summaryrefslogtreecommitdiff
path: root/drivers/media/media-entity.c
blob: 2ace0410d277c373853ec2fcb58edb30b8bcfc0c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
/*
 * Media entity
 *
 * Copyright (C) 2010 Nokia Corporation
 *
 * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 *	     Sakari Ailus <sakari.ailus@iki.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/bitmap.h>
#include <linux/module.h>
#include <linux/property.h>
#include <linux/slab.h>
#include <media/media-entity.h>
#include <media/media-device.h>

static inline const char *gobj_type(enum media_gobj_type type)
{
	switch (type) {
	case MEDIA_GRAPH_ENTITY:
		return "entity";
	case MEDIA_GRAPH_PAD:
		return "pad";
	case MEDIA_GRAPH_LINK:
		return "link";
	case MEDIA_GRAPH_INTF_DEVNODE:
		return "intf-devnode";
	default:
		return "unknown";
	}
}

static inline const char *intf_type(struct media_interface *intf)
{
	switch (intf->type) {
	case MEDIA_INTF_T_DVB_FE:
		return "dvb-frontend";
	case MEDIA_INTF_T_DVB_DEMUX:
		return "dvb-demux";
	case MEDIA_INTF_T_DVB_DVR:
		return "dvb-dvr";
	case MEDIA_INTF_T_DVB_CA:
		return  "dvb-ca";
	case MEDIA_INTF_T_DVB_NET:
		return "dvb-net";
	case MEDIA_INTF_T_V4L_VIDEO:
		return "v4l-video";
	case MEDIA_INTF_T_V4L_VBI:
		return "v4l-vbi";
	case MEDIA_INTF_T_V4L_RADIO:
		return "v4l-radio";
	case MEDIA_INTF_T_V4L_SUBDEV:
		return "v4l-subdev";
	case MEDIA_INTF_T_V4L_SWRADIO:
		return "v4l-swradio";
	case MEDIA_INTF_T_V4L_TOUCH:
		return "v4l-touch";
	case MEDIA_INTF_T_ALSA_PCM_CAPTURE:
		return "alsa-pcm-capture";
	case MEDIA_INTF_T_ALSA_PCM_PLAYBACK:
		return "alsa-pcm-playback";
	case MEDIA_INTF_T_ALSA_CONTROL:
		return "alsa-control";
	case MEDIA_INTF_T_ALSA_COMPRESS:
		return "alsa-compress";
	case MEDIA_INTF_T_ALSA_RAWMIDI:
		return "alsa-rawmidi";
	case MEDIA_INTF_T_ALSA_HWDEP:
		return "alsa-hwdep";
	case MEDIA_INTF_T_ALSA_SEQUENCER:
		return "alsa-sequencer";
	case MEDIA_INTF_T_ALSA_TIMER:
		return "alsa-timer";
	default:
		return "unknown-intf";
	}
};

__must_check int __media_entity_enum_init(struct media_entity_enum *ent_enum,
					  int idx_max)
{
	idx_max = ALIGN(idx_max, BITS_PER_LONG);
	ent_enum->bmap = kcalloc(idx_max / BITS_PER_LONG, sizeof(long),
				 GFP_KERNEL);
	if (!ent_enum->bmap)
		return -ENOMEM;

	bitmap_zero(ent_enum->bmap, idx_max);
	ent_enum->idx_max = idx_max;

	return 0;
}
EXPORT_SYMBOL_GPL(__media_entity_enum_init);

void media_entity_enum_cleanup(struct media_entity_enum *ent_enum)
{
	kfree(ent_enum->bmap);
}
EXPORT_SYMBOL_GPL(media_entity_enum_cleanup);

