/*
 * Copyright (c) 2012, Microsoft Corporation.
 *
 * Author:
 *   Haiyang Zhang <haiyangz@microsoft.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 * NON INFRINGEMENT.  See the GNU General Public License for more
 * details.
 */

/*
 * Hyper-V Synthetic Video Frame Buffer Driver
 *
 * This is the driver for the Hyper-V Synthetic Video, which supports
 * screen resolution up to Full HD 1920x1080 with 32 bit color on Windows
 * Server 2012, and 1600x1200 with 16 bit color on Windows Server 2008 R2
 * or earlier.
 *
 * It also solves the double mouse cursor issue of the emulated video mode.
 *
 * The default screen resolution is 1152x864, which may be changed by a
 * kernel parameter:
 *     video=hyperv_fb:<width>x<height>
 *     For example: video=hyperv_fb:1280x1024
 *
 * Portrait orientation is also supported:
 *     For example: video=hyperv_fb:864x1152
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/fb.h>
#include <linux/pci.h>
#include <linux/efi.h>

#include <linux/hyperv.h>


/* Hyper-V Synthetic Video Protocol definitions and structures */
#define MAX_VMBUS_PKT_SIZE 0x4000

#define SYNTHVID_VERSION(major, minor) ((minor) << 16 | (major))
#define SYNTHVID_VERSION_WIN7 SYNTHVID_VERSION(3, 0)
#define SYNTHVID_VERSION_WIN8 SYNTHVID_VERSION(3, 2)

#define SYNTHVID_DEPTH_WIN7 16
#define SYNTHVID_DEPTH_WIN8 32

#define SYNTHVID_FB_SIZE_WIN7 (4 * 1024 * 1024)
#define SYNTHVID_WIDTH_MAX_WIN7 1600
#define SYNTHVID_HEIGHT_MAX_WIN7 1200

#define SYNTHVID_FB_SIZE_WIN8 (8 * 1024 * 1024)

#define PCI_VENDOR_ID_MICROSOFT 0x1414
#define PCI_DEVICE_ID_HYPERV_VIDEO 0x5353


enum pipe_msg_type {
        PIPE_MSG_INVALID,
        PIPE_MSG_DATA,
        PIPE_MSG_MAX
};

struct pipe_msg_hdr {
        u32 type;
        u32 size; /* size of message after this field */
} __packed;


enum synthvid_msg_type {
        SYNTHVID_ERROR                  = 0,
        SYNTHVID_VERSION_REQUEST        = 1,
        SYNTHVID_VERSION_RESPONSE       = 2,
        SYNTHVID_VRAM_LOCATION          = 3,
        SYNTHVID_VRAM_LOCATION_ACK      = 4,
        SYNTHVID_SITUATION_UPDATE       = 5,
        SYNTHVID_SITUATION_UPDATE_ACK   = 6,
        SYNTHVID_POINTER_POSITION       = 7,
        SYNTHVID_POINTER_SHAPE          = 8,
        SYNTHVID_FEATURE_CHANGE         = 9,
        SYNTHVID_DIRT                   = 10,

        SYNTHVID_MAX                    = 11
};

struct synthvid_msg_hdr {
        u32 type;
        u32 size;  /* size of this header + payload after this field*/
} __packed;


struct synthvid_version_req {
        u32 version;
} __packed;

struct synthvid_version_resp {
        u32 version;
        u8 is_accepted;
        u8 max_video_outputs;
} __packed;

struct synthvid_vram_location {
        u64 user_ctx;
        u8 is_vram_gpa_specified;
        u64 vram_gpa;
} __packed;

struct synthvid_vram_location_ack {
        u64 user_ctx;
} __packed;

struct video_output_situation {
        u8 active;
        u32 vram_offset;
        u8 depth_bits;
        u32 width_pixels;
        u32 height_pixels;
        u32 pitch_bytes;
} __packed;

struct synthvid_situation_update {
        u64 user_ctx;
        u8 video_output_count;
        struct video_output_situation video_output[1];
} __packed;

struct synthvid_situation_update_ack {
        u64 user_ctx;
} __packed;

struct synthvid_pointer_position {
        u8 is_visible;
        u8 video_output;
        s32 image_x;
        s32 image_y;
} __packed;


