/*
 * Copyright (c) 2009, Microsoft Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307 USA.
 *
 * Authors:
 *   Haiyang Zhang <haiyangz@microsoft.com>
 *   Hank Janssen  <hjanssen@microsoft.com>
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/slab.h>

#include "hyperv.h"
#include "hyperv_net.h"


/* Globals */
static const char *driver_name = "netvsc";

/* {F8615163-DF3E-46c5-913F-F2D2F965ED0E} */
static const struct hv_guid netvsc_device_type = {
        .data = {
                0x63, 0x51, 0x61, 0xF8, 0x3E, 0xDF, 0xc5, 0x46,
                0x91, 0x3F, 0xF2, 0xD2, 0xF9, 0x65, 0xED, 0x0E
        }
};


static struct netvsc_device *alloc_net_device(struct hv_device *device)
{
        struct netvsc_device *net_device;

        net_device = kzalloc(sizeof(struct netvsc_device), GFP_KERNEL);
        if (!net_device)
                return NULL;

        /* Set to 2 to allow both inbound and outbound traffic */
        atomic_cmpxchg(&net_device->refcnt, 0, 2);

        net_device->dev = device;
        device->ext = net_device;

        return net_device;
}

static void free_net_device(struct netvsc_device *device)
{
        WARN_ON(atomic_read(&device->refcnt) != 0);
        device->dev->ext = NULL;
        kfree(device);
}


/* Get the net device object iff exists and its refcount > 1 */
static struct netvsc_device *get_outbound_net_device(struct hv_device *device)
{
        struct netvsc_device *net_device;

        net_device = device->ext;
        if (net_device && atomic_read(&net_device->refcnt) > 1)
                atomic_inc(&net_device->refcnt);
        else
                net_device = NULL;

        return net_device;
}

/* Get the net device object iff exists and its refcount > 0 */
static struct netvsc_device *get_inbound_net_device(struct hv_device *device)
{
        struct netvsc_device *net_device;

        net_device = device->ext;
        if (net_device && atomic_read(&net_device->refcnt))
                atomic_inc(&net_device->refcnt);
        else
                net_device = NULL;

        return net_device;
}

static void put_net_device(struct hv_device *device)
{
        struct netvsc_device *net_device;

        net_device = device->ext;

        atomic_dec(&net_device->refcnt);
}

static struct netvsc_device *release_outbound_net_device(
                struct hv_device *device)
{
        struct netvsc_device *net_device;

        net_device = device->ext;
        if (net_device == NULL)
                return NULL;

        /* Busy wait until the ref drop to 2, then set it to 1 */
        while (atomic_cmpxchg(&net_device->refcnt, 2, 1) != 2)
                udelay(100);

        return net_device;
}

static struct netvsc_device *release_inbound_net_device(
                struct hv_device *device)
{
        struct netvsc_device *net_device;

        net_device = device->ext;
        if (net_device == NULL)
                return NULL;

        /* Busy wait until the ref drop to 1, then set it to 0 */
        while (atomic_cmpxchg(&net_device->refcnt, 1, 0) != 1)
                udelay(100);

        device->ext = NULL;
        return net_device;
}

static int netvsc_destroy_recv_buf(struct netvsc_device *net_device)
{
        struct nvsp_message *revoke_packet;
        int ret = 0;

        /*
         * If we got a section count, it means we received a
         * SendReceiveBufferComplete msg (ie sent
         * NvspMessage1TypeSendReceiveBuffer msg) therefore, we need
         * to send a revoke msg here
         */
        if (net_device->recv_section_cnt) {
                /* Send the revoke receive buffer */
                revoke_packet = &net_device->revoke_packet;
                memset(revoke_packet, 0, sizeof(struct nvsp_message));

                revoke_packet->hdr.msg_type =
                        NVSP_MSG1_TYPE_REVOKE_RECV_BUF;
                revoke_packet->msg.v1_msg.
                revoke_recv_buf.id = NETVSC_RECEIVE_BUFFER_ID;

                ret = vmbus_sendpacket(net_device->dev->channel,
                                       revoke_packet,
                                       sizeof(struct nvsp_message),
                                       (unsigned long)revoke_packet,
                                       VM_PKT_DATA_INBAND, 0);
                /*
                 * If we failed here, we might as well return and
                 * have a leak rather than continue and a bugchk
                 */
                if (ret != 0) {
                        dev_err(&net_device->dev->device, "unable to send "
                                "revoke receive buffer to netvsp");
                        return -1;
                }
        }

