drivers/gpu/drm/drm_atomic.c

   1 /*
   2  * Copyright (C) 2014 Red Hat
   3  * Copyright (C) 2014 Intel Corp.
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining a
   6  * copy of this software and associated documentation files (the "Software"),
   7  * to deal in the Software without restriction, including without limitation
   8  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   9  * and/or sell copies of the Software, and to permit persons to whom the
  10  * Software is furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be included in
  13  * all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
  19  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  20  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  21  * OTHER DEALINGS IN THE SOFTWARE.
  22  *
  23  * Authors:
  24  * Rob Clark <robdclark@gmail.com>
  25  * Daniel Vetter <daniel.vetter@ffwll.ch>
  26  */
  27
  28
  29 #include <drm/drmP.h>
  30 #include <drm/drm_atomic.h>
  31 #include <drm/drm_plane_helper.h>
  32
  33 static void kfree_state(struct drm_atomic_state *state)
  34 {
  35         kfree(state->connectors);
  36         kfree(state->connector_states);
  37         kfree(state->crtcs);
  38         kfree(state->crtc_states);
  39         kfree(state->planes);
  40         kfree(state->plane_states);
  41         kfree(state);
  42 }
  43
  44 /**
  45  * drm_atomic_state_alloc - allocate atomic state
  46  * @dev: DRM device
  47  *
  48  * This allocates an empty atomic state to track updates.
  49  */
  50 struct drm_atomic_state *
  51 drm_atomic_state_alloc(struct drm_device *dev)
  52 {
  53         struct drm_atomic_state *state;
  54
  55         state = kzalloc(sizeof(*state), GFP_KERNEL);
  56         if (!state)
  57                 return NULL;
  58
  59         state->num_connector = ACCESS_ONCE(dev->mode_config.num_connector);
  60
  61         state->crtcs = kcalloc(dev->mode_config.num_crtc,
  62                                sizeof(*state->crtcs), GFP_KERNEL);
  63         if (!state->crtcs)
  64                 goto fail;
  65         state->crtc_states = kcalloc(dev->mode_config.num_crtc,
  66                                      sizeof(*state->crtc_states), GFP_KERNEL);
  67         if (!state->crtc_states)
  68                 goto fail;
  69         state->planes = kcalloc(dev->mode_config.num_total_plane,
  70                                 sizeof(*state->planes), GFP_KERNEL);
  71         if (!state->planes)
  72                 goto fail;
  73         state->plane_states = kcalloc(dev->mode_config.num_total_plane,
  74                                       sizeof(*state->plane_states), GFP_KERNEL);
  75         if (!state->plane_states)
  76                 goto fail;
  77         state->connectors = kcalloc(state->num_connector,
  78                                     sizeof(*state->connectors),
  79                                     GFP_KERNEL);
  80         if (!state->connectors)
  81                 goto fail;
  82         state->connector_states = kcalloc(state->num_connector,
  83                                           sizeof(*state->connector_states),
  84                                           GFP_KERNEL);
  85         if (!state->connector_states)
  86                 goto fail;
  87
  88         state->dev = dev;
  89
  90         DRM_DEBUG_KMS("Allocate atomic state %p\n", state);
  91
  92         return state;
  93 fail:
  94         kfree_state(state);
  95
  96         return NULL;
  97 }
  98 EXPORT_SYMBOL(drm_atomic_state_alloc);
  99
 100 /**
 101  * drm_atomic_state_clear - clear state object
 102  * @state: atomic state
 103  *
 104  * When the w/w mutex algorithm detects a deadlock we need to back off and drop
 105  * all locks. So someone else could sneak in and change the current modeset
 106  * configuration. Which means that all the state assembled in @state is no
 107  * longer an atomic update to the current state, but to some arbitrary earlier
 108  * state. Which could break assumptions the driver's ->atomic_check likely
 109  * relies on.
 110  *
 111  * Hence we must clear all cached state and completely start over, using this
 112  * function.
