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/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);