#define CURSOR_MAX_X 96
#define CURSOR_MAX_Y 96
#define CURSOR_ARGB_PIXEL_SIZE 4
#define CURSOR_MAX_SIZE (CURSOR_MAX_X * CURSOR_MAX_Y * CURSOR_ARGB_PIXEL_SIZE)
#define CURSOR_COMPLETE (-1)

struct synthvid_pointer_shape {
        u8 part_idx;
        u8 is_argb;
        u32 width; /* CURSOR_MAX_X at most */
        u32 height; /* CURSOR_MAX_Y at most */
        u32 hot_x; /* hotspot relative to upper-left of pointer image */
        u32 hot_y;
        u8 data[4];
} __packed;

struct synthvid_feature_change {
        u8 is_dirt_needed;
        u8 is_ptr_pos_needed;
        u8 is_ptr_shape_needed;
        u8 is_situ_needed;
} __packed;

struct rect {
        s32 x1, y1; /* top left corner */
        s32 x2, y2; /* bottom right corner, exclusive */
} __packed;

struct synthvid_dirt {
        u8 video_output;
        u8 dirt_count;
        struct rect rect[1];
} __packed;

struct synthvid_msg {
        struct pipe_msg_hdr pipe_hdr;
        struct synthvid_msg_hdr vid_hdr;
        union {
                struct synthvid_version_req ver_req;
                struct synthvid_version_resp ver_resp;
                struct synthvid_vram_location vram;
                struct synthvid_vram_location_ack vram_ack;
                struct synthvid_situation_update situ;
                struct synthvid_situation_update_ack situ_ack;
                struct synthvid_pointer_position ptr_pos;
                struct synthvid_pointer_shape ptr_shape;
                struct synthvid_feature_change feature_chg;
                struct synthvid_dirt dirt;
        };
} __packed;



/* FB driver definitions and structures */
#define HVFB_WIDTH 1152 /* default screen width */
#define HVFB_HEIGHT 864 /* default screen height */
#define HVFB_WIDTH_MIN 640
#define HVFB_HEIGHT_MIN 480

#define RING_BUFSIZE (256 * 1024)
#define VSP_TIMEOUT (10 * HZ)
#define HVFB_UPDATE_DELAY (HZ / 20)

struct hvfb_par {
        struct fb_info *info;
        struct resource mem;
        bool fb_ready; /* fb device is ready */
        struct completion wait;
        u32 synthvid_version;

        struct delayed_work dwork;
        bool update;

        u32 pseudo_palette[16];
        u8 init_buf[MAX_VMBUS_PKT_SIZE];
        u8 recv_buf[MAX_VMBUS_PKT_SIZE];

        /* If true, the VSC notifies the VSP on every framebuffer change */
        bool synchronous_fb;

        struct notifier_block hvfb_panic_nb;
};

static uint screen_width = HVFB_WIDTH;
static uint screen_height = HVFB_HEIGHT;
static uint screen_depth;
static uint screen_fb_size;

/* Send message to Hyper-V host */
static inline int synthvid_send(struct hv_device *hdev,
                                struct synthvid_msg *msg)
{
        static atomic64_t request_id = ATOMIC64_INIT(0);
        int ret;

        msg->pipe_hdr.type = PIPE_MSG_DATA;
        msg->pipe_hdr.size = msg->vid_hdr.size;

        ret = vmbus_sendpacket(hdev->channel, msg,
                               msg->vid_hdr.size + sizeof(struct pipe_msg_hdr),
                               atomic64_inc_return(&request_id),
                               VM_PKT_DATA_INBAND, 0);

        if (ret)
                pr_err("Unable to send packet via vmbus\n");

        return ret;
}


/* Send screen resolution info to host */
static int synthvid_send_situ(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct synthvid_msg msg;

        if (!info)
                return -ENODEV;

        memset(&msg, 0, sizeof(struct synthvid_msg));