        /* Teardown the gpadl on the vsp end */
        if (net_device->recv_buf_gpadl_handle) {
                ret = vmbus_teardown_gpadl(net_device->dev->channel,
                           net_device->recv_buf_gpadl_handle);

                /* If we failed here, we might as well return and have a leak
                 * rather than continue and a bugchk
                 */
                if (ret != 0) {
                        dev_err(&net_device->dev->device,
                                   "unable to teardown receive buffer's gpadl");
                        return -1;
                }
                net_device->recv_buf_gpadl_handle = 0;
        }

        if (net_device->recv_buf) {
                /* Free up the receive buffer */
                free_pages((unsigned long)net_device->recv_buf,
                        get_order(net_device->recv_buf_size));
                net_device->recv_buf = NULL;
        }

        if (net_device->recv_section) {
                net_device->recv_section_cnt = 0;
                kfree(net_device->recv_section);
                net_device->recv_section = NULL;
        }

        return ret;
}

static int netvsc_init_recv_buf(struct hv_device *device)
{
        int ret = 0;
        int t;
        struct netvsc_device *net_device;
        struct nvsp_message *init_packet;

        net_device = get_outbound_net_device(device);
        if (!net_device) {
                dev_err(&device->device, "unable to get net device..."
                           "device being destroyed?");
                return -1;
        }

        net_device->recv_buf =
                (void *)__get_free_pages(GFP_KERNEL|__GFP_ZERO,
                                get_order(net_device->recv_buf_size));
        if (!net_device->recv_buf) {
                dev_err(&device->device, "unable to allocate receive "
                        "buffer of size %d", net_device->recv_buf_size);
                ret = -1;
                goto cleanup;
        }

        /*
         * Establish the gpadl handle for this buffer on this
         * channel.  Note: This call uses the vmbus connection rather
         * than the channel to establish the gpadl handle.
         */
        ret = vmbus_establish_gpadl(device->channel, net_device->recv_buf,
                                    net_device->recv_buf_size,
                                    &net_device->recv_buf_gpadl_handle);
        if (ret != 0) {
                dev_err(&device->device,
                        "unable to establish receive buffer's gpadl");
                goto cleanup;
        }


        /* Notify the NetVsp of the gpadl handle */
        init_packet = &net_device->channel_init_pkt;

        memset(init_packet, 0, sizeof(struct nvsp_message));

        init_packet->hdr.msg_type = NVSP_MSG1_TYPE_SEND_RECV_BUF;
        init_packet->msg.v1_msg.send_recv_buf.
                gpadl_handle = net_device->recv_buf_gpadl_handle;
        init_packet->msg.v1_msg.
                send_recv_buf.id = NETVSC_RECEIVE_BUFFER_ID;

        /* Send the gpadl notification request */
        ret = vmbus_sendpacket(device->channel, init_packet,
                               sizeof(struct nvsp_message),
                               (unsigned long)init_packet,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret != 0) {
                dev_err(&device->device,
                        "unable to send receive buffer's gpadl to netvsp");
                goto cleanup;
        }

        t = wait_for_completion_timeout(&net_device->channel_init_wait, 5*HZ);
        BUG_ON(t == 0);


        /* Check the response */
        if (init_packet->msg.v1_msg.
            send_recv_buf_complete.status != NVSP_STAT_SUCCESS) {
                dev_err(&device->device, "Unable to complete receive buffer "
                           "initialzation with NetVsp - status %d",
                           init_packet->msg.v1_msg.
                           send_recv_buf_complete.status);
                ret = -1;
                goto cleanup;
        }

