a20218c2fda8be0a98b4a219bff743db2a0b5018
[linux-2.6.git] / drivers / video / 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 #include <linux/console.h>
22 #include <linux/kernel.h>
23 #include <linux/errno.h>
24 #include <linux/fb.h>
25 #include <linux/module.h>
26 #include <linux/slab.h>
27 #include <linux/vmalloc.h>
28 #include <linux/mm.h>
29
30 #include <asm/xen/hypervisor.h>
31
32 #include <xen/xen.h>
33 #include <xen/events.h>
34 #include <xen/page.h>
35 #include <xen/interface/io/fbif.h>
36 #include <xen/interface/io/protocols.h>
37 #include <xen/xenbus.h>
38
39 struct xenfb_info {
40         unsigned char           *fb;
41         struct fb_info          *fb_info;
42         int                     x1, y1, x2, y2; /* dirty rectangle,
43                                                    protected by dirty_lock */
44         spinlock_t              dirty_lock;
45         int                     nr_pages;
46         int                     irq;
47         struct xenfb_page       *page;
48         unsigned long           *mfns;
49         int                     update_wanted; /* XENFB_TYPE_UPDATE wanted */
50         int                     feature_resize; /* XENFB_TYPE_RESIZE ok */
51         struct xenfb_resize     resize;         /* protected by resize_lock */
52         int                     resize_dpy;     /* ditto */
53         spinlock_t              resize_lock;
54
55         struct xenbus_device    *xbdev;
56 };
57
58 #define XENFB_DEFAULT_FB_LEN (XENFB_WIDTH * XENFB_HEIGHT * XENFB_DEPTH / 8)
59
60 enum { KPARAM_MEM, KPARAM_WIDTH, KPARAM_HEIGHT, KPARAM_CNT };
61 static int video[KPARAM_CNT] = { 2, XENFB_WIDTH, XENFB_HEIGHT };
62 module_param_array(video, int, NULL, 0);
63 MODULE_PARM_DESC(video,
64         "Video memory size in MB, width, height in pixels (default 2,800,600)");
65
66 static void xenfb_make_preferred_console(void);
67 static int xenfb_remove(struct xenbus_device *);
68 static void xenfb_init_shared_page(struct xenfb_info *, struct fb_info *);
69 static int xenfb_connect_backend(struct xenbus_device *, struct xenfb_info *);
70 static void xenfb_disconnect_backend(struct xenfb_info *);
71
72 static void xenfb_send_event(struct xenfb_info *info,
73                              union xenfb_out_event *event)
74 {
75         u32 prod;
76
77         prod = info->page->out_prod;
78         /* caller ensures !xenfb_queue_full() */
79         mb();                   /* ensure ring space available */
80         XENFB_OUT_RING_REF(info->page, prod) = *event;
81         wmb();                  /* ensure ring contents visible */
82         info->page->out_prod = prod + 1;
83
84         notify_remote_via_irq(info->irq);
85 }
86
87 static void xenfb_do_update(struct xenfb_info *info,
88                             int x, int y, int w, int h)
89 {
90         union xenfb_out_event event;
91
92         memset(&event, 0, sizeof(event));
93         event.type = XENFB_TYPE_UPDATE;
94         event.update.x = x;
95         event.update.y = y;
96         event.update.width = w;
97         event.update.height = h;
98
99         /* caller ensures !xenfb_queue_full() */
100         xenfb_send_event(info, &event);
101 }
102
103 static void xenfb_do_resize(struct xenfb_info *info)
104 {
105         union xenfb_out_event event;
106
107         memset(&event, 0, sizeof(event));
108         event.resize = info->resize;
109
110         /* caller ensures !xenfb_queue_full() */
111         xenfb_send_event(info, &event);
112 }
113
114 static int xenfb_queue_full(struct xenfb_info *info)
115 {
116         u32 cons, prod;
117
118         prod = info->page->out_prod;
119         cons = info->page->out_cons;
120         return prod - cons == XENFB_OUT_RING_LEN;
121 }
122
123 static void xenfb_handle_resize_dpy(struct xenfb_info *info)
124 {
125         unsigned long flags;
126
