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         retcode = drm_open_helper(inode, filp, dev);
 137         if (!retcode) {
 138                 atomic_inc(&dev->counts[_DRM_STAT_OPENS]);
 139                 if (!dev->open_count++) {
 140                         retcode = drm_setup(dev);
 141                         if (retcode)
 142                                 dev->open_count--;
 143                 }
 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         old_fops = filp->f_op;
 188         filp->f_op = fops_get(&dev->driver->fops);
 189         if (filp->f_op == NULL) {
 190                 filp->f_op = old_fops;
 191                 goto out;
 192         }
 193         if (filp->f_op->open && (err = filp->f_op->open(inode, filp))) {
 194                 fops_put(filp->f_op);
 195                 filp->f_op = fops_get(old_fops);
 196         }
 197         fops_put(old_fops);
 198
 199 out:
 200         mutex_unlock(&drm_global_mutex);
 201         return err;
 202 }
 203
 204 /**
 205  * Check whether DRI will run on this CPU.
 206  *
 207  * \return non-zero if the DRI will run on this CPU, or zero otherwise.
 208  */
 209 static int drm_cpu_valid(void)
 210 {
 211 #if defined(__i386__)
 212         if (boot_cpu_data.x86 == 3)
 213                 return 0;       /* No cmpxchg on a 386 */
 214 #endif
 215 #if defined(__sparc__) && !defined(__sparc_v9__)
 216         return 0;               /* No cmpxchg before v9 sparc. */
 217 #endif
 218         return 1;
 219 }
 220
 221 /**
 222  * drm_new_set_master - Allocate a new master object and become master for the
 223  * associated master realm.
 224  *
 225  * @dev: The associated device.
 226  * @fpriv: File private identifying the client.
 227  *
 228  * This function must be called with dev::struct_mutex held.
 229  * Returns negative error code on failure. Zero on success.
 230  */
 231 int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv)
 232 {
 233         struct drm_master *old_master;
 234         int ret;
 235
 236         lockdep_assert_held_once(&dev->struct_mutex);
 237
 238         /* create a new master */
 239         fpriv->minor->master = drm_master_create(fpriv->minor);
 240         if (!fpriv->minor->master)
 241                 return -ENOMEM;
 242
 243         /* take another reference for the copy in the local file priv */
 244         old_master = fpriv->master;
 245         fpriv->master = drm_master_get(fpriv->minor->master);
 246
 247         if (dev->driver->master_create) {
 248                 mutex_unlock(&dev->struct_mutex);
 249                 ret = dev->driver->master_create(dev, fpriv->master);
 250                 mutex_lock(&dev->struct_mutex);
 251                 if (ret)
 252                         goto out_err;
 253         }
 254         if (dev->driver->master_set) {
 255                 ret = dev->driver->master_set(dev, fpriv, true);
 256                 if (ret)
 257                         goto out_err;
 258         }
 259
 260         fpriv->is_master = 1;
 261         fpriv->allowed_master = 1;
 262         fpriv->authenticated = 1;
 263         if (old_master)
 264                 drm_master_put(&old_master);
 265
 266         return 0;
 267
 268 out_err:
 269         /* drop both references and restore old master on failure */
 270         drm_master_put(&fpriv->minor->master);
 271         drm_master_put(&fpriv->master);
 272         fpriv->master = old_master;
 273
 274         return ret;
 275 }
 276
 277 /**
 278  * Called whenever a process opens /dev/drm.
 279  *
 280  * \param inode device inode.
 281  * \param filp file pointer.
 282  * \param dev device.
 283  * \return zero on success or a negative number on failure.
 284  *
 285  * Creates and initializes a drm_file structure for the file private data in \p
 286  * filp and add it into the double linked list in \p dev.
