drivers/gpu/drm/drm_fops.c

   1 /**
   2  * \file drm_fops.c
   3  * File operations for DRM
   4  *
   5  * \author Rickard E. (Rik) Faith <faith@valinux.com>
   6  * \author Daryll Strauss <daryll@valinux.com>
   7  * \author Gareth Hughes <gareth@valinux.com>
   8  */
   9
  10 /*
  11  * Created: Mon Jan  4 08:58:31 1999 by faith@valinux.com
  12  *
  13  * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
  14  * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
  15  * All Rights Reserved.
  16  *
  17  * Permission is hereby granted, free of charge, to any person obtaining a
  18  * copy of this software and associated documentation files (the "Software"),
  19  * to deal in the Software without restriction, including without limitation
  20  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  21  * and/or sell copies of the Software, and to permit persons to whom the
  22  * Software is furnished to do so, subject to the following conditions:
  23  *
  24  * The above copyright notice and this permission notice (including the next
  25  * paragraph) shall be included in all copies or substantial portions of the
  26  * Software.
  27  *
  28  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  29  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  30  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  31  * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  32  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  33  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  34  * OTHER DEALINGS IN THE SOFTWARE.
  35  */
  36
  37 #include "drmP.h"
  38 #include <linux/poll.h>
  39 #include <linux/slab.h>
  40 #include <linux/module.h>
  41
  42 /* from BKL pushdown: note that nothing else serializes idr_find() */
  43 DEFINE_MUTEX(drm_global_mutex);
  44 EXPORT_SYMBOL(drm_global_mutex);
  45
  46 static int drm_open_helper(struct inode *inode, struct file *filp,
  47                            struct drm_device * dev);
  48
  49 static int drm_setup(struct drm_device * dev)
  50 {
  51         int i;
  52         int ret;
  53
  54         if (dev->driver->firstopen) {
  55                 ret = dev->driver->firstopen(dev);
  56                 if (ret != 0)
  57                         return ret;
  58         }
  59
  60         atomic_set(&dev->ioctl_count, 0);
  61         atomic_set(&dev->vma_count, 0);
  62
  63         if (drm_core_check_feature(dev, DRIVER_HAVE_DMA) &&
  64             !drm_core_check_feature(dev, DRIVER_MODESET)) {
  65                 dev->buf_use = 0;
  66                 atomic_set(&dev->buf_alloc, 0);
  67
  68                 i = drm_dma_setup(dev);
  69                 if (i < 0)
  70                         return i;
  71         }
  72
  73         for (i = 0; i < ARRAY_SIZE(dev->counts); i++)
  74                 atomic_set(&dev->counts[i], 0);
  75
  76         dev->sigdata.lock = NULL;
  77
  78         dev->queue_count = 0;
  79         dev->queue_reserved = 0;
  80         dev->queue_slots = 0;
  81         dev->queuelist = NULL;
  82         dev->context_flag = 0;
  83         dev->interrupt_flag = 0;
  84         dev->dma_flag = 0;
  85         dev->last_context = 0;
  86         dev->last_switch = 0;
  87         dev->last_checked = 0;
  88         init_waitqueue_head(&dev->context_wait);
  89         dev->if_version = 0;
  90
  91         dev->ctx_start = 0;
  92         dev->lck_start = 0;
  93
  94         dev->buf_async = NULL;
  95         init_waitqueue_head(&dev->buf_readers);
  96         init_waitqueue_head(&dev->buf_writers);
  97
  98         DRM_DEBUG("\n");
  99
 100         /*
 101          * The kernel's context could be created here, but is now created
 102          * in drm_dma_enqueue.  This is more resource-efficient for
 103          * hardware that does not do DMA, but may mean that
 104          * drm_select_queue fails between the time the interrupt is
 105          * initialized and the time the queues are initialized.
 106          */
 107
 108         return 0;
 109 }
 110
 111 /**
 112  * Open file.
 113  *
 114  * \param inode device inode
 115  * \param filp file pointer.
 116  * \return zero on success or a negative number on failure.
 117  *
 118  * Searches the DRM device with the same minor number, calls open_helper(), and
 119  * increments the device open count. If the open count was previous at zero,
 120  * i.e., it's the first that the device is open, then calls setup().
