xref: /linux/drivers/of/base.c (revision 765532c8aaac624b5f8687af6d319c6a1138a257)
1 /*
2  * Procedures for creating, accessing and interpreting the device tree.
3  *
4  * Paul Mackerras	August 1996.
5  * Copyright (C) 1996-2005 Paul Mackerras.
6  *
7  *  Adapted for 64bit PowerPC by Dave Engebretsen and Peter Bergner.
8  *    {engebret|bergner}@us.ibm.com
9  *
10  *  Adapted for sparc and sparc64 by David S. Miller davem@davemloft.net
11  *
12  *  Reconsolidated from arch/x/kernel/prom.c by Stephen Rothwell and
13  *  Grant Likely.
14  *
15  *      This program is free software; you can redistribute it and/or
16  *      modify it under the terms of the GNU General Public License
17  *      as published by the Free Software Foundation; either version
18  *      2 of the License, or (at your option) any later version.
19  */
20 #include <linux/module.h>
21 #include <linux/of.h>
22 #include <linux/spinlock.h>
23 #include <linux/slab.h>
24 #include <linux/proc_fs.h>
25 
26 struct device_node *allnodes;
27 struct device_node *of_chosen;
28 
29 /* use when traversing tree through the allnext, child, sibling,
30  * or parent members of struct device_node.
31  */
32 DEFINE_RWLOCK(devtree_lock);
33 
34 int of_n_addr_cells(struct device_node *np)
35 {
36 	const __be32 *ip;
37 
38 	do {
39 		if (np->parent)
40 			np = np->parent;
41 		ip = of_get_property(np, "#address-cells", NULL);
42 		if (ip)
43 			return be32_to_cpup(ip);
44 	} while (np->parent);
45 	/* No #address-cells property for the root node */
46 	return OF_ROOT_NODE_ADDR_CELLS_DEFAULT;
47 }
48 EXPORT_SYMBOL(of_n_addr_cells);
49 
50 int of_n_size_cells(struct device_node *np)
51 {
52 	const __be32 *ip;
53 
54 	do {
55 		if (np->parent)
56 			np = np->parent;
57 		ip = of_get_property(np, "#size-cells", NULL);
58 		if (ip)
59 			return be32_to_cpup(ip);
60 	} while (np->parent);
61 	/* No #size-cells property for the root node */
62 	return OF_ROOT_NODE_SIZE_CELLS_DEFAULT;
63 }
64 EXPORT_SYMBOL(of_n_size_cells);
65 
66 #if !defined(CONFIG_SPARC)   /* SPARC doesn't do ref counting (yet) */
67 /**
68  *	of_node_get - Increment refcount of a node
69  *	@node:	Node to inc refcount, NULL is supported to
70  *		simplify writing of callers
71  *
72  *	Returns node.
73  */
74 struct device_node *of_node_get(struct device_node *node)
75 {
76 	if (node)
77 		kref_get(&node->kref);
78 	return node;
79 }
80 EXPORT_SYMBOL(of_node_get);
81 
82 static inline struct device_node *kref_to_device_node(struct kref *kref)
83 {
84 	return container_of(kref, struct device_node, kref);
85 }
86 
87 /**
88  *	of_node_release - release a dynamically allocated node
89  *	@kref:  kref element of the node to be released
90  *
91  *	In of_node_put() this function is passed to kref_put()
92  *	as the destructor.
