GNU Linux-libre 5.10.219-gnu1
[releases.git] / drivers / gpu / drm / drm_atomic_state_helper.c
1 /*
2  * Copyright (C) 2018 Intel Corp.
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a
5  * copy of this software and associated documentation files (the "Software"),
6  * to deal in the Software without restriction, including without limitation
7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8  * and/or sell copies of the Software, and to permit persons to whom the
9  * Software is furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice shall be included in
12  * all copies or substantial portions of the Software.
13  *
14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
17  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
18  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
19  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
20  * OTHER DEALINGS IN THE SOFTWARE.
21  *
22  * Authors:
23  * Rob Clark <robdclark@gmail.com>
24  * Daniel Vetter <daniel.vetter@ffwll.ch>
25  */
26
27 #include <drm/drm_atomic.h>
28 #include <drm/drm_atomic_state_helper.h>
29 #include <drm/drm_bridge.h>
30 #include <drm/drm_connector.h>
31 #include <drm/drm_crtc.h>
32 #include <drm/drm_device.h>
33 #include <drm/drm_plane.h>
34 #include <drm/drm_print.h>
35 #include <drm/drm_vblank.h>
36 #include <drm/drm_writeback.h>
37
38 #include <linux/slab.h>
39 #include <linux/dma-fence.h>
40
41 /**
42  * DOC: atomic state reset and initialization
43  *
44  * Both the drm core and the atomic helpers assume that there is always the full
45  * and correct atomic software state for all connectors, CRTCs and planes
46  * available. Which is a bit a problem on driver load and also after system
47  * suspend. One way to solve this is to have a hardware state read-out
48  * infrastructure which reconstructs the full software state (e.g. the i915
49  * driver).
50  *
51  * The simpler solution is to just reset the software state to everything off,
52  * which is easiest to do by calling drm_mode_config_reset(). To facilitate this
53  * the atomic helpers provide default reset implementations for all hooks.
54  *
55  * On the upside the precise state tracking of atomic simplifies system suspend
56  * and resume a lot. For drivers using drm_mode_config_reset() a complete recipe
57  * is implemented in drm_atomic_helper_suspend() and drm_atomic_helper_resume().
58  * For other drivers the building blocks are split out, see the documentation
59  * for these functions.
60  */
61
62 /**
63  * __drm_atomic_helper_crtc_state_reset - reset the CRTC state
64  * @crtc_state: atomic CRTC state, must not be NULL
65  * @crtc: CRTC object, must not be NULL
66  *
67  * Initializes the newly allocated @crtc_state with default
68  * values. This is useful for drivers that subclass the CRTC state.
69  */
70 void
71 __drm_atomic_helper_crtc_state_reset(struct drm_crtc_state *crtc_state,
72                                      struct drm_crtc *crtc)
73 {
74         crtc_state->crtc = crtc;
75 }
76 EXPORT_SYMBOL(__drm_atomic_helper_crtc_state_reset);
77
78 /**
79  * __drm_atomic_helper_crtc_reset - reset state on CRTC
80  * @crtc: drm CRTC
81  * @crtc_state: CRTC state to assign
82  *
83  * Initializes the newly allocated @crtc_state and assigns it to
84  * the &drm_crtc->state pointer of @crtc, usually required when
85  * initializing the drivers or when called from the &drm_crtc_funcs.reset
86  * hook.
87  *
88  * This is useful for drivers that subclass the CRTC state.
89  */
90 void
91 __drm_atomic_helper_crtc_reset(struct drm_crtc *crtc,
92                                struct drm_crtc_state *crtc_state)
93 {
94         if (crtc_state)
95                 __drm_atomic_helper_crtc_state_reset(crtc_state, crtc);
96
97         if (drm_dev_has_vblank(crtc->dev))
98                 drm_crtc_vblank_reset(crtc);
99
100         crtc->state = crtc_state;
101 }
102 EXPORT_SYMBOL(__drm_atomic_helper_crtc_reset);
103
104 /**
105  * drm_atomic_helper_crtc_reset - default &drm_crtc_funcs.reset hook for CRTCs
106  * @crtc: drm CRTC
107  *
108  * Resets the atomic state for @crtc by freeing the state pointer (which might
109  * be NULL, e.g. at driver load time) and allocating a new empty state object.