 113  */
 114 void drm_atomic_state_clear(struct drm_atomic_state *state)
 115 {
 116         struct drm_device *dev = state->dev;
 117         struct drm_mode_config *config = &dev->mode_config;
 118         int i;
 119
 120         DRM_DEBUG_KMS("Clearing atomic state %p\n", state);
 121
 122         for (i = 0; i < state->num_connector; i++) {
 123                 struct drm_connector *connector = state->connectors[i];
 124
 125                 if (!connector)
 126                         continue;
 127
 128                 WARN_ON(!drm_modeset_is_locked(&config->connection_mutex));
 129
 130                 connector->funcs->atomic_destroy_state(connector,
 131                                                        state->connector_states[i]);
 132         }
 133
 134         for (i = 0; i < config->num_crtc; i++) {
 135                 struct drm_crtc *crtc = state->crtcs[i];
 136
 137                 if (!crtc)
 138                         continue;
 139
 140                 crtc->funcs->atomic_destroy_state(crtc,
 141                                                   state->crtc_states[i]);
 142         }
 143
 144         for (i = 0; i < config->num_total_plane; i++) {
 145                 struct drm_plane *plane = state->planes[i];
 146
 147                 if (!plane)
 148                         continue;
 149
 150                 plane->funcs->atomic_destroy_state(plane,
 151                                                    state->plane_states[i]);
 152         }
 153 }
 154 EXPORT_SYMBOL(drm_atomic_state_clear);
 155
 156 /**
 157  * drm_atomic_state_free - free all memory for an atomic state
 158  * @state: atomic state to deallocate
 159  *
 160  * This frees all memory associated with an atomic state, including all the
 161  * per-object state for planes, crtcs and connectors.
 162  */
 163 void drm_atomic_state_free(struct drm_atomic_state *state)
 164 {
 165         drm_atomic_state_clear(state);
 166
 167         DRM_DEBUG_KMS("Freeing atomic state %p\n", state);
 168
 169         kfree_state(state);
 170 }
 171 EXPORT_SYMBOL(drm_atomic_state_free);
 172
 173 /**
 174  * drm_atomic_get_crtc_state - get crtc state
 175  * @state: global atomic state object
 176  * @crtc: crtc to get state object for
 177  *
 178  * This function returns the crtc state for the given crtc, allocating it if
 179  * needed. It will also grab the relevant crtc lock to make sure that the state
 180  * is consistent.
 181  *
 182  * Returns:
 183  *
 184  * Either the allocated state or the error code encoded into the pointer. When
 185  * the error is EDEADLK then the w/w mutex code has detected a deadlock and the
 186  * entire atomic sequence must be restarted. All other errors are fatal.
 187  */
 188 struct drm_crtc_state *
 189 drm_atomic_get_crtc_state(struct drm_atomic_state *state,
 190                           struct drm_crtc *crtc)
 191 {
 192         int ret, index;
 193         struct drm_crtc_state *crtc_state;
 194
 195         index = drm_crtc_index(crtc);
 196
 197         if (state->crtc_states[index])
 198                 return state->crtc_states[index];
 199
 200         ret = drm_modeset_lock(&crtc->mutex, state->acquire_ctx);
 201         if (ret)
 202                 return ERR_PTR(ret);
 203
 204         crtc_state = crtc->funcs->atomic_duplicate_state(crtc);
 205         if (!crtc_state)
 206                 return ERR_PTR(-ENOMEM);
 207
 208         state->crtc_states[index] = crtc_state;
 209         state->crtcs[index] = crtc;
 210         crtc_state->state = state;
 211
 212         DRM_DEBUG_KMS("Added [CRTC:%d] %p state to %p\n",
 213                       crtc->base.id, crtc_state, state);
 214
 215         return crtc_state;
 216 }
 217 EXPORT_SYMBOL(drm_atomic_get_crtc_state);
 218
 219 /**
 220  * drm_atomic_get_plane_state - get plane state
 221  * @state: global atomic state object
 222  * @plane: plane to get state object for
 223  *
 224  * This function returns the plane state for the given plane, allocating it if
 225  * needed. It will also grab the relevant plane lock to make sure that the state
 226  * is consistent.
 227  *
 228  * Returns:
 229  *
 230  * Either the allocated state or the error code encoded into the pointer. When
 231  * the error is EDEADLK then the w/w mutex code has detected a deadlock and the
 232  * entire atomic sequence must be restarted. All other errors are fatal.
