/*
   * Xen para-virtual frame buffer device
   *
   * Copyright (C) 2005-2006 Anthony Liguori <aliguori@us.ibm.com>
   * Copyright (C) 2006-2008 Red Hat, Inc., Markus Armbruster <armbru@redhat.com>
   *
   *  Based on linux/drivers/video/q40fb.c
   *
   *  This file is subject to the terms and conditions of the GNU General Public
   *  License. See the file COPYING in the main directory of this archive for
   *  more details.
   */
  
  /*
   * TODO:
   *
   * Switch to grant tables when they become capable of dealing with the
   * frame buffer.
   */
  
  #include <linux/console.h>
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/fb.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/vmalloc.h>
  #include <linux/mm.h>
  
  #include <asm/xen/hypervisor.h>
  
  #include <xen/xen.h>
  #include <xen/events.h>
  #include <xen/page.h>
  #include <xen/interface/io/fbif.h>
  #include <xen/interface/io/protocols.h>
  #include <xen/xenbus.h>
  #include <xen/platform_pci.h>
  
  struct xenfb_info {
  	unsigned char		*fb;
  	struct fb_info		*fb_info;
  	int			x1, y1, x2, y2;	/* dirty rectangle,
  						   protected by dirty_lock */
  	spinlock_t		dirty_lock;
  	int			nr_pages;
  	int			irq;
  	struct xenfb_page	*page;
  	unsigned long 		*mfns;
  	int			update_wanted; /* XENFB_TYPE_UPDATE wanted */
  	int			feature_resize; /* XENFB_TYPE_RESIZE ok */
  	struct xenfb_resize	resize;		/* protected by resize_lock */
  	int			resize_dpy;	/* ditto */
  	spinlock_t		resize_lock;
  
  	struct xenbus_device	*xbdev;
  };
  
  #define XENFB_DEFAULT_FB_LEN (XENFB_WIDTH * XENFB_HEIGHT * XENFB_DEPTH / 8)
  
  enum { KPARAM_MEM, KPARAM_WIDTH, KPARAM_HEIGHT, KPARAM_CNT };
  static int video[KPARAM_CNT] = { 2, XENFB_WIDTH, XENFB_HEIGHT };
  module_param_array(video, int, NULL, 0);
  MODULE_PARM_DESC(video,
  	"Video memory size in MB, width, height in pixels (default 2,800,600)");
  
  static void xenfb_make_preferred_console(void);
  static int xenfb_remove(struct xenbus_device *);
  static void xenfb_init_shared_page(struct xenfb_info *, struct fb_info *);
  static int xenfb_connect_backend(struct xenbus_device *, struct xenfb_info *);
  static void xenfb_disconnect_backend(struct xenfb_info *);
  
  static void xenfb_send_event(struct xenfb_info *info,
  			     union xenfb_out_event *event)
  {
  	u32 prod;
  
  	prod = info->page->out_prod;
  	/* caller ensures !xenfb_queue_full() */
  	mb();			/* ensure ring space available */
  	XENFB_OUT_RING_REF(info->page, prod) = *event;
  	wmb();			/* ensure ring contents visible */
  	info->page->out_prod = prod + 1;
  
  	notify_remote_via_irq(info->irq);
  }
  
  static void xenfb_do_update(struct xenfb_info *info,
  			    int x, int y, int w, int h)
  {
  	union xenfb_out_event event;
  
  	memset(&event, 0, sizeof(event));
  	event.type = XENFB_TYPE_UPDATE;
  	event.update.x = x;
  	event.update.y = y;
  	event.update.width = w;
  	event.update.height = h;
  
  	/* caller ensures !xenfb_queue_full() */
  	xenfb_send_event(info, &event);
  }
  
  static void xenfb_do_resize(struct xenfb_info *info)
  {
  	union xenfb_out_event event;
  
  	memset(&event, 0, sizeof(event));
  	event.resize = info->resize;
  
