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 int of_overlay_apply_single_property(struct of_overlay *ov,
  62                 struct device_node *target, struct property *prop)
  63 {
  64         struct property *propn, *tprop;
  65
  66         /* NOTE: Multiple changes of single properties not supported */
  67         tprop = of_find_property(target, prop->name, NULL);
  68
  69         /* special properties are not meant to be updated (silent NOP) */
  70         if (of_prop_cmp(prop->name, "name") == 0 ||
  71             of_prop_cmp(prop->name, "phandle") == 0 ||
  72             of_prop_cmp(prop->name, "linux,phandle") == 0)
  73                 return 0;
  74
  75         propn = __of_prop_dup(prop, GFP_KERNEL);
  76         if (propn == NULL)
  77                 return -ENOMEM;
  78
  79         /* not found? add */
  80         if (tprop == NULL)
  81                 return of_changeset_add_property(&ov->cset, target, propn);
  82
  83         /* found? update */
  84         return of_changeset_update_property(&ov->cset, target, propn);
  85 }
  86
  87 static int of_overlay_apply_single_device_node(struct of_overlay *ov,
  88                 struct device_node *target, struct device_node *child)
  89 {
  90         const char *cname;
  91         struct device_node *tchild;
  92         int ret = 0;
  93
  94         cname = kbasename(child->full_name);
  95         if (cname == NULL)
  96                 return -ENOMEM;
  97
  98         /* NOTE: Multiple mods of created nodes not supported */
  99         tchild = of_get_child_by_name(target, cname);
 100         if (tchild != NULL) {
 101                 /* apply overlay recursively */
 102                 ret = of_overlay_apply_one(ov, tchild, child);
 103                 of_node_put(tchild);
 104         } else {
 105                 /* create empty tree as a target */
 106                 tchild = __of_node_dup(child, "%s/%s", target->full_name, cname);
 107                 if (!tchild)
 108                         return -ENOMEM;
 109
 110                 /* point to parent */
 111                 tchild->parent = target;
 112
 113                 ret = of_changeset_attach_node(&ov->cset, tchild);
 114                 if (ret)
 115                         return ret;
 116
 117                 ret = of_overlay_apply_one(ov, tchild, child);
 118                 if (ret)
 119                         return ret;
 120         }
 121
 122         return ret;
 123 }
 124
 125 /*
 126  * Apply a single overlay node recursively.
 127  *
 128  * Note that the in case of an error the target node is left
 129  * in a inconsistent state. Error recovery should be performed
 130  * by using the changeset.
 131  */
 132 static int of_overlay_apply_one(struct of_overlay *ov,
 133                 struct device_node *target, const struct device_node *overlay)
 134 {
 135         struct device_node *child;
 136         struct property *prop;
 137         int ret;
 138
 139         for_each_property_of_node(overlay, prop) {
 140                 ret = of_overlay_apply_single_property(ov, target, prop);
 141                 if (ret) {
 142                         pr_err("Failed to apply prop @%s/%s\n",
 143                                target->full_name, prop->name);
 144                         return ret;
 145                 }
 146         }
 147
 148         for_each_child_of_node(overlay, child) {
 149                 ret = of_overlay_apply_single_device_node(ov, target, child);
 150                 if (ret != 0) {
 151                         pr_err("Failed to apply single node @%s/%s\n",
 152                                target->full_name, child->name);
 153                         of_node_put(child);
 154                         return ret;
 155                 }
 156         }
 157
 158         return 0;
 159 }
 160
 161 /**
 162  * of_overlay_apply() - Apply @count overlays pointed at by @ovinfo_tab
 163  * @ov:         Overlay to apply
 164  *
 165  * Applies the overlays given, while handling all error conditions
 166  * appropriately. Either the operation succeeds, or if it fails the
 167  * live tree is reverted to the state before the attempt.
 168  * Returns 0, or an error if the overlay attempt failed.