110  */
111 void drm_atomic_helper_crtc_reset(struct drm_crtc *crtc)
112 {
113         struct drm_crtc_state *crtc_state =
114                 kzalloc(sizeof(*crtc->state), GFP_KERNEL);
115
116         if (crtc->state)
117                 crtc->funcs->atomic_destroy_state(crtc, crtc->state);
118
119         __drm_atomic_helper_crtc_reset(crtc, crtc_state);
120 }
121 EXPORT_SYMBOL(drm_atomic_helper_crtc_reset);
122
123 /**
124  * __drm_atomic_helper_crtc_duplicate_state - copy atomic CRTC state
125  * @crtc: CRTC object
126  * @state: atomic CRTC state
127  *
128  * Copies atomic state from a CRTC's current state and resets inferred values.
129  * This is useful for drivers that subclass the CRTC state.
130  */
131 void __drm_atomic_helper_crtc_duplicate_state(struct drm_crtc *crtc,
132                                               struct drm_crtc_state *state)
133 {
134         memcpy(state, crtc->state, sizeof(*state));
135
136         if (state->mode_blob)
137                 drm_property_blob_get(state->mode_blob);
138         if (state->degamma_lut)
139                 drm_property_blob_get(state->degamma_lut);
140         if (state->ctm)
141                 drm_property_blob_get(state->ctm);
142         if (state->gamma_lut)
143                 drm_property_blob_get(state->gamma_lut);
144         state->mode_changed = false;
145         state->active_changed = false;
146         state->planes_changed = false;
147         state->connectors_changed = false;
148         state->color_mgmt_changed = false;
149         state->zpos_changed = false;
150         state->commit = NULL;
151         state->event = NULL;
152         state->async_flip = false;
153
154         /* Self refresh should be canceled when a new update is available */
155         state->active = drm_atomic_crtc_effectively_active(state);
156         state->self_refresh_active = false;
157 }
158 EXPORT_SYMBOL(__drm_atomic_helper_crtc_duplicate_state);
159
160 /**
161  * drm_atomic_helper_crtc_duplicate_state - default state duplicate hook
162  * @crtc: drm CRTC
163  *
164  * Default CRTC state duplicate hook for drivers which don't have their own
165  * subclassed CRTC state structure.
166  */
167 struct drm_crtc_state *
168 drm_atomic_helper_crtc_duplicate_state(struct drm_crtc *crtc)
169 {
170         struct drm_crtc_state *state;
171
172         if (WARN_ON(!crtc->state))
173                 return NULL;
174
175         state = kmalloc(sizeof(*state), GFP_KERNEL);
176         if (state)
177                 __drm_atomic_helper_crtc_duplicate_state(crtc, state);
178
179         return state;
180 }
181 EXPORT_SYMBOL(drm_atomic_helper_crtc_duplicate_state);
182
183 /**
184  * __drm_atomic_helper_crtc_destroy_state - release CRTC state
185  * @state: CRTC state object to release
186  *
187  * Releases all resources stored in the CRTC state without actually freeing
188  * the memory of the CRTC state. This is useful for drivers that subclass the
189  * CRTC state.
190  */
191 void __drm_atomic_helper_crtc_destroy_state(struct drm_crtc_state *state)
192 {
193         if (state->commit) {
194                 /*
195                  * In the event that a non-blocking commit returns
196                  * -ERESTARTSYS before the commit_tail work is queued, we will
197                  * have an extra reference to the commit object. Release it, if
198                  * the event has not been consumed by the worker.
199                  *
200                  * state->event may be freed, so we can't directly look at
201                  * state->event->base.completion.
202                  */
203                 if (state->event && state->commit->abort_completion)
204                         drm_crtc_commit_put(state->commit);
205
206                 kfree(state->commit->event);
207                 state->commit->event = NULL;
208
209                 drm_crtc_commit_put(state->commit);
210         }
211
212         drm_property_blob_put(state->mode_blob);
213         drm_property_blob_put(state->degamma_lut);
214         drm_property_blob_put(state->ctm);
215         drm_property_blob_put(state->gamma_lut);
216 }
217 EXPORT_SYMBOL(__drm_atomic_helper_crtc_destroy_state);
218
219 /**
220  * drm_atomic_helper_crtc_destroy_state - default state destroy hook
221  * @crtc: drm CRTC
222  * @state: CRTC state object to release
223  *
224  * Default CRTC state destroy hook for drivers which don't have their own
225  * subclassed CRTC state structure.