        msg.vid_hdr.type = SYNTHVID_SITUATION_UPDATE;
        msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_situation_update);
        msg.situ.user_ctx = 0;
        msg.situ.video_output_count = 1;
        msg.situ.video_output[0].active = 1;
        msg.situ.video_output[0].vram_offset = 0;
        msg.situ.video_output[0].depth_bits = info->var.bits_per_pixel;
        msg.situ.video_output[0].width_pixels = info->var.xres;
        msg.situ.video_output[0].height_pixels = info->var.yres;
        msg.situ.video_output[0].pitch_bytes = info->fix.line_length;

        synthvid_send(hdev, &msg);

        return 0;
}

/* Send mouse pointer info to host */
static int synthvid_send_ptr(struct hv_device *hdev)
{
        struct synthvid_msg msg;

        memset(&msg, 0, sizeof(struct synthvid_msg));
        msg.vid_hdr.type = SYNTHVID_POINTER_POSITION;
        msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_pointer_position);
        msg.ptr_pos.is_visible = 1;
        msg.ptr_pos.video_output = 0;
        msg.ptr_pos.image_x = 0;
        msg.ptr_pos.image_y = 0;
        synthvid_send(hdev, &msg);

        memset(&msg, 0, sizeof(struct synthvid_msg));
        msg.vid_hdr.type = SYNTHVID_POINTER_SHAPE;
        msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_pointer_shape);
        msg.ptr_shape.part_idx = CURSOR_COMPLETE;
        msg.ptr_shape.is_argb = 1;
        msg.ptr_shape.width = 1;
        msg.ptr_shape.height = 1;
        msg.ptr_shape.hot_x = 0;
        msg.ptr_shape.hot_y = 0;
        msg.ptr_shape.data[0] = 0;
        msg.ptr_shape.data[1] = 1;
        msg.ptr_shape.data[2] = 1;
        msg.ptr_shape.data[3] = 1;
        synthvid_send(hdev, &msg);

        return 0;
}

/* Send updated screen area (dirty rectangle) location to host */
static int synthvid_update(struct fb_info *info)
{
        struct hv_device *hdev = device_to_hv_device(info->device);
        struct synthvid_msg msg;

        memset(&msg, 0, sizeof(struct synthvid_msg));

        msg.vid_hdr.type = SYNTHVID_DIRT;
        msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_dirt);
        msg.dirt.video_output = 0;
        msg.dirt.dirt_count = 1;
        msg.dirt.rect[0].x1 = 0;
        msg.dirt.rect[0].y1 = 0;
        msg.dirt.rect[0].x2 = info->var.xres;
        msg.dirt.rect[0].y2 = info->var.yres;

        synthvid_send(hdev, &msg);

        return 0;
}


/*
 * Actions on received messages from host:
 * Complete the wait event.
 * Or, reply with screen and cursor info.
 */
static void synthvid_recv_sub(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par;
        struct synthvid_msg *msg;

        if (!info)
                return;

        par = info->par;
        msg = (struct synthvid_msg *)par->recv_buf;

        /* Complete the wait event */
        if (msg->vid_hdr.type == SYNTHVID_VERSION_RESPONSE ||
            msg->vid_hdr.type == SYNTHVID_VRAM_LOCATION_ACK) {
                memcpy(par->init_buf, msg, MAX_VMBUS_PKT_SIZE);
                complete(&par->wait);
                return;
        }

        /* Reply with screen and cursor info */
        if (msg->vid_hdr.type == SYNTHVID_FEATURE_CHANGE) {
                if (par->fb_ready) {
                        synthvid_send_ptr(hdev);
                        synthvid_send_situ(hdev);
                }

                par->update = msg->feature_chg.is_dirt_needed;
                if (par->update)
                        schedule_delayed_work(&par->dwork, HVFB_UPDATE_DELAY);
        }
}

/* Receive callback for messages from the host */
static void synthvid_receive(void *ctx)
{
        struct hv_device *hdev = ctx;
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par;
        struct synthvid_msg *recv_buf;
        u32 bytes_recvd;
        u64 req_id;
        int ret;

        if (!info)
                return;

        par = info->par;
        recv_buf = (struct synthvid_msg *)par->recv_buf;

        do {
                ret = vmbus_recvpacket(hdev->channel, recv_buf,
                                       MAX_VMBUS_PKT_SIZE,
                                       &bytes_recvd, &req_id);
                if (bytes_recvd > 0 &&
                    recv_buf->pipe_hdr.type == PIPE_MSG_DATA)
                        synthvid_recv_sub(hdev);
        } while (bytes_recvd > 0 && ret == 0);
}

