1/*
2 * Xen para-virtual frame buffer device
3 *
4 * Copyright (C) 2005-2006 Anthony Liguori <aliguori@us.ibm.com>
5 * Copyright (C) 2006-2008 Red Hat, Inc., Markus Armbruster <armbru@redhat.com>
6 *
7 *  Based on linux/drivers/video/q40fb.c
8 *
9 *  This file is subject to the terms and conditions of the GNU General Public
10 *  License. See the file COPYING in the main directory of this archive for
11 *  more details.
12 */
13
14/*
15 * TODO:
16 *
17 * Switch to grant tables when they become capable of dealing with the
18 * frame buffer.
19 */
20
21#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
22
23#include <linux/console.h>
24#include <linux/kernel.h>
25#include <linux/errno.h>
26#include <linux/fb.h>
27#include <linux/module.h>
28#include <linux/slab.h>
29#include <linux/vmalloc.h>
30#include <linux/mm.h>
31
32#include <asm/xen/hypervisor.h>
33
34#include <xen/xen.h>
35#include <xen/events.h>
36#include <xen/page.h>
37#include <xen/interface/io/fbif.h>
38#include <xen/interface/io/protocols.h>
39#include <xen/xenbus.h>
40#include <xen/platform_pci.h>
41
42struct xenfb_info {
43	unsigned char		*fb;
44	struct fb_info		*fb_info;
45	int			x1, y1, x2, y2;	/* dirty rectangle,
46						   protected by dirty_lock */
47	spinlock_t		dirty_lock;
48	int			nr_pages;
49	int			irq;
50	struct xenfb_page	*page;
51	unsigned long 		*gfns;
52	int			update_wanted; /* XENFB_TYPE_UPDATE wanted */
53	int			feature_resize; /* XENFB_TYPE_RESIZE ok */
54	struct xenfb_resize	resize;		/* protected by resize_lock */
55	int			resize_dpy;	/* ditto */
56	spinlock_t		resize_lock;
57
58	struct xenbus_device	*xbdev;
59};
60
61#define XENFB_DEFAULT_FB_LEN (XENFB_WIDTH * XENFB_HEIGHT * XENFB_DEPTH / 8)
62
63enum { KPARAM_MEM, KPARAM_WIDTH, KPARAM_HEIGHT, KPARAM_CNT };
64static int video[KPARAM_CNT] = { 2, XENFB_WIDTH, XENFB_HEIGHT };
65module_param_array(video, int, NULL, 0);
66MODULE_PARM_DESC(video,
67	"Video memory size in MB, width, height in pixels (default 2,800,600)");
68
69static void xenfb_make_preferred_console(void);
70static int xenfb_remove(struct xenbus_device *);
71static void xenfb_init_shared_page(struct xenfb_info *, struct fb_info *);
72static int xenfb_connect_backend(struct xenbus_device *, struct xenfb_info *);
73static void xenfb_disconnect_backend(struct xenfb_info *);
74
75static void xenfb_send_event(struct xenfb_info *info,
76			     union xenfb_out_event *event)
77{
78	u32 prod;
79
80	prod = info->page->out_prod;
81	/* caller ensures !xenfb_queue_full() */
82	mb();			/* ensure ring space available */
83	XENFB_OUT_RING_REF(info->page, prod) = *event;
84	wmb();			/* ensure ring contents visible */
85	info->page->out_prod = prod + 1;
86
87	notify_remote_via_irq(info->irq);
88}
89
90static void xenfb_do_update(struct xenfb_info *info,
91			    int x, int y, int w, int h)
92{
93	union xenfb_out_event event;
94
95	memset(&event, 0, sizeof(event));
96	event.type = XENFB_TYPE_UPDATE;
97	event.update.x = x;
98	event.update.y = y;
99	event.update.width = w;
100	event.update.height = h;
101
102	/* caller ensures !xenfb_queue_full() */
103	xenfb_send_event(info, &event);
104}
105
106static void xenfb_do_resize(struct xenfb_info *info)
107{
108	union xenfb_out_event event;
109
110	memset(&event, 0, sizeof(event));