226  */
227 void drm_atomic_helper_crtc_destroy_state(struct drm_crtc *crtc,
228                                           struct drm_crtc_state *state)
229 {
230         __drm_atomic_helper_crtc_destroy_state(state);
231         kfree(state);
232 }
233 EXPORT_SYMBOL(drm_atomic_helper_crtc_destroy_state);
234
235 /**
236  * __drm_atomic_helper_plane_state_reset - resets plane state to default values
237  * @plane_state: atomic plane state, must not be NULL
238  * @plane: plane object, must not be NULL
239  *
240  * Initializes the newly allocated @plane_state with default
241  * values. This is useful for drivers that subclass the CRTC state.
242  */
243 void __drm_atomic_helper_plane_state_reset(struct drm_plane_state *plane_state,
244                                            struct drm_plane *plane)
245 {
246         plane_state->plane = plane;
247         plane_state->rotation = DRM_MODE_ROTATE_0;
248
249         plane_state->alpha = DRM_BLEND_ALPHA_OPAQUE;
250         plane_state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
251 }
252 EXPORT_SYMBOL(__drm_atomic_helper_plane_state_reset);
253
254 /**
255  * __drm_atomic_helper_plane_reset - reset state on plane
256  * @plane: drm plane
257  * @plane_state: plane state to assign
258  *
259  * Initializes the newly allocated @plane_state and assigns it to
260  * the &drm_crtc->state pointer of @plane, usually required when
261  * initializing the drivers or when called from the &drm_plane_funcs.reset
262  * hook.
263  *
264  * This is useful for drivers that subclass the plane state.
265  */
266 void __drm_atomic_helper_plane_reset(struct drm_plane *plane,
267                                      struct drm_plane_state *plane_state)
268 {
269         if (plane_state)
270                 __drm_atomic_helper_plane_state_reset(plane_state, plane);
271
272         plane->state = plane_state;
273 }
274 EXPORT_SYMBOL(__drm_atomic_helper_plane_reset);
275
276 /**
277  * drm_atomic_helper_plane_reset - default &drm_plane_funcs.reset hook for planes
278  * @plane: drm plane
279  *
280  * Resets the atomic state for @plane by freeing the state pointer (which might
281  * be NULL, e.g. at driver load time) and allocating a new empty state object.
282  */
283 void drm_atomic_helper_plane_reset(struct drm_plane *plane)
284 {
285         if (plane->state)
286                 __drm_atomic_helper_plane_destroy_state(plane->state);
287
288         kfree(plane->state);
289         plane->state = kzalloc(sizeof(*plane->state), GFP_KERNEL);
290         if (plane->state)
291                 __drm_atomic_helper_plane_reset(plane, plane->state);
292 }
293 EXPORT_SYMBOL(drm_atomic_helper_plane_reset);
294
295 /**
296  * __drm_atomic_helper_plane_duplicate_state - copy atomic plane state
297  * @plane: plane object
298  * @state: atomic plane state
299  *
300  * Copies atomic state from a plane's current state. This is useful for
301  * drivers that subclass the plane state.
302  */
303 void __drm_atomic_helper_plane_duplicate_state(struct drm_plane *plane,
304                                                struct drm_plane_state *state)
305 {
306         memcpy(state, plane->state, sizeof(*state));
307
308         if (state->fb)
309                 drm_framebuffer_get(state->fb);
310
311         state->fence = NULL;
312         state->commit = NULL;
313         state->fb_damage_clips = NULL;
314 }
315 EXPORT_SYMBOL(__drm_atomic_helper_plane_duplicate_state);
316
317 /**
318  * drm_atomic_helper_plane_duplicate_state - default state duplicate hook
319  * @plane: drm plane
320  *
321  * Default plane state duplicate hook for drivers which don't have their own
322  * subclassed plane state structure.