        /* Parse the response */

        net_device->recv_section_cnt = init_packet->msg.
                v1_msg.send_recv_buf_complete.num_sections;

        net_device->recv_section = kmalloc(net_device->recv_section_cnt
                * sizeof(struct nvsp_1_receive_buffer_section), GFP_KERNEL);
        if (net_device->recv_section == NULL) {
                ret = -1;
                goto cleanup;
        }

        memcpy(net_device->recv_section,
                init_packet->msg.v1_msg.
               send_recv_buf_complete.sections,
                net_device->recv_section_cnt *
               sizeof(struct nvsp_1_receive_buffer_section));

        /*
         * For 1st release, there should only be 1 section that represents the
         * entire receive buffer
         */
        if (net_device->recv_section_cnt != 1 ||
            net_device->recv_section->offset != 0) {
                ret = -1;
                goto cleanup;
        }

        goto exit;

cleanup:
        netvsc_destroy_recv_buf(net_device);

exit:
        put_net_device(device);
        return ret;
}


static int netvsc_connect_vsp(struct hv_device *device)
{
        int ret, t;
        struct netvsc_device *net_device;
        struct nvsp_message *init_packet;
        int ndis_version;

        net_device = get_outbound_net_device(device);
        if (!net_device) {
                dev_err(&device->device, "unable to get net device..."
                           "device being destroyed?");
                return -1;
        }

        init_packet = &net_device->channel_init_pkt;

        memset(init_packet, 0, sizeof(struct nvsp_message));
        init_packet->hdr.msg_type = NVSP_MSG_TYPE_INIT;
        init_packet->msg.init_msg.init.min_protocol_ver =
                NVSP_MIN_PROTOCOL_VERSION;
        init_packet->msg.init_msg.init.max_protocol_ver =
                NVSP_MAX_PROTOCOL_VERSION;

        /* Send the init request */
        ret = vmbus_sendpacket(device->channel, init_packet,
                               sizeof(struct nvsp_message),
                               (unsigned long)init_packet,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);

        if (ret != 0)
                goto cleanup;

        t = wait_for_completion_timeout(&net_device->channel_init_wait, 5*HZ);

        if (t == 0) {
                ret = -ETIMEDOUT;
                goto cleanup;
        }

        if (init_packet->msg.init_msg.init_complete.status !=
            NVSP_STAT_SUCCESS) {
                ret = -1;
                goto cleanup;
        }

        if (init_packet->msg.init_msg.init_complete.
            negotiated_protocol_ver != NVSP_PROTOCOL_VERSION_1) {
                ret = -1;
                goto cleanup;
        }
        /* Send the ndis version */
        memset(init_packet, 0, sizeof(struct nvsp_message));

        ndis_version = 0x00050000;

        init_packet->hdr.msg_type = NVSP_MSG1_TYPE_SEND_NDIS_VER;
        init_packet->msg.v1_msg.
                send_ndis_ver.ndis_major_ver =
                                (ndis_version & 0xFFFF0000) >> 16;
        init_packet->msg.v1_msg.
                send_ndis_ver.ndis_minor_ver =
                                ndis_version & 0xFFFF;

        /* Send the init request */
        ret = vmbus_sendpacket(device->channel, init_packet,
                                sizeof(struct nvsp_message),
                                (unsigned long)init_packet,
                                VM_PKT_DATA_INBAND, 0);
        if (ret != 0) {
                ret = -1;
                goto cleanup;
        }

        /* Post the big receive buffer to NetVSP */
        ret = netvsc_init_recv_buf(device);

cleanup:
        put_net_device(device);
        return ret;
}

static void netvsc_disconnect_vsp(struct netvsc_device *net_device)
{
        netvsc_destroy_recv_buf(net_device);
}

/*
 * netvsc_device_remove - Callback when the root bus device is removed
 */
int netvsc_device_remove(struct hv_device *device)
{
        struct netvsc_device *net_device;
        struct hv_netvsc_packet *netvsc_packet, *pos;

