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