/**
 *  dev_dbg_obj - Prints in debug mode a change on some object
 *
 * @event_name:	Name of the event to report. Could be __func__
 * @gobj:	Pointer to the object
 *
 * Enabled only if DEBUG or CONFIG_DYNAMIC_DEBUG. Otherwise, it
 * won't produce any code.
 */
static void dev_dbg_obj(const char *event_name,  struct media_gobj *gobj)
{
#if defined(DEBUG) || defined (CONFIG_DYNAMIC_DEBUG)
	switch (media_type(gobj)) {
	case MEDIA_GRAPH_ENTITY:
		dev_dbg(gobj->mdev->dev,
			"%s id %u: entity '%s'\n",
			event_name, media_id(gobj),
			gobj_to_entity(gobj)->name);
		break;
	case MEDIA_GRAPH_LINK:
	{
		struct media_link *link = gobj_to_link(gobj);

		dev_dbg(gobj->mdev->dev,
			"%s id %u: %s link id %u ==> id %u\n",
			event_name, media_id(gobj),
			media_type(link->gobj0) == MEDIA_GRAPH_PAD ?
				"data" : "interface",
			media_id(link->gobj0),
			media_id(link->gobj1));
		break;
	}
	case MEDIA_GRAPH_PAD:
	{
		struct media_pad *pad = gobj_to_pad(gobj);

		dev_dbg(gobj->mdev->dev,
			"%s id %u: %s%spad '%s':%d\n",
			event_name, media_id(gobj),
			pad->flags & MEDIA_PAD_FL_SINK   ? "sink " : "",
			pad->flags & MEDIA_PAD_FL_SOURCE ? "source " : "",
			pad->entity->name, pad->index);
		break;
	}
	case MEDIA_GRAPH_INTF_DEVNODE:
	{
		struct media_interface *intf = gobj_to_intf(gobj);
		struct media_intf_devnode *devnode = intf_to_devnode(intf);

		dev_dbg(gobj->mdev->dev,
			"%s id %u: intf_devnode %s - major: %d, minor: %d\n",
			event_name, media_id(gobj),
			intf_type(intf),
			devnode->major, devnode->minor);
		break;
	}
	}
#endif
}

void media_gobj_create(struct media_device *mdev,
			   enum media_gobj_type type,
			   struct media_gobj *gobj)
{
	BUG_ON(!mdev);

	gobj->mdev = mdev;

	/* Create a per-type unique object ID */
	gobj->id = media_gobj_gen_id(type, ++mdev->id);

	switch (type) {
	case MEDIA_GRAPH_ENTITY:
		list_add_tail(&gobj->list, &mdev->entities);
		break;
	case MEDIA_GRAPH_PAD:
		list_add_tail(&gobj->list, &mdev->pads);
		break;
	case MEDIA_GRAPH_LINK:
		list_add_tail(&gobj->list, &mdev->links);
		break;
	case MEDIA_GRAPH_INTF_DEVNODE:
		list_add_tail(&gobj->list, &mdev->interfaces);
		break;
	}

	mdev->topology_version++;

	dev_dbg_obj(__func__, gobj);
}

void media_gobj_destroy(struct media_gobj *gobj)
{
	/* Do nothing if the object is not linked. */
	if (gobj->mdev == NULL)
		return;

	dev_dbg_obj(__func__, gobj);

	gobj->mdev->topology_version++;

	/* Remove the object from mdev list */
	list_del(&gobj->list);

	gobj->mdev = NULL;
}

int media_entity_pads_init(struct media_entity *entity, u16 num_pads,
			   struct media_pad *pads)
{
	struct media_device *mdev = entity->graph_obj.mdev;
	unsigned int i;

	entity->num_pads = num_pads;
	entity->pads = pads;

	if (mdev)
		mutex_lock(&mdev->graph_mutex);

	for (i = 0; i < num_pads; i++) {
		pads[i].entity = entity;
		pads[i].index = i;
		if (mdev)
			media_gobj_create(mdev, MEDIA_GRAPH_PAD,
					&entity->pads[i].graph_obj);
	}

	if (mdev)
		mutex_unlock(&mdev->graph_mutex);

	return 0;
}
EXPORT_SYMBOL_GPL(media_entity_pads_init);