        /* Stop outbound traffic ie sends and receives completions */
        net_device = release_outbound_net_device(device);
        if (!net_device) {
                dev_err(&device->device, "No net device present!!");
                return -1;
        }

        /* Wait for all send completions */
        while (atomic_read(&net_device->num_outstanding_sends)) {
                dev_err(&device->device,
                        "waiting for %d requests to complete...",
                        atomic_read(&net_device->num_outstanding_sends));
                udelay(100);
        }

        netvsc_disconnect_vsp(net_device);

        /* Stop inbound traffic ie receives and sends completions */
        net_device = release_inbound_net_device(device);

        /* At this point, no one should be accessing netDevice except in here */
        dev_notice(&device->device, "net device safe to remove");

        /* Now, we can close the channel safely */
        vmbus_close(device->channel);

        /* Release all resources */
        list_for_each_entry_safe(netvsc_packet, pos,
                                 &net_device->recv_pkt_list, list_ent) {
                list_del(&netvsc_packet->list_ent);
                kfree(netvsc_packet);
        }

        free_net_device(net_device);
        return 0;
}

static void netvsc_send_completion(struct hv_device *device,
                                   struct vmpacket_descriptor *packet)
{
        struct netvsc_device *net_device;
        struct nvsp_message *nvsp_packet;
        struct hv_netvsc_packet *nvsc_packet;

        net_device = get_inbound_net_device(device);
        if (!net_device) {
                dev_err(&device->device, "unable to get net device..."
                           "device being destroyed?");
                return;
        }

        nvsp_packet = (struct nvsp_message *)((unsigned long)packet +
                        (packet->offset8 << 3));

        if ((nvsp_packet->hdr.msg_type == NVSP_MSG_TYPE_INIT_COMPLETE) ||
            (nvsp_packet->hdr.msg_type ==
             NVSP_MSG1_TYPE_SEND_RECV_BUF_COMPLETE) ||
            (nvsp_packet->hdr.msg_type ==
             NVSP_MSG1_TYPE_SEND_SEND_BUF_COMPLETE)) {
                /* Copy the response back */
                memcpy(&net_device->channel_init_pkt, nvsp_packet,
                       sizeof(struct nvsp_message));
                complete(&net_device->channel_init_wait);
        } else if (nvsp_packet->hdr.msg_type ==
                   NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE) {
                /* Get the send context */
                nvsc_packet = (struct hv_netvsc_packet *)(unsigned long)
                        packet->trans_id;

                /* Notify the layer above us */
                nvsc_packet->completion.send.send_completion(
                        nvsc_packet->completion.send.send_completion_ctx);

                atomic_dec(&net_device->num_outstanding_sends);
        } else {
                dev_err(&device->device, "Unknown send completion packet type- "
                           "%d received!!", nvsp_packet->hdr.msg_type);
        }

        put_net_device(device);
}

int netvsc_send(struct hv_device *device,
                        struct hv_netvsc_packet *packet)
{
        struct netvsc_device *net_device;
        int ret = 0;

        struct nvsp_message sendMessage;

        net_device = get_outbound_net_device(device);
        if (!net_device) {
                dev_err(&device->device, "net device (%p) shutting down..."
                           "ignoring outbound packets", net_device);
                return -2;
        }

        sendMessage.hdr.msg_type = NVSP_MSG1_TYPE_SEND_RNDIS_PKT;
        if (packet->is_data_pkt) {
                /* 0 is RMC_DATA; */
                sendMessage.msg.v1_msg.send_rndis_pkt.channel_type = 0;
        } else {
                /* 1 is RMC_CONTROL; */
                sendMessage.msg.v1_msg.send_rndis_pkt.channel_type = 1;
        }