 121  */
 122 int drm_open(struct inode *inode, struct file *filp)
 123 {
 124         struct drm_device *dev = NULL;
 125         int minor_id = iminor(inode);
 126         struct drm_minor *minor;
 127         int retcode = 0;
 128
 129         minor = idr_find(&drm_minors_idr, minor_id);
 130         if (!minor)
 131                 return -ENODEV;
 132
 133         if (!(dev = minor->dev))
 134                 return -ENODEV;
 135
 136         if (drm_device_is_unplugged(dev))
 137                 return -ENODEV;
 138
 139         retcode = drm_open_helper(inode, filp, dev);
 140         if (!retcode) {
 141                 atomic_inc(&dev->counts[_DRM_STAT_OPENS]);
 142                 if (!dev->open_count++) {
 143                         retcode = drm_setup(dev);
 144                         if (retcode)
 145                                 dev->open_count--;
 146                 }
 147         }
 148         if (!retcode) {
 149                 mutex_lock(&dev->struct_mutex);
 150                 if (minor->type == DRM_MINOR_LEGACY) {
 151                         if (dev->dev_mapping == NULL)
 152                                 dev->dev_mapping = inode->i_mapping;
 153                         else if (dev->dev_mapping != inode->i_mapping)
 154                                 retcode = -ENODEV;
 155                 }
 156                 mutex_unlock(&dev->struct_mutex);
 157         }
 158
 159         return retcode;
 160 }
 161 EXPORT_SYMBOL(drm_open);
 162
 163 /**
 164  * File \c open operation.
 165  *
 166  * \param inode device inode.
 167  * \param filp file pointer.
 168  *
 169  * Puts the dev->fops corresponding to the device minor number into
 170  * \p filp, call the \c open method, and restore the file operations.
 171  */
 172 int drm_stub_open(struct inode *inode, struct file *filp)
 173 {
 174         struct drm_device *dev = NULL;
 175         struct drm_minor *minor;
 176         int minor_id = iminor(inode);
 177         int err = -ENODEV;
 178         const struct file_operations *old_fops;
 179
 180         DRM_DEBUG("\n");
 181
 182         mutex_lock(&drm_global_mutex);
 183         minor = idr_find(&drm_minors_idr, minor_id);
 184         if (!minor)
 185                 goto out;
 186
 187         if (!(dev = minor->dev))
 188                 goto out;
 189
 190         if (drm_device_is_unplugged(dev))
 191                 goto out;
 192
 193         old_fops = filp->f_op;
 194         filp->f_op = fops_get(dev->driver->fops);
 195         if (filp->f_op == NULL) {
 196                 filp->f_op = old_fops;
 197                 goto out;
 198         }
 199         if (filp->f_op->open && (err = filp->f_op->open(inode, filp))) {
 200                 fops_put(filp->f_op);
 201                 filp->f_op = fops_get(old_fops);
 202         }
 203         fops_put(old_fops);
 204
 205 out:
 206         mutex_unlock(&drm_global_mutex);
 207         return err;
 208 }
 209
 210 /**
 211  * Check whether DRI will run on this CPU.
 212  *
 213  * \return non-zero if the DRI will run on this CPU, or zero otherwise.
 214  */
 215 static int drm_cpu_valid(void)
 216 {
 217 #if defined(__i386__)
 218         if (boot_cpu_data.x86 == 3)
 219                 return 0;       /* No cmpxchg on a 386 */
 220 #endif
 221 #if defined(__sparc__) && !defined(__sparc_v9__)
 222         return 0;               /* No cmpxchg before v9 sparc. */
 223 #endif
 224         return 1;
 225 }
 226
 227 /**
 228  * Called whenever a process opens /dev/drm.
 229  *
 230  * \param inode device inode.
 231  * \param filp file pointer.
 232  * \param dev device.
 233  * \return zero on success or a negative number on failure.
 234  *
 235  * Creates and initializes a drm_file structure for the file private data in \p
 236  * filp and add it into the double linked list in \p dev.