 233  */
 234 struct drm_plane_state *
 235 drm_atomic_get_plane_state(struct drm_atomic_state *state,
 236                           struct drm_plane *plane)
 237 {
 238         int ret, index;
 239         struct drm_plane_state *plane_state;
 240
 241         index = drm_plane_index(plane);
 242
 243         if (state->plane_states[index])
 244                 return state->plane_states[index];
 245
 246         ret = drm_modeset_lock(&plane->mutex, state->acquire_ctx);
 247         if (ret)
 248                 return ERR_PTR(ret);
 249
 250         plane_state = plane->funcs->atomic_duplicate_state(plane);
 251         if (!plane_state)
 252                 return ERR_PTR(-ENOMEM);
 253
 254         state->plane_states[index] = plane_state;
 255         state->planes[index] = plane;
 256         plane_state->state = state;
 257
 258         DRM_DEBUG_KMS("Added [PLANE:%d] %p state to %p\n",
 259                       plane->base.id, plane_state, state);
 260
 261         if (plane_state->crtc) {
 262                 struct drm_crtc_state *crtc_state;
 263
 264                 crtc_state = drm_atomic_get_crtc_state(state,
 265                                                        plane_state->crtc);
 266                 if (IS_ERR(crtc_state))
 267                         return ERR_CAST(crtc_state);
 268         }
 269
 270         return plane_state;
 271 }
 272 EXPORT_SYMBOL(drm_atomic_get_plane_state);
 273
 274 /**
 275  * drm_atomic_get_connector_state - get connector state
 276  * @state: global atomic state object
 277  * @connector: connector to get state object for
 278  *
 279  * This function returns the connector state for the given connector,
 280  * allocating it if needed. It will also grab the relevant connector lock to
 281  * make sure that the state is consistent.
 282  *
 283  * Returns:
 284  *
 285  * Either the allocated state or the error code encoded into the pointer. When
 286  * the error is EDEADLK then the w/w mutex code has detected a deadlock and the
 287  * entire atomic sequence must be restarted. All other errors are fatal.
 288  */
 289 struct drm_connector_state *
 290 drm_atomic_get_connector_state(struct drm_atomic_state *state,
 291                           struct drm_connector *connector)
 292 {
 293         int ret, index;
 294         struct drm_mode_config *config = &connector->dev->mode_config;
 295         struct drm_connector_state *connector_state;
 296
 297         ret = drm_modeset_lock(&config->connection_mutex, state->acquire_ctx);
 298         if (ret)
 299                 return ERR_PTR(ret);
 300
 301         index = drm_connector_index(connector);
 302
 303         /*
 304          * Construction of atomic state updates can race with a connector
 305          * hot-add which might overflow. In this case flip the table and just
 306          * restart the entire ioctl - no one is fast enough to livelock a cpu
 307          * with physical hotplug events anyway.
 308          *
 309          * Note that we only grab the indexes once we have the right lock to
 310          * prevent hotplug/unplugging of connectors. So removal is no problem,
 311          * at most the array is a bit too large.
 312          */
 313         if (index >= state->num_connector) {
 314                 DRM_DEBUG_KMS("Hot-added connector would overflow state array, restarting\n");
 315                 return ERR_PTR(-EAGAIN);
 316         }
 317
 318         if (state->connector_states[index])
 319                 return state->connector_states[index];
 320
 321         connector_state = connector->funcs->atomic_duplicate_state(connector);
 322         if (!connector_state)
 323                 return ERR_PTR(-ENOMEM);
 324
 325         state->connector_states[index] = connector_state;
 326         state->connectors[index] = connector;
 327         connector_state->state = state;
 328
 329         DRM_DEBUG_KMS("Added [CONNECTOR:%d] %p state to %p\n",
 330                       connector->base.id, connector_state, state);
 331
 332         if (connector_state->crtc) {
 333                 struct drm_crtc_state *crtc_state;
 334
 335                 crtc_state = drm_atomic_get_crtc_state(state,
 336                                                        connector_state->crtc);
 337                 if (IS_ERR(crtc_state))
 338                         return ERR_CAST(crtc_state);
 339         }
 340
 341         return connector_state;
 342 }
 343 EXPORT_SYMBOL(drm_atomic_get_connector_state);
 344
 345 /**
 346  * drm_atomic_set_crtc_for_plane - set crtc for plane
 347  * @state: the incoming atomic state
 348  * @plane: the plane whose incoming state to update
 349  * @crtc: crtc to use for the plane
 350  *
 351  * Changing the assigned crtc for a plane requires us to grab the lock and state
 352  * for the new crtc, as needed. This function takes care of all these details
 353  * besides updating the pointer in the state object itself.