        /* Not using send buffer section */
        sendMessage.msg.v1_msg.send_rndis_pkt.send_buf_section_index =
                0xFFFFFFFF;
        sendMessage.msg.v1_msg.send_rndis_pkt.send_buf_section_size = 0;

        if (packet->page_buf_cnt) {
                ret = vmbus_sendpacket_pagebuffer(device->channel,
                                                  packet->page_buf,
                                                  packet->page_buf_cnt,
                                                  &sendMessage,
                                                  sizeof(struct nvsp_message),
                                                  (unsigned long)packet);
        } else {
                ret = vmbus_sendpacket(device->channel, &sendMessage,
                                sizeof(struct nvsp_message),
                                (unsigned long)packet,
                                VM_PKT_DATA_INBAND,
                                VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);

        }

        if (ret != 0)
                dev_err(&device->device, "Unable to send packet %p ret %d",
                           packet, ret);

        atomic_inc(&net_device->num_outstanding_sends);
        put_net_device(device);
        return ret;
}

static void netvsc_send_recv_completion(struct hv_device *device,
                                        u64 transaction_id)
{
        struct nvsp_message recvcompMessage;
        int retries = 0;
        int ret;

        recvcompMessage.hdr.msg_type =
                                NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE;

        /* FIXME: Pass in the status */
        recvcompMessage.msg.v1_msg.send_rndis_pkt_complete.status =
                NVSP_STAT_SUCCESS;

retry_send_cmplt:
        /* Send the completion */
        ret = vmbus_sendpacket(device->channel, &recvcompMessage,
                               sizeof(struct nvsp_message), transaction_id,
                               VM_PKT_COMP, 0);
        if (ret == 0) {
                /* success */
                /* no-op */
        } else if (ret == -1) {
                /* no more room...wait a bit and attempt to retry 3 times */
                retries++;
                dev_err(&device->device, "unable to send receive completion pkt"
                        " (tid %llx)...retrying %d", transaction_id, retries);

                if (retries < 4) {
                        udelay(100);
                        goto retry_send_cmplt;
                } else {
                        dev_err(&device->device, "unable to send receive "
                                "completion pkt (tid %llx)...give up retrying",
                                transaction_id);
                }
        } else {
                dev_err(&device->device, "unable to send receive "
                        "completion pkt - %llx", transaction_id);
        }
}

/* Send a receive completion packet to RNDIS device (ie NetVsp) */
static void netvsc_receive_completion(void *context)
{
        struct hv_netvsc_packet *packet = context;
        struct hv_device *device = (struct hv_device *)packet->device;
        struct netvsc_device *net_device;
        u64 transaction_id = 0;
        bool fsend_receive_comp = false;
        unsigned long flags;

        /*
         * Even though it seems logical to do a GetOutboundNetDevice() here to
         * send out receive completion, we are using GetInboundNetDevice()
         * since we may have disable outbound traffic already.
         */
        net_device = get_inbound_net_device(device);
        if (!net_device) {
                dev_err(&device->device, "unable to get net device..."
                           "device being destroyed?");
                return;
        }

        /* Overloading use of the lock. */
        spin_lock_irqsave(&net_device->recv_pkt_list_lock, flags);

        packet->xfer_page_pkt->count--;

        /*
         * Last one in the line that represent 1 xfer page packet.
         * Return the xfer page packet itself to the freelist
         */
        if (packet->xfer_page_pkt->count == 0) {
                fsend_receive_comp = true;
                transaction_id = packet->completion.recv.recv_completion_tid;
                list_add_tail(&packet->xfer_page_pkt->list_ent,
                              &net_device->recv_pkt_list);

        }

        /* Put the packet back */
        list_add_tail(&packet->list_ent, &net_device->recv_pkt_list);
        spin_unlock_irqrestore(&net_device->recv_pkt_list_lock, flags);

        /* Send a receive completion for the xfer page packet */
        if (fsend_receive_comp)
                netvsc_send_recv_completion(device, transaction_id);

        put_net_device(device);
}

static void netvsc_receive(struct hv_device *device,
                            struct vmpacket_descriptor *packet)
{
        struct netvsc_device *net_device;
        struct vmtransfer_page_packet_header *vmxferpage_packet;
        struct nvsp_message *nvsp_packet;
        struct hv_netvsc_packet *netvsc_packet = NULL;
        unsigned long start;
        unsigned long end, end_virtual;
        /* struct netvsc_driver *netvscDriver; */
        struct xferpage_packet *xferpage_packet = NULL;
        int i, j;
        int count = 0, bytes_remain = 0;
        unsigned long flags;