 237  */
 238 static int drm_open_helper(struct inode *inode, struct file *filp,
 239                            struct drm_device * dev)
 240 {
 241         int minor_id = iminor(inode);
 242         struct drm_file *priv;
 243         int ret;
 244
 245         if (filp->f_flags & O_EXCL)
 246                 return -EBUSY;  /* No exclusive opens */
 247         if (!drm_cpu_valid())
 248                 return -EINVAL;
 249         if (dev->switch_power_state != DRM_SWITCH_POWER_ON)
 250                 return -EINVAL;
 251
 252         DRM_DEBUG("pid = %d, minor = %d\n", task_pid_nr(current), minor_id);
 253
 254         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 255         if (!priv)
 256                 return -ENOMEM;
 257
 258         filp->private_data = priv;
 259         priv->filp = filp;
 260         priv->uid = current_euid();
 261         priv->pid = task_pid_nr(current);
 262         priv->minor = idr_find(&drm_minors_idr, minor_id);
 263         priv->ioctl_count = 0;
 264         /* for compatibility root is always authenticated */
 265         priv->authenticated = capable(CAP_SYS_ADMIN);
 266         priv->lock_count = 0;
 267
 268         INIT_LIST_HEAD(&priv->lhead);
 269         INIT_LIST_HEAD(&priv->fbs);
 270         INIT_LIST_HEAD(&priv->event_list);
 271         init_waitqueue_head(&priv->event_wait);
 272         priv->event_space = 4096; /* set aside 4k for event buffer */
 273
 274         if (dev->driver->driver_features & DRIVER_GEM)
 275                 drm_gem_open(dev, priv);
 276
 277         if (drm_core_check_feature(dev, DRIVER_PRIME))
 278                 drm_prime_init_file_private(&priv->prime);
 279
 280         if (dev->driver->open) {
 281                 ret = dev->driver->open(dev, priv);
 282                 if (ret < 0)
 283                         goto out_free;
 284         }
 285
 286
 287         /* if there is no current master make this fd it */
 288         mutex_lock(&dev->struct_mutex);
 289         if (!priv->minor->master) {
 290                 /* create a new master */
 291                 priv->minor->master = drm_master_create(priv->minor);
 292                 if (!priv->minor->master) {
 293                         mutex_unlock(&dev->struct_mutex);
 294                         ret = -ENOMEM;
 295                         goto out_free;
 296                 }
 297
 298                 priv->is_master = 1;
 299                 /* take another reference for the copy in the local file priv */
 300                 priv->master = drm_master_get(priv->minor->master);
 301
 302                 priv->authenticated = 1;
 303
 304                 mutex_unlock(&dev->struct_mutex);
 305                 if (dev->driver->master_create) {
 306                         ret = dev->driver->master_create(dev, priv->master);
 307                         if (ret) {
 308                                 mutex_lock(&dev->struct_mutex);
 309                                 /* drop both references if this fails */
 310                                 drm_master_put(&priv->minor->master);
 311                                 drm_master_put(&priv->master);
 312                                 mutex_unlock(&dev->struct_mutex);
 313                                 goto out_free;
 314                         }
 315                 }
 316                 mutex_lock(&dev->struct_mutex);
 317                 if (dev->driver->master_set) {
 318                         ret = dev->driver->master_set(dev, priv, true);
 319                         if (ret) {
 320                                 /* drop both references if this fails */
 321                                 drm_master_put(&priv->minor->master);
 322                                 drm_master_put(&priv->master);
 323                                 mutex_unlock(&dev->struct_mutex);
 324                                 goto out_free;
 325                         }
 326                 }
 327                 mutex_unlock(&dev->struct_mutex);
 328         } else {
 329                 /* get a reference to the master */
 330                 priv->master = drm_master_get(priv->minor->master);
 331                 mutex_unlock(&dev->struct_mutex);
 332         }
 333
 334         mutex_lock(&dev->struct_mutex);
 335         list_add(&priv->lhead, &dev->filelist);
 336         mutex_unlock(&dev->struct_mutex);
 337
 338 #ifdef __alpha__
 339         /*
 340          * Default the hose
 341          */
 342         if (!dev->hose) {
 343                 struct pci_dev *pci_dev;
 344                 pci_dev = pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, NULL);
 345                 if (pci_dev) {
 346                         dev->hose = pci_dev->sysdata;
 347                         pci_dev_put(pci_dev);
 348                 }
 349                 if (!dev->hose) {
 350                         struct pci_bus *b = pci_bus_b(pci_root_buses.next);
 351                         if (b)
 352                                 dev->hose = b->sysdata;
 353                 }
 354         }
 355 #endif
 356
 357         return 0;
 358       out_free:
 359         kfree(priv);
 360         filp->private_data = NULL;
 361         return ret;
 362 }
 363
 364 /** No-op. */
 365 int drm_fasync(int fd, struct file *filp, int on)
 366 {
 367         struct drm_file *priv = filp->private_data;
 368         struct drm_device *dev = priv->minor->dev;
 369
 370         DRM_DEBUG("fd = %d, device = 0x%lx\n", fd,
 371                   (long)old_encode_dev(priv->minor->device));
 372         return fasync_helper(fd, filp, on, &dev->buf_async);
 373 }
 374 EXPORT_SYMBOL(drm_fasync);
 375
 376 /*
 377  * Reclaim locked buffers; note that this may be a bad idea if the current
 378  * context doesn't have the hw lock...
