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 void 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, struct list_head *pagereflist)
185 {
186 	struct xenfb_info *info = fb_info->par;
187 	struct fb_deferred_io_pageref *pageref;
188 	unsigned long beg, end;
189 	int y1, y2, miny, maxy;
190 
191 	miny = INT_MAX;
192 	maxy = 0;
193 	list_for_each_entry(pageref, pagereflist, list) {
194 		beg = pageref->offset;
195 		end = beg + PAGE_SIZE - 1;
196 		y1 = beg / fb_info->fix.line_length;
197 		y2 = end / fb_info->fix.line_length;
198 		if (y2 >= fb_info->var.yres)
199 			y2 = fb_info->var.yres - 1;
200 		if (miny > y1)
201 			miny = y1;
202 		if (maxy < y2)
203 			maxy = y2;
204 	}
205 	xenfb_refresh(info, 0, miny, fb_info->var.xres, maxy - miny + 1);
206 }
207 
208 static struct fb_deferred_io xenfb_defio = {
209 	.delay		= HZ / 20,
210 	.deferred_io	= xenfb_deferred_io,
211 };
212 
213 static int xenfb_setcolreg(unsigned regno, unsigned red, unsigned green,
214 			   unsigned blue, unsigned transp,
215 			   struct fb_info *info)
216 {
217 	u32 v;
218 
219 	if (regno > info->cmap.len)
220 		return 1;
221 
222 #define CNVT_TOHW(val, width) ((((val)<<(width))+0x7FFF-(val))>>16)
223 	red = CNVT_TOHW(red, info->var.red.length);
224 	green = CNVT_TOHW(green, info->var.green.length);
225 	blue = CNVT_TOHW(blue, info->var.blue.length);
226 #undef CNVT_TOHW
227 
228 	v = (red << info->var.red.offset) |
229 	    (green << info->var.green.offset) |
230 	    (blue << info->var.blue.offset);
231 
232 	switch (info->var.bits_per_pixel) {
233 	case 16:
234 	case 24:
235 	case 32:
236 		((u32 *)info->pseudo_palette)[regno] = v;
237 		break;
238 	}
239 
240 	return 0;
241 }
242 
243 static void xenfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
244 {
245 	struct xenfb_info *info = p->par;
246 
247 	sys_fillrect(p, rect);
248 	xenfb_refresh(info, rect->dx, rect->dy, rect->width, rect->height);
249 }
250 
251 static void xenfb_imageblit(struct fb_info *p, const struct fb_image *image)
252 {
253 	struct xenfb_info *info = p->par;
254 
255 	sys_imageblit(p, image);
256 	xenfb_refresh(info, image->dx, image->dy, image->width, image->height);
257 }
258 
259 static void xenfb_copyarea(struct fb_info *p, const struct fb_copyarea *area)
260 {
261 	struct xenfb_info *info = p->par;
262 
263 	sys_copyarea(p, area);
264 	xenfb_refresh(info, area->dx, area->dy, area->width, area->height);
265 }
266 
267 static ssize_t xenfb_write(struct fb_info *p, const char __user *buf,
268 			size_t count, loff_t *ppos)
269 {
270 	struct xenfb_info *info = p->par;
271 	ssize_t res;
272 
273 	res = fb_sys_write(p, buf, count, ppos);
274 	xenfb_refresh(info, 0, 0, info->page->width, info->page->height);
275 	return res;
276 }
277 
278 static int
279 xenfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
280 {
281 	struct xenfb_info *xenfb_info;
282 	int required_mem_len;
283 
284 	xenfb_info = info->par;
285 
286 	if (!xenfb_info->feature_resize) {
287 		if (var->xres == video[KPARAM_WIDTH] &&
288 		    var->yres == video[KPARAM_HEIGHT] &&
289 		    var->bits_per_pixel == xenfb_info->page->depth) {
290 			return 0;
291 		}
292 		return -EINVAL;