127         spin_lock_irqsave(&info->resize_lock, flags);
128         if (info->resize_dpy) {
129                 if (!xenfb_queue_full(info)) {
130                         info->resize_dpy = 0;
131                         xenfb_do_resize(info);
132                 }
133         }
134         spin_unlock_irqrestore(&info->resize_lock, flags);
135 }
136
137 static void xenfb_refresh(struct xenfb_info *info,
138                           int x1, int y1, int w, int h)
139 {
140         unsigned long flags;
141         int x2 = x1 + w - 1;
142         int y2 = y1 + h - 1;
143
144         xenfb_handle_resize_dpy(info);
145
146         if (!info->update_wanted)
147                 return;
148
149         spin_lock_irqsave(&info->dirty_lock, flags);
150
151         /* Combine with dirty rectangle: */
152         if (info->y1 < y1)
153                 y1 = info->y1;
154         if (info->y2 > y2)
155                 y2 = info->y2;
156         if (info->x1 < x1)
157                 x1 = info->x1;
158         if (info->x2 > x2)
159                 x2 = info->x2;
160
161         if (xenfb_queue_full(info)) {
162                 /* Can't send right now, stash it in the dirty rectangle */
163                 info->x1 = x1;
164                 info->x2 = x2;
165                 info->y1 = y1;
166                 info->y2 = y2;
167                 spin_unlock_irqrestore(&info->dirty_lock, flags);
168                 return;
169         }
170
171         /* Clear dirty rectangle: */
172         info->x1 = info->y1 = INT_MAX;
173         info->x2 = info->y2 = 0;
174
175         spin_unlock_irqrestore(&info->dirty_lock, flags);
176
177         if (x1 <= x2 && y1 <= y2)
178                 xenfb_do_update(info, x1, y1, x2 - x1 + 1, y2 - y1 + 1);
179 }
180
181 static void xenfb_deferred_io(struct fb_info *fb_info,
182                               struct list_head *pagelist)
183 {
184         struct xenfb_info *info = fb_info->par;
185         struct page *page;
186         unsigned long beg, end;
187         int y1, y2, miny, maxy;
188
189         miny = INT_MAX;
190         maxy = 0;
191         list_for_each_entry(page, pagelist, lru) {
192                 beg = page->index << PAGE_SHIFT;
193                 end = beg + PAGE_SIZE - 1;
194                 y1 = beg / fb_info->fix.line_length;
195                 y2 = end / fb_info->fix.line_length;
196                 if (y2 >= fb_info->var.yres)
197                         y2 = fb_info->var.yres - 1;
198                 if (miny > y1)
199                         miny = y1;
200                 if (maxy < y2)
201                         maxy = y2;
202         }
203         xenfb_refresh(info, 0, miny, fb_info->var.xres, maxy - miny + 1);
204 }
205
206 static struct fb_deferred_io xenfb_defio = {
207         .delay          = HZ / 20,
208         .deferred_io    = xenfb_deferred_io,
209 };
210
211 static int xenfb_setcolreg(unsigned regno, unsigned red, unsigned green,
212                            unsigned blue, unsigned transp,
213                            struct fb_info *info)
214 {
215         u32 v;
216
217         if (regno > info->cmap.len)
218                 return 1;
219
220 #define CNVT_TOHW(val, width) ((((val)<<(width))+0x7FFF-(val))>>16)
221         red = CNVT_TOHW(red, info->var.red.length);
222         green = CNVT_TOHW(green, info->var.green.length);
223         blue = CNVT_TOHW(blue, info->var.blue.length);
224         transp = CNVT_TOHW(transp, info->var.transp.length);
225 #undef CNVT_TOHW
226
227         v = (red << info->var.red.offset) |
228             (green << info->var.green.offset) |
229             (blue << info->var.blue.offset);
230
231         switch (info->var.bits_per_pixel) {
232         case 16:
233         case 24:
234         case 32:
235                 ((u32 *)info->pseudo_palette)[regno] = v;
236                 break;
237         }