93  */
94 static void of_node_release(struct kref *kref)
95 {
96 	struct device_node *node = kref_to_device_node(kref);
97 	struct property *prop = node->properties;
98 
99 	/* We should never be releasing nodes that haven't been detached. */
100 	if (!of_node_check_flag(node, OF_DETACHED)) {
101 		pr_err("ERROR: Bad of_node_put() on %s\n", node->full_name);
102 		dump_stack();
103 		kref_init(&node->kref);
104 		return;
105 	}
106 
107 	if (!of_node_check_flag(node, OF_DYNAMIC))
108 		return;
109 
110 	while (prop) {
111 		struct property *next = prop->next;
112 		kfree(prop->name);
113 		kfree(prop->value);
114 		kfree(prop);
115 		prop = next;
116 
117 		if (!prop) {
118 			prop = node->deadprops;
119 			node->deadprops = NULL;
120 		}
121 	}
122 	kfree(node->full_name);
123 	kfree(node->data);
124 	kfree(node);
125 }
126 
127 /**
128  *	of_node_put - Decrement refcount of a node
129  *	@node:	Node to dec refcount, NULL is supported to
130  *		simplify writing of callers
131  *
132  */
133 void of_node_put(struct device_node *node)
134 {
135 	if (node)
136 		kref_put(&node->kref, of_node_release);
137 }
138 EXPORT_SYMBOL(of_node_put);
139 #endif /* !CONFIG_SPARC */
140 
141 struct property *of_find_property(const struct device_node *np,
142 				  const char *name,
143 				  int *lenp)
144 {
145 	struct property *pp;
146 
147 	if (!np)
148 		return NULL;
149 
150 	read_lock(&devtree_lock);
151 	for (pp = np->properties; pp != 0; pp = pp->next) {
152 		if (of_prop_cmp(pp->name, name) == 0) {
153 			if (lenp != 0)
154 				*lenp = pp->length;
155 			break;
156 		}
157 	}
158 	read_unlock(&devtree_lock);
159 
160 	return pp;
161 }
162 EXPORT_SYMBOL(of_find_property);
163 
164 /**
165  * of_find_all_nodes - Get next node in global list
166  * @prev:	Previous node or NULL to start iteration
167  *		of_node_put() will be called on it
168  *
169  * Returns a node pointer with refcount incremented, use
170  * of_node_put() on it when done.
171  */
172 struct device_node *of_find_all_nodes(struct device_node *prev)
173 {
174 	struct device_node *np;
175 
176 	read_lock(&devtree_lock);
177 	np = prev ? prev->allnext : allnodes;
178 	for (; np != NULL; np = np->allnext)
179 		if (of_node_get(np))
180 			break;
181 	of_node_put(prev);
182 	read_unlock(&devtree_lock);
183 	return np;
184 }
185 EXPORT_SYMBOL(of_find_all_nodes);
186 
187 /*
188  * Find a property with a given name for a given node
189  * and return the value.
190  */
191 const void *of_get_property(const struct device_node *np, const char *name,
192 			 int *lenp)
193 {
194 	struct property *pp = of_find_property(np, name, lenp);
195 
196 	return pp ? pp->value : NULL;
197 }
198 EXPORT_SYMBOL(of_get_property);
199 
200 /** Checks if the given "compat" string matches one of the strings in
201  * the device's "compatible" property
202  */
203 int of_device_is_compatible(const struct device_node *device,
204 		const char *compat)
205 {
206 	const char* cp;
207 	int cplen, l;
208 
209 	cp = of_get_property(device, "compatible", &cplen);
210 	if (cp == NULL)
211 		return 0;
212 	while (cplen > 0) {
213 		if (of_compat_cmp(cp, compat, strlen(compat)) == 0)
214 			return 1;
215 		l = strlen(cp) + 1;
216 		cp += l;
217 		cplen -= l;
218 	}
219 
220 	return 0;
221 }
222 EXPORT_SYMBOL(of_device_is_compatible);
223 
224 /**
225  * of_machine_is_compatible - Test root of device tree for a given compatible value
226  * @compat: compatible string to look for in root node's compatible property.
227  *
228  * Returns true if the root node has the given value in its
229  * compatible property.
230  */
231 int of_machine_is_compatible(const char *compat)
232 {
233 	struct device_node *root;
234 	int rc = 0;
235 
236 	root = of_find_node_by_path("/");
237 	if (root) {
238 		rc = of_device_is_compatible(root, compat);
239 		of_node_put(root);
240 	}
241 	return rc;
242 }
243 EXPORT_SYMBOL(of_machine_is_compatible);
244 
245 /**
246  *  of_device_is_available - check if a device is available for use
247  *
248  *  @device: Node to check for availability
249  *
250  *  Returns 1 if the status property is absent or set to "okay" or "ok",
251  *  0 otherwise
252  */
253 int of_device_is_available(const struct device_node *device)
254 {
255 	const char *status;
256 	int statlen;
257 
258 	status = of_get_property(device, "status", &statlen);
259 	if (status == NULL)
260 		return 1;
261 
262 	if (statlen > 0) {
263 		if (!strcmp(status, "okay") || !strcmp(status, "ok"))
264 			return 1;
265 	}
266 
267 	return 0;
268 }
269 EXPORT_SYMBOL(of_device_is_available);
270 
271 /**
272  *	of_get_parent - Get a node's parent if any
273  *	@node:	Node to get parent
274  *
275  *	Returns a node pointer with refcount incremented, use
276  *	of_node_put() on it when done.
