summaryrefslogtreecommitdiff
path: root/drivers/of/overlay.c
blob: 3397d764295849fa2c0c753c28e036a514171d83 (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
// SPDX-License-Identifier: GPL-2.0
/*
 * Functions for working with device tree overlays
 *
 * Copyright (C) 2012 Pantelis Antoniou <panto@antoniou-consulting.com>
 * Copyright (C) 2012 Texas Instruments Inc.
 */

#define pr_fmt(fmt)	"OF: overlay: " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/idr.h>

#include "of_private.h"

/**
 * struct fragment - info about fragment nodes in overlay expanded device tree
 * @target:	target of the overlay operation
 * @overlay:	pointer to the __overlay__ node
 */
struct fragment {
	struct device_node *target;
	struct device_node *overlay;
};

/**
 * struct overlay_changeset
 * @ovcs_list:		list on which we are located
 * @overlay_tree:	expanded device tree that contains the fragment nodes
 * @count:		count of fragment structures
 * @fragments:		fragment nodes in the overlay expanded device tree
 * @symbols_fragment:	last element of @fragments[] is the  __symbols__ node
 * @cset:		changeset to apply fragments to live device tree
 */
struct overlay_changeset {
	int id;
	struct list_head ovcs_list;
	struct device_node *overlay_tree;
	int count;
	struct fragment *fragments;
	bool symbols_fragment;
	struct of_changeset cset;
};

/* flags are sticky - once set, do not reset */
static int devicetree_state_flags;
#define DTSF_APPLY_FAIL		0x01
#define DTSF_REVERT_FAIL	0x02

/*
 * If a changeset apply or revert encounters an error, an attempt will
 * be made to undo partial changes, but may fail.  If the undo fails
 * we do not know the state of the devicetree.
 */
static int devicetree_corrupt(void)
{
	return devicetree_state_flags &
		(DTSF_APPLY_FAIL | DTSF_REVERT_FAIL);
}

static int build_changeset_next_level(struct overlay_changeset *ovcs,
		struct device_node *target_node,
		const struct device_node *overlay_node);

/*
 * of_resolve_phandles() finds the largest phandle in the live tree.
 * of_overlay_apply() may add a larger phandle to the live tree.
 * Do not allow race between two overlays being applied simultaneously:
 *    mutex_lock(&of_overlay_phandle_mutex)
 *    of_resolve_phandles()
 *    of_overlay_apply()
 *    mutex_unlock(&of_overlay_phandle_mutex)
 */
static DEFINE_MUTEX(of_overlay_phandle_mutex);

void of_overlay_mutex_lock(void)
{
	mutex_lock(&of_overlay_phandle_mutex);
}

void of_overlay_mutex_unlock(void)
{
	mutex_unlock(&of_overlay_phandle_mutex);
}


static LIST_HEAD(ovcs_list);
static DEFINE_IDR(ovcs_idr);

static BLOCKING_NOTIFIER_HEAD(overlay_notify_chain);

int of_overlay_notifier_register(struct notifier_block *nb)
{
	return blocking_notifier_chain_register(&overlay_notify_chain, nb);
}
EXPORT_SYMBOL_GPL(of_overlay_notifier_register);

int of_overlay_notifier_unregister(struct notifier_block *nb)
{
	return blocking_notifier_chain_unregister(&overlay_notify_chain, nb);
}
EXPORT_SYMBOL_GPL(of_overlay_notifier_unregister);

static char *of_overlay_action_name[] = {
	"pre-apply",
	"post-apply",
	"pre-remove",
	"post-remove",
};

static int overlay_notify(struct overlay_changeset *ovcs,
		enum of_overlay_notify_action action)
{
	struct of_overlay_notify_data nd;
	int i, ret;

	for (i = 0; i < ovcs->count; i++) {
		struct fragment *fragment = &ovcs->fragments[i];

		nd.target = fragment->target;
		nd.overlay = fragment->overlay;

		ret = blocking_notifier_call_chain(&overlay_notify_chain,
						   action, &nd);
		if (ret == NOTIFY_OK || ret == NOTIFY_STOP)
			return 0;
		if (ret) {
			ret = notifier_to_errno(ret);
			pr_err("overlay changeset %s notifier error %d, target: %pOF\n",
			       of_overlay_action_name[action], ret, nd.target);
			return ret;
		}
	}