 354  *
 355  * Returns:
 356  * 0 on success or can fail with -EDEADLK or -ENOMEM. When the error is EDEADLK
 357  * then the w/w mutex code has detected a deadlock and the entire atomic
 358  * sequence must be restarted. All other errors are fatal.
 359  */
 360 int
 361 drm_atomic_set_crtc_for_plane(struct drm_atomic_state *state,
 362                               struct drm_plane *plane, struct drm_crtc *crtc)
 363 {
 364         struct drm_plane_state *plane_state =
 365                         drm_atomic_get_plane_state(state, plane);
 366         struct drm_crtc_state *crtc_state;
 367
 368         if (WARN_ON(IS_ERR(plane_state)))
 369                 return PTR_ERR(plane_state);
 370
 371         if (plane_state->crtc) {
 372                 crtc_state = drm_atomic_get_crtc_state(plane_state->state,
 373                                                        plane_state->crtc);
 374                 if (WARN_ON(IS_ERR(crtc_state)))
 375                         return PTR_ERR(crtc_state);
 376
 377                 crtc_state->plane_mask &= ~(1 << drm_plane_index(plane));
 378         }
 379
 380         plane_state->crtc = crtc;
 381
 382         if (crtc) {
 383                 crtc_state = drm_atomic_get_crtc_state(plane_state->state,
 384                                                        crtc);
 385                 if (IS_ERR(crtc_state))
 386                         return PTR_ERR(crtc_state);
 387                 crtc_state->plane_mask |= (1 << drm_plane_index(plane));
 388         }
 389
 390         if (crtc)
 391                 DRM_DEBUG_KMS("Link plane state %p to [CRTC:%d]\n",
 392                               plane_state, crtc->base.id);
 393         else
 394                 DRM_DEBUG_KMS("Link plane state %p to [NOCRTC]\n", plane_state);
 395
 396         return 0;
 397 }
 398 EXPORT_SYMBOL(drm_atomic_set_crtc_for_plane);
 399
 400 /**
 401  * drm_atomic_set_fb_for_plane - set crtc for plane
 402  * @plane_state: atomic state object for the plane
 403  * @fb: fb to use for the plane
 404  *
 405  * Changing the assigned framebuffer for a plane requires us to grab a reference
 406  * to the new fb and drop the reference to the old fb, if there is one. This
 407  * function takes care of all these details besides updating the pointer in the
 408  * state object itself.
 409  */
 410 void
 411 drm_atomic_set_fb_for_plane(struct drm_plane_state *plane_state,
 412                             struct drm_framebuffer *fb)
 413 {
 414         if (plane_state->fb)
 415                 drm_framebuffer_unreference(plane_state->fb);
 416         if (fb)
 417                 drm_framebuffer_reference(fb);
 418         plane_state->fb = fb;
 419
 420         if (fb)
 421                 DRM_DEBUG_KMS("Set [FB:%d] for plane state %p\n",
 422                               fb->base.id, plane_state);
 423         else
 424                 DRM_DEBUG_KMS("Set [NOFB] for plane state %p\n", plane_state);
 425 }
 426 EXPORT_SYMBOL(drm_atomic_set_fb_for_plane);
 427
 428 /**
 429  * drm_atomic_set_crtc_for_connector - set crtc for connector
 430  * @conn_state: atomic state object for the connector
 431  * @crtc: crtc to use for the connector
 432  *
 433  * Changing the assigned crtc for a connector requires us to grab the lock and
 434  * state for the new crtc, as needed. This function takes care of all these
 435  * details besides updating the pointer in the state object itself.
 436  *
 437  * Returns:
 438  * 0 on success or can fail with -EDEADLK or -ENOMEM. When the error is EDEADLK
 439  * then the w/w mutex code has detected a deadlock and the entire atomic
 440  * sequence must be restarted. All other errors are fatal.