/* Check synthetic video protocol version with the host */
static int synthvid_negotiate_ver(struct hv_device *hdev, u32 ver)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par = info->par;
        struct synthvid_msg *msg = (struct synthvid_msg *)par->init_buf;
        int ret = 0;
        unsigned long t;

        memset(msg, 0, sizeof(struct synthvid_msg));
        msg->vid_hdr.type = SYNTHVID_VERSION_REQUEST;
        msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_version_req);
        msg->ver_req.version = ver;
        synthvid_send(hdev, msg);

        t = wait_for_completion_timeout(&par->wait, VSP_TIMEOUT);
        if (!t) {
                pr_err("Time out on waiting version response\n");
                ret = -ETIMEDOUT;
                goto out;
        }
        if (!msg->ver_resp.is_accepted) {
                ret = -ENODEV;
                goto out;
        }

        par->synthvid_version = ver;

out:
        return ret;
}

/* Connect to VSP (Virtual Service Provider) on host */
static int synthvid_connect_vsp(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par = info->par;
        int ret;

        ret = vmbus_open(hdev->channel, RING_BUFSIZE, RING_BUFSIZE,
                         NULL, 0, synthvid_receive, hdev);
        if (ret) {
                pr_err("Unable to open vmbus channel\n");
                return ret;
        }

        /* Negotiate the protocol version with host */
        if (vmbus_proto_version == VERSION_WS2008 ||
            vmbus_proto_version == VERSION_WIN7)
                ret = synthvid_negotiate_ver(hdev, SYNTHVID_VERSION_WIN7);
        else
                ret = synthvid_negotiate_ver(hdev, SYNTHVID_VERSION_WIN8);

        if (ret) {
                pr_err("Synthetic video device version not accepted\n");
                goto error;
        }

        if (par->synthvid_version == SYNTHVID_VERSION_WIN7)
                screen_depth = SYNTHVID_DEPTH_WIN7;
        else
                screen_depth = SYNTHVID_DEPTH_WIN8;

        screen_fb_size = hdev->channel->offermsg.offer.
                                mmio_megabytes * 1024 * 1024;

        return 0;

error:
        vmbus_close(hdev->channel);
        return ret;
}

/* Send VRAM and Situation messages to the host */
static int synthvid_send_config(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par = info->par;
        struct synthvid_msg *msg = (struct synthvid_msg *)par->init_buf;
        int ret = 0;
        unsigned long t;

        /* Send VRAM location */
        memset(msg, 0, sizeof(struct synthvid_msg));
        msg->vid_hdr.type = SYNTHVID_VRAM_LOCATION;
        msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_vram_location);
        msg->vram.user_ctx = msg->vram.vram_gpa = info->fix.smem_start;
        msg->vram.is_vram_gpa_specified = 1;
        synthvid_send(hdev, msg);

        t = wait_for_completion_timeout(&par->wait, VSP_TIMEOUT);
        if (!t) {
                pr_err("Time out on waiting vram location ack\n");
                ret = -ETIMEDOUT;
                goto out;
        }
        if (msg->vram_ack.user_ctx != info->fix.smem_start) {
                pr_err("Unable to set VRAM location\n");
                ret = -ENODEV;
                goto out;
        }

        /* Send pointer and situation update */
        synthvid_send_ptr(hdev);
        synthvid_send_situ(hdev);

out:
        return ret;
}


/*
 * Delayed work callback:
 * It is called at HVFB_UPDATE_DELAY or longer time interval to process
 * screen updates. It is re-scheduled if further update is necessary.
 */
static void hvfb_update_work(struct work_struct *w)
{
        struct hvfb_par *par = container_of(w, struct hvfb_par, dwork.work);
        struct fb_info *info = par->info;

        if (par->fb_ready)
                synthvid_update(info);

        if (par->update)
                schedule_delayed_work(&par->dwork, HVFB_UPDATE_DELAY);
}

static int hvfb_on_panic(struct notifier_block *nb,
                         unsigned long e, void *p)
{
        struct hvfb_par *par;
        struct fb_info *info;

