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1/*
2 * Functions for working with device tree overlays
3 *
4 * Copyright (C) 2012 Pantelis Antoniou <panto@antoniou-consulting.com>
5 * Copyright (C) 2012 Texas Instruments Inc.
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * version 2 as published by the Free Software Foundation.
10 */
11
12#define pr_fmt(fmt) "OF: overlay: " fmt
13
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/of.h>
17#include <linux/of_device.h>
18#include <linux/string.h>
19#include <linux/ctype.h>
20#include <linux/errno.h>
21#include <linux/string.h>
22#include <linux/slab.h>
23#include <linux/err.h>
24#include <linux/idr.h>
25
26#include "of_private.h"
27
28/**
29 * struct of_overlay_info - Holds a single overlay info
30 * @target: target of the overlay operation
31 * @overlay: pointer to the overlay contents node
32 *
33 * Holds a single overlay state, including all the overlay logs &
34 * records.
35 */
36struct of_overlay_info {
37 struct device_node *target;
38 struct device_node *overlay;
39};
40
41/**
42 * struct of_overlay - Holds a complete overlay transaction
43 * @node: List on which we are located
44 * @count: Count of ovinfo structures
45 * @ovinfo_tab: Overlay info table (count sized)
46 * @cset: Changeset to be used
47 *
48 * Holds a complete overlay transaction
49 */
50struct of_overlay {
51 int id;
52 struct list_head node;
53 int count;
54 struct of_overlay_info *ovinfo_tab;
55 struct of_changeset cset;
56};
57
58static int of_overlay_apply_one(struct of_overlay *ov,
59 struct device_node *target, const struct device_node *overlay);
60
61static BLOCKING_NOTIFIER_HEAD(of_overlay_chain);
62
63int of_overlay_notifier_register(struct notifier_block *nb)
64{
65 return blocking_notifier_chain_register(&of_overlay_chain, nb);
66}
67EXPORT_SYMBOL_GPL(of_overlay_notifier_register);
68
69int of_overlay_notifier_unregister(struct notifier_block *nb)
70{
71 return blocking_notifier_chain_unregister(&of_overlay_chain, nb);
72}
73EXPORT_SYMBOL_GPL(of_overlay_notifier_unregister);
74
75static int of_overlay_notify(struct of_overlay *ov,
76 enum of_overlay_notify_action action)
77{
78 struct of_overlay_notify_data nd;
79 int i, ret;
80
81 for (i = 0; i < ov->count; i++) {
82 struct of_overlay_info *ovinfo = &ov->ovinfo_tab[i];
83
84 nd.target = ovinfo->target;
85 nd.overlay = ovinfo->overlay;
86
87 ret = blocking_notifier_call_chain(&of_overlay_chain,
88 action, &nd);
89 if (ret)
90 return notifier_to_errno(ret);
91 }
92
93 return 0;
94}
95
96static int of_overlay_apply_single_property(struct of_overlay *ov,
97 struct device_node *target, struct property *prop)
98{
99 struct property *propn, *tprop;
100
101 /* NOTE: Multiple changes of single properties not supported */
102 tprop = of_find_property(target, prop->name, NULL);
103
104 /* special properties are not meant to be updated (silent NOP) */
105 if (of_prop_cmp(prop->name, "name") == 0 ||
106 of_prop_cmp(prop->name, "phandle") == 0 ||
107 of_prop_cmp(prop->name, "linux,phandle") == 0)
108 return 0;
109
110 propn = __of_prop_dup(prop, GFP_KERNEL);
111 if (propn == NULL)
112 return -ENOMEM;
113
114 /* not found? add */
115 if (tprop == NULL)
116 return of_changeset_add_property(&ov->cset, target, propn);
117
118 /* found? update */
119 return of_changeset_update_property(&ov->cset, target, propn);
120}
121
122static int of_overlay_apply_single_device_node(struct of_overlay *ov,
123 struct device_node *target, struct device_node *child)
124{
125 const char *cname;
126 struct device_node *tchild;
127 int ret = 0;
128
129 cname = kbasename(child->full_name);
130 if (cname == NULL)
131 return -ENOMEM;
132
133 /* NOTE: Multiple mods of created nodes not supported */
134 tchild = of_get_child_by_name(target, cname);
135 if (tchild != NULL) {
136 /* apply overlay recursively */
137 ret = of_overlay_apply_one(ov, tchild, child);
138 of_node_put(tchild);
139 } else {
140 /* create empty tree as a target */
141 tchild = __of_node_dup(child, "%s/%s", target->full_name, cname);
142 if (!tchild)
143 return -ENOMEM;
144
145 /* point to parent */
146 tchild->parent = target;
147
148 ret = of_changeset_attach_node(&ov->cset, tchild);
149 if (ret)
150 return ret;
151
152 ret = of_overlay_apply_one(ov, tchild, child);
153 if (ret)
154 return ret;
155 }
156
157 return ret;
158}
159
160/*
161 * Apply a single overlay node recursively.