 441  */
 442 int
 443 drm_atomic_set_crtc_for_connector(struct drm_connector_state *conn_state,
 444                                   struct drm_crtc *crtc)
 445 {
 446         struct drm_crtc_state *crtc_state;
 447
 448         if (crtc) {
 449                 crtc_state = drm_atomic_get_crtc_state(conn_state->state, crtc);
 450                 if (IS_ERR(crtc_state))
 451                         return PTR_ERR(crtc_state);
 452         }
 453
 454         conn_state->crtc = crtc;
 455
 456         if (crtc)
 457                 DRM_DEBUG_KMS("Link connector state %p to [CRTC:%d]\n",
 458                               conn_state, crtc->base.id);
 459         else
 460                 DRM_DEBUG_KMS("Link connector state %p to [NOCRTC]\n",
 461                               conn_state);
 462
 463         return 0;
 464 }
 465 EXPORT_SYMBOL(drm_atomic_set_crtc_for_connector);
 466
 467 /**
 468  * drm_atomic_add_affected_connectors - add connectors for crtc
 469  * @state: atomic state
 470  * @crtc: DRM crtc
 471  *
 472  * This function walks the current configuration and adds all connectors
 473  * currently using @crtc to the atomic configuration @state. Note that this
 474  * function must acquire the connection mutex. This can potentially cause
 475  * unneeded seralization if the update is just for the planes on one crtc. Hence
 476  * drivers and helpers should only call this when really needed (e.g. when a
 477  * full modeset needs to happen due to some change).
 478  *
 479  * Returns:
 480  * 0 on success or can fail with -EDEADLK or -ENOMEM. When the error is EDEADLK
 481  * then the w/w mutex code has detected a deadlock and the entire atomic
 482  * sequence must be restarted. All other errors are fatal.
 483  */
 484 int
 485 drm_atomic_add_affected_connectors(struct drm_atomic_state *state,
 486                                    struct drm_crtc *crtc)
 487 {
 488         struct drm_mode_config *config = &state->dev->mode_config;
 489         struct drm_connector *connector;
 490         struct drm_connector_state *conn_state;
 491         int ret;
 492
 493         ret = drm_modeset_lock(&config->connection_mutex, state->acquire_ctx);
 494         if (ret)
 495                 return ret;
 496
 497         DRM_DEBUG_KMS("Adding all current connectors for [CRTC:%d] to %p\n",
 498                       crtc->base.id, state);
 499
 500         /*
 501          * Changed connectors are already in @state, so only need to look at the
 502          * current configuration.
 503          */
 504         list_for_each_entry(connector, &config->connector_list, head) {
 505                 if (connector->state->crtc != crtc)
 506                         continue;
 507
 508                 conn_state = drm_atomic_get_connector_state(state, connector);
 509                 if (IS_ERR(conn_state))
 510                         return PTR_ERR(conn_state);
 511         }
 512
 513         return 0;
 514 }
 515 EXPORT_SYMBOL(drm_atomic_add_affected_connectors);
 516
 517 /**
 518  * drm_atomic_connectors_for_crtc - count number of connected outputs
 519  * @state: atomic state
 520  * @crtc: DRM crtc
 521  *
 522  * This function counts all connectors which will be connected to @crtc
 523  * according to @state. Useful to recompute the enable state for @crtc.
 524  */
 525 int
 526 drm_atomic_connectors_for_crtc(struct drm_atomic_state *state,
 527                                struct drm_crtc *crtc)
 528 {
 529         int i, num_connected_connectors = 0;
 530
 531         for (i = 0; i < state->num_connector; i++) {
 532                 struct drm_connector_state *conn_state;
 533
 534                 conn_state = state->connector_states[i];
 535
 536                 if (conn_state && conn_state->crtc == crtc)
 537                         num_connected_connectors++;
 538         }
 539
 540         DRM_DEBUG_KMS("State %p has %i connectors for [CRTC:%d]\n",
 541                       state, num_connected_connectors, crtc->base.id);
 542
 543         return num_connected_connectors;
 544 }
 545 EXPORT_SYMBOL(drm_atomic_connectors_for_crtc);
 546
 547 /**
 548  * drm_atomic_legacy_backoff - locking backoff for legacy ioctls
 549  * @state: atomic state
 550  *
 551  * This function should be used by legacy entry points which don't understand
 552  * -EDEADLK semantics. For simplicity this one will grab all modeset locks after
 553  *  the slowpath completed.