        par = container_of(nb, struct hvfb_par, hvfb_panic_nb);
        par->synchronous_fb = true;
        info = par->info;
        synthvid_update(info);

        return NOTIFY_DONE;
}

/* Framebuffer operation handlers */

static int hvfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
{
        if (var->xres < HVFB_WIDTH_MIN || var->yres < HVFB_HEIGHT_MIN ||
            var->xres > screen_width || var->yres >  screen_height ||
            var->bits_per_pixel != screen_depth)
                return -EINVAL;

        var->xres_virtual = var->xres;
        var->yres_virtual = var->yres;

        return 0;
}

static int hvfb_set_par(struct fb_info *info)
{
        struct hv_device *hdev = device_to_hv_device(info->device);

        return synthvid_send_situ(hdev);
}


static inline u32 chan_to_field(u32 chan, struct fb_bitfield *bf)
{
        return ((chan & 0xffff) >> (16 - bf->length)) << bf->offset;
}

static int hvfb_setcolreg(unsigned regno, unsigned red, unsigned green,
                          unsigned blue, unsigned transp, struct fb_info *info)
{
        u32 *pal = info->pseudo_palette;

        if (regno > 15)
                return -EINVAL;

        pal[regno] = chan_to_field(red, &info->var.red)
                | chan_to_field(green, &info->var.green)
                | chan_to_field(blue, &info->var.blue)
                | chan_to_field(transp, &info->var.transp);

        return 0;
}

static int hvfb_blank(int blank, struct fb_info *info)
{
        return 1;       /* get fb_blank to set the colormap to all black */
}

static void hvfb_cfb_fillrect(struct fb_info *p,
                              const struct fb_fillrect *rect)
{
        struct hvfb_par *par = p->par;

        cfb_fillrect(p, rect);
        if (par->synchronous_fb)
                synthvid_update(p);
}

static void hvfb_cfb_copyarea(struct fb_info *p,
                              const struct fb_copyarea *area)
{
        struct hvfb_par *par = p->par;

        cfb_copyarea(p, area);
        if (par->synchronous_fb)
                synthvid_update(p);
}

static void hvfb_cfb_imageblit(struct fb_info *p,
                               const struct fb_image *image)
{
        struct hvfb_par *par = p->par;

        cfb_imageblit(p, image);
        if (par->synchronous_fb)
                synthvid_update(p);
}

static struct fb_ops hvfb_ops = {
        .owner = THIS_MODULE,
        .fb_check_var = hvfb_check_var,
        .fb_set_par = hvfb_set_par,
        .fb_setcolreg = hvfb_setcolreg,
        .fb_fillrect = hvfb_cfb_fillrect,
        .fb_copyarea = hvfb_cfb_copyarea,
        .fb_imageblit = hvfb_cfb_imageblit,
        .fb_blank = hvfb_blank,
};


/* Get options from kernel paramenter "video=" */
static void hvfb_get_option(struct fb_info *info)
{
        struct hvfb_par *par = info->par;
        char *opt = NULL, *p;
        uint x = 0, y = 0;

        if (fb_get_options(KBUILD_MODNAME, &opt) || !opt || !*opt)
                return;

        p = strsep(&opt, "x");
        if (!*p || kstrtouint(p, 0, &x) ||
            !opt || !*opt || kstrtouint(opt, 0, &y)) {
                pr_err("Screen option is invalid: skipped\n");
                return;
        }

        if (x < HVFB_WIDTH_MIN || y < HVFB_HEIGHT_MIN ||
            (par->synthvid_version == SYNTHVID_VERSION_WIN8 &&
             x * y * screen_depth / 8 > SYNTHVID_FB_SIZE_WIN8) ||
            (par->synthvid_version == SYNTHVID_VERSION_WIN7 &&
             (x > SYNTHVID_WIDTH_MAX_WIN7 || y > SYNTHVID_HEIGHT_MAX_WIN7))) {
                pr_err("Screen resolution option is out of range: skipped\n");
                return;
        }

        screen_width = x;
        screen_height = y;
        return;
}


/* Get framebuffer memory from Hyper-V video pci space */
static int hvfb_getmem(struct fb_info *info)
{
        struct hvfb_par *par = info->par;
        struct pci_dev *pdev  = NULL;
        void __iomem *fb_virt;
        int gen2vm = efi_enabled(EFI_BOOT);
        int ret;