238
239         return 0;
240 }
241
242 static void xenfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
243 {
244         struct xenfb_info *info = p->par;
245
246         sys_fillrect(p, rect);
247         xenfb_refresh(info, rect->dx, rect->dy, rect->width, rect->height);
248 }
249
250 static void xenfb_imageblit(struct fb_info *p, const struct fb_image *image)
251 {
252         struct xenfb_info *info = p->par;
253
254         sys_imageblit(p, image);
255         xenfb_refresh(info, image->dx, image->dy, image->width, image->height);
256 }
257
258 static void xenfb_copyarea(struct fb_info *p, const struct fb_copyarea *area)
259 {
260         struct xenfb_info *info = p->par;
261
262         sys_copyarea(p, area);
263         xenfb_refresh(info, area->dx, area->dy, area->width, area->height);
264 }
265
266 static ssize_t xenfb_write(struct fb_info *p, const char __user *buf,
267                         size_t count, loff_t *ppos)
268 {
269         struct xenfb_info *info = p->par;
270         ssize_t res;
271
272         res = fb_sys_write(p, buf, count, ppos);
273         xenfb_refresh(info, 0, 0, info->page->width, info->page->height);
274         return res;
275 }
276
277 static int
278 xenfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
279 {
280         struct xenfb_info *xenfb_info;
281         int required_mem_len;
282
283         xenfb_info = info->par;
284
285         if (!xenfb_info->feature_resize) {
286                 if (var->xres == video[KPARAM_WIDTH] &&
287                     var->yres == video[KPARAM_HEIGHT] &&
288                     var->bits_per_pixel == xenfb_info->page->depth) {
289                         return 0;
290                 }
291                 return -EINVAL;
292         }
293
294         /* Can't resize past initial width and height */
295         if (var->xres > video[KPARAM_WIDTH] || var->yres > video[KPARAM_HEIGHT])
296                 return -EINVAL;
297
298         required_mem_len = var->xres * var->yres * xenfb_info->page->depth / 8;
299         if (var->bits_per_pixel == xenfb_info->page->depth &&
300             var->xres <= info->fix.line_length / (XENFB_DEPTH / 8) &&
301             required_mem_len <= info->fix.smem_len) {
302                 var->xres_virtual = var->xres;
303                 var->yres_virtual = var->yres;
304                 return 0;
305         }
306         return -EINVAL;
307 }
308
309 static int xenfb_set_par(struct fb_info *info)
310 {
311         struct xenfb_info *xenfb_info;
312         unsigned long flags;
313
314         xenfb_info = info->par;
315
316         spin_lock_irqsave(&xenfb_info->resize_lock, flags);
317         xenfb_info->resize.type = XENFB_TYPE_RESIZE;
318         xenfb_info->resize.width = info->var.xres;
319         xenfb_info->resize.height = info->var.yres;
320         xenfb_info->resize.stride = info->fix.line_length;
321         xenfb_info->resize.depth = info->var.bits_per_pixel;
322         xenfb_info->resize.offset = 0;
323         xenfb_info->resize_dpy = 1;
324         spin_unlock_irqrestore(&xenfb_info->resize_lock, flags);
325         return 0;
326 }
327
328 static struct fb_ops xenfb_fb_ops = {
329         .owner          = THIS_MODULE,
330         .fb_read        = fb_sys_read,
331         .fb_write       = xenfb_write,
332         .fb_setcolreg   = xenfb_setcolreg,
333         .fb_fillrect    = xenfb_fillrect,
334         .fb_copyarea    = xenfb_copyarea,
335         .fb_imageblit   = xenfb_imageblit,
336         .fb_check_var   = xenfb_check_var,
337         .fb_set_par     = xenfb_set_par,
338 };
339
340 static irqreturn_t xenfb_event_handler(int rq, void *dev_id)
341 {
342         /*
343          * No in events recognized, simply ignore them all.
344          * If you need to recognize some, see xen-kbdfront's
345          * input_handler() for how to do that.