111	event.resize = info->resize;
112
113	/* caller ensures !xenfb_queue_full() */
114	xenfb_send_event(info, &event);
115}
116
117static int xenfb_queue_full(struct xenfb_info *info)
118{
119	u32 cons, prod;
120
121	prod = info->page->out_prod;
122	cons = info->page->out_cons;
123	return prod - cons == XENFB_OUT_RING_LEN;
124}
125
126static void xenfb_handle_resize_dpy(struct xenfb_info *info)
127{
128	unsigned long flags;
129
130	spin_lock_irqsave(&info->resize_lock, flags);
131	if (info->resize_dpy) {
132		if (!xenfb_queue_full(info)) {
133			info->resize_dpy = 0;
134			xenfb_do_resize(info);
135		}
136	}
137	spin_unlock_irqrestore(&info->resize_lock, flags);
138}
139
140static void xenfb_refresh(struct xenfb_info *info,
141			  int x1, int y1, int w, int h)
142{
143	unsigned long flags;
144	int x2 = x1 + w - 1;
145	int y2 = y1 + h - 1;
146
147	xenfb_handle_resize_dpy(info);
148
149	if (!info->update_wanted)
150		return;
151
152	spin_lock_irqsave(&info->dirty_lock, flags);
153
154	/* Combine with dirty rectangle: */
155	if (info->y1 < y1)
156		y1 = info->y1;
157	if (info->y2 > y2)
158		y2 = info->y2;
159	if (info->x1 < x1)
160		x1 = info->x1;
161	if (info->x2 > x2)
162		x2 = info->x2;
163
164	if (xenfb_queue_full(info)) {
165		/* Can't send right now, stash it in the dirty rectangle */
166		info->x1 = x1;
167		info->x2 = x2;
168		info->y1 = y1;
169		info->y2 = y2;
170		spin_unlock_irqrestore(&info->dirty_lock, flags);
171		return;
172	}
173
174	/* Clear dirty rectangle: */
175	info->x1 = info->y1 = INT_MAX;
176	info->x2 = info->y2 = 0;
177
178	spin_unlock_irqrestore(&info->dirty_lock, flags);
179
180	if (x1 <= x2 && y1 <= y2)
181		xenfb_do_update(info, x1, y1, x2 - x1 + 1, y2 - y1 + 1);
182}
183
184static void xenfb_deferred_io(struct fb_info *fb_info,
185			      struct list_head *pagelist)
186{
187	struct xenfb_info *info = fb_info->par;
188	struct page *page;
189	unsigned long beg, end;
190	int y1, y2, miny, maxy;
191
192	miny = INT_MAX;
193	maxy = 0;
194	list_for_each_entry(page, pagelist, lru) {
195		beg = page->index << PAGE_SHIFT;
196		end = beg + PAGE_SIZE - 1;
197		y1 = beg / fb_info->fix.line_length;
198		y2 = end / fb_info->fix.line_length;
199		if (y2 >= fb_info->var.yres)
200			y2 = fb_info->var.yres - 1;
201		if (miny > y1)
202			miny = y1;
203		if (maxy < y2)
204			maxy = y2;
205	}
206	xenfb_refresh(info, 0, miny, fb_info->var.xres, maxy - miny + 1);
207}
208
209static struct fb_deferred_io xenfb_defio = {
210	.delay		= HZ / 20,
211	.deferred_io	= xenfb_deferred_io,
212};
213
214static int xenfb_setcolreg(unsigned regno, unsigned red, unsigned green,
215			   unsigned blue, unsigned transp,
216			   struct fb_info *info)
217{
218	u32 v;
219
220	if (regno > info->cmap.len)
221		return 1;
222
223#define CNVT_TOHW(val, width) ((((val)<<(width))+0x7FFF-(val))>>16)
224	red = CNVT_TOHW(red, info->var.red.length);
225	green = CNVT_TOHW(green, info->var.green.length);
226	blue = CNVT_TOHW(blue, info->var.blue.length);
227	transp = CNVT_TOHW(transp, info->var.transp.length);
228#undef CNVT_TOHW
229
230	v = (red << info->var.red.offset) |
231	    (green << info->var.green.offset) |
232	    (blue << info->var.blue.offset);
233
234	switch (info->var.bits_per_pixel) {
235	case 16:
236	case 24:
237	case 32:
238		((u32 *)info->pseudo_palette)[regno] = v;
239		break;
240	}
241
242	return 0;
243}
244
245static void xenfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
246{
247	struct xenfb_info *info = p->par;
248
249	sys_fillrect(p, rect);
250	xenfb_refresh(info, rect->dx, rect->dy, rect->width, rect->height);
251}
252
253static void xenfb_imageblit(struct fb_info *p, const struct fb_image *image)
254{
255	struct xenfb_info *info = p->par;
256
257	sys_imageblit(p, image);
258	xenfb_refresh(info, image->dx, image->dy, image->width, image->height);
259}
260
261static void xenfb_copyarea(struct fb_info *p, const struct fb_copyarea *area)
262{
263	struct xenfb_info *info = p->par;
264
265	sys_copyarea(p, area);
266	xenfb_refresh(info, area->dx, area->dy, area->width, area->height);
267}
268
269static ssize_t xenfb_write(struct fb_info *p, const char __user *buf,
270			size_t count, loff_t *ppos)
271{
272	struct xenfb_info *info = p->par;
273	ssize_t res;
274
275	res = fb_sys_write(p, buf, count, ppos);
276	xenfb_refresh(info, 0, 0, info->page->width, info->page->height);
277	return res;
278}
279
280static int
281xenfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
282{
283	struct xenfb_info *xenfb_info;
284	int required_mem_len;
285
286	xenfb_info = info->par;
287
288	if (!xenfb_info->feature_resize) {
289		if (var->xres == video[KPARAM_WIDTH] &&
290		    var->yres == video[KPARAM_HEIGHT] &&
291		    var->bits_per_pixel == xenfb_info->page->depth) {
292			return 0;
293		}
294		return -EINVAL;
295	}
296
297	/* Can't resize past initial width and height */
298	if (var->xres > video[KPARAM_WIDTH] || var->yres > video[KPARAM_HEIGHT])
299		return -EINVAL;
300
301	required_mem_len = var->xres * var->yres * xenfb_info->page->depth / 8;
302	if (var->bits_per_pixel == xenfb_info->page->depth &&
303	    var->xres <= info->fix.line_length / (XENFB_DEPTH / 8) &&
304	    required_mem_len <= info->fix.smem_len) {
305		var->xres_virtual = var->xres;
306		var->yres_virtual = var->yres;
307		return 0;
308	}
309	return -EINVAL;
310}
311
312static int xenfb_set_par(struct fb_info *info)
313{
314	struct xenfb_info *xenfb_info;
315	unsigned long flags;
316
317	xenfb_info = info->par;
318
319	spin_lock_irqsave(&xenfb_info->resize_lock, flags);
320	xenfb_info->resize.type = XENFB_TYPE_RESIZE;
321	xenfb_info->resize.width = info->var.xres;
322	xenfb_info->resize.height = info->var.yres;
323	xenfb_info->resize.stride = info->fix.line_length;
324	xenfb_info->resize.depth = info->var.bits_per_pixel;
325	xenfb_info->resize.offset = 0;
326	xenfb_info->resize_dpy = 1;
327	spin_unlock_irqrestore(&xenfb_info->resize_lock, flags);
328	return 0;
329}
330
331static const struct fb_ops xenfb_fb_ops = {
332	.owner		= THIS_MODULE,
333	.fb_read	= fb_sys_read,
334	.fb_write	= xenfb_write,
335	.fb_setcolreg	= xenfb_setcolreg,
336	.fb_fillrect	= xenfb_fillrect,
337	.fb_copyarea	= xenfb_copyarea,
338	.fb_imageblit	= xenfb_imageblit,
339	.fb_check_var	= xenfb_check_var,
340	.fb_set_par     = xenfb_set_par,
341};
342
343static irqreturn_t xenfb_event_handler(int rq, void *dev_id)
344{
345	/*
346	 * No in events recognized, simply ignore them all.
347	 * If you need to recognize some, see xen-kbdfront's
348	 * input_handler() for how to do that.