	return 0;
}

/*
 * The values of properties in the "/__symbols__" node are paths in
 * the ovcs->overlay_tree.  When duplicating the properties, the paths
 * need to be adjusted to be the correct path for the live device tree.
 *
 * The paths refer to a node in the subtree of a fragment node's "__overlay__"
 * node, for example "/fragment@0/__overlay__/symbol_path_tail",
 * where symbol_path_tail can be a single node or it may be a multi-node path.
 *
 * The duplicated property value will be modified by replacing the
 * "/fragment_name/__overlay/" portion of the value  with the target
 * path from the fragment node.
 */
static struct property *dup_and_fixup_symbol_prop(
		struct overlay_changeset *ovcs, const struct property *prop)
{
	struct fragment *fragment;
	struct property *new_prop;
	struct device_node *fragment_node;
	struct device_node *overlay_node;
	const char *path;
	const char *path_tail;
	const char *target_path;
	int k;
	int overlay_name_len;
	int path_len;
	int path_tail_len;
	int target_path_len;

	if (!prop->value)
		return NULL;
	if (strnlen(prop->value, prop->length) >= prop->length)
		return NULL;
	path = prop->value;
	path_len = strlen(path);

	if (path_len < 1)
		return NULL;
	fragment_node = __of_find_node_by_path(ovcs->overlay_tree, path + 1);
	overlay_node = __of_find_node_by_path(fragment_node, "__overlay__/");
	of_node_put(fragment_node);
	of_node_put(overlay_node);

	for (k = 0; k < ovcs->count; k++) {
		fragment = &ovcs->fragments[k];
		if (fragment->overlay == overlay_node)
			break;
	}
	if (k >= ovcs->count)
		return NULL;

	overlay_name_len = snprintf(NULL, 0, "%pOF", fragment->overlay);

	if (overlay_name_len > path_len)
		return NULL;
	path_tail = path + overlay_name_len;
	path_tail_len = strlen(path_tail);

	target_path = kasprintf(GFP_KERNEL, "%pOF", fragment->target);
	if (!target_path)
		return NULL;
	target_path_len = strlen(target_path);

	new_prop = kzalloc(sizeof(*new_prop), GFP_KERNEL);
	if (!new_prop)
		goto err_free_target_path;

	new_prop->name = kstrdup(prop->name, GFP_KERNEL);
	new_prop->length = target_path_len + path_tail_len + 1;
	new_prop->value = kzalloc(new_prop->length, GFP_KERNEL);
	if (!new_prop->name || !new_prop->value)
		goto err_free_new_prop;

	strcpy(new_prop->value, target_path);
	strcpy(new_prop->value + target_path_len, path_tail);

	of_property_set_flag(new_prop, OF_DYNAMIC);

	return new_prop;

err_free_new_prop:
	kfree(new_prop->name);
	kfree(new_prop->value);
	kfree(new_prop);
err_free_target_path:
	kfree(target_path);

	return NULL;
}

/**
 * add_changeset_property() - add @overlay_prop to overlay changeset
 * @ovcs:		overlay changeset
 * @target_node:	where to place @overlay_prop in live tree
 * @overlay_prop:	property to add or update, from overlay tree
 * @is_symbols_prop:	1 if @overlay_prop is from node "/__symbols__"
 *
 * If @overlay_prop does not already exist in @target_node, add changeset entry
 * to add @overlay_prop in @target_node, else add changeset entry to update
 * value of @overlay_prop.
 *
 * Some special properties are not updated (no error returned).
 *
 * Update of property in symbols node is not allowed.
 *
 * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
 * invalid @overlay.
 */
static int add_changeset_property(struct overlay_changeset *ovcs,
		struct device_node *target_node,
		struct property *overlay_prop,
		bool is_symbols_prop)
{
	struct property *new_prop = NULL, *prop;
	int ret = 0;

	prop = of_find_property(target_node, overlay_prop->name, NULL);

	if (!of_prop_cmp(overlay_prop->name, "name") ||
	    !of_prop_cmp(overlay_prop->name, "phandle") ||
	    !of_prop_cmp(overlay_prop->name, "linux,phandle"))
		return 0;

	if (is_symbols_prop) {
		if (prop)
			return -EINVAL;
		new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
	} else {
		new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
	}

	if (!new_prop)
		return -ENOMEM;

	if (!prop)
		ret = of_changeset_add_property(&ovcs->cset, target_node,
						new_prop);
	else
		ret = of_changeset_update_property(&ovcs->cset, target_node,
						   new_prop);

	if (ret) {
		kfree(new_prop->name);
		kfree(new_prop->value);
		kfree(new_prop);
	}
	return ret;
}

