_skb;
                        sign = ctx->tx_rem_sign;
                        ctx->tx_rem_skb = NULL;

                        /* check for end of skb */
                        if (skb == NULL)
                                break;
                }

                /* get the appropriate NDP for this skb */
                if (ctx->is_ndp16)
                        ndp.ndp16 = cdc_ncm_ndp16(ctx, skb_out, sign, skb->len + ctx->tx_modulus + ctx->tx_remainder);
                else
                        ndp.ndp32 = cdc_ncm_ndp32(ctx, skb_out, sign, skb->len + ctx->tx_modulus + ctx->tx_remainder);

                /* align beginning of next frame */
                cdc_ncm_align_tail(skb_out,  ctx->tx_modulus, ctx->tx_remainder, ctx->tx_curr_size);

                /* check if we had enough room left for both NDP and frame */
                if ((ctx->is_ndp16 && !ndp.ndp16) || (!ctx->is_ndp16 && !ndp.ndp32) ||
                    skb_out->len + skb->len + delayed_ndp_size > ctx->tx_curr_size) {
                        if (n == 0) {
                                /* won't fit, MTU problem? */
                                dev_kfree_skb_any(skb);
                                skb = NULL;
                                dev->net->stats.tx_dropped++;
                        } else {
                                /* no room for skb - store for later */
                                if (ctx->tx_rem_skb != NULL) {
                                        dev_kfree_skb_any(ctx->tx_rem_skb);
                                        dev->net->stats.tx_dropped++;
                                }
                                ctx->tx_rem_skb = skb;
                                ctx->tx_rem_sign = sign;
                                skb = NULL;
                                ready2send = 1;
                                ctx->tx_reason_ntb_full++;      /* count reason for transmitting */
                        }
                        break;
                }

                /* calculate frame number within this NDP */
                if (ctx->is_ndp16) {
                        ndplen = le16_to_cpu(ndp.ndp16->wLength);
                        index = (ndplen - sizeof(struct usb_cdc_ncm_ndp16)) / sizeof(struct usb_cdc_ncm_dpe16) - 1;

                        /* OK, add this skb */
                        ndp.ndp16->dpe16[index].wDatagramLength = cpu_to_le16(skb->len);
                        ndp.ndp16->dpe16[index].wDatagramIndex = cpu_to_le16(skb_out->len);
                        ndp.ndp16->wLength = cpu_to_le16(ndplen + sizeof(struct usb_cdc_ncm_dpe16));
                } else {
                        ndplen = le16_to_cpu(ndp.ndp32->wLength);
                        index = (ndplen - sizeof(struct usb_cdc_ncm_ndp32)) / sizeof(struct usb_cdc_ncm_dpe32) - 1;

                        ndp.ndp32->dpe32[index].dwDatagramLength = cpu_to_le32(skb->len);
                        ndp.ndp32->dpe32[index].dwDatagramIndex = cpu_to_le32(skb_out->len);
                        ndp.ndp32->wLength = cpu_to_le16(ndplen + sizeof(struct usb_cdc_ncm_dpe32));
                }
                skb_put_data(skb_out, skb->data, skb->len);
                ctx->tx_curr_frame_payload += skb->len; /* count real tx payload data */
                dev_kfree_skb_any(skb);
                skb = NULL;

                /* send now if this NDP is full */
                if (index >= CDC_NCM_DPT_DATAGRAMS_MAX) {
                        ready2send = 1;
                        ctx->tx_reason_ndp_full++;      /* count reason for transmitting */
                        break;
                }
        }

        /* free up any dangling skb */
        if (skb != NULL) {
                dev_kfree_skb_any(skb);
                skb = NULL;
                dev->net->stats.tx_dropped++;
        }

        ctx->tx_curr_frame_num = n;

        if (n == 0) {
                /* wait for more frames */
                /* push variables */
                ctx->tx_curr_skb = skb_out;
                goto exit_no_skb;

        } else if ((n < ctx->tx_max_datagrams) && (ready2send == 0) && (ctx->timer_interval > 0)) {
                /* wait for more frames */
                /* push variables */
                ctx->tx_curr_skb = skb_out;
                /* set the pending count */
                if (n < CDC_NCM_RESTART_TIMER_DATAGRAM_CNT)
                        ctx->tx_timer_pending = CDC_NCM_TIMER_PENDING_CNT;
                goto exit_no_skb;