  	/* caller ensures !xenfb_queue_full() */
  	xenfb_send_event(info, &event);
  }
  
  static int xenfb_queue_full(struct xenfb_info *info)
  {
  	u32 cons, prod;
  
  	prod = info->page->out_prod;
  	cons = info->page->out_cons;
  	return prod - cons == XENFB_OUT_RING_LEN;
  }
  
  static void xenfb_handle_resize_dpy(struct xenfb_info *info)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&info->resize_lock, flags);
  	if (info->resize_dpy) {
  		if (!xenfb_queue_full(info)) {
  			info->resize_dpy = 0;
  			xenfb_do_resize(info);
  		}
  	}
  	spin_unlock_irqrestore(&info->resize_lock, flags);
  }
  
  static void xenfb_refresh(struct xenfb_info *info,
  			  int x1, int y1, int w, int h)
  {
  	unsigned long flags;
  	int x2 = x1 + w - 1;
  	int y2 = y1 + h - 1;
  
  	xenfb_handle_resize_dpy(info);
  
  	if (!info->update_wanted)
  		return;
  
  	spin_lock_irqsave(&info->dirty_lock, flags);
  
  	/* Combine with dirty rectangle: */
  	if (info->y1 < y1)
  		y1 = info->y1;
  	if (info->y2 > y2)
  		y2 = info->y2;
  	if (info->x1 < x1)
  		x1 = info->x1;
  	if (info->x2 > x2)
  		x2 = info->x2;
  
  	if (xenfb_queue_full(info)) {
  		/* Can't send right now, stash it in the dirty rectangle */
  		info->x1 = x1;
  		info->x2 = x2;
  		info->y1 = y1;
  		info->y2 = y2;
  		spin_unlock_irqrestore(&info->dirty_lock, flags);
  		return;
  	}
  
  	/* Clear dirty rectangle: */
  	info->x1 = info->y1 = INT_MAX;
  	info->x2 = info->y2 = 0;
  
  	spin_unlock_irqrestore(&info->dirty_lock, flags);
  
  	if (x1 <= x2 && y1 <= y2)
  		xenfb_do_update(info, x1, y1, x2 - x1 + 1, y2 - y1 + 1);
  }
  
  static void xenfb_deferred_io(struct fb_info *fb_info,
  			      struct list_head *pagelist)
  {
  	struct xenfb_info *info = fb_info->par;
  	struct page *page;
  	unsigned long beg, end;
  	int y1, y2, miny, maxy;
  
  	miny = INT_MAX;
  	maxy = 0;
  	list_for_each_entry(page, pagelist, lru) {
  		beg = page->index << PAGE_SHIFT;
  		end = beg + PAGE_SIZE - 1;
  		y1 = beg / fb_info->fix.line_length;
  		y2 = end / fb_info->fix.line_length;
  		if (y2 >= fb_info->var.yres)
  			y2 = fb_info->var.yres - 1;
  		if (miny > y1)
  			miny = y1;
  		if (maxy < y2)
  			maxy = y2;
  	}
  	xenfb_refresh(info, 0, miny, fb_info->var.xres, maxy - miny + 1);
  }
  
  static struct fb_deferred_io xenfb_defio = {
  	.delay		= HZ / 20,
  	.deferred_io	= xenfb_deferred_io,
  };
  
  static int xenfb_setcolreg(unsigned regno, unsigned red, unsigned green,
  			   unsigned blue, unsigned transp,
  			   struct fb_info *info)
  {
  	u32 v;
  
  	if (regno > info->cmap.len)
  		return 1;
  
  #define CNVT_TOHW(val, width) ((((val)<<(width))+0x7FFF-(val))>>16)
  	red = CNVT_TOHW(red, info->var.red.length);
  	green = CNVT_TOHW(green, info->var.green.length);
  	blue = CNVT_TOHW(blue, info->var.blue.length);
  	transp = CNVT_TOHW(transp, info->var.transp.length);
  #undef CNVT_TOHW
  
  	v = (red << info->var.red.offset) |
  	    (green << info->var.green.offset) |
  	    (blue << info->var.blue.offset);
  
  	switch (info->var.bits_per_pixel) {
  	case 16:
  	case 24:
  	case 32:
  		((u32 *)info->pseudo_palette)[regno] = v;
  		break;
  	}
  
  	return 0;
  }
  
  static void xenfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
  {
  	struct xenfb_info *info = p->par;
  
  	sys_fillrect(p, rect);
  	xenfb_refresh(info, rect->dx, rect->dy, rect->width, rect->height);
  }
  