/**
 * add_changeset_node() - add @node (and children) to overlay changeset
 * @ovcs:		overlay changeset
 * @target_node:	where to place @node in live tree
 * @node:		node from within overlay device tree fragment
 *
 * If @node does not already exist in @target_node, add changeset entry
 * to add @node in @target_node.
 *
 * If @node already exists in @target_node, and the existing node has
 * a phandle, the overlay node is not allowed to have a phandle.
 *
 * If @node has child nodes, add the children recursively via
 * build_changeset_next_level().
 *
 * NOTE: Multiple mods of created nodes not supported.
 *       If more than one fragment contains a node that does not already exist
 *       in the live tree, then for each fragment of_changeset_attach_node()
 *       will add a changeset entry to add the node.  When the changeset is
 *       applied, __of_attach_node() will attach the node twice (once for
 *       each fragment).  At this point the device tree will be corrupted.
 *
 *       TODO: add integrity check to ensure that multiple fragments do not
 *             create the same node.
 *
 * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
 * invalid @overlay.
 */
static int add_changeset_node(struct overlay_changeset *ovcs,
		struct device_node *target_node, struct device_node *node)
{
	const char *node_kbasename;
	struct device_node *tchild;
	int ret = 0;

	node_kbasename = kbasename(node->full_name);

	for_each_child_of_node(target_node, tchild)
		if (!of_node_cmp(node_kbasename, kbasename(tchild->full_name)))
			break;

	if (!tchild) {
		tchild = __of_node_dup(node, "%pOF/%s",
				       target_node, node_kbasename);
		if (!tchild)
			return -ENOMEM;

		tchild->parent = target_node;

		ret = of_changeset_attach_node(&ovcs->cset, tchild);
		if (ret)
			return ret;

		return build_changeset_next_level(ovcs, tchild, node);
	}

	if (node->phandle && tchild->phandle)
		ret = -EINVAL;
	else
		ret = build_changeset_next_level(ovcs, tchild, node);
	of_node_put(tchild);

	return ret;
}

/**
 * build_changeset_next_level() - add level of overlay changeset
 * @ovcs:		overlay changeset
 * @target_node:	where to place @overlay_node in live tree
 * @overlay_node:	node from within an overlay device tree fragment
 *
 * Add the properties (if any) and nodes (if any) from @overlay_node to the
 * @ovcs->cset changeset.  If an added node has child nodes, they will
 * be added recursively.
 *
 * Do not allow symbols node to have any children.
 *
 * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
 * invalid @overlay_node.
 */
static int build_changeset_next_level(struct overlay_changeset *ovcs,
		struct device_node *target_node,
		const struct device_node *overlay_node)
{
	struct device_node *child;
	struct property *prop;
	int ret;

	for_each_property_of_node(overlay_node, prop) {
		ret = add_changeset_property(ovcs, target_node, prop, 0);
		if (ret) {
			pr_debug("Failed to apply prop @%pOF/%s, err=%d\n",
				 target_node, prop->name, ret);
			return ret;
		}
	}

	for_each_child_of_node(overlay_node, child) {
		ret = add_changeset_node(ovcs, target_node, child);
		if (ret) {
			pr_debug("Failed to apply node @%pOF/%s, err=%d\n",
				 target_node, child->name, ret);
			of_node_put(child);
			return ret;
		}
	}

	return 0;
}

/*
 * Add the properties from __overlay__ node to the @ovcs->cset changeset.
 */
static int build_changeset_symbols_node(struct overlay_changeset *ovcs,
		struct device_node *target_node,
		const struct device_node *overlay_symbols_node)
{
	struct property *prop;
	int ret;