/* -----------------------------------------------------------------------------
 * Graph traversal
 */

static struct media_entity *
media_entity_other(struct media_entity *entity, struct media_link *link)
{
	if (link->source->entity == entity)
		return link->sink->entity;
	else
		return link->source->entity;
}

/* push an entity to traversal stack */
static void stack_push(struct media_graph *graph,
		       struct media_entity *entity)
{
	if (graph->top == MEDIA_ENTITY_ENUM_MAX_DEPTH - 1) {
		WARN_ON(1);
		return;
	}
	graph->top++;
	graph->stack[graph->top].link = entity->links.next;
	graph->stack[graph->top].entity = entity;
}

static struct media_entity *stack_pop(struct media_graph *graph)
{
	struct media_entity *entity;

	entity = graph->stack[graph->top].entity;
	graph->top--;

	return entity;
}

#define link_top(en)	((en)->stack[(en)->top].link)
#define stack_top(en)	((en)->stack[(en)->top].entity)

/*
 * TODO: Get rid of this.
 */
#define MEDIA_ENTITY_MAX_PADS		512

/**
 * media_graph_walk_init - Allocate resources for graph walk
 * @graph: Media graph structure that will be used to walk the graph
 * @mdev: Media device
 *
 * Reserve resources for graph walk in media device's current
 * state. The memory must be released using
 * media_graph_walk_free().
 *
 * Returns error on failure, zero on success.
 */
__must_check int media_graph_walk_init(
	struct media_graph *graph, struct media_device *mdev)
{
	return media_entity_enum_init(&graph->ent_enum, mdev);
}
EXPORT_SYMBOL_GPL(media_graph_walk_init);

/**
 * media_graph_walk_cleanup - Release resources related to graph walking
 * @graph: Media graph structure that was used to walk the graph
 */
void media_graph_walk_cleanup(struct media_graph *graph)
{
	media_entity_enum_cleanup(&graph->ent_enum);
}
EXPORT_SYMBOL_GPL(media_graph_walk_cleanup);

void media_graph_walk_start(struct media_graph *graph,
			    struct media_entity *entity)
{
	media_entity_enum_zero(&graph->ent_enum);
	media_entity_enum_set(&graph->ent_enum, entity);

	graph->top = 0;
	graph->stack[graph->top].entity = NULL;
	stack_push(graph, entity);
	dev_dbg(entity->graph_obj.mdev->dev,
		"begin graph walk at '%s'\n", entity->name);
}
EXPORT_SYMBOL_GPL(media_graph_walk_start);

static void media_graph_walk_iter(struct media_graph *graph)
{
	struct media_entity *entity = stack_top(graph);
	struct media_link *link;
	struct media_entity *next;

	link = list_entry(link_top(graph), typeof(*link), list);

	/* The link is not enabled so we do not follow. */
	if (!(link->flags & MEDIA_LNK_FL_ENABLED)) {
		link_top(graph) = link_top(graph)->next;
		dev_dbg(entity->graph_obj.mdev->dev,
			"walk: skipping disabled link '%s':%u -> '%s':%u\n",
			link->source->entity->name, link->source->index,
			link->sink->entity->name, link->sink->index);
		return;
	}

	/* Get the entity in the other end of the link . */
	next = media_entity_other(entity, link);

	/* Has the entity already been visited? */
	if (media_entity_enum_test_and_set(&graph->ent_enum, next)) {
		link_top(graph) = link_top(graph)->next;
		dev_dbg(entity->graph_obj.mdev->dev,
			"walk: skipping entity '%s' (already seen)\n",
			next->name);
		return;
	}

	/* Push the new entity to stack and start over. */
	link_top(graph) = link_top(graph)->next;
	stack_push(graph, next);
	dev_dbg(entity->graph_obj.mdev->dev, "walk: pushing '%s' on stack\n",
		next->name);
}

struct media_entity *media_graph_walk_next(struct media_graph *graph)
{
	struct media_entity *entity;

	if (stack_top(graph) == NULL)
		return NULL;