        LIST_HEAD(listHead);

        net_device = get_inbound_net_device(device);
        if (!net_device) {
                dev_err(&device->device, "unable to get net device..."
                           "device being destroyed?");
                return;
        }

        /*
         * All inbound packets other than send completion should be xfer page
         * packet
         */
        if (packet->type != VM_PKT_DATA_USING_XFER_PAGES) {
                dev_err(&device->device, "Unknown packet type received - %d",
                           packet->type);
                put_net_device(device);
                return;
        }

        nvsp_packet = (struct nvsp_message *)((unsigned long)packet +
                        (packet->offset8 << 3));

        /* Make sure this is a valid nvsp packet */
        if (nvsp_packet->hdr.msg_type !=
            NVSP_MSG1_TYPE_SEND_RNDIS_PKT) {
                dev_err(&device->device, "Unknown nvsp packet type received-"
                        " %d", nvsp_packet->hdr.msg_type);
                put_net_device(device);
                return;
        }

        vmxferpage_packet = (struct vmtransfer_page_packet_header *)packet;

        if (vmxferpage_packet->xfer_pageset_id != NETVSC_RECEIVE_BUFFER_ID) {
                dev_err(&device->device, "Invalid xfer page set id - "
                           "expecting %x got %x", NETVSC_RECEIVE_BUFFER_ID,
                           vmxferpage_packet->xfer_pageset_id);
                put_net_device(device);
                return;
        }

        /*
         * Grab free packets (range count + 1) to represent this xfer
         * page packet. +1 to represent the xfer page packet itself.
         * We grab it here so that we know exactly how many we can
         * fulfil
         */
        spin_lock_irqsave(&net_device->recv_pkt_list_lock, flags);
        while (!list_empty(&net_device->recv_pkt_list)) {
                list_move_tail(net_device->recv_pkt_list.next, &listHead);
                if (++count == vmxferpage_packet->range_cnt + 1)
                        break;
        }
        spin_unlock_irqrestore(&net_device->recv_pkt_list_lock, flags);

        /*
         * We need at least 2 netvsc pkts (1 to represent the xfer
         * page and at least 1 for the range) i.e. we can handled
         * some of the xfer page packet ranges...
         */
        if (count < 2) {
                dev_err(&device->device, "Got only %d netvsc pkt...needed "
                        "%d pkts. Dropping this xfer page packet completely!",
                        count, vmxferpage_packet->range_cnt + 1);

                /* Return it to the freelist */
                spin_lock_irqsave(&net_device->recv_pkt_list_lock, flags);
                for (i = count; i != 0; i--) {
                        list_move_tail(listHead.next,
                                       &net_device->recv_pkt_list);
                }
                spin_unlock_irqrestore(&net_device->recv_pkt_list_lock,
                                       flags);

                netvsc_send_recv_completion(device,
                                            vmxferpage_packet->d.trans_id);

                put_net_device(device);
                return;
        }

        /* Remove the 1st packet to represent the xfer page packet itself */
        xferpage_packet = (struct xferpage_packet *)listHead.next;
        list_del(&xferpage_packet->list_ent);

        /* This is how much we can satisfy */
        xferpage_packet->count = count - 1;

        if (xferpage_packet->count != vmxferpage_packet->range_cnt) {
                dev_err(&device->device, "Needed %d netvsc pkts to satisy "
                        "this xfer page...got %d",
                        vmxferpage_packet->range_cnt, xferpage_packet->count);
        }

        /* Each range represents 1 RNDIS pkt that contains 1 ethernet frame */
        for (i = 0; i < (count - 1); i++) {
                netvsc_packet = (struct hv_netvsc_packet *)listHead.next;
                list_del(&netvsc_packet->list_ent);