	for_each_property_of_node(overlay_symbols_node, prop) {
		ret = add_changeset_property(ovcs, target_node, prop, 1);
		if (ret) {
			pr_debug("Failed to apply prop @%pOF/%s, err=%d\n",
				 target_node, prop->name, ret);
			return ret;
		}
	}

	return 0;
}

/**
 * build_changeset() - populate overlay changeset in @ovcs from @ovcs->fragments
 * @ovcs:	Overlay changeset
 *
 * Create changeset @ovcs->cset to contain the nodes and properties of the
 * overlay device tree fragments in @ovcs->fragments[].  If an error occurs,
 * any portions of the changeset that were successfully created will remain
 * in @ovcs->cset.
 *
 * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
 * invalid overlay in @ovcs->fragments[].
 */
static int build_changeset(struct overlay_changeset *ovcs)
{
	struct fragment *fragment;
	int fragments_count, i, ret;

	/*
	 * if there is a symbols fragment in ovcs->fragments[i] it is
	 * the final element in the array
	 */
	if (ovcs->symbols_fragment)
		fragments_count = ovcs->count - 1;
	else
		fragments_count = ovcs->count;

	for (i = 0; i < fragments_count; i++) {
		fragment = &ovcs->fragments[i];

		ret = build_changeset_next_level(ovcs, fragment->target,
						 fragment->overlay);
		if (ret) {
			pr_debug("apply failed '%pOF'\n", fragment->target);
			return ret;
		}
	}

	if (ovcs->symbols_fragment) {
		fragment = &ovcs->fragments[ovcs->count - 1];
		ret = build_changeset_symbols_node(ovcs, fragment->target,
						   fragment->overlay);
		if (ret) {
			pr_debug("apply failed '%pOF'\n", fragment->target);
			return ret;
		}
	}

	return 0;
}

/*
 * Find the target node using a number of different strategies
 * in order of preference:
 *
 * 1) "target" property containing the phandle of the target
 * 2) "target-path" property containing the path of the target
 */
static struct device_node *find_target_node(struct device_node *info_node)
{
	const char *path;
	u32 val;
	int ret;

	ret = of_property_read_u32(info_node, "target", &val);
	if (!ret)
		return of_find_node_by_phandle(val);

	ret = of_property_read_string(info_node, "target-path", &path);
	if (!ret)
		return of_find_node_by_path(path);

	pr_err("Failed to find target for node %p (%s)\n",
		info_node, info_node->name);

	return NULL;
}

/**
 * init_overlay_changeset() - initialize overlay changeset from overlay tree
 * @ovcs	Overlay changeset to build
 * @tree:	Contains all the overlay fragments and overlay fixup nodes
 *
 * Initialize @ovcs.  Populate @ovcs->fragments with node information from
 * the top level of @tree.  The relevant top level nodes are the fragment
 * nodes and the __symbols__ node.  Any other top level node will be ignored.
 *
 * Returns 0 on success, -ENOMEM if memory allocation failure, -EINVAL if error
 * detected in @tree, or -ENOSPC if idr_alloc() error.
 */
static int init_overlay_changeset(struct overlay_changeset *ovcs,
		struct device_node *tree)
{
	struct device_node *node, *overlay_node;
	struct fragment *fragment;
	struct fragment *fragments;
	int cnt, id, ret;

	/*
	 * Warn for some issues.  Can not return -EINVAL for these until
	 * of_unittest_apply_overlay() is fixed to pass these checks.
	 */
	if (!of_node_check_flag(tree, OF_DYNAMIC))
		pr_debug("%s() tree is not dynamic\n", __func__);

	if (!of_node_check_flag(tree, OF_DETACHED))
		pr_debug("%s() tree is not detached\n", __func__);

	if (!of_node_is_root(tree))
		pr_debug("%s() tree is not root\n", __func__);

	ovcs->overlay_tree = tree;

	INIT_LIST_HEAD(&ovcs->ovcs_list);

	of_changeset_init(&ovcs->cset);

	id = idr_alloc(&ovcs_idr, ovcs, 1, 0, GFP_KERNEL);
	if (id <= 0)
		return id;

	cnt = 0;