	/*
	 * Depth first search. Push entity to stack and continue from
	 * top of the stack until no more entities on the level can be
	 * found.
	 */
	while (link_top(graph) != &stack_top(graph)->links)
		media_graph_walk_iter(graph);

	entity = stack_pop(graph);
	dev_dbg(entity->graph_obj.mdev->dev,
		"walk: returning entity '%s'\n", entity->name);

	return entity;
}
EXPORT_SYMBOL_GPL(media_graph_walk_next);

int media_entity_get_fwnode_pad(struct media_entity *entity,
				struct fwnode_handle *fwnode,
				unsigned long direction_flags)
{
	struct fwnode_endpoint endpoint;
	unsigned int i;
	int ret;

	if (!entity->ops || !entity->ops->get_fwnode_pad) {
		for (i = 0; i < entity->num_pads; i++) {
			if (entity->pads[i].flags & direction_flags)
				return i;
		}

		return -ENXIO;
	}

	ret = fwnode_graph_parse_endpoint(fwnode, &endpoint);
	if (ret)
		return ret;

	ret = entity->ops->get_fwnode_pad(&endpoint);
	if (ret < 0)
		return ret;

	if (ret >= entity->num_pads)
		return -ENXIO;

	if (!(entity->pads[ret].flags & direction_flags))
		return -ENXIO;

	return ret;
}
EXPORT_SYMBOL_GPL(media_entity_get_fwnode_pad);

/* -----------------------------------------------------------------------------
 * Pipeline management
 */

__must_check int __media_pipeline_start(struct media_entity *entity,
					struct media_pipeline *pipe)
{
	struct media_device *mdev = entity->graph_obj.mdev;
	struct media_graph *graph = &pipe->graph;
	struct media_entity *entity_err = entity;
	struct media_link *link;
	int ret;

	if (!pipe->streaming_count++) {
		ret = media_graph_walk_init(&pipe->graph, mdev);
		if (ret)
			goto error_graph_walk_start;
	}

	media_graph_walk_start(&pipe->graph, entity);

	while ((entity = media_graph_walk_next(graph))) {
		DECLARE_BITMAP(active, MEDIA_ENTITY_MAX_PADS);
		DECLARE_BITMAP(has_no_links, MEDIA_ENTITY_MAX_PADS);

		entity->stream_count++;

		if (WARN_ON(entity->pipe && entity->pipe != pipe)) {
			ret = -EBUSY;
			goto error;
		}

		entity->pipe = pipe;

		/* Already streaming --- no need to check. */
		if (entity->stream_count > 1)
			continue;

		if (!entity->ops || !entity->ops->link_validate)
			continue;

		bitmap_zero(active, entity->num_pads);
		bitmap_fill(has_no_links, entity->num_pads);

		list_for_each_entry(link, &entity->links, list) {
			struct media_pad *pad = link->sink->entity == entity
						? link->sink : link->source;

			/* Mark that a pad is connected by a link. */
			bitmap_clear(has_no_links, pad->index, 1);

			/*
			 * Pads that either do not need to connect or
			 * are connected through an enabled link are
			 * fine.
			 */
			if (!(pad->flags & MEDIA_PAD_FL_MUST_CONNECT) ||
			    link->flags & MEDIA_LNK_FL_ENABLED)
				bitmap_set(active, pad->index, 1);

			/*
			 * Link validation will only take place for
			 * sink ends of the link that are enabled.
			 */
			if (link->sink != pad ||
			    !(link->flags & MEDIA_LNK_FL_ENABLED))
				continue;

			ret = entity->ops->link_validate(link);
			if (ret < 0 && ret != -ENOIOCTLCMD) {
				dev_dbg(entity->graph_obj.mdev->dev,
					"link validation failed for '%s':%u -> '%s':%u, error %d\n",
					link->source->entity->name,
					link->source->index,
					entity->name, link->sink->index, ret);
				goto error;
			}
		}