 379  */
 380 static void drm_reclaim_locked_buffers(struct drm_device *dev, struct file *f)
 381 {
 382         struct drm_file *file_priv = f->private_data;
 383
 384         if (drm_i_have_hw_lock(dev, file_priv)) {
 385                 dev->driver->reclaim_buffers_locked(dev, file_priv);
 386         } else {
 387                 unsigned long _end = jiffies + 3 * DRM_HZ;
 388                 int locked = 0;
 389
 390                 drm_idlelock_take(&file_priv->master->lock);
 391
 392                 /*
 393                  * Wait for a while.
 394                  */
 395                 do {
 396                         spin_lock_bh(&file_priv->master->lock.spinlock);
 397                         locked = file_priv->master->lock.idle_has_lock;
 398                         spin_unlock_bh(&file_priv->master->lock.spinlock);
 399                         if (locked)
 400                                 break;
 401                         schedule();
 402                 } while (!time_after_eq(jiffies, _end));
 403
 404                 if (!locked) {
 405                         DRM_ERROR("reclaim_buffers_locked() deadlock. Please rework this\n"
 406                                   "\tdriver to use reclaim_buffers_idlelocked() instead.\n"
 407                                   "\tI will go on reclaiming the buffers anyway.\n");
 408                 }
 409
 410                 dev->driver->reclaim_buffers_locked(dev, file_priv);
 411                 drm_idlelock_release(&file_priv->master->lock);
 412         }
 413 }
 414
 415 static void drm_master_release(struct drm_device *dev, struct file *filp)
 416 {
 417         struct drm_file *file_priv = filp->private_data;
 418
 419         if (dev->driver->reclaim_buffers_locked &&
 420             file_priv->master->lock.hw_lock)
 421                 drm_reclaim_locked_buffers(dev, filp);
 422
 423         if (dev->driver->reclaim_buffers_idlelocked &&
 424             file_priv->master->lock.hw_lock) {
 425                 drm_idlelock_take(&file_priv->master->lock);
 426                 dev->driver->reclaim_buffers_idlelocked(dev, file_priv);
 427                 drm_idlelock_release(&file_priv->master->lock);
 428         }
 429
 430
 431         if (drm_i_have_hw_lock(dev, file_priv)) {
 432                 DRM_DEBUG("File %p released, freeing lock for context %d\n",
 433                           filp, _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
 434                 drm_lock_free(&file_priv->master->lock,
 435                               _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
 436         }
 437
 438         if (drm_core_check_feature(dev, DRIVER_HAVE_DMA) &&
 439             !dev->driver->reclaim_buffers_locked) {
 440                 dev->driver->reclaim_buffers(dev, file_priv);
 441         }
 442 }
 443
 444 static void drm_events_release(struct drm_file *file_priv)
 445 {
 446         struct drm_device *dev = file_priv->minor->dev;
 447         struct drm_pending_event *e, *et;
 448         struct drm_pending_vblank_event *v, *vt;
 449         unsigned long flags;
 450
 451         spin_lock_irqsave(&dev->event_lock, flags);
 452
 453         /* Remove pending flips */
 454         list_for_each_entry_safe(v, vt, &dev->vblank_event_list, base.link)
 455                 if (v->base.file_priv == file_priv) {
 456                         list_del(&v->base.link);
 457                         drm_vblank_put(dev, v->pipe);
 458                         v->base.destroy(&v->base);
 459                 }
 460
 461         /* Remove unconsumed events */
 462         list_for_each_entry_safe(e, et, &file_priv->event_list, link)
 463                 e->destroy(e);
 464
 465         spin_unlock_irqrestore(&dev->event_lock, flags);
 466 }
 467
 468 /**
 469  * Release file.
