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