		/* Either no links or validated links are fine. */
		bitmap_or(active, active, has_no_links, entity->num_pads);

		if (!bitmap_full(active, entity->num_pads)) {
			ret = -ENOLINK;
			dev_dbg(entity->graph_obj.mdev->dev,
				"'%s':%u must be connected by an enabled link\n",
				entity->name,
				(unsigned)find_first_zero_bit(
					active, entity->num_pads));
			goto error;
		}
	}

	return 0;

error:
	/*
	 * Link validation on graph failed. We revert what we did and
	 * return the error.
	 */
	media_graph_walk_start(graph, entity_err);

	while ((entity_err = media_graph_walk_next(graph))) {
		/* Sanity check for negative stream_count */
		if (!WARN_ON_ONCE(entity_err->stream_count <= 0)) {
			entity_err->stream_count--;
			if (entity_err->stream_count == 0)
				entity_err->pipe = NULL;
		}

		/*
		 * We haven't increased stream_count further than this
		 * so we quit here.
		 */
		if (entity_err == entity)
			break;
	}

error_graph_walk_start:
	if (!--pipe->streaming_count)
		media_graph_walk_cleanup(graph);

	return ret;
}
EXPORT_SYMBOL_GPL(__media_pipeline_start);

__must_check int media_pipeline_start(struct media_entity *entity,
				      struct media_pipeline *pipe)
{
	struct media_device *mdev = entity->graph_obj.mdev;
	int ret;

	mutex_lock(&mdev->graph_mutex);
	ret = __media_pipeline_start(entity, pipe);
	mutex_unlock(&mdev->graph_mutex);
	return ret;
}
EXPORT_SYMBOL_GPL(media_pipeline_start);

void __media_pipeline_stop(struct media_entity *entity)
{
	struct media_graph *graph = &entity->pipe->graph;
	struct media_pipeline *pipe = entity->pipe;

	/*
	 * If the following check fails, the driver has performed an
	 * unbalanced call to media_pipeline_stop()
	 */
	if (WARN_ON(!pipe))
		return;

	media_graph_walk_start(graph, entity);

	while ((entity = media_graph_walk_next(graph))) {
		/* Sanity check for negative stream_count */
		if (!WARN_ON_ONCE(entity->stream_count <= 0)) {
			entity->stream_count--;
			if (entity->stream_count == 0)
				entity->pipe = NULL;
		}
	}

	if (!--pipe->streaming_count)
		media_graph_walk_cleanup(graph);

}
EXPORT_SYMBOL_GPL(__media_pipeline_stop);

void media_pipeline_stop(struct media_entity *entity)
{
	struct media_device *mdev = entity->graph_obj.mdev;

	mutex_lock(&mdev->graph_mutex);
	__media_pipeline_stop(entity);
	mutex_unlock(&mdev->graph_mutex);
}
EXPORT_SYMBOL_GPL(media_pipeline_stop);

/* -----------------------------------------------------------------------------
 * Module use count
 */

struct media_entity *media_entity_get(struct media_entity *entity)
{
	if (entity == NULL)
		return NULL;

	if (entity->graph_obj.mdev->dev &&
	    !try_module_get(entity->graph_obj.mdev->dev->driver->owner))
		return NULL;

	return entity;
}
EXPORT_SYMBOL_GPL(media_entity_get);

void media_entity_put(struct media_entity *entity)
{
	if (entity == NULL)
		return;

	if (entity->graph_obj.mdev->dev)
		module_put(entity->graph_obj.mdev->dev->driver->owner);
}
EXPORT_SYMBOL_GPL(media_entity_put);