 287  */
 288 static int drm_open_helper(struct inode *inode, struct file *filp,
 289                            struct drm_device * dev)
 290 {
 291         int minor_id = iminor(inode);
 292         struct drm_file *priv;
 293         int ret;
 294
 295         if (filp->f_flags & O_EXCL)
 296                 return -EBUSY;  /* No exclusive opens */
 297         if (!drm_cpu_valid())
 298                 return -EINVAL;
 299         if (dev->switch_power_state != DRM_SWITCH_POWER_ON)
 300                 return -EINVAL;
 301
 302         DRM_DEBUG("pid = %d, minor = %d\n", task_pid_nr(current), minor_id);
 303
 304         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 305         if (!priv)
 306                 return -ENOMEM;
 307
 308         filp->private_data = priv;
 309         priv->filp = filp;
 310         priv->uid = current_euid();
 311         priv->pid = task_pid_nr(current);
 312         priv->minor = idr_find(&drm_minors_idr, minor_id);
 313         priv->ioctl_count = 0;
 314         /* for compatibility root is always authenticated */
 315         priv->authenticated = capable(CAP_SYS_ADMIN);
 316         priv->lock_count = 0;
 317
 318         INIT_LIST_HEAD(&priv->lhead);
 319         INIT_LIST_HEAD(&priv->fbs);
 320         INIT_LIST_HEAD(&priv->event_list);
 321         init_waitqueue_head(&priv->event_wait);
 322         priv->event_space = 4096; /* set aside 4k for event buffer */
 323
 324         if (dev->driver->driver_features & DRIVER_GEM)
 325                 drm_gem_open(dev, priv);
 326
 327         if (dev->driver->open) {
 328                 ret = dev->driver->open(dev, priv);
 329                 if (ret < 0)
 330                         goto out_free;
 331         }
 332
 333
 334         /* if there is no current master make this fd it */
 335         mutex_lock(&dev->struct_mutex);
 336         if (!priv->minor->master) {
 337                 /* create a new master */
 338                 ret = drm_new_set_master(dev, priv);
 339                 mutex_unlock(&dev->struct_mutex);
 340                 if (ret)
 341                         goto out_free;
 342         } else {
 343                 /* get a reference to the master */
 344                 priv->master = drm_master_get(priv->minor->master);
 345                 mutex_unlock(&dev->struct_mutex);
 346         }
 347
 348         mutex_lock(&dev->struct_mutex);
 349         list_add(&priv->lhead, &dev->filelist);
 350         mutex_unlock(&dev->struct_mutex);
 351
 352 #ifdef __alpha__
 353         /*
 354          * Default the hose
 355          */
 356         if (!dev->hose) {
 357                 struct pci_dev *pci_dev;
 358                 pci_dev = pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, NULL);
 359                 if (pci_dev) {
 360                         dev->hose = pci_dev->sysdata;
 361                         pci_dev_put(pci_dev);
 362                 }
 363                 if (!dev->hose) {
 364                         struct pci_bus *b = pci_bus_b(pci_root_buses.next);
 365                         if (b)
 366                                 dev->hose = b->sysdata;
 367                 }
 368         }
 369 #endif
 370
 371         return 0;
 372       out_free:
 373         kfree(priv);
 374         filp->private_data = NULL;
 375         return ret;
 376 }
 377
 378 /** No-op. */
 379 int drm_fasync(int fd, struct file *filp, int on)
 380 {
 381         struct drm_file *priv = filp->private_data;
 382         struct drm_device *dev = priv->minor->dev;
 383
 384         DRM_DEBUG("fd = %d, device = 0x%lx\n", fd,
 385                   (long)old_encode_dev(priv->minor->device));
 386         return fasync_helper(fd, filp, on, &dev->buf_async);
 387 }
 388 EXPORT_SYMBOL(drm_fasync);
 389
 390 /*
 391  * Reclaim locked buffers; note that this may be a bad idea if the current
 392  * context doesn't have the hw lock...
 393  */
 394 static void drm_reclaim_locked_buffers(struct drm_device *dev, struct file *f)
 395 {
 396         struct drm_file *file_priv = f->private_data;
 397
 398         if (drm_i_have_hw_lock(dev, file_priv)) {
 399                 dev->driver->reclaim_buffers_locked(dev, file_priv);
 400         } else {
 401                 unsigned long _end = jiffies + 3 * DRM_HZ;
 402                 int locked = 0;
 403
 404                 drm_idlelock_take(&file_priv->master->lock);
 405
 406                 /*
 407                  * Wait for a while.