162 *
163 * Note that the in case of an error the target node is left
164 * in a inconsistent state. Error recovery should be performed
165 * by using the changeset.
166 */
167static int of_overlay_apply_one(struct of_overlay *ov,
168 struct device_node *target, const struct device_node *overlay)
169{
170 struct device_node *child;
171 struct property *prop;
172 int ret;
173
174 for_each_property_of_node(overlay, prop) {
175 ret = of_overlay_apply_single_property(ov, target, prop);
176 if (ret) {
177 pr_err("Failed to apply prop @%s/%s\n",
178 target->full_name, prop->name);
179 return ret;
180 }
181 }
182
183 for_each_child_of_node(overlay, child) {
184 ret = of_overlay_apply_single_device_node(ov, target, child);
185 if (ret != 0) {
186 pr_err("Failed to apply single node @%s/%s\n",
187 target->full_name, child->name);
188 of_node_put(child);
189 return ret;
190 }
191 }
192
193 return 0;
194}
195
196/**
197 * of_overlay_apply() - Apply @count overlays pointed at by @ovinfo_tab
198 * @ov: Overlay to apply
199 *
200 * Applies the overlays given, while handling all error conditions
201 * appropriately. Either the operation succeeds, or if it fails the
202 * live tree is reverted to the state before the attempt.
203 * Returns 0, or an error if the overlay attempt failed.
204 */
205static int of_overlay_apply(struct of_overlay *ov)
206{
207 int i, err;
208
209 /* first we apply the overlays atomically */
210 for (i = 0; i < ov->count; i++) {
211 struct of_overlay_info *ovinfo = &ov->ovinfo_tab[i];
212
213 err = of_overlay_apply_one(ov, ovinfo->target, ovinfo->overlay);
214 if (err != 0) {
215 pr_err("apply failed '%s'\n", ovinfo->target->full_name);
216 return err;
217 }
218 }
219
220 return 0;
221}
222
223/*
224 * Find the target node using a number of different strategies
225 * in order of preference
226 *
227 * "target" property containing the phandle of the target
228 * "target-path" property containing the path of the target
229 */
230static struct device_node *find_target_node(struct device_node *info_node)
231{
232 const char *path;
233 u32 val;
234 int ret;
235
236 /* first try to go by using the target as a phandle */
237 ret = of_property_read_u32(info_node, "target", &val);
238 if (ret == 0)
239 return of_find_node_by_phandle(val);
240
241 /* now try to locate by path */
242 ret = of_property_read_string(info_node, "target-path", &path);
243 if (ret == 0)
244 return of_find_node_by_path(path);
245
246 pr_err("Failed to find target for node %p (%s)\n",
247 info_node, info_node->name);
248
249 return NULL;
250}
251
252/**
253 * of_fill_overlay_info() - Fill an overlay info structure
254 * @ov Overlay to fill
255 * @info_node: Device node containing the overlay
256 * @ovinfo: Pointer to the overlay info structure to fill
257 *
258 * Fills an overlay info structure with the overlay information
259 * from a device node. This device node must have a target property
260 * which contains a phandle of the overlay target node, and an
261 * __overlay__ child node which has the overlay contents.
262 * Both ovinfo->target & ovinfo->overlay have their references taken.
263 *
264 * Returns 0 on success, or a negative error value.
265 */
266static int of_fill_overlay_info(struct of_overlay *ov,
267 struct device_node *info_node, struct of_overlay_info *ovinfo)
268{
269 ovinfo->overlay = of_get_child_by_name(info_node, "__overlay__");
270 if (ovinfo->overlay == NULL)
271 goto err_fail;
272
273 ovinfo->target = find_target_node(info_node);
274 if (ovinfo->target == NULL)
275 goto err_fail;
276
277 return 0;
278
279err_fail:
280 of_node_put(ovinfo->target);
281 of_node_put(ovinfo->overlay);
282
283 memset(ovinfo, 0, sizeof(*ovinfo));
284 return -EINVAL;
285}
286
287/**
288 * of_build_overlay_info() - Build an overlay info array
289 * @ov Overlay to build
290 * @tree: Device node containing all the overlays
291 *
292 * Helper function that given a tree containing overlay information,
293 * allocates and builds an overlay info array containing it, ready
294 * for use using of_overlay_apply.