        } else {
                if (n == ctx->tx_max_datagrams)
                        ctx->tx_reason_max_datagram++;  /* count reason for transmitting */
                /* frame goes out */
                /* variables will be reset at next call */
        }

        /* If requested, put NDP at end of frame. */
        if (ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END) {
                if (ctx->is_ndp16) {
                        nth.nth16 = (struct usb_cdc_ncm_nth16 *)skb_out->data;
                        cdc_ncm_align_tail(skb_out, ctx->tx_ndp_modulus, 0, ctx->tx_curr_size - ctx->max_ndp_size);
                        nth.nth16->wNdpIndex = cpu_to_le16(skb_out->len);
                        skb_put_data(skb_out, ctx->delayed_ndp16, ctx->max_ndp_size);

                        /* Zero out delayed NDP - signature checking will naturally fail. */
                        ndp.ndp16 = memset(ctx->delayed_ndp16, 0, ctx->max_ndp_size);
                } else {
                        nth.nth32 = (struct usb_cdc_ncm_nth32 *)skb_out->data;
                        cdc_ncm_align_tail(skb_out, ctx->tx_ndp_modulus, 0, ctx->tx_curr_size - ctx->max_ndp_size);
                        nth.nth32->dwNdpIndex = cpu_to_le32(skb_out->len);
                        skb_put_data(skb_out, ctx->delayed_ndp32, ctx->max_ndp_size);

                        ndp.ndp32 = memset(ctx->delayed_ndp32, 0, ctx->max_ndp_size);
                }
        }

        /* If collected data size is less or equal ctx->min_tx_pkt
         * bytes, we send buffers as it is. If we get more data, it
         * would be more efficient for USB HS mobile device with DMA
         * engine to receive a full size NTB, than canceling DMA
         * transfer and receiving a short packet.
         *
         * This optimization support is pointless if we end up sending
         * a ZLP after full sized NTBs.
         */
        if (!(dev->driver_info->flags & FLAG_SEND_ZLP) &&
            skb_out->len > ctx->min_tx_pkt) {
                padding_count = ctx->tx_curr_size - skb_out->len;
                if (!WARN_ON(padding_count > ctx->tx_curr_size))
                        skb_put_zero(skb_out, padding_count);
        } else if (skb_out->len < ctx->tx_curr_size &&
                   (skb_out->len % dev->maxpacket) == 0) {
                skb_put_u8(skb_out, 0); /* force short packet */
        }

        /* set final frame length */
        if (ctx->is_ndp16) {
                nth.nth16 = (struct usb_cdc_ncm_nth16 *)skb_out->data;
                nth.nth16->wBlockLength = cpu_to_le16(skb_out->len);
        } else {
                nth.nth32 = (struct usb_cdc_ncm_nth32 *)skb_out->data;
                nth.nth32->dwBlockLength = cpu_to_le32(skb_out->len);
        }

        /* return skb */
        ctx->tx_curr_skb = NULL;

        /* keep private stats: framing overhead and number of NTBs */
        ctx->tx_overhead += skb_out->len - ctx->tx_curr_frame_payload;
        ctx->tx_ntbs++;

        /* usbnet will count all the framing overhead by default.
         * Adjust the stats so that the tx_bytes counter show real
         * payload data instead.
         */
        usbnet_set_skb_tx_stats(skb_out, n,
                                (long)ctx->tx_curr_frame_payload - skb_out->len);

        return skb_out;

alloc_failed:
        if (skb) {
                dev_kfree_skb_any(skb);
                dev->net->stats.tx_dropped++;
        }
exit_no_skb:
        /* Start timer, if there is a remaining non-empty skb */
        if (ctx->tx_curr_skb != NULL && n > 0)
                cdc_ncm_tx_timeout_start(ctx);
        return NULL;
}
EXPORT_SYMBOL_GPL(cdc_ncm_fill_tx_frame);

static void cdc_ncm_tx_timeout_start(struct cdc_ncm_ctx *ctx)
{
        /* start timer, if not already started */
        if (!(hrtimer_active(&ctx->tx_timer) || atomic_read(&ctx->stop)))
                hrtimer_start(&ctx->tx_timer,
                                ctx->timer_interval,
                                HRTIMER_MODE_REL);
}

static enum hrtimer_restart cdc_ncm_tx_timer_cb(struct hrtimer *timer)
{
        struct cdc_ncm_ctx *ctx =
                        container_of(timer, struct cdc_ncm_ctx, tx_timer);

