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         }
 145         if (!retcode) {
 146                 mutex_lock(&dev->struct_mutex);
 147                 if (minor->type == DRM_MINOR_LEGACY) {
 148                         if (dev->dev_mapping == NULL)
 149                                 dev->dev_mapping = inode->i_mapping;
 150                         else if (dev->dev_mapping != inode->i_mapping)
 151                                 retcode = -ENODEV;
 152                 }
 153                 mutex_unlock(&dev->struct_mutex);
 154         }
 155
 156         return retcode;
 157 }
 158 EXPORT_SYMBOL(drm_open);
 159
 160 /**
 161  * File \c open operation.
 162  *
 163  * \param inode device inode.
 164  * \param filp file pointer.
 165  *
 166  * Puts the dev->fops corresponding to the device minor number into
 167  * \p filp, call the \c open method, and restore the file operations.
 168  */
 169 int drm_stub_open(struct inode *inode, struct file *filp)
 170 {
 171         struct drm_device *dev = NULL;
 172         struct drm_minor *minor;
 173         int minor_id = iminor(inode);
 174         int err = -ENODEV;
 175         const struct file_operations *old_fops;
 176
 177         DRM_DEBUG("\n");
 178
 179         mutex_lock(&drm_global_mutex);
 180         minor = idr_find(&drm_minors_idr, minor_id);
 181         if (!minor)
 182                 goto out;
 183
 184         if (!(dev = minor->dev))
 185                 goto out;
 186
 187         if (drm_device_is_unplugged(dev))
 188                 goto out;
 189
 190         old_fops = filp->f_op;
 191         filp->f_op = fops_get(dev->driver->fops);
 192         if (filp->f_op == NULL) {
 193                 filp->f_op = old_fops;
 194                 goto out;
 195         }
 196         if (filp->f_op->open && (err = filp->f_op->open(inode, filp))) {
 197                 fops_put(filp->f_op);
 198                 filp->f_op = fops_get(old_fops);
 199         }
 200         fops_put(old_fops);
 201
 202 out:
 203         mutex_unlock(&drm_global_mutex);
 204         return err;
 205 }
 206
 207 /**
 208  * Check whether DRI will run on this CPU.
 209  *
 210  * \return non-zero if the DRI will run on this CPU, or zero otherwise.
 211  */
 212 static int drm_cpu_valid(void)
 213 {
 214 #if defined(__i386__)
 215         if (boot_cpu_data.x86 == 3)
 216                 return 0;       /* No cmpxchg on a 386 */
 217 #endif
 218 #if defined(__sparc__) && !defined(__sparc_v9__)
 219         return 0;               /* No cmpxchg before v9 sparc. */
 220 #endif
 221         return 1;
 222 }
 223
 224 /**
 225  * Called whenever a process opens /dev/drm.
 226  *
 227  * \param inode device inode.
 228  * \param filp file pointer.
 229  * \param dev device.
 230  * \return zero on success or a negative number on failure.
 231  *
 232  * Creates and initializes a drm_file structure for the file private data in \p
 233  * filp and add it into the double linked list in \p dev.