293 	}
294 
295 	/* Can't resize past initial width and height */
296 	if (var->xres > video[KPARAM_WIDTH] || var->yres > video[KPARAM_HEIGHT])
297 		return -EINVAL;
298 
299 	required_mem_len = var->xres * var->yres * xenfb_info->page->depth / 8;
300 	if (var->bits_per_pixel == xenfb_info->page->depth &&
301 	    var->xres <= info->fix.line_length / (XENFB_DEPTH / 8) &&
302 	    required_mem_len <= info->fix.smem_len) {
303 		var->xres_virtual = var->xres;
304 		var->yres_virtual = var->yres;
305 		return 0;
306 	}
307 	return -EINVAL;
308 }
309 
310 static int xenfb_set_par(struct fb_info *info)
311 {
312 	struct xenfb_info *xenfb_info;
313 	unsigned long flags;
314 
315 	xenfb_info = info->par;
316 
317 	spin_lock_irqsave(&xenfb_info->resize_lock, flags);
318 	xenfb_info->resize.type = XENFB_TYPE_RESIZE;
319 	xenfb_info->resize.width = info->var.xres;
320 	xenfb_info->resize.height = info->var.yres;
321 	xenfb_info->resize.stride = info->fix.line_length;
322 	xenfb_info->resize.depth = info->var.bits_per_pixel;
323 	xenfb_info->resize.offset = 0;
324 	xenfb_info->resize_dpy = 1;
325 	spin_unlock_irqrestore(&xenfb_info->resize_lock, flags);
326 	return 0;
327 }
328 
329 static const struct fb_ops xenfb_fb_ops = {
330 	.owner		= THIS_MODULE,
331 	.fb_read	= fb_sys_read,
332 	.fb_write	= xenfb_write,
333 	.fb_setcolreg	= xenfb_setcolreg,
334 	.fb_fillrect	= xenfb_fillrect,
335 	.fb_copyarea	= xenfb_copyarea,
336 	.fb_imageblit	= xenfb_imageblit,
337 	.fb_check_var	= xenfb_check_var,
338 	.fb_set_par     = xenfb_set_par,
339 	.fb_mmap	= fb_deferred_io_mmap,
340 };
341 
342 static irqreturn_t xenfb_event_handler(int rq, void *dev_id)
343 {
344 	/*
345 	 * No in events recognized, simply ignore them all.
346 	 * If you need to recognize some, see xen-kbdfront's
347 	 * input_handler() for how to do that.
348 	 */
349 	struct xenfb_info *info = dev_id;
350 	struct xenfb_page *page = info->page;
351 
352 	if (page->in_cons != page->in_prod) {
353 		info->page->in_cons = info->page->in_prod;
354 		notify_remote_via_irq(info->irq);
355 	}
356 
357 	/* Flush dirty rectangle: */
358 	xenfb_refresh(info, INT_MAX, INT_MAX, -INT_MAX, -INT_MAX);
359 
360 	return IRQ_HANDLED;
361 }
362 
363 static int xenfb_probe(struct xenbus_device *dev,
364 		       const struct xenbus_device_id *id)
365 {
366 	struct xenfb_info *info;
367 	struct fb_info *fb_info;
368 	int fb_size;
369 	int val;
370 	int ret = 0;
371 
372 	info = kzalloc(sizeof(*info), GFP_KERNEL);
373 	if (info == NULL) {
374 		xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
375 		return -ENOMEM;
376 	}
377 
378 	/* Limit kernel param videoram amount to what is in xenstore */
379 	if (xenbus_scanf(XBT_NIL, dev->otherend, "videoram", "%d", &val) == 1) {
380 		if (val < video[KPARAM_MEM])
381 			video[KPARAM_MEM] = val;
382 	}
383 
384 	video[KPARAM_WIDTH] = xenbus_read_unsigned(dev->otherend, "width",
385 						   video[KPARAM_WIDTH]);
386 	video[KPARAM_HEIGHT] = xenbus_read_unsigned(dev->otherend, "height",
387 						    video[KPARAM_HEIGHT]);
388 
389 	/* If requested res does not fit in available memory, use default */
390 	fb_size = video[KPARAM_MEM] * 1024 * 1024;