295 *
296 * Returns 0 on success with the @cntp @ovinfop pointers valid,
297 * while on error a negative error value is returned.
298 */
299static int of_build_overlay_info(struct of_overlay *ov,
300 struct device_node *tree)
301{
302 struct device_node *node;
303 struct of_overlay_info *ovinfo;
304 int cnt, err;
305
306 /* worst case; every child is a node */
307 cnt = 0;
308 for_each_child_of_node(tree, node)
309 cnt++;
310
311 ovinfo = kcalloc(cnt, sizeof(*ovinfo), GFP_KERNEL);
312 if (ovinfo == NULL)
313 return -ENOMEM;
314
315 cnt = 0;
316 for_each_child_of_node(tree, node) {
317 memset(&ovinfo[cnt], 0, sizeof(*ovinfo));
318 err = of_fill_overlay_info(ov, node, &ovinfo[cnt]);
319 if (err == 0)
320 cnt++;
321 }
322
323 /* if nothing filled, return error */
324 if (cnt == 0) {
325 kfree(ovinfo);
326 return -ENODEV;
327 }
328
329 ov->count = cnt;
330 ov->ovinfo_tab = ovinfo;
331
332 return 0;
333}
334
335/**
336 * of_free_overlay_info() - Free an overlay info array
337 * @ov Overlay to free the overlay info from
338 * @ovinfo_tab: Array of overlay_info's to free
339 *
340 * Releases the memory of a previously allocated ovinfo array
341 * by of_build_overlay_info.
342 * Returns 0, or an error if the arguments are bogus.
343 */
344static int of_free_overlay_info(struct of_overlay *ov)
345{
346 struct of_overlay_info *ovinfo;
347 int i;
348
349 /* do it in reverse */
350 for (i = ov->count - 1; i >= 0; i--) {
351 ovinfo = &ov->ovinfo_tab[i];
352
353 of_node_put(ovinfo->target);
354 of_node_put(ovinfo->overlay);
355 }
356 kfree(ov->ovinfo_tab);
357
358 return 0;
359}
360
361static LIST_HEAD(ov_list);
362static DEFINE_IDR(ov_idr);
363
364/**
365 * of_overlay_create() - Create and apply an overlay
366 * @tree: Device node containing all the overlays
367 *
368 * Creates and applies an overlay while also keeping track
369 * of the overlay in a list. This list can be used to prevent
370 * illegal overlay removals.
371 *
372 * Returns the id of the created overlay, or a negative error number
373 */
374int of_overlay_create(struct device_node *tree)
375{
376 struct of_overlay *ov;
377 int err, id;
378
379 /* allocate the overlay structure */
380 ov = kzalloc(sizeof(*ov), GFP_KERNEL);
381 if (ov == NULL)
382 return -ENOMEM;
383 ov->id = -1;
384
385 INIT_LIST_HEAD(&ov->node);
386
387 of_changeset_init(&ov->cset);
388
389 mutex_lock(&of_mutex);
390
391 id = idr_alloc(&ov_idr, ov, 0, 0, GFP_KERNEL);
392 if (id < 0) {
393 err = id;
394 goto err_destroy_trans;
395 }
396 ov->id = id;
397
398 /* build the overlay info structures */
399 err = of_build_overlay_info(ov, tree);
400 if (err) {
401 pr_err("of_build_overlay_info() failed for tree@%s\n",
402 tree->full_name);
403 goto err_free_idr;
404 }
405
406 err = of_overlay_notify(ov, OF_OVERLAY_PRE_APPLY);
407 if (err < 0) {
408 pr_err("%s: Pre-apply notifier failed (err=%d)\n",
409 __func__, err);
410 goto err_free_idr;
411 }
412
413 /* apply the overlay */
414 err = of_overlay_apply(ov);
415 if (err)
416 goto err_abort_trans;
417
418 /* apply the changeset */
419 err = __of_changeset_apply(&ov->cset);
420 if (err)
421 goto err_revert_overlay;
422
423
424 /* add to the tail of the overlay list */
425 list_add_tail(&ov->node, &ov_list);
426
427 of_overlay_notify(ov, OF_OVERLAY_POST_APPLY);
428
429 mutex_unlock(&of_mutex);
430
431 return id;
432
433err_revert_overlay:
434err_abort_trans:
435 of_free_overlay_info(ov);
436err_free_idr:
437 idr_remove(&ov_idr, ov->id);
438err_destroy_trans:
439 of_changeset_destroy(&ov->cset);
440 kfree(ov);
441 mutex_unlock(&of_mutex);
442
443 return err;
444}
445EXPORT_SYMBOL_GPL(of_overlay_create);
446