323  */
324 struct drm_plane_state *
325 drm_atomic_helper_plane_duplicate_state(struct drm_plane *plane)
326 {
327         struct drm_plane_state *state;
328
329         if (WARN_ON(!plane->state))
330                 return NULL;
331
332         state = kmalloc(sizeof(*state), GFP_KERNEL);
333         if (state)
334                 __drm_atomic_helper_plane_duplicate_state(plane, state);
335
336         return state;
337 }
338 EXPORT_SYMBOL(drm_atomic_helper_plane_duplicate_state);
339
340 /**
341  * __drm_atomic_helper_plane_destroy_state - release plane state
342  * @state: plane state object to release
343  *
344  * Releases all resources stored in the plane state without actually freeing
345  * the memory of the plane state. This is useful for drivers that subclass the
346  * plane state.
347  */
348 void __drm_atomic_helper_plane_destroy_state(struct drm_plane_state *state)
349 {
350         if (state->fb)
351                 drm_framebuffer_put(state->fb);
352
353         if (state->fence)
354                 dma_fence_put(state->fence);
355
356         if (state->commit)
357                 drm_crtc_commit_put(state->commit);
358
359         drm_property_blob_put(state->fb_damage_clips);
360 }
361 EXPORT_SYMBOL(__drm_atomic_helper_plane_destroy_state);
362
363 /**
364  * drm_atomic_helper_plane_destroy_state - default state destroy hook
365  * @plane: drm plane
366  * @state: plane state object to release
367  *
368  * Default plane state destroy hook for drivers which don't have their own
369  * subclassed plane state structure.
370  */
371 void drm_atomic_helper_plane_destroy_state(struct drm_plane *plane,
372                                            struct drm_plane_state *state)
373 {
374         __drm_atomic_helper_plane_destroy_state(state);
375         kfree(state);
376 }
377 EXPORT_SYMBOL(drm_atomic_helper_plane_destroy_state);
378
379 /**
380  * __drm_atomic_helper_connector_state_reset - reset the connector state
381  * @conn_state: atomic connector state, must not be NULL
382  * @connector: connectotr object, must not be NULL
383  *
384  * Initializes the newly allocated @conn_state with default
385  * values. This is useful for drivers that subclass the connector state.
386  */
387 void
388 __drm_atomic_helper_connector_state_reset(struct drm_connector_state *conn_state,
389                                           struct drm_connector *connector)
390 {
391         conn_state->connector = connector;
392 }
393 EXPORT_SYMBOL(__drm_atomic_helper_connector_state_reset);
394
395 /**
396  * __drm_atomic_helper_connector_reset - reset state on connector
397  * @connector: drm connector
398  * @conn_state: connector state to assign
399  *
400  * Initializes the newly allocated @conn_state and assigns it to
401  * the &drm_connector->state pointer of @connector, usually required when
402  * initializing the drivers or when called from the &drm_connector_funcs.reset
403  * hook.
404  *
405  * This is useful for drivers that subclass the connector state.
406  */
407 void
408 __drm_atomic_helper_connector_reset(struct drm_connector *connector,
409                                     struct drm_connector_state *conn_state)
410 {
411         if (conn_state)
412                 __drm_atomic_helper_connector_state_reset(conn_state, connector);
413
414         connector->state = conn_state;
415 }
416 EXPORT_SYMBOL(__drm_atomic_helper_connector_reset);
417
418 /**
419  * drm_atomic_helper_connector_reset - default &drm_connector_funcs.reset hook for connectors
420  * @connector: drm connector
421  *
422  * Resets the atomic state for @connector by freeing the state pointer (which
423  * might be NULL, e.g. at driver load time) and allocating a new empty state
424  * object.
425  */
426 void drm_atomic_helper_connector_reset(struct drm_connector *connector)
427 {
428         struct drm_connector_state *conn_state =
429                 kzalloc(sizeof(*conn_state), GFP_KERNEL);
430
431         if (connector->state)
432                 __drm_atomic_helper_connector_destroy_state(connector->state);
433
434         kfree(connector->state);
435         __drm_atomic_helper_connector_reset(connector, conn_state);
436 }
437 EXPORT_SYMBOL(drm_atomic_helper_connector_reset);
438
439 /**
440  * drm_atomic_helper_connector_tv_reset - Resets TV connector properties
441  * @connector: DRM connector
442  *
443  * Resets the TV-related properties attached to a connector.