/* -----------------------------------------------------------------------------
 * Links management
 */

static struct media_link *media_add_link(struct list_head *head)
{
	struct media_link *link;

	link = kzalloc(sizeof(*link), GFP_KERNEL);
	if (link == NULL)
		return NULL;

	list_add_tail(&link->list, head);

	return link;
}

static void __media_entity_remove_link(struct media_entity *entity,
				       struct media_link *link)
{
	struct media_link *rlink, *tmp;
	struct media_entity *remote;

	if (link->source->entity == entity)
		remote = link->sink->entity;
	else
		remote = link->source->entity;

	list_for_each_entry_safe(rlink, tmp, &remote->links, list) {
		if (rlink != link->reverse)
			continue;

		if (link->source->entity == entity)
			remote->num_backlinks--;

		/* Remove the remote link */
		list_del(&rlink->list);
		media_gobj_destroy(&rlink->graph_obj);
		kfree(rlink);

		if (--remote->num_links == 0)
			break;
	}
	list_del(&link->list);
	media_gobj_destroy(&link->graph_obj);
	kfree(link);
}

int
media_create_pad_link(struct media_entity *source, u16 source_pad,
			 struct media_entity *sink, u16 sink_pad, u32 flags)
{
	struct media_link *link;
	struct media_link *backlink;

	BUG_ON(source == NULL || sink == NULL);
	BUG_ON(source_pad >= source->num_pads);
	BUG_ON(sink_pad >= sink->num_pads);

	link = media_add_link(&source->links);
	if (link == NULL)
		return -ENOMEM;

	link->source = &source->pads[source_pad];
	link->sink = &sink->pads[sink_pad];
	link->flags = flags & ~MEDIA_LNK_FL_INTERFACE_LINK;

	/* Initialize graph object embedded at the new link */
	media_gobj_create(source->graph_obj.mdev, MEDIA_GRAPH_LINK,
			&link->graph_obj);

	/* Create the backlink. Backlinks are used to help graph traversal and
	 * are not reported to userspace.
	 */
	backlink = media_add_link(&sink->links);
	if (backlink == NULL) {
		__media_entity_remove_link(source, link);
		return -ENOMEM;
	}

	backlink->source = &source->pads[source_pad];
	backlink->sink = &sink->pads[sink_pad];
	backlink->flags = flags;
	backlink->is_backlink = true;

	/* Initialize graph object embedded at the new link */
	media_gobj_create(sink->graph_obj.mdev, MEDIA_GRAPH_LINK,
			&backlink->graph_obj);

	link->reverse = backlink;
	backlink->reverse = link;

	sink->num_backlinks++;
	sink->num_links++;
	source->num_links++;

	return 0;
}
EXPORT_SYMBOL_GPL(media_create_pad_link);

int media_create_pad_links(const struct media_device *mdev,
			   const u32 source_function,
			   struct media_entity *source,
			   const u16 source_pad,
			   const u32 sink_function,
			   struct media_entity *sink,
			   const u16 sink_pad,
			   u32 flags,
			   const bool allow_both_undefined)
{
	struct media_entity *entity;
	unsigned function;
	int ret;

	/* Trivial case: 1:1 relation */
	if (source && sink)
		return media_create_pad_link(source, source_pad,
					     sink, sink_pad, flags);

	/* Worse case scenario: n:n relation */
	if (!source && !sink) {
		if (!allow_both_undefined)
			return 0;
		media_device_for_each_entity(source, mdev) {
			if (source->function != source_function)
				continue;
			media_device_for_each_entity(sink, mdev) {
				if (sink->function != sink_function)
					continue;
				ret = media_create_pad_link(source, source_pad,
							    sink, sink_pad,
							    flags);
				if (ret)
					return ret;
				flags &= ~(MEDIA_LNK_FL_ENABLED |
					   MEDIA_LNK_FL_IMMUTABLE);
			}
		}
		return 0;
	}

