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 
42 struct 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 
63 enum { KPARAM_MEM, KPARAM_WIDTH, KPARAM_HEIGHT, KPARAM_CNT };
64 static int video[KPARAM_CNT] = { 2, XENFB_WIDTH, XENFB_HEIGHT };
65 module_param_array(video, int, NULL, 0);
66 MODULE_PARM_DESC(video,
67 	"Video memory size in MB, width, height in pixels (default 2,800,600)");
68 
69 static void xenfb_make_preferred_console(void);
70 static int xenfb_remove(struct xenbus_device *);
71 static void xenfb_init_shared_page(struct xenfb_info *, struct fb_info *);
72 static int xenfb_connect_backend(struct xenbus_device *, struct xenfb_info *);
73 static void xenfb_disconnect_backend(struct xenfb_info *);
74 
75 static 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 
90 static 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 
106 static 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 
117 static 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 
126 static 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 
140 static 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 
184 static 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 
209 static struct fb_deferred_io xenfb_defio = {
210 	.delay		= HZ / 20,
211 	.deferred_io	= xenfb_deferred_io,
212 };
213 
214 static 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 
245 static 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 
253 static 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 
261 static 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 
269 static 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 
280 static int
281 xenfb_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 
312 static 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 
331 static 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 
343 static 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 
364 static 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 
487 error_fb:
488 	fb_deferred_io_cleanup(fb_info);
489 	fb_dealloc_cmap(&fb_info->cmap);
490 	framebuffer_release(fb_info);
491 error_nomem:
492 	if (!ret) {
493 		ret = -ENOMEM;
494 		xenbus_dev_fatal(dev, ret, "allocating device memory");
495 	}
496 error:
497 	xenfb_remove(dev);
498 	return ret;
499 }
500 
501 static 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 
522 static 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 
531 static 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 
550 static unsigned long vmalloc_to_gfn(void *address)
551 {
552 	return xen_page_to_gfn(vmalloc_to_page(address));
553 }
554 
555 static 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 
576 static 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 
633 static 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 
642 static 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 
687 static const struct xenbus_device_id xenfb_ids[] = {
688 	{ "vfb" },
689 	{ "" }
690 };
691 
692 static 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 	.not_essential = true,
699 };
700 
701 static int __init xenfb_init(void)
702 {
703 	if (!xen_domain())
704 		return -ENODEV;
705 
706 	/* Nothing to do if running in dom0. */
707 	if (xen_initial_domain())
708 		return -ENODEV;
709 
710 	if (!xen_has_pv_devices())
711 		return -ENODEV;
712 
713 	return xenbus_register_frontend(&xenfb_driver);
714 }
715 
716 static void __exit xenfb_cleanup(void)
717 {
718 	xenbus_unregister_driver(&xenfb_driver);
719 }
720 
721 module_init(xenfb_init);
722 module_exit(xenfb_cleanup);
723 
724 MODULE_DESCRIPTION("Xen virtual framebuffer device frontend");
725 MODULE_LICENSE("GPL");
726 MODULE_ALIAS("xen:vfb");
727