                /* Initialize the netvsc packet */
                netvsc_packet->xfer_page_pkt = xferpage_packet;
                netvsc_packet->completion.recv.recv_completion =
                                        netvsc_receive_completion;
                netvsc_packet->completion.recv.recv_completion_ctx =
                                        netvsc_packet;
                netvsc_packet->device = device;
                /* Save this so that we can send it back */
                netvsc_packet->completion.recv.recv_completion_tid =
                                        vmxferpage_packet->d.trans_id;

                netvsc_packet->total_data_buflen =
                                        vmxferpage_packet->ranges[i].byte_count;
                netvsc_packet->page_buf_cnt = 1;

                netvsc_packet->page_buf[0].len =
                                        vmxferpage_packet->ranges[i].byte_count;

                start = virt_to_phys((void *)((unsigned long)net_device->
                recv_buf + vmxferpage_packet->ranges[i].byte_offset));

                netvsc_packet->page_buf[0].pfn = start >> PAGE_SHIFT;
                end_virtual = (unsigned long)net_device->recv_buf
                    + vmxferpage_packet->ranges[i].byte_offset
                    + vmxferpage_packet->ranges[i].byte_count - 1;
                end = virt_to_phys((void *)end_virtual);

                /* Calculate the page relative offset */
                netvsc_packet->page_buf[0].offset =
                        vmxferpage_packet->ranges[i].byte_offset &
                        (PAGE_SIZE - 1);
                if ((end >> PAGE_SHIFT) != (start >> PAGE_SHIFT)) {
                        /* Handle frame across multiple pages: */
                        netvsc_packet->page_buf[0].len =
                                (netvsc_packet->page_buf[0].pfn <<
                                 PAGE_SHIFT)
                                + PAGE_SIZE - start;
                        bytes_remain = netvsc_packet->total_data_buflen -
                                        netvsc_packet->page_buf[0].len;
                        for (j = 1; j < NETVSC_PACKET_MAXPAGE; j++) {
                                netvsc_packet->page_buf[j].offset = 0;
                                if (bytes_remain <= PAGE_SIZE) {
                                        netvsc_packet->page_buf[j].len =
                                                bytes_remain;
                                        bytes_remain = 0;
                                } else {
                                        netvsc_packet->page_buf[j].len =
                                                PAGE_SIZE;
                                        bytes_remain -= PAGE_SIZE;
                                }
                                netvsc_packet->page_buf[j].pfn =
                                    virt_to_phys((void *)(end_virtual -
                                                bytes_remain)) >> PAGE_SHIFT;
                                netvsc_packet->page_buf_cnt++;
                                if (bytes_remain == 0)
                                        break;
                        }
                }

                /* Pass it to the upper layer */
                rndis_filter_receive(device, netvsc_packet);

                netvsc_receive_completion(netvsc_packet->
                                completion.recv.recv_completion_ctx);
        }

        put_net_device(device);
}

static void netvsc_channel_cb(void *context)
{
        int ret;
        struct hv_device *device = context;
        struct netvsc_device *net_device;
        u32 bytes_recvd;
        u64 request_id;
        unsigned char *packet;
        struct vmpacket_descriptor *desc;
        unsigned char *buffer;
        int bufferlen = NETVSC_PACKET_SIZE;

        packet = kzalloc(NETVSC_PACKET_SIZE * sizeof(unsigned char),
                         GFP_ATOMIC);
        if (!packet)
                return;
        buffer = packet;

        net_device = get_inbound_net_device(device);
        if (!net_device) {
                dev_err(&device->device, "net device (%p) shutting down..."
                           "ignoring inbound packets", net_device);
                goto out;
        }

        do {
                ret = vmbus_recvpacket_raw(device->channel, buffer, bufferlen,
                                           &bytes_recvd, &request_id);
                if (ret == 0) {
                        if (bytes_recvd > 0) {
                                desc = (struct vmpacket_descriptor *)buffer;
                                switch (desc->type) {
                                case VM_PKT_COMP:
                                        netvsc_send_completion(device, desc);
                                        break;

