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 #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  */
  34 struct 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  */
  48 struct 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
  56 static int of_overlay_apply_one(struct of_overlay *ov,
  57                 struct device_node *target, const struct device_node *overlay);
  58
  59 static 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
  85 static 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  */
 130 static 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                         return ret;
 153                 }
 154         }
 155
 156         return 0;
 157 }
 158
 159 /**
 160  * of_overlay_apply() - Apply @count overlays pointed at by @ovinfo_tab
 161  * @ov:         Overlay to apply
 162  *
 163  * Applies the overlays given, while handling all error conditions
 164  * appropriately. Either the operation succeeds, or if it fails the
 165  * live tree is reverted to the state before the attempt.
 166  * Returns 0, or an error if the overlay attempt failed.
 167  */
 168 static int of_overlay_apply(struct of_overlay *ov)
 169 {
 170         int i, err;
 171
 172         /* first we apply the overlays atomically */
 173         for (i = 0; i < ov->count; i++) {
 174                 struct of_overlay_info *ovinfo = &ov->ovinfo_tab[i];
 175
 176                 err = of_overlay_apply_one(ov, ovinfo->target, ovinfo->overlay);
 177                 if (err != 0) {
 178                         pr_err("%s: overlay failed '%s'\n",
 179                                 __func__, ovinfo->target->full_name);
 180                         return err;
 181                 }
 182         }
 183
 184         return 0;
 185 }
 186
 187 /*
 188  * Find the target node using a number of different strategies
 189  * in order of preference
 190  *
 191  * "target" property containing the phandle of the target
 192  * "target-path" property containing the path of the target
 193  */
 194 static struct device_node *find_target_node(struct device_node *info_node)
 195 {
 196         const char *path;
 197         u32 val;
 198         int ret;
 199
 200         /* first try to go by using the target as a phandle */
 201         ret = of_property_read_u32(info_node, "target", &val);
 202         if (ret == 0)
 203                 return of_find_node_by_phandle(val);
 204
 205         /* now try to locate by path */
 206         ret = of_property_read_string(info_node, "target-path", &path);
 207         if (ret == 0)
 208                 return of_find_node_by_path(path);
 209
 210         pr_err("%s: Failed to find target for node %p (%s)\n", __func__,
 211                 info_node, info_node->name);
 212
 213         return NULL;
 214 }
 215
 216 /**
 217  * of_fill_overlay_info() - Fill an overlay info structure
 218  * @ov          Overlay to fill
 219  * @info_node:  Device node containing the overlay
 220  * @ovinfo:     Pointer to the overlay info structure to fill
 221  *
 222  * Fills an overlay info structure with the overlay information
 223  * from a device node. This device node must have a target property
 224  * which contains a phandle of the overlay target node, and an
 225  * __overlay__ child node which has the overlay contents.
 226  * Both ovinfo->target & ovinfo->overlay have their references taken.
 227  *
 228  * Returns 0 on success, or a negative error value.
 229  */
 230 static int of_fill_overlay_info(struct of_overlay *ov,
 231                 struct device_node *info_node, struct of_overlay_info *ovinfo)
 232 {
 233         ovinfo->overlay = of_get_child_by_name(info_node, "__overlay__");
 234         if (ovinfo->overlay == NULL)
 235                 goto err_fail;
 236
 237         ovinfo->target = find_target_node(info_node);
 238         if (ovinfo->target == NULL)
 239                 goto err_fail;
 240
 241         return 0;
 242
 243 err_fail:
 244         of_node_put(ovinfo->target);
 245         of_node_put(ovinfo->overlay);
 246
 247         memset(ovinfo, 0, sizeof(*ovinfo));
 248         return -EINVAL;
 249 }
 250
 251 /**
 252  * of_build_overlay_info() - Build an overlay info array
 253  * @ov          Overlay to build
 254  * @tree:       Device node containing all the overlays
 255  *
 256  * Helper function that given a tree containing overlay information,
 257  * allocates and builds an overlay info array containing it, ready
 258  * for use using of_overlay_apply.
 259  *
 260  * Returns 0 on success with the @cntp @ovinfop pointers valid,
 261  * while on error a negative error value is returned.
