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