  static void xenfb_imageblit(struct fb_info *p, const struct fb_image *image)
  {
  	struct xenfb_info *info = p->par;
  
  	sys_imageblit(p, image);
  	xenfb_refresh(info, image->dx, image->dy, image->width, image->height);
  }
  
  static void xenfb_copyarea(struct fb_info *p, const struct fb_copyarea *area)
  {
  	struct xenfb_info *info = p->par;
  
  	sys_copyarea(p, area);
  	xenfb_refresh(info, area->dx, area->dy, area->width, area->height);
  }
  
  static ssize_t xenfb_write(struct fb_info *p, const char __user *buf,
  			size_t count, loff_t *ppos)
  {
  	struct xenfb_info *info = p->par;
  	ssize_t res;
  
  	res = fb_sys_write(p, buf, count, ppos);
  	xenfb_refresh(info, 0, 0, info->page->width, info->page->height);
  	return res;
  }
  
  static int
  xenfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
  {
  	struct xenfb_info *xenfb_info;
  	int required_mem_len;
  
  	xenfb_info = info->par;
  
  	if (!xenfb_info->feature_resize) {
  		if (var->xres == video[KPARAM_WIDTH] &&
  		    var->yres == video[KPARAM_HEIGHT] &&
  		    var->bits_per_pixel == xenfb_info->page->depth) {
  			return 0;
  		}
  		return -EINVAL;
  	}
  
  	/* Can't resize past initial width and height */
  	if (var->xres > video[KPARAM_WIDTH] || var->yres > video[KPARAM_HEIGHT])
  		return -EINVAL;
  
  	required_mem_len = var->xres * var->yres * xenfb_info->page->depth / 8;
  	if (var->bits_per_pixel == xenfb_info->page->depth &&
  	    var->xres <= info->fix.line_length / (XENFB_DEPTH / 8) &&
  	    required_mem_len <= info->fix.smem_len) {
  		var->xres_virtual = var->xres;
  		var->yres_virtual = var->yres;
  		return 0;
  	}
  	return -EINVAL;
  }
  
  static int xenfb_set_par(struct fb_info *info)
  {
  	struct xenfb_info *xenfb_info;
  	unsigned long flags;
  
  	xenfb_info = info->par;
  
  	spin_lock_irqsave(&xenfb_info->resize_lock, flags);
  	xenfb_info->resize.type = XENFB_TYPE_RESIZE;
  	xenfb_info->resize.width = info->var.xres;
  	xenfb_info->resize.height = info->var.yres;
  	xenfb_info->resize.stride = info->fix.line_length;
  	xenfb_info->resize.depth = info->var.bits_per_pixel;
  	xenfb_info->resize.offset = 0;
  	xenfb_info->resize_dpy = 1;
  	spin_unlock_irqrestore(&xenfb_info->resize_lock, flags);
  	return 0;
  }
  
  static struct fb_ops xenfb_fb_ops = {
  	.owner		= THIS_MODULE,
  	.fb_read	= fb_sys_read,
  	.fb_write	= xenfb_write,
  	.fb_setcolreg	= xenfb_setcolreg,
  	.fb_fillrect	= xenfb_fillrect,
  	.fb_copyarea	= xenfb_copyarea,
  	.fb_imageblit	= xenfb_imageblit,
  	.fb_check_var	= xenfb_check_var,
  	.fb_set_par     = xenfb_set_par,
  };
  
  static irqreturn_t xenfb_event_handler(int rq, void *dev_id)
  {
  	/*
  	 * No in events recognized, simply ignore them all.
  	 * If you need to recognize some, see xen-kbdfront's
  	 * input_handler() for how to do that.
  	 */
  	struct xenfb_info *info = dev_id;
  	struct xenfb_page *page = info->page;
  
  	if (page->in_cons != page->in_prod) {
  		info->page->in_cons = info->page->in_prod;
  		notify_remote_via_irq(info->irq);
  	}
  