	/* fragment nodes */
	for_each_child_of_node(tree, node) {
		overlay_node = of_get_child_by_name(node, "__overlay__");
		if (overlay_node) {
			cnt++;
			of_node_put(overlay_node);
		}
	}

	node = of_get_child_by_name(tree, "__symbols__");
	if (node) {
		cnt++;
		of_node_put(node);
	}

	fragments = kcalloc(cnt, sizeof(*fragments), GFP_KERNEL);
	if (!fragments) {
		ret = -ENOMEM;
		goto err_free_idr;
	}

	cnt = 0;
	for_each_child_of_node(tree, node) {
		overlay_node = of_get_child_by_name(node, "__overlay__");
		if (!overlay_node)
			continue;

		fragment = &fragments[cnt];
		fragment->overlay = overlay_node;
		fragment->target = find_target_node(node);
		if (!fragment->target) {
			of_node_put(fragment->overlay);
			ret = -EINVAL;
			goto err_free_fragments;
		}

		cnt++;
	}

	/*
	 * if there is a symbols fragment in ovcs->fragments[i] it is
	 * the final element in the array
	 */
	node = of_get_child_by_name(tree, "__symbols__");
	if (node) {
		ovcs->symbols_fragment = 1;
		fragment = &fragments[cnt];
		fragment->overlay = node;
		fragment->target = of_find_node_by_path("/__symbols__");

		if (!fragment->target) {
			pr_err("symbols in overlay, but not in live tree\n");
			ret = -EINVAL;
			goto err_free_fragments;
		}

		cnt++;
	}

	if (!cnt) {
		ret = -EINVAL;
		goto err_free_fragments;
	}

	ovcs->id = id;
	ovcs->count = cnt;
	ovcs->fragments = fragments;

	return 0;

err_free_fragments:
	kfree(fragments);
err_free_idr:
	idr_remove(&ovcs_idr, id);

	pr_err("%s() failed, ret = %d\n", __func__, ret);

	return ret;
}

static void free_overlay_changeset(struct overlay_changeset *ovcs)
{
	int i;

	if (ovcs->cset.entries.next)
		of_changeset_destroy(&ovcs->cset);

	if (ovcs->id)
		idr_remove(&ovcs_idr, ovcs->id);

	for (i = 0; i < ovcs->count; i++) {
		of_node_put(ovcs->fragments[i].target);
		of_node_put(ovcs->fragments[i].overlay);
	}
	kfree(ovcs->fragments);

	kfree(ovcs);
}

/**
 * of_overlay_apply() - Create and apply an overlay changeset
 * @tree:	Expanded overlay device tree
 * @ovcs_id:	Pointer to overlay changeset id
 *
 * Creates and applies an overlay changeset.
 *
 * If an error occurs in a pre-apply notifier, then no changes are made
 * to the device tree.
 *

 * A non-zero return value will not have created the changeset if error is from:
 *   - parameter checks
 *   - building the changeset
 *   - overlay changeset pre-apply notifier
 *
 * If an error is returned by an overlay changeset pre-apply notifier
 * then no further overlay changeset pre-apply notifier will be called.
 *
 * A non-zero return value will have created the changeset if error is from:
 *   - overlay changeset entry notifier
 *   - overlay changeset post-apply notifier
 *
 * If an error is returned by an overlay changeset post-apply notifier
 * then no further overlay changeset post-apply notifier will be called.
 *
 * If more than one notifier returns an error, then the last notifier
 * error to occur is returned.
 *
 * If an error occurred while applying the overlay changeset, then an
 * attempt is made to revert any changes that were made to the
 * device tree.  If there were any errors during the revert attempt
 * then the state of the device tree can not be determined, and any
 * following attempt to apply or remove an overlay changeset will be
 * refused.
 *
 * Returns 0 on success, or a negative error number.  Overlay changeset
 * id is returned to *ovcs_id.
 */

int of_overlay_apply(struct device_node *tree, int *ovcs_id)
{
	struct overlay_changeset *ovcs;
	int ret = 0, ret_revert, ret_tmp;