 408                  */
 409                 do {
 410                         spin_lock_bh(&file_priv->master->lock.spinlock);
 411                         locked = file_priv->master->lock.idle_has_lock;
 412                         spin_unlock_bh(&file_priv->master->lock.spinlock);
 413                         if (locked)
 414                                 break;
 415                         schedule();
 416                 } while (!time_after_eq(jiffies, _end));
 417
 418                 if (!locked) {
 419                         DRM_ERROR("reclaim_buffers_locked() deadlock. Please rework this\n"
 420                                   "\tdriver to use reclaim_buffers_idlelocked() instead.\n"
 421                                   "\tI will go on reclaiming the buffers anyway.\n");
 422                 }
 423
 424                 dev->driver->reclaim_buffers_locked(dev, file_priv);
 425                 drm_idlelock_release(&file_priv->master->lock);
 426         }
 427 }
 428
 429 static void drm_master_release(struct drm_device *dev, struct file *filp)
 430 {
 431         struct drm_file *file_priv = filp->private_data;
 432
 433         if (dev->driver->reclaim_buffers_locked &&
 434             file_priv->master->lock.hw_lock)
 435                 drm_reclaim_locked_buffers(dev, filp);
 436
 437         if (dev->driver->reclaim_buffers_idlelocked &&
 438             file_priv->master->lock.hw_lock) {
 439                 drm_idlelock_take(&file_priv->master->lock);
 440                 dev->driver->reclaim_buffers_idlelocked(dev, file_priv);
 441                 drm_idlelock_release(&file_priv->master->lock);
 442         }
 443
 444
 445         if (drm_i_have_hw_lock(dev, file_priv)) {
 446                 DRM_DEBUG("File %p released, freeing lock for context %d\n",
 447                           filp, _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
 448                 drm_lock_free(&file_priv->master->lock,
 449                               _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
 450         }
 451
 452         if (drm_core_check_feature(dev, DRIVER_HAVE_DMA) &&
 453             !dev->driver->reclaim_buffers_locked) {
 454                 dev->driver->reclaim_buffers(dev, file_priv);
 455         }
 456 }
 457
 458 static void drm_events_release(struct drm_file *file_priv)
 459 {
 460         struct drm_device *dev = file_priv->minor->dev;
 461         struct drm_pending_event *e, *et;
 462         struct drm_pending_vblank_event *v, *vt;
 463         unsigned long flags;
 464
 465         spin_lock_irqsave(&dev->event_lock, flags);
 466
 467         /* Remove pending flips */
 468         list_for_each_entry_safe(v, vt, &dev->vblank_event_list, base.link)
 469                 if (v->base.file_priv == file_priv) {
 470                         list_del(&v->base.link);
 471                         drm_vblank_put(dev, v->pipe);
 472                         v->base.destroy(&v->base);
 473                 }
 474
 475         /* Remove unconsumed events */
 476         list_for_each_entry_safe(e, et, &file_priv->event_list, link)
 477                 e->destroy(e);
 478
 479         spin_unlock_irqrestore(&dev->event_lock, flags);
 480 }
 481
 482 /**
 483  * Release file.
 484  *
 485  * \param inode device inode
 486  * \param file_priv DRM file private.
 487  * \return zero on success or a negative number on failure.
 488  *
 489  * If the hardware lock is held then free it, and take it again for the kernel
 490  * context since it's necessary to reclaim buffers. Unlink the file private
 491  * data from its list and free it. Decreases the open count and if it reaches
 492  * zero calls drm_lastclose().
 493  */
 494 int drm_release(struct inode *inode, struct file *filp)
 495 {
 496         struct drm_file *file_priv = filp->private_data;
 497         struct drm_device *dev = file_priv->minor->dev;
 498         int retcode = 0;
 499
 500         mutex_lock(&drm_global_mutex);
 501
 502         DRM_DEBUG("open_count = %d\n", dev->open_count);
 503
 504         if (dev->driver->preclose)
 505                 dev->driver->preclose(dev, file_priv);
 506
 507         /* ========================================================
 508          * Begin inline drm_release
 509          */
 510
 511         DRM_DEBUG("pid = %d, device = 0x%lx, open_count = %d\n",
 512                   task_pid_nr(current),
 513                   (long)old_encode_dev(file_priv->minor->device),
 514                   dev->open_count);
 515
 516         /* Release any auth tokens that might point to this file_priv,
 517            (do that under the drm_global_mutex) */
 518         if (file_priv->magic)
 519                 (void) drm_remove_magic(file_priv->master, file_priv->magic);
 520
 521         /* if the master has gone away we can't do anything with the lock */
 522         if (file_priv->minor->master)
 523                 drm_master_release(dev, filp);
 524
 525         drm_events_release(file_priv);
 526
 527         if (dev->driver->driver_features & DRIVER_GEM)
 528                 drm_gem_release(dev, file_priv);
 529
 530         if (dev->driver->driver_features & DRIVER_MODESET)
 531                 drm_fb_release(file_priv);
 532
 533         mutex_lock(&dev->ctxlist_mutex);
 534         if (!list_empty(&dev->ctxlist)) {
 535                 struct drm_ctx_list *pos, *n;
 536
 537                 list_for_each_entry_safe(pos, n, &dev->ctxlist, head) {
 538                         if (pos->tag == file_priv &&
 539                             pos->handle != DRM_KERNEL_CONTEXT) {
 540                                 if (dev->driver->context_dtor)
 541                                         dev->driver->context_dtor(dev,
 542                                                                   pos->handle);
 543
 544                                 drm_ctxbitmap_free(dev, pos->handle);
 545
 546                                 list_del(&pos->head);
 547                                 kfree(pos);
 548                                 --dev->ctx_count;
 549                         }
 550                 }
 551         }
 552         mutex_unlock(&dev->ctxlist_mutex);
 553
 554         mutex_lock(&dev->struct_mutex);
 555
 556         if (file_priv->is_master) {
 557                 struct drm_master *master = file_priv->master;
 558                 struct drm_file *temp;
 559                 list_for_each_entry(temp, &dev->filelist, lhead) {
 560                         if ((temp->master == file_priv->master) &&
 561                             (temp != file_priv))
 562                                 temp->authenticated = 0;
 563                 }
 564
 565                 /**
 566                  * Since the master is disappearing, so is the
 567                  * possibility to lock.