  	/* Flush dirty rectangle: */
  	xenfb_refresh(info, INT_MAX, INT_MAX, -INT_MAX, -INT_MAX);
  
  	return IRQ_HANDLED;
  }
  
  static int xenfb_probe(struct xenbus_device *dev,
  		       const struct xenbus_device_id *id)
  {
  	struct xenfb_info *info;
  	struct fb_info *fb_info;
  	int fb_size;
  	int val;
  	int ret = 0;
  
  	info = kzalloc(sizeof(*info), GFP_KERNEL);
  	if (info == NULL) {
  		xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
  		return -ENOMEM;
  	}
  
  	/* Limit kernel param videoram amount to what is in xenstore */
  	if (xenbus_scanf(XBT_NIL, dev->otherend, "videoram", "%d", &val) == 1) {
  		if (val < video[KPARAM_MEM])
  			video[KPARAM_MEM] = val;
  	}
  
  	/* If requested res does not fit in available memory, use default */
  	fb_size = video[KPARAM_MEM] * 1024 * 1024;
  	if (video[KPARAM_WIDTH] * video[KPARAM_HEIGHT] * XENFB_DEPTH / 8
  	    > fb_size) {
  		video[KPARAM_WIDTH] = XENFB_WIDTH;
  		video[KPARAM_HEIGHT] = XENFB_HEIGHT;
  		fb_size = XENFB_DEFAULT_FB_LEN;
  	}
  
  	dev_set_drvdata(&dev->dev, info);
  	info->xbdev = dev;
  	info->irq = -1;
  	info->x1 = info->y1 = INT_MAX;
  	spin_lock_init(&info->dirty_lock);
  	spin_lock_init(&info->resize_lock);
  
  	info->fb = vzalloc(fb_size);
  	if (info->fb == NULL)
  		goto error_nomem;
  
  	info->nr_pages = (fb_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
  
  	info->mfns = vmalloc(sizeof(unsigned long) * info->nr_pages);
  	if (!info->mfns)
  		goto error_nomem;
  
  	/* set up shared page */
  	info->page = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
  	if (!info->page)
  		goto error_nomem;
  
  	/* abusing framebuffer_alloc() to allocate pseudo_palette */
  	fb_info = framebuffer_alloc(sizeof(u32) * 256, NULL);
  	if (fb_info == NULL)
  		goto error_nomem;
  
  	/* complete the abuse: */
  	fb_info->pseudo_palette = fb_info->par;
  	fb_info->par = info;
  
  	fb_info->screen_base = info->fb;
  
  	fb_info->fbops = &xenfb_fb_ops;
  	fb_info->var.xres_virtual = fb_info->var.xres = video[KPARAM_WIDTH];
  	fb_info->var.yres_virtual = fb_info->var.yres = video[KPARAM_HEIGHT];
  	fb_info->var.bits_per_pixel = XENFB_DEPTH;
  
  	fb_info->var.red = (struct fb_bitfield){16, 8, 0};
  	fb_info->var.green = (struct fb_bitfield){8, 8, 0};
  	fb_info->var.blue = (struct fb_bitfield){0, 8, 0};
  
  	fb_info->var.activate = FB_ACTIVATE_NOW;
  	fb_info->var.height = -1;
  	fb_info->var.width = -1;
  	fb_info->var.vmode = FB_VMODE_NONINTERLACED;
  
  	fb_info->fix.visual = FB_VISUAL_TRUECOLOR;
  	fb_info->fix.line_length = fb_info->var.xres * XENFB_DEPTH / 8;
  	fb_info->fix.smem_start = 0;
  	fb_info->fix.smem_len = fb_size;
  	strcpy(fb_info->fix.id, "xen");
  	fb_info->fix.type = FB_TYPE_PACKED_PIXELS;
  	fb_info->fix.accel = FB_ACCEL_NONE;
  
  	fb_info->flags = FBINFO_FLAG_DEFAULT | FBINFO_VIRTFB;
  
  	ret = fb_alloc_cmap(&fb_info->cmap, 256, 0);
  	if (ret < 0) {
  		framebuffer_release(fb_info);
  		xenbus_dev_fatal(dev, ret, "fb_alloc_cmap");
  		goto error;
  	}
  
  	fb_info->fbdefio = &xenfb_defio;
  	fb_deferred_io_init(fb_info);
  
  	xenfb_init_shared_page(info, fb_info);
  