 234  */
 235 static int drm_open_helper(struct inode *inode, struct file *filp,
 236                            struct drm_device * dev)
 237 {
 238         int minor_id = iminor(inode);
 239         struct drm_file *priv;
 240         int ret;
 241
 242         if (filp->f_flags & O_EXCL)
 243                 return -EBUSY;  /* No exclusive opens */
 244         if (!drm_cpu_valid())
 245                 return -EINVAL;
 246         if (dev->switch_power_state != DRM_SWITCH_POWER_ON)
 247                 return -EINVAL;
 248
 249         DRM_DEBUG("pid = %d, minor = %d\n", task_pid_nr(current), minor_id);
 250
 251         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 252         if (!priv)
 253                 return -ENOMEM;
 254
 255         filp->private_data = priv;
 256         priv->filp = filp;
 257         priv->uid = current_euid();
 258         priv->pid = task_pid_nr(current);
 259         priv->minor = idr_find(&drm_minors_idr, minor_id);
 260         priv->ioctl_count = 0;
 261         /* for compatibility root is always authenticated */
 262         priv->authenticated = capable(CAP_SYS_ADMIN);
 263         priv->lock_count = 0;
 264
 265         INIT_LIST_HEAD(&priv->lhead);
 266         INIT_LIST_HEAD(&priv->fbs);
 267         INIT_LIST_HEAD(&priv->event_list);
 268         init_waitqueue_head(&priv->event_wait);
 269         priv->event_space = 4096; /* set aside 4k for event buffer */
 270
 271         if (dev->driver->driver_features & DRIVER_GEM)
 272                 drm_gem_open(dev, priv);
 273
 274         if (drm_core_check_feature(dev, DRIVER_PRIME))
 275                 drm_prime_init_file_private(&priv->prime);
 276
 277         if (dev->driver->open) {
 278                 ret = dev->driver->open(dev, priv);
 279                 if (ret < 0)
 280                         goto out_free;
 281         }
 282
 283
 284         /* if there is no current master make this fd it */
 285         mutex_lock(&dev->struct_mutex);
 286         if (!priv->minor->master) {
 287                 /* create a new master */
 288                 priv->minor->master = drm_master_create(priv->minor);
 289                 if (!priv->minor->master) {
 290                         mutex_unlock(&dev->struct_mutex);
 291                         ret = -ENOMEM;
 292                         goto out_free;
 293                 }
 294
 295                 priv->is_master = 1;
 296                 /* take another reference for the copy in the local file priv */
 297                 priv->master = drm_master_get(priv->minor->master);
 298
 299                 priv->authenticated = 1;
 300
 301                 mutex_unlock(&dev->struct_mutex);
 302                 if (dev->driver->master_create) {
 303                         ret = dev->driver->master_create(dev, priv->master);
 304                         if (ret) {
 305                                 mutex_lock(&dev->struct_mutex);
 306                                 /* drop both references if this fails */
 307                                 drm_master_put(&priv->minor->master);
 308                                 drm_master_put(&priv->master);
 309                                 mutex_unlock(&dev->struct_mutex);
 310                                 goto out_free;
 311                         }
 312                 }
 313                 mutex_lock(&dev->struct_mutex);
 314                 if (dev->driver->master_set) {
 315                         ret = dev->driver->master_set(dev, priv, true);
 316                         if (ret) {
 317                                 /* drop both references if this fails */
 318                                 drm_master_put(&priv->minor->master);
 319                                 drm_master_put(&priv->master);
 320                                 mutex_unlock(&dev->struct_mutex);
 321                                 goto out_free;
 322                         }
 323                 }
 324                 mutex_unlock(&dev->struct_mutex);
 325         } else {
 326                 /* get a reference to the master */
 327                 priv->master = drm_master_get(priv->minor->master);
 328                 mutex_unlock(&dev->struct_mutex);
 329         }
 330
 331         mutex_lock(&dev->struct_mutex);
 332         list_add(&priv->lhead, &dev->filelist);
 333         mutex_unlock(&dev->struct_mutex);
 334
 335 #ifdef __alpha__
 336         /*
 337          * Default the hose
 338          */
 339         if (!dev->hose) {
 340                 struct pci_dev *pci_dev;
 341                 pci_dev = pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, NULL);
 342                 if (pci_dev) {
 343                         dev->hose = pci_dev->sysdata;
 344                         pci_dev_put(pci_dev);
 345                 }
 346                 if (!dev->hose) {
 347                         struct pci_bus *b = pci_bus_b(pci_root_buses.next);
 348                         if (b)
 349                                 dev->hose = b->sysdata;
 350                 }
 351         }
 352 #endif
 353
 354         return 0;
 355       out_free:
 356         kfree(priv);
 357         filp->private_data = NULL;
 358         return ret;
 359 }
 360
 361 /** No-op. */
 362 int drm_fasync(int fd, struct file *filp, int on)
 363 {
 364         struct drm_file *priv = filp->private_data;
 365         struct drm_device *dev = priv->minor->dev;
 366
 367         DRM_DEBUG("fd = %d, device = 0x%lx\n", fd,
 368                   (long)old_encode_dev(priv->minor->device));
 369         return fasync_helper(fd, filp, on, &dev->buf_async);
 370 }
 371 EXPORT_SYMBOL(drm_fasync);
 372
 373 /*
 374  * Reclaim locked buffers; note that this may be a bad idea if the current
 375  * context doesn't have the hw lock...