277  */
278 struct device_node *of_get_parent(const struct device_node *node)
279 {
280 	struct device_node *np;
281 
282 	if (!node)
283 		return NULL;
284 
285 	read_lock(&devtree_lock);
286 	np = of_node_get(node->parent);
287 	read_unlock(&devtree_lock);
288 	return np;
289 }
290 EXPORT_SYMBOL(of_get_parent);
291 
292 /**
293  *	of_get_next_parent - Iterate to a node's parent
294  *	@node:	Node to get parent of
295  *
296  * 	This is like of_get_parent() except that it drops the
297  * 	refcount on the passed node, making it suitable for iterating
298  * 	through a node's parents.
299  *
300  *	Returns a node pointer with refcount incremented, use
301  *	of_node_put() on it when done.
302  */
303 struct device_node *of_get_next_parent(struct device_node *node)
304 {
305 	struct device_node *parent;
306 
307 	if (!node)
308 		return NULL;
309 
310 	read_lock(&devtree_lock);
311 	parent = of_node_get(node->parent);
312 	of_node_put(node);
313 	read_unlock(&devtree_lock);
314 	return parent;
315 }
316 
317 /**
318  *	of_get_next_child - Iterate a node childs
319  *	@node:	parent node
320  *	@prev:	previous child of the parent node, or NULL to get first
321  *
322  *	Returns a node pointer with refcount incremented, use
323  *	of_node_put() on it when done.
324  */
325 struct device_node *of_get_next_child(const struct device_node *node,
326 	struct device_node *prev)
327 {
328 	struct device_node *next;
329 
330 	read_lock(&devtree_lock);
331 	next = prev ? prev->sibling : node->child;
332 	for (; next; next = next->sibling)
333 		if (of_node_get(next))
334 			break;
335 	of_node_put(prev);
336 	read_unlock(&devtree_lock);
337 	return next;
338 }
339 EXPORT_SYMBOL(of_get_next_child);
340 
341 /**
342  *	of_find_node_by_path - Find a node matching a full OF path
343  *	@path:	The full path to match
344  *
345  *	Returns a node pointer with refcount incremented, use
346  *	of_node_put() on it when done.
347  */
348 struct device_node *of_find_node_by_path(const char *path)
349 {
350 	struct device_node *np = allnodes;
351 
352 	read_lock(&devtree_lock);
353 	for (; np; np = np->allnext) {
354 		if (np->full_name && (of_node_cmp(np->full_name, path) == 0)
355 		    && of_node_get(np))
356 			break;
357 	}
358 	read_unlock(&devtree_lock);
359 	return np;
360 }
361 EXPORT_SYMBOL(of_find_node_by_path);
362 
363 /**
364  *	of_find_node_by_name - Find a node by its "name" property
365  *	@from:	The node to start searching from or NULL, the node
366  *		you pass will not be searched, only the next one
367  *		will; typically, you pass what the previous call
368  *		returned. of_node_put() will be called on it
369  *	@name:	The name string to match against
370  *
371  *	Returns a node pointer with refcount incremented, use
372  *	of_node_put() on it when done.
373  */
374 struct device_node *of_find_node_by_name(struct device_node *from,
375 	const char *name)
376 {
377 	struct device_node *np;
378 
379 	read_lock(&devtree_lock);
380 	np = from ? from->allnext : allnodes;
381 	for (; np; np = np->allnext)
382 		if (np->name && (of_node_cmp(np->name, name) == 0)
383 		    && of_node_get(np))
384 			break;
385 	of_node_put(from);
386 	read_unlock(&devtree_lock);
387 	return np;
388 }
389 EXPORT_SYMBOL(of_find_node_by_name);
390 
391 /**
392  *	of_find_node_by_type - Find a node by its "device_type" property
393  *	@from:	The node to start searching from, or NULL to start searching
394  *		the entire device tree. The node you pass will not be
395  *		searched, only the next one will; typically, you pass
396  *		what the previous call returned. of_node_put() will be
397  *		called on from for you.