	/* Handle 1:n and n:1 cases */
	if (source)
		function = sink_function;
	else
		function = source_function;

	media_device_for_each_entity(entity, mdev) {
		if (entity->function != function)
			continue;

		if (source)
			ret = media_create_pad_link(source, source_pad,
						    entity, sink_pad, flags);
		else
			ret = media_create_pad_link(entity, source_pad,
						    sink, sink_pad, flags);
		if (ret)
			return ret;
		flags &= ~(MEDIA_LNK_FL_ENABLED | MEDIA_LNK_FL_IMMUTABLE);
	}
	return 0;
}
EXPORT_SYMBOL_GPL(media_create_pad_links);

void __media_entity_remove_links(struct media_entity *entity)
{
	struct media_link *link, *tmp;

	list_for_each_entry_safe(link, tmp, &entity->links, list)
		__media_entity_remove_link(entity, link);

	entity->num_links = 0;
	entity->num_backlinks = 0;
}
EXPORT_SYMBOL_GPL(__media_entity_remove_links);

void media_entity_remove_links(struct media_entity *entity)
{
	struct media_device *mdev = entity->graph_obj.mdev;

	/* Do nothing if the entity is not registered. */
	if (mdev == NULL)
		return;

	mutex_lock(&mdev->graph_mutex);
	__media_entity_remove_links(entity);
	mutex_unlock(&mdev->graph_mutex);
}
EXPORT_SYMBOL_GPL(media_entity_remove_links);

static int __media_entity_setup_link_notify(struct media_link *link, u32 flags)
{
	int ret;

	/* Notify both entities. */
	ret = media_entity_call(link->source->entity, link_setup,
				link->source, link->sink, flags);
	if (ret < 0 && ret != -ENOIOCTLCMD)
		return ret;

	ret = media_entity_call(link->sink->entity, link_setup,
				link->sink, link->source, flags);
	if (ret < 0 && ret != -ENOIOCTLCMD) {
		media_entity_call(link->source->entity, link_setup,
				  link->source, link->sink, link->flags);
		return ret;
	}

	link->flags = flags;
	link->reverse->flags = link->flags;

	return 0;
}

int __media_entity_setup_link(struct media_link *link, u32 flags)
{
	const u32 mask = MEDIA_LNK_FL_ENABLED;
	struct media_device *mdev;
	struct media_entity *source, *sink;
	int ret = -EBUSY;

	if (link == NULL)
		return -EINVAL;

	/* The non-modifiable link flags must not be modified. */
	if ((link->flags & ~mask) != (flags & ~mask))
		return -EINVAL;

	if (link->flags & MEDIA_LNK_FL_IMMUTABLE)
		return link->flags == flags ? 0 : -EINVAL;

	if (link->flags == flags)
		return 0;

	source = link->source->entity;
	sink = link->sink->entity;

	if (!(link->flags & MEDIA_LNK_FL_DYNAMIC) &&
	    (source->stream_count || sink->stream_count))
		return -EBUSY;

	mdev = source->graph_obj.mdev;

	if (mdev->ops && mdev->ops->link_notify) {
		ret = mdev->ops->link_notify(link, flags,
					     MEDIA_DEV_NOTIFY_PRE_LINK_CH);
		if (ret < 0)
			return ret;
	}

	ret = __media_entity_setup_link_notify(link, flags);

	if (mdev->ops && mdev->ops->link_notify)
		mdev->ops->link_notify(link, flags,
				       MEDIA_DEV_NOTIFY_POST_LINK_CH);

	return ret;
}
EXPORT_SYMBOL_GPL(__media_entity_setup_link);

int media_entity_setup_link(struct media_link *link, u32 flags)
{
	int ret;

	mutex_lock(&link->graph_obj.mdev->graph_mutex);
	ret = __media_entity_setup_link(link, flags);
	mutex_unlock(&link->graph_obj.mdev->graph_mutex);

	return ret;
}
EXPORT_SYMBOL_GPL(media_entity_setup_link);

struct media_link *
media_entity_find_link(struct media_pad *source, struct media_pad *sink)
{
	struct media_link *link;

	list_for_each_entry(link, &source->entity->links, list) {
		if (link->source->entity == source->entity &&
		    link->source->index == source->index &&
		    link->sink->entity == sink->entity &&
		    link->sink->index == sink->index)
			return link;
	}

	return NULL;
}
EXPORT_SYMBOL_GPL(media_entity_find_link);

struct media_pad *media_entity_remote_pad(const struct media_pad *pad)
{
	struct media_link *link;

	list_for_each_entry(link, &pad->entity->links, list) {
		if (!(link->flags & MEDIA_LNK_FL_ENABLED))
			continue;

		if (link->source == pad)
			return link->sink;

		if (link->sink == pad)
			return link->source;
	}

	return NULL;