391 	if (video[KPARAM_WIDTH] * video[KPARAM_HEIGHT] * XENFB_DEPTH / 8
392 	    > fb_size) {
393 		pr_warn("display parameters %d,%d,%d invalid, use defaults\n",
394 			video[KPARAM_MEM], video[KPARAM_WIDTH],
395 			video[KPARAM_HEIGHT]);
396 		video[KPARAM_WIDTH] = XENFB_WIDTH;
397 		video[KPARAM_HEIGHT] = XENFB_HEIGHT;
398 		fb_size = XENFB_DEFAULT_FB_LEN;
399 	}
400 
401 	dev_set_drvdata(&dev->dev, info);
402 	info->xbdev = dev;
403 	info->irq = -1;
404 	info->x1 = info->y1 = INT_MAX;
405 	spin_lock_init(&info->dirty_lock);
406 	spin_lock_init(&info->resize_lock);
407 
408 	info->fb = vzalloc(fb_size);
409 	if (info->fb == NULL)
410 		goto error_nomem;
411 
412 	info->nr_pages = (fb_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
413 
414 	info->gfns = vmalloc(array_size(sizeof(unsigned long), info->nr_pages));
415 	if (!info->gfns)
416 		goto error_nomem;
417 
418 	/* set up shared page */
419 	info->page = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
420 	if (!info->page)
421 		goto error_nomem;
422 
423 	/* abusing framebuffer_alloc() to allocate pseudo_palette */
424 	fb_info = framebuffer_alloc(sizeof(u32) * 256, NULL);
425 	if (fb_info == NULL)
426 		goto error_nomem;
427 
428 	/* complete the abuse: */
429 	fb_info->pseudo_palette = fb_info->par;
430 	fb_info->par = info;
431 
432 	fb_info->screen_base = info->fb;
433 
434 	fb_info->fbops = &xenfb_fb_ops;
435 	fb_info->var.xres_virtual = fb_info->var.xres = video[KPARAM_WIDTH];
436 	fb_info->var.yres_virtual = fb_info->var.yres = video[KPARAM_HEIGHT];
437 	fb_info->var.bits_per_pixel = XENFB_DEPTH;
438 
439 	fb_info->var.red = (struct fb_bitfield){16, 8, 0};
440 	fb_info->var.green = (struct fb_bitfield){8, 8, 0};
441 	fb_info->var.blue = (struct fb_bitfield){0, 8, 0};
442 
443 	fb_info->var.activate = FB_ACTIVATE_NOW;
444 	fb_info->var.height = -1;
445 	fb_info->var.width = -1;
446 	fb_info->var.vmode = FB_VMODE_NONINTERLACED;
447 
448 	fb_info->fix.visual = FB_VISUAL_TRUECOLOR;
449 	fb_info->fix.line_length = fb_info->var.xres * XENFB_DEPTH / 8;
450 	fb_info->fix.smem_start = 0;
451 	fb_info->fix.smem_len = fb_size;
452 	strcpy(fb_info->fix.id, "xen");
453 	fb_info->fix.type = FB_TYPE_PACKED_PIXELS;
454 	fb_info->fix.accel = FB_ACCEL_NONE;
455 
456 	fb_info->flags = FBINFO_FLAG_DEFAULT | FBINFO_VIRTFB;
457 
458 	ret = fb_alloc_cmap(&fb_info->cmap, 256, 0);
459 	if (ret < 0) {
460 		framebuffer_release(fb_info);
461 		xenbus_dev_fatal(dev, ret, "fb_alloc_cmap");
462 		goto error;
463 	}
464 
465 	fb_info->fbdefio = &xenfb_defio;
466 	fb_deferred_io_init(fb_info);
467 
468 	xenfb_init_shared_page(info, fb_info);
469 
470 	ret = xenfb_connect_backend(dev, info);
471 	if (ret < 0) {
472 		xenbus_dev_fatal(dev, ret, "xenfb_connect_backend");
473 		goto error_fb;
474 	}
475 
476 	ret = register_framebuffer(fb_info);
477 	if (ret) {
478 		xenbus_dev_fatal(dev, ret, "register_framebuffer");
479 		goto error_fb;
480 	}
481 	info->fb_info = fb_info;
482 
483 	xenfb_make_preferred_console();
484 	return 0;
485 
486 error_fb:
487 	fb_deferred_io_cleanup(fb_info);
488 	fb_dealloc_cmap(&fb_info->cmap);
489 	framebuffer_release(fb_info);
490 error_nomem:
491 	if (!ret) {