                                case VM_PKT_DATA_USING_XFER_PAGES:
                                        netvsc_receive(device, desc);
                                        break;

                                default:
                                        dev_err(&device->device,
                                                   "unhandled packet type %d, "
                                                   "tid %llx len %d\n",
                                                   desc->type, request_id,
                                                   bytes_recvd);
                                        break;
                                }

                                /* reset */
                                if (bufferlen > NETVSC_PACKET_SIZE) {
                                        kfree(buffer);
                                        buffer = packet;
                                        bufferlen = NETVSC_PACKET_SIZE;
                                }
                        } else {
                                /* reset */
                                if (bufferlen > NETVSC_PACKET_SIZE) {
                                        kfree(buffer);
                                        buffer = packet;
                                        bufferlen = NETVSC_PACKET_SIZE;
                                }

                                break;
                        }
                } else if (ret == -2) {
                        /* Handle large packet */
                        buffer = kmalloc(bytes_recvd, GFP_ATOMIC);
                        if (buffer == NULL) {
                                /* Try again next time around */
                                dev_err(&device->device,
                                           "unable to allocate buffer of size "
                                           "(%d)!!", bytes_recvd);
                                break;
                        }

                        bufferlen = bytes_recvd;
                }
        } while (1);

        put_net_device(device);
out:
        kfree(buffer);
        return;
}

/*
 * netvsc_device_add - Callback when the device belonging to this
 * driver is added
 */
int netvsc_device_add(struct hv_device *device, void *additional_info)
{
        int ret = 0;
        int i;
        int ring_size =
        ((struct netvsc_device_info *)additional_info)->ring_size;
        struct netvsc_device *net_device;
        struct hv_netvsc_packet *packet, *pos;

        net_device = alloc_net_device(device);
        if (!net_device) {
                ret = -1;
                goto cleanup;
        }

        /* Initialize the NetVSC channel extension */
        net_device->recv_buf_size = NETVSC_RECEIVE_BUFFER_SIZE;
        spin_lock_init(&net_device->recv_pkt_list_lock);

        INIT_LIST_HEAD(&net_device->recv_pkt_list);

        for (i = 0; i < NETVSC_RECEIVE_PACKETLIST_COUNT; i++) {
                packet = kzalloc(sizeof(struct hv_netvsc_packet) +
                                 (NETVSC_RECEIVE_SG_COUNT *
                                  sizeof(struct hv_page_buffer)), GFP_KERNEL);
                if (!packet)
                        break;

                list_add_tail(&packet->list_ent,
                              &net_device->recv_pkt_list);
        }
        init_completion(&net_device->channel_init_wait);

        /* Open the channel */
        ret = vmbus_open(device->channel, ring_size * PAGE_SIZE,
                         ring_size * PAGE_SIZE, NULL, 0,
                         netvsc_channel_cb, device);

        if (ret != 0) {
                dev_err(&device->device, "unable to open channel: %d", ret);
                ret = -1;
                goto cleanup;
        }

        /* Channel is opened */
        pr_info("hv_netvsc channel opened successfully");

        /* Connect with the NetVsp */
        ret = netvsc_connect_vsp(device);
        if (ret != 0) {
                dev_err(&device->device,
                        "unable to connect to NetVSP - %d", ret);
                ret = -1;
                goto close;
        }

        return ret;

close:
        /* Now, we can close the channel safely */
        vmbus_close(device->channel);

cleanup:

        if (net_device) {
                list_for_each_entry_safe(packet, pos,
                                         &net_device->recv_pkt_list,
                                         list_ent) {
                        list_del(&packet->list_ent);
                        kfree(packet);
                }

                release_outbound_net_device(device);
                release_inbound_net_device(device);

                free_net_device(net_device);
        }

        return ret;
}

/*
 * netvsc_initialize - Main entry point
 */
int netvsc_initialize(struct hv_driver *drv)
{

        drv->name = driver_name;
        memcpy(&drv->dev_type, &netvsc_device_type, sizeof(struct hv_guid));

        return 0;
}