}
EXPORT_SYMBOL_GPL(media_entity_remote_pad);

static void media_interface_init(struct media_device *mdev,
				 struct media_interface *intf,
				 u32 gobj_type,
				 u32 intf_type, u32 flags)
{
	intf->type = intf_type;
	intf->flags = flags;
	INIT_LIST_HEAD(&intf->links);

	media_gobj_create(mdev, gobj_type, &intf->graph_obj);
}

/* Functions related to the media interface via device nodes */

struct media_intf_devnode *media_devnode_create(struct media_device *mdev,
						u32 type, u32 flags,
						u32 major, u32 minor)
{
	struct media_intf_devnode *devnode;

	devnode = kzalloc(sizeof(*devnode), GFP_KERNEL);
	if (!devnode)
		return NULL;

	devnode->major = major;
	devnode->minor = minor;

	media_interface_init(mdev, &devnode->intf, MEDIA_GRAPH_INTF_DEVNODE,
			     type, flags);

	return devnode;
}
EXPORT_SYMBOL_GPL(media_devnode_create);

void media_devnode_remove(struct media_intf_devnode *devnode)
{
	media_remove_intf_links(&devnode->intf);
	media_gobj_destroy(&devnode->intf.graph_obj);
	kfree(devnode);
}
EXPORT_SYMBOL_GPL(media_devnode_remove);

struct media_link *media_create_intf_link(struct media_entity *entity,
					    struct media_interface *intf,
					    u32 flags)
{
	struct media_link *link;

	link = media_add_link(&intf->links);
	if (link == NULL)
		return NULL;

	link->intf = intf;
	link->entity = entity;
	link->flags = flags | MEDIA_LNK_FL_INTERFACE_LINK;

	/* Initialize graph object embedded at the new link */
	media_gobj_create(intf->graph_obj.mdev, MEDIA_GRAPH_LINK,
			&link->graph_obj);

	return link;
}
EXPORT_SYMBOL_GPL(media_create_intf_link);

void __media_remove_intf_link(struct media_link *link)
{
	list_del(&link->list);
	media_gobj_destroy(&link->graph_obj);
	kfree(link);
}
EXPORT_SYMBOL_GPL(__media_remove_intf_link);

void media_remove_intf_link(struct media_link *link)
{
	struct media_device *mdev = link->graph_obj.mdev;

	/* Do nothing if the intf is not registered. */
	if (mdev == NULL)
		return;

	mutex_lock(&mdev->graph_mutex);
	__media_remove_intf_link(link);
	mutex_unlock(&mdev->graph_mutex);
}
EXPORT_SYMBOL_GPL(media_remove_intf_link);

void __media_remove_intf_links(struct media_interface *intf)
{
	struct media_link *link, *tmp;

	list_for_each_entry_safe(link, tmp, &intf->links, list)
		__media_remove_intf_link(link);

}
EXPORT_SYMBOL_GPL(__media_remove_intf_links);

void media_remove_intf_links(struct media_interface *intf)
{
	struct media_device *mdev = intf->graph_obj.mdev;

	/* Do nothing if the intf is not registered. */
	if (mdev == NULL)
		return;

	mutex_lock(&mdev->graph_mutex);
	__media_remove_intf_links(intf);
	mutex_unlock(&mdev->graph_mutex);
}
EXPORT_SYMBOL_GPL(media_remove_intf_links);