 470  *
 471  * \param inode device inode
 472  * \param file_priv DRM file private.
 473  * \return zero on success or a negative number on failure.
 474  *
 475  * If the hardware lock is held then free it, and take it again for the kernel
 476  * context since it's necessary to reclaim buffers. Unlink the file private
 477  * data from its list and free it. Decreases the open count and if it reaches
 478  * zero calls drm_lastclose().
 479  */
 480 int drm_release(struct inode *inode, struct file *filp)
 481 {
 482         struct drm_file *file_priv = filp->private_data;
 483         struct drm_device *dev = file_priv->minor->dev;
 484         int retcode = 0;
 485
 486         mutex_lock(&drm_global_mutex);
 487
 488         DRM_DEBUG("open_count = %d\n", dev->open_count);
 489
 490         if (dev->driver->preclose)
 491                 dev->driver->preclose(dev, file_priv);
 492
 493         /* ========================================================
 494          * Begin inline drm_release
 495          */
 496
 497         DRM_DEBUG("pid = %d, device = 0x%lx, open_count = %d\n",
 498                   task_pid_nr(current),
 499                   (long)old_encode_dev(file_priv->minor->device),
 500                   dev->open_count);
 501
 502         /* Release any auth tokens that might point to this file_priv,
 503            (do that under the drm_global_mutex) */
 504         if (file_priv->magic)
 505                 (void) drm_remove_magic(file_priv->master, file_priv->magic);
 506
 507         /* if the master has gone away we can't do anything with the lock */
 508         if (file_priv->minor->master)
 509                 drm_master_release(dev, filp);
 510
 511         drm_events_release(file_priv);
 512
 513         if (dev->driver->driver_features & DRIVER_MODESET)
 514                 drm_fb_release(file_priv);
 515
 516         if (dev->driver->driver_features & DRIVER_GEM)
 517                 drm_gem_release(dev, file_priv);
 518
 519         mutex_lock(&dev->ctxlist_mutex);
 520         if (!list_empty(&dev->ctxlist)) {
 521                 struct drm_ctx_list *pos, *n;
 522
 523                 list_for_each_entry_safe(pos, n, &dev->ctxlist, head) {
 524                         if (pos->tag == file_priv &&
 525                             pos->handle != DRM_KERNEL_CONTEXT) {
 526                                 if (dev->driver->context_dtor)
 527                                         dev->driver->context_dtor(dev,
 528                                                                   pos->handle);
 529
 530                                 drm_ctxbitmap_free(dev, pos->handle);
 531
 532                                 list_del(&pos->head);
 533                                 kfree(pos);
 534                                 --dev->ctx_count;
 535                         }
 536                 }
 537         }
 538         mutex_unlock(&dev->ctxlist_mutex);
 539
 540         mutex_lock(&dev->struct_mutex);
 541
 542         if (file_priv->is_master) {
 543                 struct drm_master *master = file_priv->master;
 544                 struct drm_file *temp;
 545                 list_for_each_entry(temp, &dev->filelist, lhead) {
 546                         if ((temp->master == file_priv->master) &&
 547                             (temp != file_priv))
 548                                 temp->authenticated = 0;
 549                 }
 550
 551                 /**
 552                  * Since the master is disappearing, so is the
 553                  * possibility to lock.
