summaryrefslogtreecommitdiffstats
path: root/drivers/video/fbdev/xen-fbfront.c
blob: 8752d389e3823f5ec81ee5fc35d268b87b22e0de (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
/*
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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 		*gfns;
	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 *pagereflist)
{
	struct xenfb_info *info = fb_info->par;
	struct fb_deferred_io_pageref *pageref;
	unsigned long beg, end;
	int y1, y2, miny, maxy;

	miny = INT_MAX;
	maxy = 0;
	list_for_each_entry(pageref, pagereflist, list) {
		beg = pageref->offset;
		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);
#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 const 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,
	.fb_mmap	= fb_deferred_io_mmap,
};

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;
	}

	video[KPARAM_WIDTH] = xenbus_read_unsigned(dev->otherend, "width",
						   video[KPARAM_WIDTH]);
	video[KPARAM_HEIGHT] = xenbus_read_unsigned(dev->otherend, "height",
						    video[KPARAM_HEIGHT]);

	/* 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) {
		pr_warn("display parameters %d,%d,%d invalid, use defaults\n",
			video[KPARAM_MEM], video[KPARAM_WIDTH],
			video[KPARAM_HEIGHT]);
		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->gfns = vmalloc(array_size(sizeof(unsigned long), info->nr_pages));
	if (!info->gfns)
		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_list_lock();
	for_each_console(c) {
		if (!strcmp(c->name, "tty") && c->index == 0)
			break;
	}
	if (c)
		console_force_preferred_locked(c);
	console_list_unlock();
}

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->gfns);
	vfree(info->fb);
	kfree(info);

	return 0;
}

static unsigned long vmalloc_to_gfn(void *address)
{
	return xen_page_to_gfn(vmalloc_to_page(address));
}

static void xenfb_init_shared_page(struct xenfb_info *info,
				   struct fb_info *fb_info)
{
	int i;
	int epd = PAGE_SIZE / sizeof(info->gfns[0]);

	for (i = 0; i < info->nr_pages; i++)
		info->gfns[i] = vmalloc_to_gfn(info->fb + i * PAGE_SIZE);

	for (i = 0; i * epd < info->nr_pages; i++)
		info->page->pd[i] = vmalloc_to_gfn(&info->gfns[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_gfn(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);

	switch (backend_state) {
	case XenbusStateInitialising:
	case XenbusStateInitialised:
	case XenbusStateReconfiguring:
	case XenbusStateReconfigured:
	case XenbusStateUnknown:
		break;

	case XenbusStateInitWait:
		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)
			/* no InitWait seen yet, fudge it */
			xenbus_switch_state(dev, XenbusStateConnected);

		if (xenbus_read_unsigned(info->xbdev->otherend,
					 "request-update", 0))
			info->update_wanted = 1;

		info->feature_resize = xenbus_read_unsigned(dev->otherend,
							"feature-resize", 0);
		break;

	case XenbusStateClosed:
		if (dev->state == XenbusStateClosed)
			break;
		fallthrough;	/* Missed the backend's CLOSING state */
	case XenbusStateClosing:
		xenbus_frontend_closed(dev);
		break;
	}
}

static const struct xenbus_device_id xenfb_ids[] = {
	{ "vfb" },
	{ "" }
};

static struct xenbus_driver xenfb_driver = {
	.ids = xenfb_ids,
	.probe = xenfb_probe,
	.remove = xenfb_remove,
	.resume = xenfb_resume,
	.otherend_changed = xenfb_backend_changed,
	.not_essential = true,
};

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");