        par->mem.name = KBUILD_MODNAME;
        par->mem.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
        if (gen2vm) {
                ret = allocate_resource(&hyperv_mmio, &par->mem,
                                        screen_fb_size,
                                        0, -1,
                                        screen_fb_size,
                                        NULL, NULL);
                if (ret != 0) {
                        pr_err("Unable to allocate framebuffer memory\n");
                        return -ENODEV;
                }
        } else {
                pdev = pci_get_device(PCI_VENDOR_ID_MICROSOFT,
                              PCI_DEVICE_ID_HYPERV_VIDEO, NULL);
                if (!pdev) {
                        pr_err("Unable to find PCI Hyper-V video\n");
                        return -ENODEV;
                }

                if (!(pci_resource_flags(pdev, 0) & IORESOURCE_MEM) ||
                    pci_resource_len(pdev, 0) < screen_fb_size)
                        goto err1;

                par->mem.end = pci_resource_end(pdev, 0);
                par->mem.start = par->mem.end - screen_fb_size + 1;
                ret = request_resource(&pdev->resource[0], &par->mem);
                if (ret != 0) {
                        pr_err("Unable to request framebuffer memory\n");
                        goto err1;
                }
        }

        fb_virt = ioremap(par->mem.start, screen_fb_size);
        if (!fb_virt)
                goto err2;

        info->apertures = alloc_apertures(1);
        if (!info->apertures)
                goto err3;

        if (gen2vm) {
                info->apertures->ranges[0].base = screen_info.lfb_base;
                info->apertures->ranges[0].size = screen_info.lfb_size;
                remove_conflicting_framebuffers(info->apertures,
                                                KBUILD_MODNAME, false);
        } else {
                info->apertures->ranges[0].base = pci_resource_start(pdev, 0);
                info->apertures->ranges[0].size = pci_resource_len(pdev, 0);
        }

        info->fix.smem_start = par->mem.start;
        info->fix.smem_len = screen_fb_size;
        info->screen_base = fb_virt;
        info->screen_size = screen_fb_size;

        if (!gen2vm)
                pci_dev_put(pdev);

        return 0;

err3:
        iounmap(fb_virt);
err2:
        release_resource(&par->mem);
err1:
        if (!gen2vm)
                pci_dev_put(pdev);

        return -ENOMEM;
}

/* Release the framebuffer */
static void hvfb_putmem(struct fb_info *info)
{
        struct hvfb_par *par = info->par;

        iounmap(info->screen_base);
        release_resource(&par->mem);
}


static int hvfb_probe(struct hv_device *hdev,
                      const struct hv_vmbus_device_id *dev_id)
{
        struct fb_info *info;
        struct hvfb_par *par;
        int ret;

        info = framebuffer_alloc(sizeof(struct hvfb_par), &hdev->device);
        if (!info) {
                pr_err("No memory for framebuffer info\n");
                return -ENOMEM;
        }

        par = info->par;
        par->info = info;
        par->fb_ready = false;
        init_completion(&par->wait);
        INIT_DELAYED_WORK(&par->dwork, hvfb_update_work);

        /* Connect to VSP */
        hv_set_drvdata(hdev, info);
        ret = synthvid_connect_vsp(hdev);
        if (ret) {
                pr_err("Unable to connect to VSP\n");
                goto error1;
        }

        ret = hvfb_getmem(info);
        if (ret) {
                pr_err("No memory for framebuffer\n");
                goto error2;
        }

        hvfb_get_option(info);
        pr_info("Screen resolution: %dx%d, Color depth: %d\n",
                screen_width, screen_height, screen_depth);