 262  */
 263 static int of_build_overlay_info(struct of_overlay *ov,
 264                 struct device_node *tree)
 265 {
 266         struct device_node *node;
 267         struct of_overlay_info *ovinfo;
 268         int cnt, err;
 269
 270         /* worst case; every child is a node */
 271         cnt = 0;
 272         for_each_child_of_node(tree, node)
 273                 cnt++;
 274
 275         ovinfo = kcalloc(cnt, sizeof(*ovinfo), GFP_KERNEL);
 276         if (ovinfo == NULL)
 277                 return -ENOMEM;
 278
 279         cnt = 0;
 280         for_each_child_of_node(tree, node) {
 281                 memset(&ovinfo[cnt], 0, sizeof(*ovinfo));
 282                 err = of_fill_overlay_info(ov, node, &ovinfo[cnt]);
 283                 if (err == 0)
 284                         cnt++;
 285         }
 286
 287         /* if nothing filled, return error */
 288         if (cnt == 0) {
 289                 kfree(ovinfo);
 290                 return -ENODEV;
 291         }
 292
 293         ov->count = cnt;
 294         ov->ovinfo_tab = ovinfo;
 295
 296         return 0;
 297 }
 298
 299 /**
 300  * of_free_overlay_info() - Free an overlay info array
 301  * @ov          Overlay to free the overlay info from
 302  * @ovinfo_tab: Array of overlay_info's to free
 303  *
 304  * Releases the memory of a previously allocated ovinfo array
 305  * by of_build_overlay_info.
 306  * Returns 0, or an error if the arguments are bogus.
 307  */
 308 static int of_free_overlay_info(struct of_overlay *ov)
 309 {
 310         struct of_overlay_info *ovinfo;
 311         int i;
 312
 313         /* do it in reverse */
 314         for (i = ov->count - 1; i >= 0; i--) {
 315                 ovinfo = &ov->ovinfo_tab[i];
 316
 317                 of_node_put(ovinfo->target);
 318                 of_node_put(ovinfo->overlay);
 319         }
 320         kfree(ov->ovinfo_tab);
 321
 322         return 0;
 323 }
 324
 325 static LIST_HEAD(ov_list);
 326 static DEFINE_IDR(ov_idr);
 327
 328 /**
 329  * of_overlay_create() - Create and apply an overlay
 330  * @tree:       Device node containing all the overlays
 331  *
 332  * Creates and applies an overlay while also keeping track
 333  * of the overlay in a list. This list can be used to prevent
 334  * illegal overlay removals.
 335  *
 336  * Returns the id of the created overlay, or a negative error number
 337  */
 338 int of_overlay_create(struct device_node *tree)
 339 {
 340         struct of_overlay *ov;
 341         int err, id;
 342
 343         /* allocate the overlay structure */
 344         ov = kzalloc(sizeof(*ov), GFP_KERNEL);
 345         if (ov == NULL)
 346                 return -ENOMEM;
 347         ov->id = -1;
 348
 349         INIT_LIST_HEAD(&ov->node);
 350
 351         of_changeset_init(&ov->cset);
 352
 353         mutex_lock(&of_mutex);
 354
 355         id = idr_alloc(&ov_idr, ov, 0, 0, GFP_KERNEL);
 356         if (id < 0) {
 357                 pr_err("%s: idr_alloc() failed for tree@%s\n",
 358                                 __func__, tree->full_name);
 359                 err = id;
 360                 goto err_destroy_trans;
 361         }
 362         ov->id = id;
 363
 364         /* build the overlay info structures */
 365         err = of_build_overlay_info(ov, tree);
 366         if (err) {
 367                 pr_err("%s: of_build_overlay_info() failed for tree@%s\n",
 368                                 __func__, tree->full_name);
 369                 goto err_free_idr;
 370         }
 371
 372         /* apply the overlay */
 373         err = of_overlay_apply(ov);
 374         if (err) {
 375                 pr_err("%s: of_overlay_apply() failed for tree@%s\n",
 376                                 __func__, tree->full_name);
 377                 goto err_abort_trans;
 378         }
 379
 380         /* apply the changeset */
 381         err = of_changeset_apply(&ov->cset);
 382         if (err) {
 383                 pr_err("%s: of_changeset_apply() failed for tree@%s\n",
 384                                 __func__, tree->full_name);
 385                 goto err_revert_overlay;
 386         }
 387
 388         /* add to the tail of the overlay list */
 389         list_add_tail(&ov->node, &ov_list);
 390
 391         mutex_unlock(&of_mutex);
 392
 393         return id;
 394
 395 err_revert_overlay:
 396 err_abort_trans:
 397         of_free_overlay_info(ov);
 398 err_free_idr:
 399         idr_remove(&ov_idr, ov->id);
 400 err_destroy_trans:
 401         of_changeset_destroy(&ov->cset);
 402         kfree(ov);
 403         mutex_unlock(&of_mutex);
 404
 405         return err;
 406 }
 407 EXPORT_SYMBOL_GPL(of_overlay_create);
 408
 409 /* check whether the given node, lies under the given tree */
 410 static int overlay_subtree_check(struct device_node *tree,
 411                 struct device_node *dn)
 412 {
 413         struct device_node *child;
 414
 415         /* match? */
 416         if (tree == dn)
 417                 return 1;
 418
 419         for_each_child_of_node(tree, child) {
 420                 if (overlay_subtree_check(child, dn))
 421                         return 1;
 422         }
 423
 424         return 0;
 425 }
 426
 427 /* check whether this overlay is the topmost */
 428 static int overlay_is_topmost(struct of_overlay *ov, struct device_node *dn)
 429 {
 430         struct of_overlay *ovt;
 431         struct of_changeset_entry *ce;
 432
 433         list_for_each_entry_reverse(ovt, &ov_list, node) {
 434                 /* if we hit ourselves, we're done */
 435                 if (ovt == ov)
 436                         break;
 437
 438                 /* check against each subtree affected by this overlay */
 439                 list_for_each_entry(ce, &ovt->cset.entries, node) {
 440                         if (overlay_subtree_check(ce->np, dn)) {
 441                                 pr_err("%s: #%d clashes #%d @%s\n",
 442                                         __func__, ov->id, ovt->id,
 443                                         dn->full_name);
 444                                 return 0;
 445                         }
 446                 }
 447         }
 448
 449         /* overlay is topmost */
 450         return 1;
 451 }
 452
 453 /*
 454  * We can safely remove the overlay only if it's the top-most one.