  	ret = xenfb_connect_backend(dev, info);
  	if (ret < 0) {
  		xenbus_dev_fatal(dev, ret, "xenfb_connect_backend");
  		goto error_fb;
  	}
  
  	ret = register_framebuffer(fb_info);
  	if (ret) {
  		xenbus_dev_fatal(dev, ret, "register_framebuffer");
  		goto error_fb;
  	}
  	info->fb_info = fb_info;
  
  	xenfb_make_preferred_console();
  	return 0;
  
  error_fb:
  	fb_deferred_io_cleanup(fb_info);
  	fb_dealloc_cmap(&fb_info->cmap);
  	framebuffer_release(fb_info);
  error_nomem:
  	if (!ret) {
  		ret = -ENOMEM;
  		xenbus_dev_fatal(dev, ret, "allocating device memory");
  	}
  error:
  	xenfb_remove(dev);
  	return ret;
  }
  
  static void xenfb_make_preferred_console(void)
  {
  	struct console *c;
  
  	if (console_set_on_cmdline)
  		return;
  
  	console_lock();
  	for_each_console(c) {
  		if (!strcmp(c->name, "tty") && c->index == 0)
  			break;
  	}
  	console_unlock();
  	if (c) {
  		unregister_console(c);
  		c->flags |= CON_CONSDEV;
  		c->flags &= ~CON_PRINTBUFFER; /* don't print again */
  		register_console(c);
  	}
  }
  
  static int xenfb_resume(struct xenbus_device *dev)
  {
  	struct xenfb_info *info = dev_get_drvdata(&dev->dev);
  
  	xenfb_disconnect_backend(info);
  	xenfb_init_shared_page(info, info->fb_info);
  	return xenfb_connect_backend(dev, info);
  }
  
  static int xenfb_remove(struct xenbus_device *dev)
  {
  	struct xenfb_info *info = dev_get_drvdata(&dev->dev);
  
  	xenfb_disconnect_backend(info);
  	if (info->fb_info) {
  		fb_deferred_io_cleanup(info->fb_info);
  		unregister_framebuffer(info->fb_info);
  		fb_dealloc_cmap(&info->fb_info->cmap);
  		framebuffer_release(info->fb_info);
  	}
  	free_page((unsigned long)info->page);
  	vfree(info->mfns);
  	vfree(info->fb);
  	kfree(info);
  
  	return 0;
  }
  
  static unsigned long vmalloc_to_mfn(void *address)
  {
  	return pfn_to_mfn(vmalloc_to_pfn(address));
  }
  
  static void xenfb_init_shared_page(struct xenfb_info *info,
  				   struct fb_info *fb_info)
  {
  	int i;
  	int epd = PAGE_SIZE / sizeof(info->mfns[0]);
  
  	for (i = 0; i < info->nr_pages; i++)
  		info->mfns[i] = vmalloc_to_mfn(info->fb + i * PAGE_SIZE);
  
  	for (i = 0; i * epd < info->nr_pages; i++)
  		info->page->pd[i] = vmalloc_to_mfn(&info->mfns[i * epd]);
  
  	info->page->width = fb_info->var.xres;
  	info->page->height = fb_info->var.yres;
  	info->page->depth = fb_info->var.bits_per_pixel;
  	info->page->line_length = fb_info->fix.line_length;
  	info->page->mem_length = fb_info->fix.smem_len;
  	info->page->in_cons = info->page->in_prod = 0;
  	info->page->out_cons = info->page->out_prod = 0;
  }
  
  static int xenfb_connect_backend(struct xenbus_device *dev,
  				 struct xenfb_info *info)
  {
  	int ret, evtchn, irq;
  	struct xenbus_transaction xbt;
  
