Merge tag 'fbdev-v4.12' of git://github.com/bzolnier/linux
[muen/linux.git] / drivers / video / fbdev / xen-fbfront.c
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 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(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                 /* Missed the backend's CLOSING state -- fallthrough */
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 };
699
700 static 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
715 static void __exit xenfb_cleanup(void)
716 {
717         xenbus_unregister_driver(&xenfb_driver);
718 }
719
720 module_init(xenfb_init);
721 module_exit(xenfb_cleanup);
722
723 MODULE_DESCRIPTION("Xen virtual framebuffer device frontend");
724 MODULE_LICENSE("GPL");
725 MODULE_ALIAS("xen:vfb");