 554  */
 555 void drm_atomic_legacy_backoff(struct drm_atomic_state *state)
 556 {
 557         int ret;
 558
 559 retry:
 560         drm_modeset_backoff(state->acquire_ctx);
 561
 562         ret = drm_modeset_lock(&state->dev->mode_config.connection_mutex,
 563                                state->acquire_ctx);
 564         if (ret)
 565                 goto retry;
 566         ret = drm_modeset_lock_all_crtcs(state->dev,
 567                                          state->acquire_ctx);
 568         if (ret)
 569                 goto retry;
 570 }
 571 EXPORT_SYMBOL(drm_atomic_legacy_backoff);
 572
 573 /**
 574  * drm_atomic_check_only - check whether a given config would work
 575  * @state: atomic configuration to check
 576  *
 577  * Note that this function can return -EDEADLK if the driver needed to acquire
 578  * more locks but encountered a deadlock. The caller must then do the usual w/w
 579  * backoff dance and restart. All other errors are fatal.
 580  *
 581  * Returns:
 582  * 0 on success, negative error code on failure.
 583  */
 584 int drm_atomic_check_only(struct drm_atomic_state *state)
 585 {
 586         struct drm_mode_config *config = &state->dev->mode_config;
 587
 588         DRM_DEBUG_KMS("checking %p\n", state);
 589
 590         if (config->funcs->atomic_check)
 591                 return config->funcs->atomic_check(state->dev, state);
 592         else
 593                 return 0;
 594 }
 595 EXPORT_SYMBOL(drm_atomic_check_only);
 596
 597 /**
 598  * drm_atomic_commit - commit configuration atomically
 599  * @state: atomic configuration to check
 600  *
 601  * Note that this function can return -EDEADLK if the driver needed to acquire
 602  * more locks but encountered a deadlock. The caller must then do the usual w/w
 603  * backoff dance and restart. All other errors are fatal.
 604  *
 605  * Also note that on successful execution ownership of @state is transferred
 606  * from the caller of this function to the function itself. The caller must not
 607  * free or in any other way access @state. If the function fails then the caller
 608  * must clean up @state itself.
 609  *
 610  * Returns:
 611  * 0 on success, negative error code on failure.
 612  */
 613 int drm_atomic_commit(struct drm_atomic_state *state)
 614 {
 615         struct drm_mode_config *config = &state->dev->mode_config;
 616         int ret;
 617
 618         ret = drm_atomic_check_only(state);
 619         if (ret)
 620                 return ret;
 621
 622         DRM_DEBUG_KMS("commiting %p\n", state);
 623
 624         return config->funcs->atomic_commit(state->dev, state, false);
 625 }
 626 EXPORT_SYMBOL(drm_atomic_commit);
 627
 628 /**
 629  * drm_atomic_async_commit - atomic&async configuration commit
 630  * @state: atomic configuration to check
 631  *
 632  * Note that this function can return -EDEADLK if the driver needed to acquire
 633  * more locks but encountered a deadlock. The caller must then do the usual w/w
 634  * backoff dance and restart. All other errors are fatal.
 635  *
 636  * Also note that on successful execution ownership of @state is transferred
 637  * from the caller of this function to the function itself. The caller must not
 638  * free or in any other way access @state. If the function fails then the caller
 639  * must clean up @state itself.
 640  *
 641  * Returns:
 642  * 0 on success, negative error code on failure.
 643  */
 644 int drm_atomic_async_commit(struct drm_atomic_state *state)
 645 {
 646         struct drm_mode_config *config = &state->dev->mode_config;
 647         int ret;
 648
 649         ret = drm_atomic_check_only(state);
 650         if (ret)
 651                 return ret;
 652
 653         DRM_DEBUG_KMS("commiting %p asynchronously\n", state);
 654
 655         return config->funcs->atomic_commit(state->dev, state, true);
 656 }
 657 EXPORT_SYMBOL(drm_atomic_async_commit);