 568                  */
 569
 570                 if (master->lock.hw_lock) {
 571                         if (dev->sigdata.lock == master->lock.hw_lock)
 572                                 dev->sigdata.lock = NULL;
 573                         master->lock.hw_lock = NULL;
 574                         master->lock.file_priv = NULL;
 575                         wake_up_interruptible_all(&master->lock.lock_queue);
 576                 }
 577
 578                 if (file_priv->minor->master == file_priv->master) {
 579                         /* drop the reference held my the minor */
 580                         if (dev->driver->master_drop)
 581                                 dev->driver->master_drop(dev, file_priv, true);
 582                         drm_master_put(&file_priv->minor->master);
 583                 }
 584         }
 585
 586         /* drop the reference held my the file priv */
 587         drm_master_put(&file_priv->master);
 588         file_priv->is_master = 0;
 589         list_del(&file_priv->lhead);
 590         mutex_unlock(&dev->struct_mutex);
 591
 592         if (dev->driver->postclose)
 593                 dev->driver->postclose(dev, file_priv);
 594         kfree(file_priv);
 595
 596         /* ========================================================
 597          * End inline drm_release
 598          */
 599
 600         atomic_inc(&dev->counts[_DRM_STAT_CLOSES]);
 601         if (!--dev->open_count) {
 602                 if (atomic_read(&dev->ioctl_count)) {
 603                         DRM_ERROR("Device busy: %d\n",
 604                                   atomic_read(&dev->ioctl_count));
 605                         retcode = -EBUSY;
 606                 } else
 607                         retcode = drm_lastclose(dev);
 608         }
 609         mutex_unlock(&drm_global_mutex);
 610
 611         return retcode;
 612 }
 613 EXPORT_SYMBOL(drm_release);
 614
 615 static bool
 616 drm_dequeue_event(struct drm_file *file_priv,
 617                   size_t total, size_t max, struct drm_pending_event **out)
 618 {
 619         struct drm_device *dev = file_priv->minor->dev;
 620         struct drm_pending_event *e;
 621         unsigned long flags;
 622         bool ret = false;
 623
 624         spin_lock_irqsave(&dev->event_lock, flags);
 625
 626         *out = NULL;
 627         if (list_empty(&file_priv->event_list))
 628                 goto out;
 629         e = list_first_entry(&file_priv->event_list,
 630                              struct drm_pending_event, link);
 631         if (e->event->length + total > max)
 632                 goto out;
 633
 634         file_priv->event_space += e->event->length;
 635         list_del(&e->link);
 636         *out = e;
 637         ret = true;
 638
 639 out:
 640         spin_unlock_irqrestore(&dev->event_lock, flags);
 641         return ret;
 642 }
 643
 644 ssize_t drm_read(struct file *filp, char __user *buffer,
 645                  size_t count, loff_t *offset)
 646 {
 647         struct drm_file *file_priv = filp->private_data;
 648         struct drm_pending_event *e;
 649         size_t total;
 650         ssize_t ret;
 651
 652         ret = wait_event_interruptible(file_priv->event_wait,
 653                                        !list_empty(&file_priv->event_list));
 654         if (ret < 0)
 655                 return ret;
 656
 657         total = 0;
 658         while (drm_dequeue_event(file_priv, total, count, &e)) {
 659                 if (copy_to_user(buffer + total,
 660                                  e->event, e->event->length)) {
 661                         total = -EFAULT;
 662                         break;
 663                 }
 664
 665                 total += e->event->length;
 666                 e->destroy(e);
 667         }
 668
 669         return total;
 670 }
 671 EXPORT_SYMBOL(drm_read);
 672
 673 unsigned int drm_poll(struct file *filp, struct poll_table_struct *wait)
 674 {
 675         struct drm_file *file_priv = filp->private_data;
 676         unsigned int mask = 0;
 677
 678         poll_wait(filp, &file_priv->event_wait, wait);
 679
 680         if (!list_empty(&file_priv->event_list))
 681                 mask |= POLLIN | POLLRDNORM;
 682
 683         return mask;
 684 }
 685 EXPORT_SYMBOL(drm_poll);