444  */
445 void drm_atomic_helper_connector_tv_reset(struct drm_connector *connector)
446 {
447         struct drm_cmdline_mode *cmdline = &connector->cmdline_mode;
448         struct drm_connector_state *state = connector->state;
449
450         state->tv.margins.left = cmdline->tv_margins.left;
451         state->tv.margins.right = cmdline->tv_margins.right;
452         state->tv.margins.top = cmdline->tv_margins.top;
453         state->tv.margins.bottom = cmdline->tv_margins.bottom;
454 }
455 EXPORT_SYMBOL(drm_atomic_helper_connector_tv_reset);
456
457 /**
458  * __drm_atomic_helper_connector_duplicate_state - copy atomic connector state
459  * @connector: connector object
460  * @state: atomic connector state
461  *
462  * Copies atomic state from a connector's current state. This is useful for
463  * drivers that subclass the connector state.
464  */
465 void
466 __drm_atomic_helper_connector_duplicate_state(struct drm_connector *connector,
467                                             struct drm_connector_state *state)
468 {
469         memcpy(state, connector->state, sizeof(*state));
470         if (state->crtc)
471                 drm_connector_get(connector);
472         state->commit = NULL;
473
474         if (state->hdr_output_metadata)
475                 drm_property_blob_get(state->hdr_output_metadata);
476
477         /* Don't copy over a writeback job, they are used only once */
478         state->writeback_job = NULL;
479 }
480 EXPORT_SYMBOL(__drm_atomic_helper_connector_duplicate_state);
481
482 /**
483  * drm_atomic_helper_connector_duplicate_state - default state duplicate hook
484  * @connector: drm connector
485  *
486  * Default connector state duplicate hook for drivers which don't have their own
487  * subclassed connector state structure.
488  */
489 struct drm_connector_state *
490 drm_atomic_helper_connector_duplicate_state(struct drm_connector *connector)
491 {
492         struct drm_connector_state *state;
493
494         if (WARN_ON(!connector->state))
495                 return NULL;
496
497         state = kmalloc(sizeof(*state), GFP_KERNEL);
498         if (state)
499                 __drm_atomic_helper_connector_duplicate_state(connector, state);
500
501         return state;
502 }
503 EXPORT_SYMBOL(drm_atomic_helper_connector_duplicate_state);
504
505 /**
506  * __drm_atomic_helper_connector_destroy_state - release connector state
507  * @state: connector state object to release
508  *
509  * Releases all resources stored in the connector state without actually
510  * freeing the memory of the connector state. This is useful for drivers that
511  * subclass the connector state.
512  */
513 void
514 __drm_atomic_helper_connector_destroy_state(struct drm_connector_state *state)
515 {
516         if (state->crtc)
517                 drm_connector_put(state->connector);
518
519         if (state->commit)
520                 drm_crtc_commit_put(state->commit);
521
522         if (state->writeback_job)
523                 drm_writeback_cleanup_job(state->writeback_job);
524
525         drm_property_blob_put(state->hdr_output_metadata);
526 }
527 EXPORT_SYMBOL(__drm_atomic_helper_connector_destroy_state);
528
529 /**
530  * drm_atomic_helper_connector_destroy_state - default state destroy hook
531  * @connector: drm connector
532  * @state: connector state object to release
533  *
534  * Default connector state destroy hook for drivers which don't have their own
535  * subclassed connector state structure.
536  */
537 void drm_atomic_helper_connector_destroy_state(struct drm_connector *connector,
538                                           struct drm_connector_state *state)
539 {
540         __drm_atomic_helper_connector_destroy_state(state);
541         kfree(state);
542 }
543 EXPORT_SYMBOL(drm_atomic_helper_connector_destroy_state);
544
545 /**
546  * __drm_atomic_helper_private_duplicate_state - copy atomic private state
547  * @obj: CRTC object
548  * @state: new private object state
549  *
550  * Copies atomic state from a private objects's current state and resets inferred values.
551  * This is useful for drivers that subclass the private state.