447/* check whether the given node, lies under the given tree */
448static int overlay_subtree_check(struct device_node *tree,
449 struct device_node *dn)
450{
451 struct device_node *child;
452
453 /* match? */
454 if (tree == dn)
455 return 1;
456
457 for_each_child_of_node(tree, child) {
458 if (overlay_subtree_check(child, dn)) {
459 of_node_put(child);
460 return 1;
461 }
462 }
463
464 return 0;
465}
466
467/* check whether this overlay is the topmost */
468static int overlay_is_topmost(struct of_overlay *ov, struct device_node *dn)
469{
470 struct of_overlay *ovt;
471 struct of_changeset_entry *ce;
472
473 list_for_each_entry_reverse(ovt, &ov_list, node) {
474 /* if we hit ourselves, we're done */
475 if (ovt == ov)
476 break;
477
478 /* check against each subtree affected by this overlay */
479 list_for_each_entry(ce, &ovt->cset.entries, node) {
480 if (overlay_subtree_check(ce->np, dn)) {
481 pr_err("%s: #%d clashes #%d @%s\n",
482 __func__, ov->id, ovt->id,
483 dn->full_name);
484 return 0;
485 }
486 }
487 }
488
489 /* overlay is topmost */
490 return 1;
491}
492
493/*
494 * We can safely remove the overlay only if it's the top-most one.
495 * Newly applied overlays are inserted at the tail of the overlay list,
496 * so a top most overlay is the one that is closest to the tail.
497 *
498 * The topmost check is done by exploiting this property. For each
499 * affected device node in the log list we check if this overlay is
500 * the one closest to the tail. If another overlay has affected this
501 * device node and is closest to the tail, then removal is not permited.
502 */
503static int overlay_removal_is_ok(struct of_overlay *ov)
504{
505 struct of_changeset_entry *ce;
506
507 list_for_each_entry(ce, &ov->cset.entries, node) {
508 if (!overlay_is_topmost(ov, ce->np)) {
509 pr_err("overlay #%d is not topmost\n", ov->id);
510 return 0;
511 }
512 }
513
514 return 1;
515}
516
517/**
518 * of_overlay_destroy() - Removes an overlay
519 * @id: Overlay id number returned by a previous call to of_overlay_create
520 *
521 * Removes an overlay if it is permissible.
522 *
523 * Returns 0 on success, or a negative error number
524 */
525int of_overlay_destroy(int id)
526{
527 struct of_overlay *ov;
528 int err;
529
530 mutex_lock(&of_mutex);
531
532 ov = idr_find(&ov_idr, id);
533 if (ov == NULL) {
534 err = -ENODEV;
535 pr_err("destroy: Could not find overlay #%d\n", id);
536 goto out;
537 }
538
539 /* check whether the overlay is safe to remove */
540 if (!overlay_removal_is_ok(ov)) {
541 err = -EBUSY;
542 goto out;
543 }
544
545 of_overlay_notify(ov, OF_OVERLAY_PRE_REMOVE);
546 list_del(&ov->node);
547 __of_changeset_revert(&ov->cset);
548 of_overlay_notify(ov, OF_OVERLAY_POST_REMOVE);
549 of_free_overlay_info(ov);
550 idr_remove(&ov_idr, id);
551 of_changeset_destroy(&ov->cset);
552 kfree(ov);
553
554 err = 0;
555
556out:
557 mutex_unlock(&of_mutex);
558
559 return err;
560}
561EXPORT_SYMBOL_GPL(of_overlay_destroy);
562
563/**
564 * of_overlay_destroy_all() - Removes all overlays from the system
565 *
566 * Removes all overlays from the system in the correct order.
567 *
568 * Returns 0 on success, or a negative error number
569 */
570int of_overlay_destroy_all(void)
571{
572 struct of_overlay *ov, *ovn;
573
574 mutex_lock(&of_mutex);
575
576 /* the tail of list is guaranteed to be safe to remove */
577 list_for_each_entry_safe_reverse(ov, ovn, &ov_list, node) {
578 list_del(&ov->node);
579 __of_changeset_revert(&ov->cset);
580 of_free_overlay_info(ov);
581 idr_remove(&ov_idr, ov->id);
582 kfree(ov);
583 }
584
585 mutex_unlock(&of_mutex);
586
587 return 0;
588}
589EXPORT_SYMBOL_GPL(of_overlay_destroy_all);