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                         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  */
 169 static 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  */
 195 static 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  */
 231 static 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
 244 err_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  */
 264 static 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  */
 309 static 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
 326 static LIST_HEAD(ov_list);
 327 static 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  */
 339 int 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
 396 err_revert_overlay:
 397 err_abort_trans:
 398         of_free_overlay_info(ov);
 399 err_free_idr:
 400         idr_remove(&ov_idr, ov->id);
 401 err_destroy_trans:
 402         of_changeset_destroy(&ov->cset);
 403         kfree(ov);
 404         mutex_unlock(&of_mutex);
 405
 406         return err;
 407 }
 408 EXPORT_SYMBOL_GPL(of_overlay_create);
 409
 410 /* check whether the given node, lies under the given tree */
 411 static 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 */
 431 static 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  */
 466 static 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  */
 489 int 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
 522 out:
 523         mutex_unlock(&of_mutex);
 524
 525         return err;
 526 }
 527 EXPORT_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  */
 536 int 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 }
 555 EXPORT_SYMBOL_GPL(of_overlay_destroy_all);