xref: /openbmc/linux/drivers/of/overlay.c (revision ae3473231e77a3f1909d48cd144cebe5e1d049b3)
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  */
36 struct 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  */
50 struct 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 
58 static int of_overlay_apply_one(struct of_overlay *ov,
59 		struct device_node *target, const struct device_node *overlay);
60 
61 static BLOCKING_NOTIFIER_HEAD(of_overlay_chain);
62 
63 int of_overlay_notifier_register(struct notifier_block *nb)
64 {
65 	return blocking_notifier_chain_register(&of_overlay_chain, nb);
66 }
67 EXPORT_SYMBOL_GPL(of_overlay_notifier_register);
68 
69 int of_overlay_notifier_unregister(struct notifier_block *nb)
70 {
71 	return blocking_notifier_chain_unregister(&of_overlay_chain, nb);
72 }
73 EXPORT_SYMBOL_GPL(of_overlay_notifier_unregister);
74 
75 static 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 
96 static 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 
122 static 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  */
167 static 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  */
205 static 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  */
230 static 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  */
266 static 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 
279 err_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  */
299 static 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  */
344 static 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 
361 static LIST_HEAD(ov_list);
362 static 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  */
374 int 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 
433 err_revert_overlay:
434 err_abort_trans:
435 	of_free_overlay_info(ov);
436 err_free_idr:
437 	idr_remove(&ov_idr, ov->id);
438 err_destroy_trans:
439 	of_changeset_destroy(&ov->cset);
440 	kfree(ov);
441 	mutex_unlock(&of_mutex);
442 
443 	return err;
444 }
445 EXPORT_SYMBOL_GPL(of_overlay_create);
446 
447 /* check whether the given node, lies under the given tree */
448 static 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 */
468 static 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  */
503 static 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  */
525 int 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 
556 out:
557 	mutex_unlock(&of_mutex);
558 
559 	return err;
560 }
561 EXPORT_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  */
570 int 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 }
589 EXPORT_SYMBOL_GPL(of_overlay_destroy_all);
590