  	ret = xenbus_alloc_evtchn(dev, &evtchn);
  	if (ret)
  		return ret;
  	irq = bind_evtchn_to_irqhandler(evtchn, xenfb_event_handler,
  					0, dev->devicetype, info);
  	if (irq < 0) {
  		xenbus_free_evtchn(dev, evtchn);
  		xenbus_dev_fatal(dev, ret, "bind_evtchn_to_irqhandler");
  		return irq;
  	}
   again:
  	ret = xenbus_transaction_start(&xbt);
  	if (ret) {
  		xenbus_dev_fatal(dev, ret, "starting transaction");
  		goto unbind_irq;
  	}
  	ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
  			    virt_to_mfn(info->page));
  	if (ret)
  		goto error_xenbus;
  	ret = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
  			    evtchn);
  	if (ret)
  		goto error_xenbus;
  	ret = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
  			    XEN_IO_PROTO_ABI_NATIVE);
  	if (ret)
  		goto error_xenbus;
  	ret = xenbus_printf(xbt, dev->nodename, "feature-update", "1");
  	if (ret)
  		goto error_xenbus;
  	ret = xenbus_transaction_end(xbt, 0);
  	if (ret) {
  		if (ret == -EAGAIN)
  			goto again;
  		xenbus_dev_fatal(dev, ret, "completing transaction");
  		goto unbind_irq;
  	}
  
  	xenbus_switch_state(dev, XenbusStateInitialised);
  	info->irq = irq;
  	return 0;
  
   error_xenbus:
  	xenbus_transaction_end(xbt, 1);
  	xenbus_dev_fatal(dev, ret, "writing xenstore");
   unbind_irq:
  	unbind_from_irqhandler(irq, info);
  	return ret;
  }
  
  static void xenfb_disconnect_backend(struct xenfb_info *info)
  {
  	/* Prevent xenfb refresh */
  	info->update_wanted = 0;
  	if (info->irq >= 0)
  		unbind_from_irqhandler(info->irq, info);
  	info->irq = -1;
  }
  
  static void xenfb_backend_changed(struct xenbus_device *dev,
  				  enum xenbus_state backend_state)
  {
  	struct xenfb_info *info = dev_get_drvdata(&dev->dev);
  	int val;
  
  	switch (backend_state) {
  	case XenbusStateInitialising:
  	case XenbusStateInitialised:
  	case XenbusStateReconfiguring:
  	case XenbusStateReconfigured:
  	case XenbusStateUnknown:
  		break;
  
  	case XenbusStateInitWait:
  InitWait:
  		xenbus_switch_state(dev, XenbusStateConnected);
  		break;
  
  	case XenbusStateConnected:
  		/*
  		 * Work around xenbus race condition: If backend goes
  		 * through InitWait to Connected fast enough, we can
  		 * get Connected twice here.
  		 */
  		if (dev->state != XenbusStateConnected)
  			goto InitWait; /* no InitWait seen yet, fudge it */
  
  		if (xenbus_scanf(XBT_NIL, info->xbdev->otherend,
  				 "request-update", "%d", &val) < 0)
  			val = 0;
  		if (val)
  			info->update_wanted = 1;
  
  		if (xenbus_scanf(XBT_NIL, dev->otherend,
  				 "feature-resize", "%d", &val) < 0)
  			val = 0;
  		info->feature_resize = val;
  		break;
  
  	case XenbusStateClosed:
  		if (dev->state == XenbusStateClosed)
  			break;
  		/* Missed the backend's CLOSING state -- fallthrough */
  	case XenbusStateClosing:
  		xenbus_frontend_closed(dev);
  		break;
  	}
  }
  
  static const struct xenbus_device_id xenfb_ids[] = {
  	{ "vfb" },
  	{ "" }
  };
  
  static DEFINE_XENBUS_DRIVER(xenfb, ,
  	.probe = xenfb_probe,
  	.remove = xenfb_remove,
  	.resume = xenfb_resume,
  	.otherend_changed = xenfb_backend_changed,
  );
  
  static int __init xenfb_init(void)
  {
  	if (!xen_domain())
  		return -ENODEV;
  
  	/* Nothing to do if running in dom0. */
  	if (xen_initial_domain())
  		return -ENODEV;
  
  	if (!xen_has_pv_devices())
  		return -ENODEV;
  
  	return xenbus_register_frontend(&xenfb_driver);
  }
  
  static void __exit xenfb_cleanup(void)
  {
  	xenbus_unregister_driver(&xenfb_driver);
  }
  
  module_init(xenfb_init);
  module_exit(xenfb_cleanup);
  
  MODULE_DESCRIPTION("Xen virtual framebuffer device frontend");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("xen:vfb");