        if (!atomic_read(&ctx->stop))
                tasklet_schedule(&ctx->bh);
        return HRTIMER_NORESTART;
}

static void cdc_ncm_txpath_bh(struct tasklet_struct *t)
{
        struct cdc_ncm_ctx *ctx = from_tasklet(ctx, t, bh);
        struct usbnet *dev = ctx->dev;

        spin_lock(&ctx->mtx);
        if (ctx->tx_timer_pending != 0) {
                ctx->tx_timer_pending--;
                cdc_ncm_tx_timeout_start(ctx);
                spin_unlock(&ctx->mtx);
        } else if (dev->net != NULL) {
                ctx->tx_reason_timeout++;       /* count reason for transmitting */
                spin_unlock(&ctx->mtx);
                netif_tx_lock_bh(dev->net);
                usbnet_start_xmit(NULL, dev->net);
                netif_tx_unlock_bh(dev->net);
        } else {
                spin_unlock(&ctx->mtx);
        }
}

struct sk_buff *
cdc_ncm_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
{
        struct sk_buff *skb_out;
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];

        /*
         * The Ethernet API we are using does not support transmitting
         * multiple Ethernet frames in a single call. This driver will
         * accumulate multiple Ethernet frames and send out a larger
         * USB frame when the USB buffer is full or when a single jiffies
         * timeout happens.
         */
        if (ctx == NULL)
                goto error;

        spin_lock_bh(&ctx->mtx);

        if (ctx->is_ndp16)
                skb_out = cdc_ncm_fill_tx_frame(dev, skb, cpu_to_le32(USB_CDC_NCM_NDP16_NOCRC_SIGN));
        else
                skb_out = cdc_ncm_fill_tx_frame(dev, skb, cpu_to_le32(USB_CDC_NCM_NDP32_NOCRC_SIGN));

        spin_unlock_bh(&ctx->mtx);
        return skb_out;

error:
        if (skb != NULL)
                dev_kfree_skb_any(skb);

        return NULL;
}
EXPORT_SYMBOL_GPL(cdc_ncm_tx_fixup);

/* verify NTB header and return offset of first NDP, or negative error */
int cdc_ncm_rx_verify_nth16(struct cdc_ncm_ctx *ctx, struct sk_buff *skb_in)
{
        struct usbnet *dev = netdev_priv(skb_in->dev);
        struct usb_cdc_ncm_nth16 *nth16;
        int len;
        int ret = -EINVAL;

        if (ctx == NULL)
                goto error;

        if (skb_in->len < (sizeof(struct usb_cdc_ncm_nth16) +
                                        sizeof(struct usb_cdc_ncm_ndp16))) {
                netif_dbg(dev, rx_err, dev->net, "frame too short\n");
                goto error;
        }

        nth16 = (struct usb_cdc_ncm_nth16 *)skb_in->data;

        if (nth16->dwSignature != cpu_to_le32(USB_CDC_NCM_NTH16_SIGN)) {
                netif_dbg(dev, rx_err, dev->net,
                          "invalid NTH16 signature <%#010x>\n",
                          le32_to_cpu(nth16->dwSignature));
                goto error;
        }

        len = le16_to_cpu(nth16->wBlockLength);
        if (len > ctx->rx_max) {
                netif_dbg(dev, rx_err, dev->net,
                          "unsupported NTB block length %u/%u\n", len,
                          ctx->rx_max);
                goto error;
        }

        if ((ctx->rx_seq + 1) != le16_to_cpu(nth16->wSequence) &&
            (ctx->rx_seq || le16_to_cpu(nth16->wSequence)) &&
            !((ctx->rx_seq == 0xffff) && !le16_to_cpu(nth16->wSequence))) {
                netif_dbg(dev, rx_err, dev->net,
                          "sequence number glitch prev=%d curr=%d\n",
                          ctx->rx_seq, le16_to_cpu(nth16->wSequence));
        }
        ctx->rx_seq = le16_to_cpu(nth16->wSequence);

        ret = le16_to_cpu(nth16->wNdpIndex);
error:
        return ret;
}
EXPORT_SYMBOL_GPL(cdc_ncm_rx_verify_nth16);