	*ovcs_id = 0;

	if (devicetree_corrupt()) {
		pr_err("devicetree state suspect, refuse to apply overlay\n");
		ret = -EBUSY;
		goto out;
	}

	ovcs = kzalloc(sizeof(*ovcs), GFP_KERNEL);
	if (!ovcs) {
		ret = -ENOMEM;
		goto out;
	}

	of_overlay_mutex_lock();
	mutex_lock(&of_mutex);

	ret = of_resolve_phandles(tree);
	if (ret)
		goto err_free_overlay_changeset;

	ret = init_overlay_changeset(ovcs, tree);
	if (ret)
		goto err_free_overlay_changeset;

	ret = overlay_notify(ovcs, OF_OVERLAY_PRE_APPLY);
	if (ret) {
		pr_err("overlay changeset pre-apply notify error %d\n", ret);
		goto err_free_overlay_changeset;
	}

	ret = build_changeset(ovcs);
	if (ret)
		goto err_free_overlay_changeset;

	ret_revert = 0;
	ret = __of_changeset_apply_entries(&ovcs->cset, &ret_revert);
	if (ret) {
		if (ret_revert) {
			pr_debug("overlay changeset revert error %d\n",
				 ret_revert);
			devicetree_state_flags |= DTSF_APPLY_FAIL;
		}
		goto err_free_overlay_changeset;
	}

	ret = __of_changeset_apply_notify(&ovcs->cset);
	if (ret)
		pr_err("overlay changeset entry notify error %d\n", ret);
	/* notify failure is not fatal, continue */

	list_add_tail(&ovcs->ovcs_list, &ovcs_list);
	*ovcs_id = ovcs->id;

	ret_tmp = overlay_notify(ovcs, OF_OVERLAY_POST_APPLY);
	if (ret_tmp) {
		pr_err("overlay changeset post-apply notify error %d\n",
		       ret_tmp);
		if (!ret)
			ret = ret_tmp;
	}

	goto out_unlock;

err_free_overlay_changeset:
	free_overlay_changeset(ovcs);

out_unlock:
	mutex_unlock(&of_mutex);
	of_overlay_mutex_unlock();

out:
	pr_debug("%s() err=%d\n", __func__, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(of_overlay_apply);

/*
 * Find @np in @tree.
 *
 * Returns 1 if @np is @tree or is contained in @tree, else 0
 */
static int find_node(struct device_node *tree, struct device_node *np)
{
	struct device_node *child;

	if (tree == np)
		return 1;

	for_each_child_of_node(tree, child) {
		if (find_node(child, np)) {
			of_node_put(child);
			return 1;
		}
	}

	return 0;
}

/*
 * Is @remove_ce_node a child of, a parent of, or the same as any
 * node in an overlay changeset more topmost than @remove_ovcs?
 *
 * Returns 1 if found, else 0
 */
static int node_overlaps_later_cs(struct overlay_changeset *remove_ovcs,
		struct device_node *remove_ce_node)
{
	struct overlay_changeset *ovcs;
	struct of_changeset_entry *ce;

	list_for_each_entry_reverse(ovcs, &ovcs_list, ovcs_list) {
		if (ovcs == remove_ovcs)
			break;

		list_for_each_entry(ce, &ovcs->cset.entries, node) {
			if (find_node(ce->np, remove_ce_node)) {
				pr_err("%s: #%d overlaps with #%d @%pOF\n",
					__func__, remove_ovcs->id, ovcs->id,
					remove_ce_node);
				return 1;
			}
			if (find_node(remove_ce_node, ce->np)) {
				pr_err("%s: #%d overlaps with #%d @%pOF\n",
					__func__, remove_ovcs->id, ovcs->id,
					remove_ce_node);
				return 1;
			}
		}
	}

	return 0;
}

/*
 * We can safely remove the overlay only if it's the top-most one.
 * Newly applied overlays are inserted at the tail of the overlay list,
 * so a top most overlay is the one that is closest to the tail.
 *
 * The topmost check is done by exploiting this property. For each
 * affected device node in the log list we check if this overlay is
 * the one closest to the tail. If another overlay has affected this
 * device node and is closest to the tail, then removal is not permited.
 */
static int overlay_removal_is_ok(struct overlay_changeset *remove_ovcs)
{
	struct of_changeset_entry *remove_ce;