349	 */
350	struct xenfb_info *info = dev_id;
351	struct xenfb_page *page = info->page;
352
353	if (page->in_cons != page->in_prod) {
354		info->page->in_cons = info->page->in_prod;
355		notify_remote_via_irq(info->irq);
356	}
357
358	/* Flush dirty rectangle: */
359	xenfb_refresh(info, INT_MAX, INT_MAX, -INT_MAX, -INT_MAX);
360
361	return IRQ_HANDLED;
362}
363
364static int xenfb_probe(struct xenbus_device *dev,
365		       const struct xenbus_device_id *id)
366{
367	struct xenfb_info *info;
368	struct fb_info *fb_info;
369	int fb_size;
370	int val;
371	int ret = 0;
372
373	info = kzalloc(sizeof(*info), GFP_KERNEL);
374	if (info == NULL) {
375		xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
376		return -ENOMEM;
377	}
378
379	/* Limit kernel param videoram amount to what is in xenstore */
380	if (xenbus_scanf(XBT_NIL, dev->otherend, "videoram", "%d", &val) == 1) {
381		if (val < video[KPARAM_MEM])
382			video[KPARAM_MEM] = val;
383	}
384
385	video[KPARAM_WIDTH] = xenbus_read_unsigned(dev->otherend, "width",
386						   video[KPARAM_WIDTH]);
387	video[KPARAM_HEIGHT] = xenbus_read_unsigned(dev->otherend, "height",
388						    video[KPARAM_HEIGHT]);
389
390	/* If requested res does not fit in available memory, use default */
391	fb_size = video[KPARAM_MEM] * 1024 * 1024;
392	if (video[KPARAM_WIDTH] * video[KPARAM_HEIGHT] * XENFB_DEPTH / 8
393	    > fb_size) {
394		pr_warn("display parameters %d,%d,%d invalid, use defaults\n",
395			video[KPARAM_MEM], video[KPARAM_WIDTH],
396			video[KPARAM_HEIGHT]);
397		video[KPARAM_WIDTH] = XENFB_WIDTH;
398		video[KPARAM_HEIGHT] = XENFB_HEIGHT;
399		fb_size = XENFB_DEFAULT_FB_LEN;
400	}
401
402	dev_set_drvdata(&dev->dev, info);
403	info->xbdev = dev;
404	info->irq = -1;
405	info->x1 = info->y1 = INT_MAX;
406	spin_lock_init(&info->dirty_lock);
407	spin_lock_init(&info->resize_lock);
408
409	info->fb = vzalloc(fb_size);
410	if (info->fb == NULL)
411		goto error_nomem;
412
413	info->nr_pages = (fb_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
414
415	info->gfns = vmalloc(array_size(sizeof(unsigned long), info->nr_pages));
416	if (!info->gfns)
417		goto error_nomem;
418
419	/* set up shared page */
420	info->page = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
421	if (!info->page)
422		goto error_nomem;
423
424	/* abusing framebuffer_alloc() to allocate pseudo_palette */
425	fb_info = framebuffer_alloc(sizeof(u32) * 256, NULL);
426	if (fb_info == NULL)
427		goto error_nomem;
428
429	/* complete the abuse: */
430	fb_info->pseudo_palette = fb_info->par;
431	fb_info->par = info;
432
433	fb_info->screen_base = info->fb;
434
435	fb_info->fbops = &xenfb_fb_ops;
436	fb_info->var.xres_virtual = fb_info->var.xres = video[KPARAM_WIDTH];
437	fb_info->var.yres_virtual = fb_info->var.yres = video[KPARAM_HEIGHT];
438	fb_info->var.bits_per_pixel = XENFB_DEPTH;
439
440	fb_info->var.red = (struct fb_bitfield){16, 8, 0};
441	fb_info->var.green = (struct fb_bitfield){8, 8, 0};
442	fb_info->var.blue = (struct fb_bitfield){0, 8, 0};
443
444	fb_info->var.activate = FB_ACTIVATE_NOW;
445	fb_info->var.height = -1;
446	fb_info->var.width = -1;
447	fb_info->var.vmode = FB_VMODE_NONINTERLACED;
448
449	fb_info->fix.visual = FB_VISUAL_TRUECOLOR;
450	fb_info->fix.line_length = fb_info->var.xres * XENFB_DEPTH / 8;
451	fb_info->fix.smem_start = 0;
452	fb_info->fix.smem_len = fb_size;
453	strcpy(fb_info->fix.id, "xen");
454	fb_info->fix.type = FB_TYPE_PACKED_PIXELS;
455	fb_info->fix.accel = FB_ACCEL_NONE;
456
457	fb_info->flags = FBINFO_FLAG_DEFAULT | FBINFO_VIRTFB;