int cdc_ncm_rx_verify_nth32(struct cdc_ncm_ctx *ctx, struct sk_buff *skb_in)
{
        struct usbnet *dev = netdev_priv(skb_in->dev);
        struct usb_cdc_ncm_nth32 *nth32;
        int len;
        int ret = -EINVAL;

        if (ctx == NULL)
                goto error;

        if (skb_in->len < (sizeof(struct usb_cdc_ncm_nth32) +
                                        sizeof(struct usb_cdc_ncm_ndp32))) {
                netif_dbg(dev, rx_err, dev->net, "frame too short\n");
                goto error;
        }

        nth32 = (struct usb_cdc_ncm_nth32 *)skb_in->data;

        if (nth32->dwSignature != cpu_to_le32(USB_CDC_NCM_NTH32_SIGN)) {
                netif_dbg(dev, rx_err, dev->net,
                          "invalid NTH32 signature <%#010x>\n",
                          le32_to_cpu(nth32->dwSignature));
                goto error;
        }

        len = le32_to_cpu(nth32->dwBlockLength);
        if (len > ctx->rx_max) {
                netif_dbg(dev, rx_err, dev->net,
                          "unsupported NTB block length %u/%u\n", len,
                          ctx->rx_max);
                goto error;
        }

        if ((ctx->rx_seq + 1) != le16_to_cpu(nth32->wSequence) &&
            (ctx->rx_seq || le16_to_cpu(nth32->wSequence)) &&
            !((ctx->rx_seq == 0xffff) && !le16_to_cpu(nth32->wSequence))) {
                netif_dbg(dev, rx_err, dev->net,
                          "sequence number glitch prev=%d curr=%d\n",
                          ctx->rx_seq, le16_to_cpu(nth32->wSequence));
        }
        ctx->rx_seq = le16_to_cpu(nth32->wSequence);

        ret = le32_to_cpu(nth32->dwNdpIndex);
error:
        return ret;
}
EXPORT_SYMBOL_GPL(cdc_ncm_rx_verify_nth32);

/* verify NDP header and return number of datagrams, or negative error */
int cdc_ncm_rx_verify_ndp16(struct sk_buff *skb_in, int ndpoffset)
{
        struct usbnet *dev = netdev_priv(skb_in->dev);
        struct usb_cdc_ncm_ndp16 *ndp16;
        int ret = -EINVAL;
        size_t ndp_len;

        if ((ndpoffset + sizeof(struct usb_cdc_ncm_ndp16)) > skb_in->len) {
                netif_dbg(dev, rx_err, dev->net, "invalid NDP offset  <%u>\n",
                          ndpoffset);
                goto error;
        }
        ndp16 = (struct usb_cdc_ncm_ndp16 *)(skb_in->data + ndpoffset);

        if (le16_to_cpu(ndp16->wLength) < USB_CDC_NCM_NDP16_LENGTH_MIN) {
                netif_dbg(dev, rx_err, dev->net, "invalid DPT16 length <%u>\n",
                          le16_to_cpu(ndp16->wLength));
                goto error;
        }

        ret = ((le16_to_cpu(ndp16->wLength) -
                                        sizeof(struct usb_cdc_ncm_ndp16)) /
                                        sizeof(struct usb_cdc_ncm_dpe16));
        ret--; /* we process NDP entries except for the last one */

        ndp_len = struct_size_t(struct usb_cdc_ncm_ndp16, dpe16, ret);
        if (ndpoffset + ndp_len > skb_in->len) {
                netif_dbg(dev, rx_err, dev->net, "Invalid nframes = %d\n", ret);
                ret = -EINVAL;
        }

error:
        return ret;
}
EXPORT_SYMBOL_GPL(cdc_ncm_rx_verify_ndp16);

/* verify NDP header and return number of datagrams, or negative error */
int cdc_ncm_rx_verify_ndp32(struct sk_buff *skb_in, int ndpoffset)
{
        struct usbnet *dev = netdev_priv(skb_in->dev);
        struct usb_cdc_ncm_ndp32 *ndp32;
        int ret = -EINVAL;
        size_t ndp_len;

        if ((ndpoffset + sizeof(struct usb_cdc_ncm_ndp32)) > skb_in->len) {
                netif_dbg(dev, rx_err, dev->net, "invalid NDP offset  <%u>\n",
                          ndpoffset);
                goto error;
        }
        ndp32 = (struct usb_cdc_ncm_ndp32 *)(skb_in->data + ndpoffset);