398  *	@type:	The type string to match against
399  *
400  *	Returns a node pointer with refcount incremented, use
401  *	of_node_put() on it when done.
402  */
403 struct device_node *of_find_node_by_type(struct device_node *from,
404 	const char *type)
405 {
406 	struct device_node *np;
407 
408 	read_lock(&devtree_lock);
409 	np = from ? from->allnext : allnodes;
410 	for (; np; np = np->allnext)
411 		if (np->type && (of_node_cmp(np->type, type) == 0)
412 		    && of_node_get(np))
413 			break;
414 	of_node_put(from);
415 	read_unlock(&devtree_lock);
416 	return np;
417 }
418 EXPORT_SYMBOL(of_find_node_by_type);
419 
420 /**
421  *	of_find_compatible_node - Find a node based on type and one of the
422  *                                tokens in its "compatible" property
423  *	@from:		The node to start searching from or NULL, the node
424  *			you pass will not be searched, only the next one
425  *			will; typically, you pass what the previous call
426  *			returned. of_node_put() will be called on it
427  *	@type:		The type string to match "device_type" or NULL to ignore
428  *	@compatible:	The string to match to one of the tokens in the device
429  *			"compatible" list.
430  *
431  *	Returns a node pointer with refcount incremented, use
432  *	of_node_put() on it when done.
433  */
434 struct device_node *of_find_compatible_node(struct device_node *from,
435 	const char *type, const char *compatible)
436 {
437 	struct device_node *np;
438 
439 	read_lock(&devtree_lock);
440 	np = from ? from->allnext : allnodes;
441 	for (; np; np = np->allnext) {
442 		if (type
443 		    && !(np->type && (of_node_cmp(np->type, type) == 0)))
444 			continue;
445 		if (of_device_is_compatible(np, compatible) && of_node_get(np))
446 			break;
447 	}
448 	of_node_put(from);
449 	read_unlock(&devtree_lock);
450 	return np;
451 }
452 EXPORT_SYMBOL(of_find_compatible_node);
453 
454 /**
455  *	of_find_node_with_property - Find a node which has a property with
456  *                                   the given name.
457  *	@from:		The node to start searching from or NULL, the node
458  *			you pass will not be searched, only the next one
459  *			will; typically, you pass what the previous call
460  *			returned. of_node_put() will be called on it
461  *	@prop_name:	The name of the property to look for.
462  *
463  *	Returns a node pointer with refcount incremented, use
464  *	of_node_put() on it when done.
465  */
466 struct device_node *of_find_node_with_property(struct device_node *from,
467 	const char *prop_name)
468 {
469 	struct device_node *np;
470 	struct property *pp;
471 
472 	read_lock(&devtree_lock);
473 	np = from ? from->allnext : allnodes;
474 	for (; np; np = np->allnext) {
475 		for (pp = np->properties; pp != 0; pp = pp->next) {
476 			if (of_prop_cmp(pp->name, prop_name) == 0) {
477 				of_node_get(np);
478 				goto out;
479 			}
480 		}
481 	}
482 out:
483 	of_node_put(from);
484 	read_unlock(&devtree_lock);
485 	return np;
486 }
487 EXPORT_SYMBOL(of_find_node_with_property);
488 
489 /**
490  * of_match_node - Tell if an device_node has a matching of_match structure
491  *	@matches:	array of of device match structures to search in
492  *	@node:		the of device structure to match against
493  *
494  *	Low level utility function used by device matching.
495  */
496 const struct of_device_id *of_match_node(const struct of_device_id *matches,
497 					 const struct device_node *node)
498 {
499 	while (matches->name[0] || matches->type[0] || matches->compatible[0]) {
500 		int match = 1;
501 		if (matches->name[0])
502 			match &= node->name
503 				&& !strcmp(matches->name, node->name);
504 		if (matches->type[0])
505 			match &= node->type
506 				&& !strcmp(matches->type, node->type);
507 		if (matches->compatible[0])
508 			match &= of_device_is_compatible(node,
509 						matches->compatible);
510 		if (match)
511 			return matches;
512 		matches++;
513 	}
514 	return NULL;
515 }
516 EXPORT_SYMBOL(of_match_node);
517 
518 /**
519  *	of_find_matching_node - Find a node based on an of_device_id match
520  *				table.