492 		ret = -ENOMEM;
493 		xenbus_dev_fatal(dev, ret, "allocating device memory");
494 	}
495 error:
496 	xenfb_remove(dev);
497 	return ret;
498 }
499 
500 static void xenfb_make_preferred_console(void)
501 {
502 	struct console *c;
503 
504 	if (console_set_on_cmdline)
505 		return;
506 
507 	console_list_lock();
508 	for_each_console(c) {
509 		if (!strcmp(c->name, "tty") && c->index == 0)
510 			break;
511 	}
512 	if (c)
513 		console_force_preferred_locked(c);
514 	console_list_unlock();
515 }
516 
517 static int xenfb_resume(struct xenbus_device *dev)
518 {
519 	struct xenfb_info *info = dev_get_drvdata(&dev->dev);
520 
521 	xenfb_disconnect_backend(info);
522 	xenfb_init_shared_page(info, info->fb_info);
523 	return xenfb_connect_backend(dev, info);
524 }
525 
526 static void xenfb_remove(struct xenbus_device *dev)
527 {
528 	struct xenfb_info *info = dev_get_drvdata(&dev->dev);
529 
530 	xenfb_disconnect_backend(info);
531 	if (info->fb_info) {
532 		fb_deferred_io_cleanup(info->fb_info);
533 		unregister_framebuffer(info->fb_info);
534 		fb_dealloc_cmap(&info->fb_info->cmap);
535 		framebuffer_release(info->fb_info);
536 	}
537 	free_page((unsigned long)info->page);
538 	vfree(info->gfns);
539 	vfree(info->fb);
540 	kfree(info);
541 }
542 
543 static unsigned long vmalloc_to_gfn(void *address)
544 {
545 	return xen_page_to_gfn(vmalloc_to_page(address));
546 }
547 
548 static void xenfb_init_shared_page(struct xenfb_info *info,
549 				   struct fb_info *fb_info)
550 {
551 	int i;
552 	int epd = PAGE_SIZE / sizeof(info->gfns[0]);
553 
554 	for (i = 0; i < info->nr_pages; i++)
555 		info->gfns[i] = vmalloc_to_gfn(info->fb + i * PAGE_SIZE);
556 
557 	for (i = 0; i * epd < info->nr_pages; i++)
558 		info->page->pd[i] = vmalloc_to_gfn(&info->gfns[i * epd]);
559 
560 	info->page->width = fb_info->var.xres;
561 	info->page->height = fb_info->var.yres;
562 	info->page->depth = fb_info->var.bits_per_pixel;
563 	info->page->line_length = fb_info->fix.line_length;
564 	info->page->mem_length = fb_info->fix.smem_len;
565 	info->page->in_cons = info->page->in_prod = 0;
566 	info->page->out_cons = info->page->out_prod = 0;
567 }
568 
569 static int xenfb_connect_backend(struct xenbus_device *dev,
570 				 struct xenfb_info *info)
571 {
572 	int ret, evtchn, irq;
573 	struct xenbus_transaction xbt;
574 
575 	ret = xenbus_alloc_evtchn(dev, &evtchn);
576 	if (ret)
577 		return ret;
578 	irq = bind_evtchn_to_irqhandler(evtchn, xenfb_event_handler,
579 					0, dev->devicetype, info);
580 	if (irq < 0) {
581 		xenbus_free_evtchn(dev, evtchn);
582 		xenbus_dev_fatal(dev, ret, "bind_evtchn_to_irqhandler");
583 		return irq;
584 	}
585  again:
586 	ret = xenbus_transaction_start(&xbt);
587 	if (ret) {
588 		xenbus_dev_fatal(dev, ret, "starting transaction");
589 		goto unbind_irq;
590 	}
591 	ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
592 			    virt_to_gfn(info->page));
593 	if (ret)
594 		goto error_xenbus;
595 	ret = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
596 			    evtchn);
597 	if (ret)
598 		goto error_xenbus;
599 	ret = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
600 			    XEN_IO_PROTO_ABI_NATIVE);