346          */
347         struct xenfb_info *info = dev_id;
348         struct xenfb_page *page = info->page;
349
350         if (page->in_cons != page->in_prod) {
351                 info->page->in_cons = info->page->in_prod;
352                 notify_remote_via_irq(info->irq);
353         }
354
355         /* Flush dirty rectangle: */
356         xenfb_refresh(info, INT_MAX, INT_MAX, -INT_MAX, -INT_MAX);
357
358         return IRQ_HANDLED;
359 }
360
361 static int __devinit xenfb_probe(struct xenbus_device *dev,
362                                  const struct xenbus_device_id *id)
363 {
364         struct xenfb_info *info;
365         struct fb_info *fb_info;
366         int fb_size;
367         int val;
368         int ret;
369
370         info = kzalloc(sizeof(*info), GFP_KERNEL);
371         if (info == NULL) {
372                 xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
373                 return -ENOMEM;
374         }
375
376         /* Limit kernel param videoram amount to what is in xenstore */
377         if (xenbus_scanf(XBT_NIL, dev->otherend, "videoram", "%d", &val) == 1) {
378                 if (val < video[KPARAM_MEM])
379                         video[KPARAM_MEM] = val;
380         }
381
382         /* If requested res does not fit in available memory, use default */
383         fb_size = video[KPARAM_MEM] * 1024 * 1024;
384         if (video[KPARAM_WIDTH] * video[KPARAM_HEIGHT] * XENFB_DEPTH / 8
385             > fb_size) {
386                 video[KPARAM_WIDTH] = XENFB_WIDTH;
387                 video[KPARAM_HEIGHT] = XENFB_HEIGHT;
388                 fb_size = XENFB_DEFAULT_FB_LEN;
389         }
390
391         dev_set_drvdata(&dev->dev, info);
392         info->xbdev = dev;
393         info->irq = -1;
394         info->x1 = info->y1 = INT_MAX;
395         spin_lock_init(&info->dirty_lock);
396         spin_lock_init(&info->resize_lock);
397
398         info->fb = vmalloc(fb_size);
399         if (info->fb == NULL)
400                 goto error_nomem;
401         memset(info->fb, 0, fb_size);
402
403         info->nr_pages = (fb_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
404
405         info->mfns = vmalloc(sizeof(unsigned long) * info->nr_pages);
406         if (!info->mfns)
407                 goto error_nomem;
408
409         /* set up shared page */
410         info->page = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
411         if (!info->page)
412                 goto error_nomem;
413
414         /* abusing framebuffer_alloc() to allocate pseudo_palette */
415         fb_info = framebuffer_alloc(sizeof(u32) * 256, NULL);
416         if (fb_info == NULL)
417                 goto error_nomem;
418
419         /* complete the abuse: */
420         fb_info->pseudo_palette = fb_info->par;
421         fb_info->par = info;
422
423         fb_info->screen_base = info->fb;
424
425         fb_info->fbops = &xenfb_fb_ops;
426         fb_info->var.xres_virtual = fb_info->var.xres = video[KPARAM_WIDTH];
427         fb_info->var.yres_virtual = fb_info->var.yres = video[KPARAM_HEIGHT];
428         fb_info->var.bits_per_pixel = XENFB_DEPTH;
429
430         fb_info->var.red = (struct fb_bitfield){16, 8, 0};
431         fb_info->var.green = (struct fb_bitfield){8, 8, 0};
432         fb_info->var.blue = (struct fb_bitfield){0, 8, 0};
433
434         fb_info->var.activate = FB_ACTIVATE_NOW;
435         fb_info->var.height = -1;
436         fb_info->var.width = -1;
437         fb_info->var.vmode = FB_VMODE_NONINTERLACED;
438
439         fb_info->fix.visual = FB_VISUAL_TRUECOLOR;
440         fb_info->fix.line_length = fb_info->var.xres * XENFB_DEPTH / 8;
441         fb_info->fix.smem_start = 0;
442         fb_info->fix.smem_len = fb_size;
443         strcpy(fb_info->fix.id, "xen");
444         fb_info->fix.type = FB_TYPE_PACKED_PIXELS;
445         fb_info->fix.accel = FB_ACCEL_NONE;
446
447         fb_info->flags = FBINFO_FLAG_DEFAULT | FBINFO_VIRTFB;
448
449         ret = fb_alloc_cmap(&fb_info->cmap, 256, 0);
450         if (ret < 0) {
451                 framebuffer_release(fb_info);
452                 xenbus_dev_fatal(dev, ret, "fb_alloc_cmap");
453                 goto error;
454         }
455
456         fb_info->fbdefio = &xenfb_defio;
457         fb_deferred_io_init(fb_info);
458