        if (le16_to_cpu(ndp32->wLength) < USB_CDC_NCM_NDP32_LENGTH_MIN) {
                netif_dbg(dev, rx_err, dev->net, "invalid DPT32 length <%u>\n",
                          le16_to_cpu(ndp32->wLength));
                goto error;
        }

        ret = ((le16_to_cpu(ndp32->wLength) -
                                        sizeof(struct usb_cdc_ncm_ndp32)) /
                                        sizeof(struct usb_cdc_ncm_dpe32));
        ret--; /* we process NDP entries except for the last one */

        ndp_len = struct_size_t(struct usb_cdc_ncm_ndp32, dpe32, ret);
        if (ndpoffset + ndp_len > skb_in->len) {
                netif_dbg(dev, rx_err, dev->net, "Invalid nframes = %d\n", ret);
                ret = -EINVAL;
        }

error:
        return ret;
}
EXPORT_SYMBOL_GPL(cdc_ncm_rx_verify_ndp32);

int cdc_ncm_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in)
{
        struct sk_buff *skb;
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
        unsigned int len;
        int nframes;
        int x;
        unsigned int offset;
        union {
                struct usb_cdc_ncm_ndp16 *ndp16;
                struct usb_cdc_ncm_ndp32 *ndp32;
        } ndp;
        union {
                struct usb_cdc_ncm_dpe16 *dpe16;
                struct usb_cdc_ncm_dpe32 *dpe32;
        } dpe;

        int ndpoffset;
        int loopcount = 50; /* arbitrary max preventing infinite loop */
        u32 payload = 0;

        if (ctx->is_ndp16)
                ndpoffset = cdc_ncm_rx_verify_nth16(ctx, skb_in);
        else
                ndpoffset = cdc_ncm_rx_verify_nth32(ctx, skb_in);

        if (ndpoffset < 0)
                goto error;

next_ndp:
        if (ctx->is_ndp16) {
                nframes = cdc_ncm_rx_verify_ndp16(skb_in, ndpoffset);
                if (nframes < 0)
                        goto error;

                ndp.ndp16 = (struct usb_cdc_ncm_ndp16 *)(skb_in->data + ndpoffset);

                if (ndp.ndp16->dwSignature != cpu_to_le32(USB_CDC_NCM_NDP16_NOCRC_SIGN)) {
                        netif_dbg(dev, rx_err, dev->net,
                                  "invalid DPT16 signature <%#010x>\n",
                                  le32_to_cpu(ndp.ndp16->dwSignature));
                        goto err_ndp;
                }
                dpe.dpe16 = ndp.ndp16->dpe16;
        } else {
                nframes = cdc_ncm_rx_verify_ndp32(skb_in, ndpoffset);
                if (nframes < 0)
                        goto error;

                ndp.ndp32 = (struct usb_cdc_ncm_ndp32 *)(skb_in->data + ndpoffset);

                if (ndp.ndp32->dwSignature != cpu_to_le32(USB_CDC_NCM_NDP32_NOCRC_SIGN)) {
                        netif_dbg(dev, rx_err, dev->net,
                                  "invalid DPT32 signature <%#010x>\n",
                                  le32_to_cpu(ndp.ndp32->dwSignature));
                        goto err_ndp;
                }
                dpe.dpe32 = ndp.ndp32->dpe32;
        }

        for (x = 0; x < nframes; x++) {
                if (ctx->is_ndp16) {
                        offset = le16_to_cpu(dpe.dpe16->wDatagramIndex);
                        len = le16_to_cpu(dpe.dpe16->wDatagramLength);
                } else {
                        offset = le32_to_cpu(dpe.dpe32->dwDatagramIndex);
                        len = le32_to_cpu(dpe.dpe32->dwDatagramLength);
                }

                /*
                 * CDC NCM ch. 3.7
                 * All entries after first NULL entry are to be ignored
                 */
                if ((offset == 0) || (len == 0)) {
                        if (!x)
                                goto err_ndp; /* empty NTB */
                        break;
                }

                /* sanity checking - watch out for integer wrap*/
                if ((offset > skb_in->len) || (len > skb_in->len - offset) ||
                                (len > ctx->rx_max) || (len < ETH_HLEN)) {
                        netif_dbg(dev, rx_err, dev->net,
                                  "invalid frame detected (ignored) offset[%u]=%u, length=%u, skb=%p\n",
                                  x, offset, len, skb_in);
                        if (!x)
                                goto err_ndp;
                        break;