        /* Set up fb_info */
        info->flags = FBINFO_DEFAULT;

        info->var.xres_virtual = info->var.xres = screen_width;
        info->var.yres_virtual = info->var.yres = screen_height;
        info->var.bits_per_pixel = screen_depth;

        if (info->var.bits_per_pixel == 16) {
                info->var.red = (struct fb_bitfield){11, 5, 0};
                info->var.green = (struct fb_bitfield){5, 6, 0};
                info->var.blue = (struct fb_bitfield){0, 5, 0};
                info->var.transp = (struct fb_bitfield){0, 0, 0};
        } else {
                info->var.red = (struct fb_bitfield){16, 8, 0};
                info->var.green = (struct fb_bitfield){8, 8, 0};
                info->var.blue = (struct fb_bitfield){0, 8, 0};
                info->var.transp = (struct fb_bitfield){24, 8, 0};
        }

        info->var.activate = FB_ACTIVATE_NOW;
        info->var.height = -1;
        info->var.width = -1;
        info->var.vmode = FB_VMODE_NONINTERLACED;

        strcpy(info->fix.id, KBUILD_MODNAME);
        info->fix.type = FB_TYPE_PACKED_PIXELS;
        info->fix.visual = FB_VISUAL_TRUECOLOR;
        info->fix.line_length = screen_width * screen_depth / 8;
        info->fix.accel = FB_ACCEL_NONE;

        info->fbops = &hvfb_ops;
        info->pseudo_palette = par->pseudo_palette;

        /* Send config to host */
        ret = synthvid_send_config(hdev);
        if (ret)
                goto error;

        ret = register_framebuffer(info);
        if (ret) {
                pr_err("Unable to register framebuffer\n");
                goto error;
        }

        par->fb_ready = true;

        par->synchronous_fb = false;
        par->hvfb_panic_nb.notifier_call = hvfb_on_panic;
        atomic_notifier_chain_register(&panic_notifier_list,
                                       &par->hvfb_panic_nb);

        return 0;

error:
        hvfb_putmem(info);
error2:
        vmbus_close(hdev->channel);
error1:
        cancel_delayed_work_sync(&par->dwork);
        hv_set_drvdata(hdev, NULL);
        framebuffer_release(info);
        return ret;
}


static int hvfb_remove(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par = info->par;

        atomic_notifier_chain_unregister(&panic_notifier_list,
                                         &par->hvfb_panic_nb);

        par->update = false;
        par->fb_ready = false;

        unregister_framebuffer(info);
        cancel_delayed_work_sync(&par->dwork);

        vmbus_close(hdev->channel);
        hv_set_drvdata(hdev, NULL);

        hvfb_putmem(info);
        framebuffer_release(info);

        return 0;
}


static const struct pci_device_id pci_stub_id_table[] = {
        {
                .vendor      = PCI_VENDOR_ID_MICROSOFT,
                .device      = PCI_DEVICE_ID_HYPERV_VIDEO,
        },
        { /* end of list */ }
};

static const struct hv_vmbus_device_id id_table[] = {
        /* Synthetic Video Device GUID */
        {HV_SYNTHVID_GUID},
        {}
};

MODULE_DEVICE_TABLE(pci, pci_stub_id_table);
MODULE_DEVICE_TABLE(vmbus, id_table);

static struct hv_driver hvfb_drv = {
        .name = KBUILD_MODNAME,
        .id_table = id_table,
        .probe = hvfb_probe,
        .remove = hvfb_remove,
};

static int hvfb_pci_stub_probe(struct pci_dev *pdev,
                               const struct pci_device_id *ent)
{
        return 0;
}

static void hvfb_pci_stub_remove(struct pci_dev *pdev)
{
}

static struct pci_driver hvfb_pci_stub_driver = {
        .name =         KBUILD_MODNAME,
        .id_table =     pci_stub_id_table,
        .probe =        hvfb_pci_stub_probe,
        .remove =       hvfb_pci_stub_remove,
};

static int __init hvfb_drv_init(void)
{
        int ret;

        ret = vmbus_driver_register(&hvfb_drv);
        if (ret != 0)
                return ret;

        ret = pci_register_driver(&hvfb_pci_stub_driver);
        if (ret != 0) {
                vmbus_driver_unregister(&hvfb_drv);
                return ret;
        }

        return 0;
}

static void __exit hvfb_drv_exit(void)
{
        pci_unregister_driver(&hvfb_pci_stub_driver);
        vmbus_driver_unregister(&hvfb_drv);
}

module_init(hvfb_drv_init);
module_exit(hvfb_drv_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Microsoft Hyper-V Synthetic Video Frame Buffer Driver");