 376  */
 377 static void drm_reclaim_locked_buffers(struct drm_device *dev, struct file *f)
 378 {
 379         struct drm_file *file_priv = f->private_data;
 380
 381         if (drm_i_have_hw_lock(dev, file_priv)) {
 382                 dev->driver->reclaim_buffers_locked(dev, file_priv);
 383         } else {
 384                 unsigned long _end = jiffies + 3 * DRM_HZ;
 385                 int locked = 0;
 386
 387                 drm_idlelock_take(&file_priv->master->lock);
 388
 389                 /*
 390                  * Wait for a while.
 391                  */
 392                 do {
 393                         spin_lock_bh(&file_priv->master->lock.spinlock);
 394                         locked = file_priv->master->lock.idle_has_lock;
 395                         spin_unlock_bh(&file_priv->master->lock.spinlock);
 396                         if (locked)
 397                                 break;
 398                         schedule();
 399                 } while (!time_after_eq(jiffies, _end));
 400
 401                 if (!locked) {
 402                         DRM_ERROR("reclaim_buffers_locked() deadlock. Please rework this\n"
 403                                   "\tdriver to use reclaim_buffers_idlelocked() instead.\n"
 404                                   "\tI will go on reclaiming the buffers anyway.\n");
 405                 }
 406
 407                 dev->driver->reclaim_buffers_locked(dev, file_priv);
 408                 drm_idlelock_release(&file_priv->master->lock);
 409         }
 410 }
 411
 412 static void drm_master_release(struct drm_device *dev, struct file *filp)
 413 {
 414         struct drm_file *file_priv = filp->private_data;
 415
 416         if (dev->driver->reclaim_buffers_locked &&
 417             file_priv->master->lock.hw_lock)
 418                 drm_reclaim_locked_buffers(dev, filp);
 419
 420         if (dev->driver->reclaim_buffers_idlelocked &&
 421             file_priv->master->lock.hw_lock) {
 422                 drm_idlelock_take(&file_priv->master->lock);
 423                 dev->driver->reclaim_buffers_idlelocked(dev, file_priv);
 424                 drm_idlelock_release(&file_priv->master->lock);
 425         }
 426
 427
 428         if (drm_i_have_hw_lock(dev, file_priv)) {
 429                 DRM_DEBUG("File %p released, freeing lock for context %d\n",
 430                           filp, _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
 431                 drm_lock_free(&file_priv->master->lock,
 432                               _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
 433         }
 434
 435         if (drm_core_check_feature(dev, DRIVER_HAVE_DMA) &&
 436             !dev->driver->reclaim_buffers_locked) {
 437                 dev->driver->reclaim_buffers(dev, file_priv);
 438         }
 439 }
 440
 441 static void drm_events_release(struct drm_file *file_priv)
 442 {
 443         struct drm_device *dev = file_priv->minor->dev;
 444         struct drm_pending_event *e, *et;
 445         struct drm_pending_vblank_event *v, *vt;
 446         unsigned long flags;
 447
 448         spin_lock_irqsave(&dev->event_lock, flags);
 449
 450         /* Remove pending flips */
 451         list_for_each_entry_safe(v, vt, &dev->vblank_event_list, base.link)
 452                 if (v->base.file_priv == file_priv) {
 453                         list_del(&v->base.link);
 454                         drm_vblank_put(dev, v->pipe);
 455                         v->base.destroy(&v->base);
 456                 }
 457
 458         /* Remove unconsumed events */
 459         list_for_each_entry_safe(e, et, &file_priv->event_list, link)
 460                 e->destroy(e);
 461
 462         spin_unlock_irqrestore(&dev->event_lock, flags);
 463 }
 464
 465 /**
 466  * Release file.