 554                  */
 555
 556                 if (master->lock.hw_lock) {
 557                         if (dev->sigdata.lock == master->lock.hw_lock)
 558                                 dev->sigdata.lock = NULL;
 559                         master->lock.hw_lock = NULL;
 560                         master->lock.file_priv = NULL;
 561                         wake_up_interruptible_all(&master->lock.lock_queue);
 562                 }
 563
 564                 if (file_priv->minor->master == file_priv->master) {
 565                         /* drop the reference held my the minor */
 566                         if (dev->driver->master_drop)
 567                                 dev->driver->master_drop(dev, file_priv, true);
 568                         drm_master_put(&file_priv->minor->master);
 569                 }
 570         }
 571
 572         /* drop the reference held my the file priv */
 573         drm_master_put(&file_priv->master);
 574         file_priv->is_master = 0;
 575         list_del(&file_priv->lhead);
 576         mutex_unlock(&dev->struct_mutex);
 577
 578         if (dev->driver->postclose)
 579                 dev->driver->postclose(dev, file_priv);
 580
 581         if (drm_core_check_feature(dev, DRIVER_PRIME))
 582                 drm_prime_destroy_file_private(&file_priv->prime);
 583
 584         kfree(file_priv);
 585
 586         /* ========================================================
 587          * End inline drm_release
 588          */
 589
 590         atomic_inc(&dev->counts[_DRM_STAT_CLOSES]);
 591         if (!--dev->open_count) {
 592                 if (atomic_read(&dev->ioctl_count)) {
 593                         DRM_ERROR("Device busy: %d\n",
 594                                   atomic_read(&dev->ioctl_count));
 595                         retcode = -EBUSY;
 596                 } else
 597                         retcode = drm_lastclose(dev);
 598                 if (drm_device_is_unplugged(dev))
 599                         drm_put_dev(dev);
 600         }
 601         mutex_unlock(&drm_global_mutex);
 602
 603         return retcode;
 604 }
 605 EXPORT_SYMBOL(drm_release);
 606
 607 static bool
 608 drm_dequeue_event(struct drm_file *file_priv,
 609                   size_t total, size_t max, struct drm_pending_event **out)
 610 {
 611         struct drm_device *dev = file_priv->minor->dev;
 612         struct drm_pending_event *e;
 613         unsigned long flags;
 614         bool ret = false;
 615
 616         spin_lock_irqsave(&dev->event_lock, flags);
 617
 618         *out = NULL;
 619         if (list_empty(&file_priv->event_list))
 620                 goto out;
 621         e = list_first_entry(&file_priv->event_list,
 622                              struct drm_pending_event, link);
 623         if (e->event->length + total > max)
 624                 goto out;
 625
 626         file_priv->event_space += e->event->length;
 627         list_del(&e->link);
 628         *out = e;
 629         ret = true;
 630
 631 out:
 632         spin_unlock_irqrestore(&dev->event_lock, flags);
 633         return ret;
 634 }
 635
 636 ssize_t drm_read(struct file *filp, char __user *buffer,
 637                  size_t count, loff_t *offset)
 638 {
 639         struct drm_file *file_priv = filp->private_data;
 640         struct drm_pending_event *e;
 641         size_t total;
 642         ssize_t ret;
 643
 644         ret = wait_event_interruptible(file_priv->event_wait,
 645                                        !list_empty(&file_priv->event_list));
 646         if (ret < 0)
 647                 return ret;
 648
 649         total = 0;
 650         while (drm_dequeue_event(file_priv, total, count, &e)) {
 651                 if (copy_to_user(buffer + total,
 652                                  e->event, e->event->length)) {
 653                         total = -EFAULT;
 654                         break;
 655                 }
 656
 657                 total += e->event->length;
 658                 e->destroy(e);
 659         }
 660
 661         return total;
 662 }
 663 EXPORT_SYMBOL(drm_read);
 664
 665 unsigned int drm_poll(struct file *filp, struct poll_table_struct *wait)
 666 {
 667         struct drm_file *file_priv = filp->private_data;
 668         unsigned int mask = 0;
 669
 670         poll_wait(filp, &file_priv->event_wait, wait);
 671
 672         if (!list_empty(&file_priv->event_list))
 673                 mask |= POLLIN | POLLRDNORM;
 674
 675         return mask;
 676 }
 677 EXPORT_SYMBOL(drm_poll);