521  *	@from:		The node to start searching from or NULL, the node
522  *			you pass will not be searched, only the next one
523  *			will; typically, you pass what the previous call
524  *			returned. of_node_put() will be called on it
525  *	@matches:	array of of device match structures to search in
526  *
527  *	Returns a node pointer with refcount incremented, use
528  *	of_node_put() on it when done.
529  */
530 struct device_node *of_find_matching_node(struct device_node *from,
531 					  const struct of_device_id *matches)
532 {
533 	struct device_node *np;
534 
535 	read_lock(&devtree_lock);
536 	np = from ? from->allnext : allnodes;
537 	for (; np; np = np->allnext) {
538 		if (of_match_node(matches, np) && of_node_get(np))
539 			break;
540 	}
541 	of_node_put(from);
542 	read_unlock(&devtree_lock);
543 	return np;
544 }
545 EXPORT_SYMBOL(of_find_matching_node);
546 
547 /**
548  * of_modalias_node - Lookup appropriate modalias for a device node
549  * @node:	pointer to a device tree node
550  * @modalias:	Pointer to buffer that modalias value will be copied into
551  * @len:	Length of modalias value
552  *
553  * Based on the value of the compatible property, this routine will attempt
554  * to choose an appropriate modalias value for a particular device tree node.
555  * It does this by stripping the manufacturer prefix (as delimited by a ',')
556  * from the first entry in the compatible list property.
557  *
558  * This routine returns 0 on success, <0 on failure.
559  */
560 int of_modalias_node(struct device_node *node, char *modalias, int len)
561 {
562 	const char *compatible, *p;
563 	int cplen;
564 
565 	compatible = of_get_property(node, "compatible", &cplen);
566 	if (!compatible || strlen(compatible) > cplen)
567 		return -ENODEV;
568 	p = strchr(compatible, ',');
569 	strlcpy(modalias, p ? p + 1 : compatible, len);
570 	return 0;
571 }
572 EXPORT_SYMBOL_GPL(of_modalias_node);
573 
574 /**
575  * of_find_node_by_phandle - Find a node given a phandle
576  * @handle:	phandle of the node to find
577  *
578  * Returns a node pointer with refcount incremented, use
579  * of_node_put() on it when done.
580  */
581 struct device_node *of_find_node_by_phandle(phandle handle)
582 {
583 	struct device_node *np;
584 
585 	read_lock(&devtree_lock);
586 	for (np = allnodes; np; np = np->allnext)
587 		if (np->phandle == handle)
588 			break;
589 	of_node_get(np);
590 	read_unlock(&devtree_lock);
591 	return np;
592 }
593 EXPORT_SYMBOL(of_find_node_by_phandle);
594 
595 /**
596  * of_parse_phandle - Resolve a phandle property to a device_node pointer
597  * @np: Pointer to device node holding phandle property
598  * @phandle_name: Name of property holding a phandle value
599  * @index: For properties holding a table of phandles, this is the index into
600  *         the table
601  *
602  * Returns the device_node pointer with refcount incremented.  Use
603  * of_node_put() on it when done.
604  */
605 struct device_node *
606 of_parse_phandle(struct device_node *np, const char *phandle_name, int index)
607 {
608 	const __be32 *phandle;
609 	int size;
610 
611 	phandle = of_get_property(np, phandle_name, &size);
612 	if ((!phandle) || (size < sizeof(*phandle) * (index + 1)))
613 		return NULL;
614 
615 	return of_find_node_by_phandle(be32_to_cpup(phandle + index));
616 }
617 EXPORT_SYMBOL(of_parse_phandle);
618 
619 /**
620  * of_parse_phandles_with_args - Find a node pointed by phandle in a list
621  * @np:		pointer to a device tree node containing a list
622  * @list_name:	property name that contains a list
623  * @cells_name:	property name that specifies phandles' arguments count
624  * @index:	index of a phandle to parse out
625  * @out_node:	optional pointer to device_node struct pointer (will be filled)
626  * @out_args:	optional pointer to arguments pointer (will be filled)
627  *
628  * This function is useful to parse lists of phandles and their arguments.
629  * Returns 0 on success and fills out_node and out_args, on error returns
630  * appropriate errno value.