 467  *
 468  * \param inode device inode
 469  * \param file_priv DRM file private.
 470  * \return zero on success or a negative number on failure.
 471  *
 472  * If the hardware lock is held then free it, and take it again for the kernel
 473  * context since it's necessary to reclaim buffers. Unlink the file private
 474  * data from its list and free it. Decreases the open count and if it reaches
 475  * zero calls drm_lastclose().
 476  */
 477 int drm_release(struct inode *inode, struct file *filp)
 478 {
 479         struct drm_file *file_priv = filp->private_data;
 480         struct drm_device *dev = file_priv->minor->dev;
 481         int retcode = 0;
 482
 483         mutex_lock(&drm_global_mutex);
 484
 485         DRM_DEBUG("open_count = %d\n", dev->open_count);
 486
 487         if (dev->driver->preclose)
 488                 dev->driver->preclose(dev, file_priv);
 489
 490         /* ========================================================
 491          * Begin inline drm_release
 492          */
 493
 494         DRM_DEBUG("pid = %d, device = 0x%lx, open_count = %d\n",
 495                   task_pid_nr(current),
 496                   (long)old_encode_dev(file_priv->minor->device),
 497                   dev->open_count);
 498
 499         /* Release any auth tokens that might point to this file_priv,
 500            (do that under the drm_global_mutex) */
 501         if (file_priv->magic)
 502                 (void) drm_remove_magic(file_priv->master, file_priv->magic);
 503
 504         /* if the master has gone away we can't do anything with the lock */
 505         if (file_priv->minor->master)
 506                 drm_master_release(dev, filp);
 507
 508         drm_events_release(file_priv);
 509
 510         if (dev->driver->driver_features & DRIVER_MODESET)
 511                 drm_fb_release(file_priv);
 512
 513         if (dev->driver->driver_features & DRIVER_GEM)
 514                 drm_gem_release(dev, file_priv);
 515
 516         mutex_lock(&dev->ctxlist_mutex);
 517         if (!list_empty(&dev->ctxlist)) {
 518                 struct drm_ctx_list *pos, *n;
 519
 520                 list_for_each_entry_safe(pos, n, &dev->ctxlist, head) {
 521                         if (pos->tag == file_priv &&
 522                             pos->handle != DRM_KERNEL_CONTEXT) {
 523                                 if (dev->driver->context_dtor)
 524                                         dev->driver->context_dtor(dev,
 525                                                                   pos->handle);
 526
 527                                 drm_ctxbitmap_free(dev, pos->handle);
 528
 529                                 list_del(&pos->head);
 530                                 kfree(pos);
 531                                 --dev->ctx_count;
 532                         }
 533                 }
 534         }
 535         mutex_unlock(&dev->ctxlist_mutex);
 536
 537         mutex_lock(&dev->struct_mutex);
 538
 539         if (file_priv->is_master) {
 540                 struct drm_master *master = file_priv->master;
 541                 struct drm_file *temp;
 542                 list_for_each_entry(temp, &dev->filelist, lhead) {
 543                         if ((temp->master == file_priv->master) &&
 544                             (temp != file_priv))
 545                                 temp->authenticated = 0;
 546                 }
 547
 548                 /**
 549                  * Since the master is disappearing, so is the
 550                  * possibility to lock.
