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