458
459	ret = fb_alloc_cmap(&fb_info->cmap, 256, 0);
460	if (ret < 0) {
461		framebuffer_release(fb_info);
462		xenbus_dev_fatal(dev, ret, "fb_alloc_cmap");
463		goto error;
464	}
465
466	fb_info->fbdefio = &xenfb_defio;
467	fb_deferred_io_init(fb_info);
468
469	xenfb_init_shared_page(info, fb_info);
470
471	ret = xenfb_connect_backend(dev, info);
472	if (ret < 0) {
473		xenbus_dev_fatal(dev, ret, "xenfb_connect_backend");
474		goto error_fb;
475	}
476
477	ret = register_framebuffer(fb_info);
478	if (ret) {
479		xenbus_dev_fatal(dev, ret, "register_framebuffer");
480		goto error_fb;
481	}
482	info->fb_info = fb_info;
483
484	xenfb_make_preferred_console();
485	return 0;
486
487error_fb:
488	fb_deferred_io_cleanup(fb_info);
489	fb_dealloc_cmap(&fb_info->cmap);
490	framebuffer_release(fb_info);
491error_nomem:
492	if (!ret) {
493		ret = -ENOMEM;
494		xenbus_dev_fatal(dev, ret, "allocating device memory");
495	}
496error:
497	xenfb_remove(dev);
498	return ret;
499}
500
501static void xenfb_make_preferred_console(void)
502{
503	struct console *c;
504
505	if (console_set_on_cmdline)
506		return;
507
508	console_lock();
509	for_each_console(c) {
510		if (!strcmp(c->name, "tty") && c->index == 0)
511			break;
512	}
513	console_unlock();
514	if (c) {
515		unregister_console(c);
516		c->flags |= CON_CONSDEV;
517		c->flags &= ~CON_PRINTBUFFER; /* don't print again */
518		register_console(c);
519	}
520}
521
522static int xenfb_resume(struct xenbus_device *dev)
523{
524	struct xenfb_info *info = dev_get_drvdata(&dev->dev);
525
526	xenfb_disconnect_backend(info);
527	xenfb_init_shared_page(info, info->fb_info);
528	return xenfb_connect_backend(dev, info);
529}
530
531static int xenfb_remove(struct xenbus_device *dev)
532{
533	struct xenfb_info *info = dev_get_drvdata(&dev->dev);
534
535	xenfb_disconnect_backend(info);
536	if (info->fb_info) {
537		fb_deferred_io_cleanup(info->fb_info);
538		unregister_framebuffer(info->fb_info);
539		fb_dealloc_cmap(&info->fb_info->cmap);
540		framebuffer_release(info->fb_info);
541	}
542	free_page((unsigned long)info->page);
543	vfree(info->gfns);
544	vfree(info->fb);
545	kfree(info);
546
547	return 0;
548}
549
550static unsigned long vmalloc_to_gfn(void *address)
551{
552	return xen_page_to_gfn(vmalloc_to_page(address));
553}
554
555static void xenfb_init_shared_page(struct xenfb_info *info,
556				   struct fb_info *fb_info)
557{
558	int i;
559	int epd = PAGE_SIZE / sizeof(info->gfns[0]);
560
561	for (i = 0; i < info->nr_pages; i++)
562		info->gfns[i] = vmalloc_to_gfn(info->fb + i * PAGE_SIZE);
563
564	for (i = 0; i * epd < info->nr_pages; i++)
565		info->page->pd[i] = vmalloc_to_gfn(&info->gfns[i * epd]);
566
567	info->page->width = fb_info->var.xres;
568	info->page->height = fb_info->var.yres;
569	info->page->depth = fb_info->var.bits_per_pixel;
570	info->page->line_length = fb_info->fix.line_length;
571	info->page->mem_length = fb_info->fix.smem_len;
572	info->page->in_cons = info->page->in_prod = 0;
573	info->page->out_cons = info->page->out_prod = 0;
574}
575
576static int xenfb_connect_backend(struct xenbus_device *dev,
577				 struct xenfb_info *info)
578{
579	int ret, evtchn, irq;
580	struct xenbus_transaction xbt;
581
582	ret = xenbus_alloc_evtchn(dev, &evtchn);
583	if (ret)
584		return ret;
585	irq = bind_evtchn_to_irqhandler(evtchn, xenfb_event_handler,
586					0, dev->devicetype, info);
587	if (irq < 0) {
588		xenbus_free_evtchn(dev, evtchn);
589		xenbus_dev_fatal(dev, ret, "bind_evtchn_to_irqhandler");
590		return irq;
