drivers/of/overlay.c

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