 455  * Newly applied overlays are inserted at the tail of the overlay list,
 456  * so a top most overlay is the one that is closest to the tail.
 457  *
 458  * The topmost check is done by exploiting this property. For each
 459  * affected device node in the log list we check if this overlay is
 460  * the one closest to the tail. If another overlay has affected this
 461  * device node and is closest to the tail, then removal is not permited.
 462  */
 463 static int overlay_removal_is_ok(struct of_overlay *ov)
 464 {
 465         struct of_changeset_entry *ce;
 466
 467         list_for_each_entry(ce, &ov->cset.entries, node) {
 468                 if (!overlay_is_topmost(ov, ce->np)) {
 469                         pr_err("%s: overlay #%d is not topmost\n",
 470                                         __func__, ov->id);
 471                         return 0;
 472                 }
 473         }
 474
 475         return 1;
 476 }
 477
 478 /**
 479  * of_overlay_destroy() - Removes an overlay
 480  * @id: Overlay id number returned by a previous call to of_overlay_create
 481  *
 482  * Removes an overlay if it is permissible.
 483  *
 484  * Returns 0 on success, or a negative error number
 485  */
 486 int of_overlay_destroy(int id)
 487 {
 488         struct of_overlay *ov;
 489         int err;
 490
 491         mutex_lock(&of_mutex);
 492
 493         ov = idr_find(&ov_idr, id);
 494         if (ov == NULL) {
 495                 err = -ENODEV;
 496                 pr_err("%s: Could not find overlay #%d\n",
 497                                 __func__, id);
 498                 goto out;
 499         }
 500
 501         /* check whether the overlay is safe to remove */
 502         if (!overlay_removal_is_ok(ov)) {
 503                 err = -EBUSY;
 504                 pr_err("%s: removal check failed for overlay #%d\n",
 505                                 __func__, id);
 506                 goto out;
 507         }
 508
 509
 510         list_del(&ov->node);
 511         of_changeset_revert(&ov->cset);
 512         of_free_overlay_info(ov);
 513         idr_remove(&ov_idr, id);
 514         of_changeset_destroy(&ov->cset);
 515         kfree(ov);
 516
 517         err = 0;
 518
 519 out:
 520         mutex_unlock(&of_mutex);
 521
 522         return err;
 523 }
 524 EXPORT_SYMBOL_GPL(of_overlay_destroy);
 525
 526 /**
 527  * of_overlay_destroy_all() - Removes all overlays from the system
 528  *
 529  * Removes all overlays from the system in the correct order.
 530  *
 531  * Returns 0 on success, or a negative error number
 532  */
 533 int of_overlay_destroy_all(void)
 534 {
 535         struct of_overlay *ov, *ovn;
 536
 537         mutex_lock(&of_mutex);
 538
 539         /* the tail of list is guaranteed to be safe to remove */
 540         list_for_each_entry_safe_reverse(ov, ovn, &ov_list, node) {
 541                 list_del(&ov->node);
 542                 of_changeset_revert(&ov->cset);
 543                 of_free_overlay_info(ov);
 544                 idr_remove(&ov_idr, ov->id);
 545                 kfree(ov);
 546         }
 547
 548         mutex_unlock(&of_mutex);
 549
 550         return 0;
 551 }
 552 EXPORT_SYMBOL_GPL(of_overlay_destroy_all);