459         xenfb_init_shared_page(info, fb_info);
460
461         ret = xenfb_connect_backend(dev, info);
462         if (ret < 0)
463                 goto error;
464
465         ret = register_framebuffer(fb_info);
466         if (ret) {
467                 fb_deferred_io_cleanup(fb_info);
468                 fb_dealloc_cmap(&fb_info->cmap);
469                 framebuffer_release(fb_info);
470                 xenbus_dev_fatal(dev, ret, "register_framebuffer");
471                 goto error;
472         }
473         info->fb_info = fb_info;
474
475         xenfb_make_preferred_console();
476         return 0;
477
478  error_nomem:
479         ret = -ENOMEM;
480         xenbus_dev_fatal(dev, ret, "allocating device memory");
481  error:
482         xenfb_remove(dev);
483         return ret;
484 }
485
486 static __devinit void
487 xenfb_make_preferred_console(void)
488 {
489         struct console *c;
490
491         if (console_set_on_cmdline)
492                 return;
493
494         console_lock();
495         for_each_console(c) {
496                 if (!strcmp(c->name, "tty") && c->index == 0)
497                         break;
498         }
499         console_unlock();
500         if (c) {
501                 unregister_console(c);
502                 c->flags |= CON_CONSDEV;
503                 c->flags &= ~CON_PRINTBUFFER; /* don't print again */
504                 register_console(c);
505         }
506 }
507
508 static int xenfb_resume(struct xenbus_device *dev)
509 {
510         struct xenfb_info *info = dev_get_drvdata(&dev->dev);
511
512         xenfb_disconnect_backend(info);
513         xenfb_init_shared_page(info, info->fb_info);
514         return xenfb_connect_backend(dev, info);
515 }
516
517 static int xenfb_remove(struct xenbus_device *dev)
518 {
519         struct xenfb_info *info = dev_get_drvdata(&dev->dev);
520
521         xenfb_disconnect_backend(info);
522         if (info->fb_info) {
523                 fb_deferred_io_cleanup(info->fb_info);
524                 unregister_framebuffer(info->fb_info);
525                 fb_dealloc_cmap(&info->fb_info->cmap);
526                 framebuffer_release(info->fb_info);
527         }
528         free_page((unsigned long)info->page);
529         vfree(info->mfns);
530         vfree(info->fb);
531         kfree(info);
532
533         return 0;
534 }
535
536 static unsigned long vmalloc_to_mfn(void *address)
537 {
538         return pfn_to_mfn(vmalloc_to_pfn(address));
539 }
540
541 static void xenfb_init_shared_page(struct xenfb_info *info,
542                                    struct fb_info *fb_info)
543 {
544         int i;
545         int epd = PAGE_SIZE / sizeof(info->mfns[0]);
546
547         for (i = 0; i < info->nr_pages; i++)
548                 info->mfns[i] = vmalloc_to_mfn(info->fb + i * PAGE_SIZE);
549
550         for (i = 0; i * epd < info->nr_pages; i++)
551                 info->page->pd[i] = vmalloc_to_mfn(&info->mfns[i * epd]);
552
553         info->page->width = fb_info->var.xres;
554         info->page->height = fb_info->var.yres;
555         info->page->depth = fb_info->var.bits_per_pixel;
556         info->page->line_length = fb_info->fix.line_length;
557         info->page->mem_length = fb_info->fix.smem_len;
558         info->page->in_cons = info->page->in_prod = 0;
559         info->page->out_cons = info->page->out_prod = 0;
560 }
561
562 static int xenfb_connect_backend(struct xenbus_device *dev,
563                                  struct xenfb_info *info)
564 {
565         int ret, evtchn, irq;
566         struct xenbus_transaction xbt;
567
568         ret = xenbus_alloc_evtchn(dev, &evtchn);
569         if (ret)
570                 return ret;
571         irq = bind_evtchn_to_irqhandler(evtchn, xenfb_event_handler,
572                                         0, dev->devicetype, info);
573         if (irq < 0) {
574                 xenbus_free_evtchn(dev, evtchn);
575                 xenbus_dev_fatal(dev, ret, "bind_evtchn_to_irqhandler");
576                 return irq;
577         }
578  again:
579         ret = xenbus_transaction_start(&xbt);
580         if (ret) {
581                 xenbus_dev_fatal(dev, ret, "starting transaction");
582                 goto unbind_irq;
583         }
584         ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