591	}
592 again:
593	ret = xenbus_transaction_start(&xbt);
594	if (ret) {
595		xenbus_dev_fatal(dev, ret, "starting transaction");
596		goto unbind_irq;
597	}
598	ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
599			    virt_to_gfn(info->page));
600	if (ret)
601		goto error_xenbus;
602	ret = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
603			    evtchn);
604	if (ret)
605		goto error_xenbus;
606	ret = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
607			    XEN_IO_PROTO_ABI_NATIVE);
608	if (ret)
609		goto error_xenbus;
610	ret = xenbus_printf(xbt, dev->nodename, "feature-update", "1");
611	if (ret)
612		goto error_xenbus;
613	ret = xenbus_transaction_end(xbt, 0);
614	if (ret) {
615		if (ret == -EAGAIN)
616			goto again;
617		xenbus_dev_fatal(dev, ret, "completing transaction");
618		goto unbind_irq;
619	}
620
621	xenbus_switch_state(dev, XenbusStateInitialised);
622	info->irq = irq;
623	return 0;
624
625 error_xenbus:
626	xenbus_transaction_end(xbt, 1);
627	xenbus_dev_fatal(dev, ret, "writing xenstore");
628 unbind_irq:
629	unbind_from_irqhandler(irq, info);
630	return ret;
631}
632
633static void xenfb_disconnect_backend(struct xenfb_info *info)
634{
635	/* Prevent xenfb refresh */
636	info->update_wanted = 0;
637	if (info->irq >= 0)
638		unbind_from_irqhandler(info->irq, info);
639	info->irq = -1;
640}
641
642static void xenfb_backend_changed(struct xenbus_device *dev,
643				  enum xenbus_state backend_state)
644{
645	struct xenfb_info *info = dev_get_drvdata(&dev->dev);
646
647	switch (backend_state) {
648	case XenbusStateInitialising:
649	case XenbusStateInitialised:
650	case XenbusStateReconfiguring:
651	case XenbusStateReconfigured:
652	case XenbusStateUnknown:
653		break;
654
655	case XenbusStateInitWait:
656		xenbus_switch_state(dev, XenbusStateConnected);
657		break;
658
659	case XenbusStateConnected:
660		/*
661		 * Work around xenbus race condition: If backend goes
662		 * through InitWait to Connected fast enough, we can
663		 * get Connected twice here.
664		 */
665		if (dev->state != XenbusStateConnected)
666			/* no InitWait seen yet, fudge it */
667			xenbus_switch_state(dev, XenbusStateConnected);
668
669		if (xenbus_read_unsigned(info->xbdev->otherend,
670					 "request-update", 0))
671			info->update_wanted = 1;
672
673		info->feature_resize = xenbus_read_unsigned(dev->otherend,
674							"feature-resize", 0);
675		break;
676
677	case XenbusStateClosed:
678		if (dev->state == XenbusStateClosed)
679			break;
680		fallthrough;	/* Missed the backend's CLOSING state */
681	case XenbusStateClosing:
682		xenbus_frontend_closed(dev);
683		break;
684	}
685}
686
687static const struct xenbus_device_id xenfb_ids[] = {
688	{ "vfb" },
689	{ "" }
690};
691
692static struct xenbus_driver xenfb_driver = {
693	.ids = xenfb_ids,
694	.probe = xenfb_probe,
695	.remove = xenfb_remove,
696	.resume = xenfb_resume,
697	.otherend_changed = xenfb_backend_changed,
698};
699
700static int __init xenfb_init(void)
701{
702	if (!xen_domain())
703		return -ENODEV;
704
705	/* Nothing to do if running in dom0. */
706	if (xen_initial_domain())
707		return -ENODEV;
708
709	if (!xen_has_pv_devices())
710		return -ENODEV;
711
712	return xenbus_register_frontend(&xenfb_driver);
713}
714
715static void __exit xenfb_cleanup(void)
716{
717	xenbus_unregister_driver(&xenfb_driver);
718}
719
720module_init(xenfb_init);
721module_exit(xenfb_cleanup);
722
723MODULE_DESCRIPTION("Xen virtual framebuffer device frontend");
724MODULE_LICENSE("GPL");
725MODULE_ALIAS("xen:vfb");
726