552  */
553 void __drm_atomic_helper_private_obj_duplicate_state(struct drm_private_obj *obj,
554                                                      struct drm_private_state *state)
555 {
556         memcpy(state, obj->state, sizeof(*state));
557 }
558 EXPORT_SYMBOL(__drm_atomic_helper_private_obj_duplicate_state);
559
560 /**
561  * __drm_atomic_helper_bridge_duplicate_state() - Copy atomic bridge state
562  * @bridge: bridge object
563  * @state: atomic bridge state
564  *
565  * Copies atomic state from a bridge's current state and resets inferred values.
566  * This is useful for drivers that subclass the bridge state.
567  */
568 void __drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge,
569                                                 struct drm_bridge_state *state)
570 {
571         __drm_atomic_helper_private_obj_duplicate_state(&bridge->base,
572                                                         &state->base);
573         state->bridge = bridge;
574 }
575 EXPORT_SYMBOL(__drm_atomic_helper_bridge_duplicate_state);
576
577 /**
578  * drm_atomic_helper_bridge_duplicate_state() - Duplicate a bridge state object
579  * @bridge: bridge object
580  *
581  * Allocates a new bridge state and initializes it with the current bridge
582  * state values. This helper is meant to be used as a bridge
583  * &drm_bridge_funcs.atomic_duplicate_state hook for bridges that don't
584  * subclass the bridge state.
585  */
586 struct drm_bridge_state *
587 drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge)
588 {
589         struct drm_bridge_state *new;
590
591         if (WARN_ON(!bridge->base.state))
592                 return NULL;
593
594         new = kzalloc(sizeof(*new), GFP_KERNEL);
595         if (new)
596                 __drm_atomic_helper_bridge_duplicate_state(bridge, new);
597
598         return new;
599 }
600 EXPORT_SYMBOL(drm_atomic_helper_bridge_duplicate_state);
601
602 /**
603  * drm_atomic_helper_bridge_destroy_state() - Destroy a bridge state object
604  * @bridge: the bridge this state refers to
605  * @state: bridge state to destroy
606  *
607  * Destroys a bridge state previously created by
608  * &drm_atomic_helper_bridge_reset() or
609  * &drm_atomic_helper_bridge_duplicate_state(). This helper is meant to be
610  * used as a bridge &drm_bridge_funcs.atomic_destroy_state hook for bridges
611  * that don't subclass the bridge state.
612  */
613 void drm_atomic_helper_bridge_destroy_state(struct drm_bridge *bridge,
614                                             struct drm_bridge_state *state)
615 {
616         kfree(state);
617 }
618 EXPORT_SYMBOL(drm_atomic_helper_bridge_destroy_state);
619
620 /**
621  * __drm_atomic_helper_bridge_reset() - Initialize a bridge state to its
622  *                                      default
623  * @bridge: the bridge this state refers to
624  * @state: bridge state to initialize
625  *
626  * Initializes the bridge state to default values. This is meant to be called
627  * by the bridge &drm_bridge_funcs.atomic_reset hook for bridges that subclass
628  * the bridge state.
629  */
630 void __drm_atomic_helper_bridge_reset(struct drm_bridge *bridge,
631                                       struct drm_bridge_state *state)
632 {
633         memset(state, 0, sizeof(*state));
634         state->bridge = bridge;
635 }
636 EXPORT_SYMBOL(__drm_atomic_helper_bridge_reset);
637
638 /**
639  * drm_atomic_helper_bridge_reset() - Allocate and initialize a bridge state
640  *                                    to its default
641  * @bridge: the bridge this state refers to
642  *
643  * Allocates the bridge state and initializes it to default values. This helper
644  * is meant to be used as a bridge &drm_bridge_funcs.atomic_reset hook for
645  * bridges that don't subclass the bridge state.
646  */
647 struct drm_bridge_state *
648 drm_atomic_helper_bridge_reset(struct drm_bridge *bridge)
649 {
650         struct drm_bridge_state *bridge_state;
651
652         bridge_state = kzalloc(sizeof(*bridge_state), GFP_KERNEL);
653         if (!bridge_state)
654                 return ERR_PTR(-ENOMEM);
655
656         __drm_atomic_helper_bridge_reset(bridge, bridge_state);
657         return bridge_state;
658 }
659 EXPORT_SYMBOL(drm_atomic_helper_bridge_reset);