 551                  */
 552
 553                 if (master->lock.hw_lock) {
 554                         if (dev->sigdata.lock == master->lock.hw_lock)
 555                                 dev->sigdata.lock = NULL;
 556                         master->lock.hw_lock = NULL;
 557                         master->lock.file_priv = NULL;
 558                         wake_up_interruptible_all(&master->lock.lock_queue);
 559                 }
 560
 561                 if (file_priv->minor->master == file_priv->master) {
 562                         /* drop the reference held my the minor */
 563                         if (dev->driver->master_drop)
 564                                 dev->driver->master_drop(dev, file_priv, true);
 565                         drm_master_put(&file_priv->minor->master);
 566                 }
 567         }
 568
 569         /* drop the reference held my the file priv */
 570         drm_master_put(&file_priv->master);
 571         file_priv->is_master = 0;
 572         list_del(&file_priv->lhead);
 573         mutex_unlock(&dev->struct_mutex);
 574
 575         if (dev->driver->postclose)
 576                 dev->driver->postclose(dev, file_priv);
 577
 578         if (drm_core_check_feature(dev, DRIVER_PRIME))
 579                 drm_prime_destroy_file_private(&file_priv->prime);
 580
 581         kfree(file_priv);
 582
 583         /* ========================================================
 584          * End inline drm_release
 585          */
 586
 587         atomic_inc(&dev->counts[_DRM_STAT_CLOSES]);
 588         if (!--dev->open_count) {
 589                 if (atomic_read(&dev->ioctl_count)) {
 590                         DRM_ERROR("Device busy: %d\n",
 591                                   atomic_read(&dev->ioctl_count));
 592                         retcode = -EBUSY;
 593                 } else
 594                         retcode = drm_lastclose(dev);
 595                 if (drm_device_is_unplugged(dev))
 596                         drm_put_dev(dev);
 597         }
 598         mutex_unlock(&drm_global_mutex);
 599
 600         return retcode;
 601 }
 602 EXPORT_SYMBOL(drm_release);
 603
 604 static bool
 605 drm_dequeue_event(struct drm_file *file_priv,
 606                   size_t total, size_t max, struct drm_pending_event **out)
 607 {
 608         struct drm_device *dev = file_priv->minor->dev;
 609         struct drm_pending_event *e;
 610         unsigned long flags;
 611         bool ret = false;
 612
 613         spin_lock_irqsave(&dev->event_lock, flags);
 614
 615         *out = NULL;
 616         if (list_empty(&file_priv->event_list))
 617                 goto out;
 618         e = list_first_entry(&file_priv->event_list,
 619                              struct drm_pending_event, link);
 620         if (e->event->length + total > max)
 621                 goto out;
 622
 623         file_priv->event_space += e->event->length;
 624         list_del(&e->link);
 625         *out = e;
 626         ret = true;
 627
 628 out:
 629         spin_unlock_irqrestore(&dev->event_lock, flags);
 630         return ret;
 631 }
 632
 633 ssize_t drm_read(struct file *filp, char __user *buffer,
 634                  size_t count, loff_t *offset)
 635 {
 636         struct drm_file *file_priv = filp->private_data;
 637         struct drm_pending_event *e;
 638         size_t total;
 639         ssize_t ret;
 640
 641         ret = wait_event_interruptible(file_priv->event_wait,
 642                                        !list_empty(&file_priv->event_list));
 643         if (ret < 0)
 644                 return ret;
 645
 646         total = 0;
 647         while (drm_dequeue_event(file_priv, total, count, &e)) {
 648                 if (copy_to_user(buffer + total,
 649                                  e->event, e->event->length)) {
 650                         total = -EFAULT;
 651                         break;
 652                 }
 653
 654                 total += e->event->length;
 655                 e->destroy(e);
 656         }
 657
 658         return total;
 659 }
 660 EXPORT_SYMBOL(drm_read);
 661
 662 unsigned int drm_poll(struct file *filp, struct poll_table_struct *wait)
 663 {
 664         struct drm_file *file_priv = filp->private_data;
 665         unsigned int mask = 0;
 666
 667         poll_wait(filp, &file_priv->event_wait, wait);
 668
 669         if (!list_empty(&file_priv->event_list))
 670                 mask |= POLLIN | POLLRDNORM;
 671
 672         return mask;
 673 }
 674 EXPORT_SYMBOL(drm_poll);