                } else {
                        /* create a fresh copy to reduce truesize */
                        skb = netdev_alloc_skb_ip_align(dev->net,  len);
                        if (!skb)
                                goto error;
                        skb_put_data(skb, skb_in->data + offset, len);
                        usbnet_skb_return(dev, skb);
                        payload += len; /* count payload bytes in this NTB */
                }

                if (ctx->is_ndp16)
                        dpe.dpe16++;
                else
                        dpe.dpe32++;
        }
err_ndp:
        /* are there more NDPs to process? */
        if (ctx->is_ndp16)
                ndpoffset = le16_to_cpu(ndp.ndp16->wNextNdpIndex);
        else
                ndpoffset = le32_to_cpu(ndp.ndp32->dwNextNdpIndex);

        if (ndpoffset && loopcount--)
                goto next_ndp;

        /* update stats */
        ctx->rx_overhead += skb_in->len - payload;
        ctx->rx_ntbs++;

        return 1;
error:
        return 0;
}
EXPORT_SYMBOL_GPL(cdc_ncm_rx_fixup);

static void
cdc_ncm_speed_change(struct usbnet *dev,
                     struct usb_cdc_speed_change *data)
{
        /* RTL8156 shipped before 2021 sends notification about every 32ms. */
        dev->rx_speed = le32_to_cpu(data->DLBitRRate);
        dev->tx_speed = le32_to_cpu(data->ULBitRate);
}

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

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

        /* test for split data in 8-byte chunks */
        if (test_and_clear_bit(EVENT_STS_SPLIT, &dev->flags)) {
                cdc_ncm_speed_change(dev,
                      (struct usb_cdc_speed_change *)urb->transfer_buffer);
                return;
        }

        event = urb->transfer_buffer;

        switch (event->bNotificationType) {
        case USB_CDC_NOTIFY_NETWORK_CONNECTION:
                /*
                 * According to the CDC NCM specification ch.7.1
                 * USB_CDC_NOTIFY_NETWORK_CONNECTION notification shall be
                 * sent by device after USB_CDC_NOTIFY_SPEED_CHANGE.
                 */
                /* RTL8156 shipped before 2021 sends notification about
                 * every 32ms. Don't forward notification if state is same.
                 */
                if (netif_carrier_ok(dev->net) != !!event->wValue)
                        usbnet_link_change(dev, !!event->wValue, 0);
                break;

        case USB_CDC_NOTIFY_SPEED_CHANGE:
                if (urb->actual_length < (sizeof(*event) +
                                        sizeof(struct usb_cdc_speed_change)))
                        set_bit(EVENT_STS_SPLIT, &dev->flags);
                else
                        cdc_ncm_speed_change(dev,
                                             (struct usb_cdc_speed_change *)&event[1]);
                break;

        default:
                dev_dbg(&dev->udev->dev,
                        "NCM: unexpected notification 0x%02x!\n",
                        event->bNotificationType);
                break;
        }
}

static void cdc_ncm_update_filter(struct usbnet *dev)
{
        struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];

        if (ctx->filtering_supported)
                usbnet_cdc_update_filter(dev);
}

static const struct driver_info cdc_ncm_info = {
        .description = "CDC NCM (NO ZLP)",
        .flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT | FLAG_MULTI_PACKET
                        | FLAG_LINK_INTR | FLAG_ETHER,
        .bind = cdc_ncm_bind,
        .unbind = cdc_ncm_unbind,
        .manage_power = usbnet_manage_power,
        .status = cdc_ncm_status,
        .rx_fixup = cdc_ncm_rx_fixup,
        .tx_fixup = cdc_ncm_tx_fixup,
        .set_rx_mode = cdc_ncm_update_filter,
};

/* Same as cdc_ncm_info, but with FLAG_SEND_ZLP  */
static const struct driver_info cdc_ncm_zlp_info = {
        .description = "CDC NCM (SEND ZLP)",
        .flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT | FLAG_MULTI_PACKET
                        | FLAG_LINK_INTR | FLAG_ETHER | FLAG_SEND_ZLP,
        .bind = cdc_ncm_bind,
        .unbind = cdc_ncm_unbind,
        .manage_power = usbnet_manage_power,
        .status = cdc_ncm_status,
        .rx_fixup = cdc_ncm_rx_fixup,
        .tx_fixup = cdc_ncm_tx_fixup,
        .set_rx_mode = cdc_ncm_update_filter,
};