631  *
632  * Example:
633  *
634  * phandle1: node1 {
635  * 	#list-cells = <2>;
636  * }
637  *
638  * phandle2: node2 {
639  * 	#list-cells = <1>;
640  * }
641  *
642  * node3 {
643  * 	list = <&phandle1 1 2 &phandle2 3>;
644  * }
645  *
646  * To get a device_node of the `node2' node you may call this:
647  * of_parse_phandles_with_args(node3, "list", "#list-cells", 2, &node2, &args);
648  */
649 int of_parse_phandles_with_args(struct device_node *np, const char *list_name,
650 				const char *cells_name, int index,
651 				struct device_node **out_node,
652 				const void **out_args)
653 {
654 	int ret = -EINVAL;
655 	const __be32 *list;
656 	const __be32 *list_end;
657 	int size;
658 	int cur_index = 0;
659 	struct device_node *node = NULL;
660 	const void *args = NULL;
661 
662 	list = of_get_property(np, list_name, &size);
663 	if (!list) {
664 		ret = -ENOENT;
665 		goto err0;
666 	}
667 	list_end = list + size / sizeof(*list);
668 
669 	while (list < list_end) {
670 		const __be32 *cells;
671 		phandle phandle;
672 
673 		phandle = be32_to_cpup(list++);
674 		args = list;
675 
676 		/* one cell hole in the list = <>; */
677 		if (!phandle)
678 			goto next;
679 
680 		node = of_find_node_by_phandle(phandle);
681 		if (!node) {
682 			pr_debug("%s: could not find phandle\n",
683 				 np->full_name);
684 			goto err0;
685 		}
686 
687 		cells = of_get_property(node, cells_name, &size);
688 		if (!cells || size != sizeof(*cells)) {
689 			pr_debug("%s: could not get %s for %s\n",
690 				 np->full_name, cells_name, node->full_name);
691 			goto err1;
692 		}
693 
694 		list += be32_to_cpup(cells);
695 		if (list > list_end) {
696 			pr_debug("%s: insufficient arguments length\n",
697 				 np->full_name);
698 			goto err1;
699 		}
700 next:
701 		if (cur_index == index)
702 			break;
703 
704 		of_node_put(node);
705 		node = NULL;
706 		args = NULL;
707 		cur_index++;
708 	}
709 
710 	if (!node) {
711 		/*
712 		 * args w/o node indicates that the loop above has stopped at
713 		 * the 'hole' cell. Report this differently.
714 		 */
715 		if (args)
716 			ret = -EEXIST;
717 		else
718 			ret = -ENOENT;
719 		goto err0;
720 	}
721 
722 	if (out_node)
723 		*out_node = node;
724 	if (out_args)
725 		*out_args = args;
726 
727 	return 0;
728 err1:
729 	of_node_put(node);
730 err0:
731 	pr_debug("%s failed with status %d\n", __func__, ret);
732 	return ret;
733 }
734 EXPORT_SYMBOL(of_parse_phandles_with_args);
735 
736 /**
737  * prom_add_property - Add a property to a node
738  */
739 int prom_add_property(struct device_node *np, struct property *prop)
740 {
741 	struct property **next;
742 	unsigned long flags;
743 
744 	prop->next = NULL;
745 	write_lock_irqsave(&devtree_lock, flags);
746 	next = &np->properties;
747 	while (*next) {
748 		if (strcmp(prop->name, (*next)->name) == 0) {
749 			/* duplicate ! don't insert it */
750 			write_unlock_irqrestore(&devtree_lock, flags);
751 			return -1;
752 		}
753 		next = &(*next)->next;
754 	}
755 	*next = prop;
756 	write_unlock_irqrestore(&devtree_lock, flags);
757 
758 #ifdef CONFIG_PROC_DEVICETREE
759 	/* try to add to proc as well if it was initialized */
760 	if (np->pde)
761 		proc_device_tree_add_prop(np->pde, prop);
762 #endif /* CONFIG_PROC_DEVICETREE */
763 
764 	return 0;
765 }
766 
767 /**
768  * prom_remove_property - Remove a property from a node.
769  *
770  * Note that we don't actually remove it, since we have given out
771  * who-knows-how-many pointers to the data using get-property.
772  * Instead we just move the property to the "dead properties"
773  * list, so it won't be found any more.