	list_for_each_entry(remove_ce, &remove_ovcs->cset.entries, node) {
		if (node_overlaps_later_cs(remove_ovcs, remove_ce->np)) {
			pr_err("overlay #%d is not topmost\n", remove_ovcs->id);
			return 0;
		}
	}

	return 1;
}

/**
 * of_overlay_remove() - Revert and free an overlay changeset
 * @ovcs_id:	Pointer to overlay changeset id
 *
 * Removes an overlay if it is permissible.  @ovcs_id was previously returned
 * by of_overlay_apply().
 *
 * If an error occurred while attempting to revert the overlay changeset,
 * then an attempt is made to re-apply any changeset entry that was
 * reverted.  If an error occurs on re-apply then the state of the device
 * tree can not be determined, and any following attempt to apply or remove
 * an overlay changeset will be refused.
 *
 * A non-zero return value will not revert the changeset if error is from:
 *   - parameter checks
 *   - overlay changeset pre-remove notifier
 *   - overlay changeset entry revert
 *
 * If an error is returned by an overlay changeset pre-remove notifier
 * then no further overlay changeset pre-remove notifier will be called.
 *
 * If more than one notifier returns an error, then the last notifier
 * error to occur is returned.
 *
 * A non-zero return value will revert the changeset if error is from:
 *   - overlay changeset entry notifier
 *   - overlay changeset post-remove notifier
 *
 * If an error is returned by an overlay changeset post-remove notifier
 * then no further overlay changeset post-remove notifier will be called.
 *
 * Returns 0 on success, or a negative error number.  *ovcs_id is set to
 * zero after reverting the changeset, even if a subsequent error occurs.
 */
int of_overlay_remove(int *ovcs_id)
{
	struct overlay_changeset *ovcs;
	int ret, ret_apply, ret_tmp;

	ret = 0;

	if (devicetree_corrupt()) {
		pr_err("suspect devicetree state, refuse to remove overlay\n");
		ret = -EBUSY;
		goto out;
	}

	mutex_lock(&of_mutex);

	ovcs = idr_find(&ovcs_idr, *ovcs_id);
	if (!ovcs) {
		ret = -ENODEV;
		pr_err("remove: Could not find overlay #%d\n", *ovcs_id);
		goto out_unlock;
	}

	if (!overlay_removal_is_ok(ovcs)) {
		ret = -EBUSY;
		goto out_unlock;
	}

	ret = overlay_notify(ovcs, OF_OVERLAY_PRE_REMOVE);
	if (ret) {
		pr_err("overlay changeset pre-remove notify error %d\n", ret);
		goto out_unlock;
	}

	list_del(&ovcs->ovcs_list);

	ret_apply = 0;
	ret = __of_changeset_revert_entries(&ovcs->cset, &ret_apply);
	if (ret) {
		if (ret_apply)
			devicetree_state_flags |= DTSF_REVERT_FAIL;
		goto out_unlock;
	}

	ret = __of_changeset_revert_notify(&ovcs->cset);
	if (ret)
		pr_err("overlay changeset entry notify error %d\n", ret);
	/* notify failure is not fatal, continue */

	*ovcs_id = 0;

	ret_tmp = overlay_notify(ovcs, OF_OVERLAY_POST_REMOVE);
	if (ret_tmp) {
		pr_err("overlay changeset post-remove notify error %d\n",
		       ret_tmp);
		if (!ret)
			ret = ret_tmp;
	}

	free_overlay_changeset(ovcs);

out_unlock:
	mutex_unlock(&of_mutex);

out:
	pr_debug("%s() err=%d\n", __func__, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(of_overlay_remove);

/**
 * of_overlay_remove_all() - Reverts and frees all overlay changesets
 *
 * Removes all overlays from the system in the correct order.
 *
 * Returns 0 on success, or a negative error number
 */
int of_overlay_remove_all(void)
{
	struct overlay_changeset *ovcs, *ovcs_n;
	int ret;

	/* the tail of list is guaranteed to be safe to remove */
	list_for_each_entry_safe_reverse(ovcs, ovcs_n, &ovcs_list, ovcs_list) {
		ret = of_overlay_remove(&ovcs->id);
		if (ret)
			return ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(of_overlay_remove_all);