/* Same as cdc_ncm_info, but with FLAG_SEND_ZLP */
static const struct driver_info apple_tethering_interface_info = {
        .description = "CDC NCM (Apple Tethering)",
        .flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT | FLAG_MULTI_PACKET
                        | FLAG_LINK_INTR | FLAG_ETHER | FLAG_SEND_ZLP,
        .bind = cdc_ncm_bind,
        .unbind = cdc_ncm_unbind,
        .manage_power = usbnet_manage_power,
        .status = cdc_ncm_status,
        .rx_fixup = cdc_ncm_rx_fixup,
        .tx_fixup = cdc_ncm_tx_fixup,
        .set_rx_mode = usbnet_cdc_update_filter,
};

/* Same as apple_tethering_interface_info, but without FLAG_LINK_INTR */
static const struct driver_info apple_private_interface_info = {
        .description = "CDC NCM (Apple Private)",
        .flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT | FLAG_MULTI_PACKET
                        | FLAG_ETHER | FLAG_SEND_ZLP,
        .bind = cdc_ncm_bind,
        .unbind = cdc_ncm_unbind,
        .manage_power = usbnet_manage_power,
        .status = cdc_ncm_status,
        .rx_fixup = cdc_ncm_rx_fixup,
        .tx_fixup = cdc_ncm_tx_fixup,
        .set_rx_mode = usbnet_cdc_update_filter,
};

/* Same as cdc_ncm_info, but with FLAG_WWAN */
static const struct driver_info wwan_info = {
        .description = "Mobile Broadband Network Device",
        .flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT | FLAG_MULTI_PACKET
                        | FLAG_LINK_INTR | FLAG_WWAN,
        .bind = cdc_ncm_bind,
        .unbind = cdc_ncm_unbind,
        .manage_power = usbnet_manage_power,
        .status = cdc_ncm_status,
        .rx_fixup = cdc_ncm_rx_fixup,
        .tx_fixup = cdc_ncm_tx_fixup,
        .set_rx_mode = cdc_ncm_update_filter,
};

/* Same as wwan_info, but with FLAG_NOARP  */
static const struct driver_info wwan_noarp_info = {
        .description = "Mobile Broadband Network Device (NO ARP)",
        .flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT | FLAG_MULTI_PACKET
                        | FLAG_LINK_INTR | FLAG_WWAN | FLAG_NOARP,
        .bind = cdc_ncm_bind,
        .unbind = cdc_ncm_unbind,
        .manage_power = usbnet_manage_power,
        .status = cdc_ncm_status,
        .rx_fixup = cdc_ncm_rx_fixup,
        .tx_fixup = cdc_ncm_tx_fixup,
        .set_rx_mode = cdc_ncm_update_filter,
};

static const struct usb_device_id cdc_devs[] = {
        /* iPhone */
        { USB_DEVICE_INTERFACE_NUMBER(0x05ac, 0x12a8, 2),
                .driver_info = (unsigned long)&apple_tethering_interface_info,
        },
        { USB_DEVICE_INTERFACE_NUMBER(0x05ac, 0x12a8, 4),
                .driver_info = (unsigned long)&apple_private_interface_info,
        },

        /* iPad */
        { USB_DEVICE_INTERFACE_NUMBER(0x05ac, 0x12ab, 2),
                .driver_info = (unsigned long)&apple_tethering_interface_info,
        },
        { USB_DEVICE_INTERFACE_NUMBER(0x05ac, 0x12ab, 4),
                .driver_info = (unsigned long)&apple_private_interface_info,
        },

        /* Ericsson MBM devices like F5521gw */
        { .match_flags = USB_DEVICE_ID_MATCH_INT_INFO
                | USB_DEVICE_ID_MATCH_VENDOR,
          .idVendor = 0x0bdb,
          .bInterfaceClass = USB_CLASS_COMM,
          .bInterfaceSubClass = USB_CDC_SUBCLASS_NCM,
          .bInterfaceProtocol = USB_CDC_PROTO_NONE,
          .driver_info = (unsigned long) &wwan_info,
        },

        /* Telit LE910 V2 */
        { USB_DEVICE_AND_INTERFACE_INFO(0x1bc7, 0x0036,
                USB_CLASS_COMM,
                USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
          .driver_info = (unsigned long)&wwan_noarp_info,
        },