774  */
775 int prom_remove_property(struct device_node *np, struct property *prop)
776 {
777 	struct property **next;
778 	unsigned long flags;
779 	int found = 0;
780 
781 	write_lock_irqsave(&devtree_lock, flags);
782 	next = &np->properties;
783 	while (*next) {
784 		if (*next == prop) {
785 			/* found the node */
786 			*next = prop->next;
787 			prop->next = np->deadprops;
788 			np->deadprops = prop;
789 			found = 1;
790 			break;
791 		}
792 		next = &(*next)->next;
793 	}
794 	write_unlock_irqrestore(&devtree_lock, flags);
795 
796 	if (!found)
797 		return -ENODEV;
798 
799 #ifdef CONFIG_PROC_DEVICETREE
800 	/* try to remove the proc node as well */
801 	if (np->pde)
802 		proc_device_tree_remove_prop(np->pde, prop);
803 #endif /* CONFIG_PROC_DEVICETREE */
804 
805 	return 0;
806 }
807 
808 /*
809  * prom_update_property - Update a property in a node.
810  *
811  * Note that we don't actually remove it, since we have given out
812  * who-knows-how-many pointers to the data using get-property.
813  * Instead we just move the property to the "dead properties" list,
814  * and add the new property to the property list
815  */
816 int prom_update_property(struct device_node *np,
817 			 struct property *newprop,
818 			 struct property *oldprop)
819 {
820 	struct property **next;
821 	unsigned long flags;
822 	int found = 0;
823 
824 	write_lock_irqsave(&devtree_lock, flags);
825 	next = &np->properties;
826 	while (*next) {
827 		if (*next == oldprop) {
828 			/* found the node */
829 			newprop->next = oldprop->next;
830 			*next = newprop;
831 			oldprop->next = np->deadprops;
832 			np->deadprops = oldprop;
833 			found = 1;
834 			break;
835 		}
836 		next = &(*next)->next;
837 	}
838 	write_unlock_irqrestore(&devtree_lock, flags);
839 
840 	if (!found)
841 		return -ENODEV;
842 
843 #ifdef CONFIG_PROC_DEVICETREE
844 	/* try to add to proc as well if it was initialized */
845 	if (np->pde)
846 		proc_device_tree_update_prop(np->pde, newprop, oldprop);
847 #endif /* CONFIG_PROC_DEVICETREE */
848 
849 	return 0;
850 }
851 
852 #if defined(CONFIG_OF_DYNAMIC)
853 /*
854  * Support for dynamic device trees.
855  *
856  * On some platforms, the device tree can be manipulated at runtime.
857  * The routines in this section support adding, removing and changing
858  * device tree nodes.
859  */
860 
861 /**
862  * of_attach_node - Plug a device node into the tree and global list.
863  */
864 void of_attach_node(struct device_node *np)
865 {
866 	unsigned long flags;
867 
868 	write_lock_irqsave(&devtree_lock, flags);
869 	np->sibling = np->parent->child;
870 	np->allnext = allnodes;
871 	np->parent->child = np;
872 	allnodes = np;
873 	write_unlock_irqrestore(&devtree_lock, flags);
874 }
875 
876 /**
877  * of_detach_node - "Unplug" a node from the device tree.
878  *
879  * The caller must hold a reference to the node.  The memory associated with
880  * the node is not freed until its refcount goes to zero.
881  */
882 void of_detach_node(struct device_node *np)
883 {
884 	struct device_node *parent;
885 	unsigned long flags;
886 
887 	write_lock_irqsave(&devtree_lock, flags);
888 
889 	parent = np->parent;
890 	if (!parent)
891 		goto out_unlock;
892 
893 	if (allnodes == np)
894 		allnodes = np->allnext;
895 	else {
896 		struct device_node *prev;
897 		for (prev = allnodes;
898 		     prev->allnext != np;
899 		     prev = prev->allnext)
900 			;
901 		prev->allnext = np->allnext;
902 	}
903 
904 	if (parent->child == np)
905 		parent->child = np->sibling;
906 	else {
907 		struct device_node *prevsib;
908 		for (prevsib = np->parent->child;
909 		     prevsib->sibling != np;
910 		     prevsib = prevsib->sibling)
911 			;
912 		prevsib->sibling = np->sibling;
913 	}
914 
915 	of_node_set_flag(np, OF_DETACHED);
916 
917 out_unlock:
918 	write_unlock_irqrestore(&devtree_lock, flags);
919 }
920 #endif /* defined(CONFIG_OF_DYNAMIC) */
921 
922