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         acquire_console_sem();
 495         for_each_console(c) {
 496                 if (!strcmp(c->name, "tty") && c->index == 0)
 497                         break;
 498         }
 499         release_console_sem();
 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;
 566         struct xenbus_transaction xbt;
 567
 568         ret = xenbus_alloc_evtchn(dev, &evtchn);
 569         if (ret)
 570                 return ret;
 571         ret = bind_evtchn_to_irqhandler(evtchn, xenfb_event_handler,
 572                                         0, dev->devicetype, info);
 573         if (ret < 0) {
 574                 xenbus_free_evtchn(dev, evtchn);
 575                 xenbus_dev_fatal(dev, ret, "bind_evtchn_to_irqhandler");
 576                 return ret;
 577         }
 578         info->irq = ret;
 579
 580  again:
 581         ret = xenbus_transaction_start(&xbt);
 582         if (ret) {
 583                 xenbus_dev_fatal(dev, ret, "starting transaction");
 584                 return ret;
 585         }
 586         ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
 587                             virt_to_mfn(info->page));
 588         if (ret)
 589                 goto error_xenbus;
 590         ret = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
 591                             evtchn);
 592         if (ret)
 593                 goto error_xenbus;
 594         ret = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
 595                             XEN_IO_PROTO_ABI_NATIVE);
 596         if (ret)
 597                 goto error_xenbus;
 598         ret = xenbus_printf(xbt, dev->nodename, "feature-update", "1");
 599         if (ret)
 600                 goto error_xenbus;
 601         ret = xenbus_transaction_end(xbt, 0);
 602         if (ret) {
 603                 if (ret == -EAGAIN)
 604                         goto again;
 605                 xenbus_dev_fatal(dev, ret, "completing transaction");
 606                 return ret;
 607         }
 608
 609         xenbus_switch_state(dev, XenbusStateInitialised);
 610         return 0;
 611
 612  error_xenbus:
 613         xenbus_transaction_end(xbt, 1);
 614         xenbus_dev_fatal(dev, ret, "writing xenstore");
 615         return ret;
 616 }
 617
 618 static void xenfb_disconnect_backend(struct xenfb_info *info)
 619 {
 620         if (info->irq >= 0)
 621                 unbind_from_irqhandler(info->irq, info);
 622         info->irq = -1;
 623 }
 624
 625 static void xenfb_backend_changed(struct xenbus_device *dev,
 626                                   enum xenbus_state backend_state)
 627 {
 628         struct xenfb_info *info = dev_get_drvdata(&dev->dev);
 629         int val;
 630
 631         switch (backend_state) {
 632         case XenbusStateInitialising:
 633         case XenbusStateInitialised:
 634         case XenbusStateReconfiguring:
 635         case XenbusStateReconfigured:
 636         case XenbusStateUnknown:
 637         case XenbusStateClosed:
 638                 break;
 639
 640         case XenbusStateInitWait:
 641 InitWait:
 642                 xenbus_switch_state(dev, XenbusStateConnected);
 643                 break;
 644
 645         case XenbusStateConnected:
 646                 /*
 647                  * Work around xenbus race condition: If backend goes
 648                  * through InitWait to Connected fast enough, we can
 649                  * get Connected twice here.
 650                  */
 651                 if (dev->state != XenbusStateConnected)
 652                         goto InitWait; /* no InitWait seen yet, fudge it */
 653
 654                 if (xenbus_scanf(XBT_NIL, info->xbdev->otherend,
 655                                  "request-update", "%d", &val) < 0)
 656                         val = 0;
 657                 if (val)
 658                         info->update_wanted = 1;
 659
 660                 if (xenbus_scanf(XBT_NIL, dev->otherend,
 661                                  "feature-resize", "%d", &val) < 0)
 662                         val = 0;
 663                 info->feature_resize = val;
 664                 break;
 665
 666         case XenbusStateClosing:
 667                 xenbus_frontend_closed(dev);
 668                 break;
 669         }
 670 }
 671
 672 static struct xenbus_device_id xenfb_ids[] = {
 673         { "vfb" },
 674         { "" }
 675 };
 676
 677 static struct xenbus_driver xenfb_driver = {
 678         .name = "vfb",
 679         .owner = THIS_MODULE,
 680         .ids = xenfb_ids,
 681         .probe = xenfb_probe,
 682         .remove = xenfb_remove,
 683         .resume = xenfb_resume,
 684         .otherend_changed = xenfb_backend_changed,
 685 };
 686
 687 static int __init xenfb_init(void)
 688 {
 689         if (!xen_pv_domain())
 690                 return -ENODEV;
 691
 692         /* Nothing to do if running in dom0. */
 693         if (xen_initial_domain())
 694                 return -ENODEV;
 695
 696         return xenbus_register_frontend(&xenfb_driver);
 697 }
 698
 699 static void __exit xenfb_cleanup(void)
 700 {
 701         xenbus_unregister_driver(&xenfb_driver);
 702 }
 703
 704 module_init(xenfb_init);
 705 module_exit(xenfb_cleanup);
 706
 707 MODULE_DESCRIPTION("Xen virtual framebuffer device frontend");
 708 MODULE_LICENSE("GPL");
 709 MODULE_ALIAS("xen:vfb");