601 	if (ret)
602 		goto error_xenbus;
603 	ret = xenbus_printf(xbt, dev->nodename, "feature-update", "1");
604 	if (ret)
605 		goto error_xenbus;
606 	ret = xenbus_transaction_end(xbt, 0);
607 	if (ret) {
608 		if (ret == -EAGAIN)
609 			goto again;
610 		xenbus_dev_fatal(dev, ret, "completing transaction");
611 		goto unbind_irq;
612 	}
613 
614 	xenbus_switch_state(dev, XenbusStateInitialised);
615 	info->irq = irq;
616 	return 0;
617 
618  error_xenbus:
619 	xenbus_transaction_end(xbt, 1);
620 	xenbus_dev_fatal(dev, ret, "writing xenstore");
621  unbind_irq:
622 	unbind_from_irqhandler(irq, info);
623 	return ret;
624 }
625 
626 static void xenfb_disconnect_backend(struct xenfb_info *info)
627 {
628 	/* Prevent xenfb refresh */
629 	info->update_wanted = 0;
630 	if (info->irq >= 0)
631 		unbind_from_irqhandler(info->irq, info);
632 	info->irq = -1;
633 }
634 
635 static void xenfb_backend_changed(struct xenbus_device *dev,
636 				  enum xenbus_state backend_state)
637 {
638 	struct xenfb_info *info = dev_get_drvdata(&dev->dev);
639 
640 	switch (backend_state) {
641 	case XenbusStateInitialising:
642 	case XenbusStateInitialised:
643 	case XenbusStateReconfiguring:
644 	case XenbusStateReconfigured:
645 	case XenbusStateUnknown:
646 		break;
647 
648 	case XenbusStateInitWait:
649 		xenbus_switch_state(dev, XenbusStateConnected);
650 		break;
651 
652 	case XenbusStateConnected:
653 		/*
654 		 * Work around xenbus race condition: If backend goes
655 		 * through InitWait to Connected fast enough, we can
656 		 * get Connected twice here.
657 		 */
658 		if (dev->state != XenbusStateConnected)
659 			/* no InitWait seen yet, fudge it */
660 			xenbus_switch_state(dev, XenbusStateConnected);
661 
662 		if (xenbus_read_unsigned(info->xbdev->otherend,
663 					 "request-update", 0))
664 			info->update_wanted = 1;
665 
666 		info->feature_resize = xenbus_read_unsigned(dev->otherend,
667 							"feature-resize", 0);
668 		break;
669 
670 	case XenbusStateClosed:
671 		if (dev->state == XenbusStateClosed)
672 			break;
673 		fallthrough;	/* Missed the backend's CLOSING state */
674 	case XenbusStateClosing:
675 		xenbus_frontend_closed(dev);
676 		break;
677 	}
678 }
679 
680 static const struct xenbus_device_id xenfb_ids[] = {
681 	{ "vfb" },
682 	{ "" }
683 };
684 
685 static struct xenbus_driver xenfb_driver = {
686 	.ids = xenfb_ids,
687 	.probe = xenfb_probe,
688 	.remove = xenfb_remove,
689 	.resume = xenfb_resume,
690 	.otherend_changed = xenfb_backend_changed,
691 	.not_essential = true,
692 };
693 
694 static int __init xenfb_init(void)
695 {
696 	if (!xen_domain())
697 		return -ENODEV;
698 
699 	/* Nothing to do if running in dom0. */
700 	if (xen_initial_domain())
701 		return -ENODEV;
702 
703 	if (!xen_has_pv_devices())
704 		return -ENODEV;
705 
706 	return xenbus_register_frontend(&xenfb_driver);
707 }
708 
709 static void __exit xenfb_cleanup(void)
710 {
711 	xenbus_unregister_driver(&xenfb_driver);
712 }
713 
714 module_init(xenfb_init);
715 module_exit(xenfb_cleanup);
716 
717 MODULE_DESCRIPTION("Xen virtual framebuffer device frontend");
718 MODULE_LICENSE("GPL");
719 MODULE_ALIAS("xen:vfb");
720