        /* DW5812 LTE Verizon Mobile Broadband Card
         * Unlike DW5550 this device requires FLAG_NOARP
         */
        { USB_DEVICE_AND_INTERFACE_INFO(0x413c, 0x81bb,
                USB_CLASS_COMM,
                USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
          .driver_info = (unsigned long)&wwan_noarp_info,
        },

        /* DW5813 LTE AT&T Mobile Broadband Card
         * Unlike DW5550 this device requires FLAG_NOARP
         */
        { USB_DEVICE_AND_INTERFACE_INFO(0x413c, 0x81bc,
                USB_CLASS_COMM,
                USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
          .driver_info = (unsigned long)&wwan_noarp_info,
        },

        /* Dell branded MBM devices like DW5550 */
        { .match_flags = USB_DEVICE_ID_MATCH_INT_INFO
                | USB_DEVICE_ID_MATCH_VENDOR,
          .idVendor = 0x413c,
          .bInterfaceClass = USB_CLASS_COMM,
          .bInterfaceSubClass = USB_CDC_SUBCLASS_NCM,
          .bInterfaceProtocol = USB_CDC_PROTO_NONE,
          .driver_info = (unsigned long) &wwan_info,
        },

        /* Toshiba branded MBM devices */
        { .match_flags = USB_DEVICE_ID_MATCH_INT_INFO
                | USB_DEVICE_ID_MATCH_VENDOR,
          .idVendor = 0x0930,
          .bInterfaceClass = USB_CLASS_COMM,
          .bInterfaceSubClass = USB_CDC_SUBCLASS_NCM,
          .bInterfaceProtocol = USB_CDC_PROTO_NONE,
          .driver_info = (unsigned long) &wwan_info,
        },

        /* tag Huawei devices as wwan */
        { USB_VENDOR_AND_INTERFACE_INFO(0x12d1,
                                        USB_CLASS_COMM,
                                        USB_CDC_SUBCLASS_NCM,
                                        USB_CDC_PROTO_NONE),
          .driver_info = (unsigned long)&wwan_info,
        },

        /* Infineon(now Intel) HSPA Modem platform */
        { USB_DEVICE_AND_INTERFACE_INFO(0x1519, 0x0443,
                USB_CLASS_COMM,
                USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
          .driver_info = (unsigned long)&wwan_noarp_info,
        },

        /* u-blox TOBY-L4 */
        { USB_DEVICE_AND_INTERFACE_INFO(0x1546, 0x1010,
                USB_CLASS_COMM,
                USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
          .driver_info = (unsigned long)&wwan_info,
        },

        /* Intel modem (label from OEM reads Fibocom L850-GL) */
        { USB_DEVICE_AND_INTERFACE_INFO(0x8087, 0x095a,
                USB_CLASS_COMM,
                USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
          .driver_info = (unsigned long)&wwan_info,
        },

        /* DisplayLink docking stations */
        { .match_flags = USB_DEVICE_ID_MATCH_INT_INFO
                | USB_DEVICE_ID_MATCH_VENDOR,
          .idVendor = 0x17e9,
          .bInterfaceClass = USB_CLASS_COMM,
          .bInterfaceSubClass = USB_CDC_SUBCLASS_NCM,
          .bInterfaceProtocol = USB_CDC_PROTO_NONE,
          .driver_info = (unsigned long)&cdc_ncm_zlp_info,
        },

        /* Generic CDC-NCM devices */
        { USB_INTERFACE_INFO(USB_CLASS_COMM,
                USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
                .driver_info = (unsigned long)&cdc_ncm_info,
        },
        {
        },
};
MODULE_DEVICE_TABLE(usb, cdc_devs);

static struct usb_driver cdc_ncm_driver = {
        .name = "cdc_ncm",
        .id_table = cdc_devs,
        .probe = usbnet_probe,
        .disconnect = usbnet_disconnect,
        .suspend = usbnet_suspend,
        .resume = usbnet_resume,
        .reset_resume = usbnet_resume,
        .supports_autosuspend = 1,
        .disable_hub_initiated_lpm = 1,
};

module_usb_driver(cdc_ncm_driver);

MODULE_AUTHOR("Hans Petter Selasky");
MODULE_DESCRIPTION("USB CDC NCM host driver");
MODULE_LICENSE("Dual BSD/GPL");