585                             virt_to_mfn(info->page));
586         if (ret)
587                 goto error_xenbus;
588         ret = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
589                             evtchn);
590         if (ret)
591                 goto error_xenbus;
592         ret = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
593                             XEN_IO_PROTO_ABI_NATIVE);
594         if (ret)
595                 goto error_xenbus;
596         ret = xenbus_printf(xbt, dev->nodename, "feature-update", "1");
597         if (ret)
598                 goto error_xenbus;
599         ret = xenbus_transaction_end(xbt, 0);
600         if (ret) {
601                 if (ret == -EAGAIN)
602                         goto again;
603                 xenbus_dev_fatal(dev, ret, "completing transaction");
604                 goto unbind_irq;
605         }
606
607         xenbus_switch_state(dev, XenbusStateInitialised);
608         info->irq = irq;
609         return 0;
610
611  error_xenbus:
612         xenbus_transaction_end(xbt, 1);
613         xenbus_dev_fatal(dev, ret, "writing xenstore");
614  unbind_irq:
615         unbind_from_irqhandler(irq, info);
616         return ret;
617 }
618
619 static void xenfb_disconnect_backend(struct xenfb_info *info)
620 {
621         /* Prevent xenfb refresh */
622         info->update_wanted = 0;
623         if (info->irq >= 0)
624                 unbind_from_irqhandler(info->irq, info);
625         info->irq = -1;
626 }
627
628 static void xenfb_backend_changed(struct xenbus_device *dev,
629                                   enum xenbus_state backend_state)
630 {
631         struct xenfb_info *info = dev_get_drvdata(&dev->dev);
632         int val;
633
634         switch (backend_state) {
635         case XenbusStateInitialising:
636         case XenbusStateInitialised:
637         case XenbusStateReconfiguring:
638         case XenbusStateReconfigured:
639         case XenbusStateUnknown:
640         case XenbusStateClosed:
641                 break;
642
643         case XenbusStateInitWait:
644 InitWait:
645                 xenbus_switch_state(dev, XenbusStateConnected);
646                 break;
647
648         case XenbusStateConnected:
649                 /*
650                  * Work around xenbus race condition: If backend goes
651                  * through InitWait to Connected fast enough, we can
652                  * get Connected twice here.
653                  */
654                 if (dev->state != XenbusStateConnected)
655                         goto InitWait; /* no InitWait seen yet, fudge it */
656
657                 if (xenbus_scanf(XBT_NIL, info->xbdev->otherend,
658                                  "request-update", "%d", &val) < 0)
659                         val = 0;
660                 if (val)
661                         info->update_wanted = 1;
662
663                 if (xenbus_scanf(XBT_NIL, dev->otherend,
664                                  "feature-resize", "%d", &val) < 0)
665                         val = 0;
666                 info->feature_resize = val;
667                 break;
668
669         case XenbusStateClosing:
670                 xenbus_frontend_closed(dev);
671                 break;
672         }
673 }
674
675 static struct xenbus_device_id xenfb_ids[] = {
676         { "vfb" },
677         { "" }
678 };
679
680 static struct xenbus_driver xenfb_driver = {
681         .name = "vfb",
682         .owner = THIS_MODULE,
683         .ids = xenfb_ids,
684         .probe = xenfb_probe,
685         .remove = xenfb_remove,
686         .resume = xenfb_resume,
687         .otherend_changed = xenfb_backend_changed,
688 };
689
690 static int __init xenfb_init(void)
691 {
692         if (!xen_pv_domain())
693                 return -ENODEV;
694
695         /* Nothing to do if running in dom0. */
696         if (xen_initial_domain())
697                 return -ENODEV;
698
699         return xenbus_register_frontend(&xenfb_driver);
700 }
701
702 static void __exit xenfb_cleanup(void)
703 {
704         xenbus_unregister_driver(&xenfb_driver);
705 }
706
707 module_init(xenfb_init);
708 module_exit(xenfb_cleanup);
709
710 MODULE_DESCRIPTION("Xen virtual framebuffer device frontend");
711 MODULE_LICENSE("GPL");
712 MODULE_ALIAS("xen:vfb");