 169  */
 170 static int of_overlay_apply(struct of_overlay *ov)
 171 {
 172         int i, err;
 173
 174         /* first we apply the overlays atomically */
 175         for (i = 0; i < ov->count; i++) {
 176                 struct of_overlay_info *ovinfo = &ov->ovinfo_tab[i];
 177
 178                 err = of_overlay_apply_one(ov, ovinfo->target, ovinfo->overlay);
 179                 if (err != 0) {
 180                         pr_err("apply failed '%s'\n", 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("Failed to find target for node %p (%s)\n",
 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                 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("of_build_overlay_info() failed for tree@%s\n",
 367                        tree->full_name);
 368                 goto err_free_idr;
 369         }
 370
 371         /* apply the overlay */
 372         err = of_overlay_apply(ov);
 373         if (err)
 374                 goto err_abort_trans;
 375
 376         /* apply the changeset */
 377         err = __of_changeset_apply(&ov->cset);
 378         if (err)
 379                 goto err_revert_overlay;
 380
 381
 382         /* add to the tail of the overlay list */
 383         list_add_tail(&ov->node, &ov_list);
 384
 385         mutex_unlock(&of_mutex);
 386
 387         return id;
 388
 389 err_revert_overlay:
 390 err_abort_trans:
 391         of_free_overlay_info(ov);
 392 err_free_idr:
 393         idr_remove(&ov_idr, ov->id);
 394 err_destroy_trans:
 395         of_changeset_destroy(&ov->cset);
 396         kfree(ov);
 397         mutex_unlock(&of_mutex);
 398
 399         return err;
 400 }
 401 EXPORT_SYMBOL_GPL(of_overlay_create);
 402
 403 /* check whether the given node, lies under the given tree */
 404 static int overlay_subtree_check(struct device_node *tree,
 405                 struct device_node *dn)
 406 {
 407         struct device_node *child;
 408
 409         /* match? */
 410         if (tree == dn)
 411                 return 1;
 412
 413         for_each_child_of_node(tree, child) {
 414                 if (overlay_subtree_check(child, dn)) {
 415                         of_node_put(child);
 416                         return 1;
 417                 }
 418         }
 419
 420         return 0;
 421 }
 422
 423 /* check whether this overlay is the topmost */
 424 static int overlay_is_topmost(struct of_overlay *ov, struct device_node *dn)
 425 {
 426         struct of_overlay *ovt;
 427         struct of_changeset_entry *ce;
 428
 429         list_for_each_entry_reverse(ovt, &ov_list, node) {
 430                 /* if we hit ourselves, we're done */
 431                 if (ovt == ov)
 432                         break;
 433
 434                 /* check against each subtree affected by this overlay */
 435                 list_for_each_entry(ce, &ovt->cset.entries, node) {
 436                         if (overlay_subtree_check(ce->np, dn)) {
 437                                 pr_err("%s: #%d clashes #%d @%s\n",
 438                                         __func__, ov->id, ovt->id,
 439                                         dn->full_name);
 440                                 return 0;
 441                         }
 442                 }
 443         }
 444
 445         /* overlay is topmost */
 446         return 1;
 447 }
 448
 449 /*
 450  * We can safely remove the overlay only if it's the top-most one.
 451  * Newly applied overlays are inserted at the tail of the overlay list,
 452  * so a top most overlay is the one that is closest to the tail.
 453  *
 454  * The topmost check is done by exploiting this property. For each
 455  * affected device node in the log list we check if this overlay is
 456  * the one closest to the tail. If another overlay has affected this
 457  * device node and is closest to the tail, then removal is not permited.
 458  */
 459 static int overlay_removal_is_ok(struct of_overlay *ov)
 460 {
 461         struct of_changeset_entry *ce;
 462
 463         list_for_each_entry(ce, &ov->cset.entries, node) {
 464                 if (!overlay_is_topmost(ov, ce->np)) {
 465                         pr_err("overlay #%d is not topmost\n", ov->id);
 466                         return 0;
 467                 }
 468         }
 469
 470         return 1;
 471 }
 472
 473 /**
 474  * of_overlay_destroy() - Removes an overlay
 475  * @id: Overlay id number returned by a previous call to of_overlay_create
 476  *
 477  * Removes an overlay if it is permissible.
 478  *
 479  * Returns 0 on success, or a negative error number
 480  */
 481 int of_overlay_destroy(int id)
 482 {
 483         struct of_overlay *ov;
 484         int err;
 485
 486         mutex_lock(&of_mutex);
 487
 488         ov = idr_find(&ov_idr, id);
 489         if (ov == NULL) {
 490                 err = -ENODEV;
 491                 pr_err("destroy: Could not find overlay #%d\n", id);
 492                 goto out;
 493         }
 494
 495         /* check whether the overlay is safe to remove */
 496         if (!overlay_removal_is_ok(ov)) {
 497                 err = -EBUSY;
 498                 goto out;
 499         }
 500
 501
 502         list_del(&ov->node);
 503         __of_changeset_revert(&ov->cset);
 504         of_free_overlay_info(ov);
 505         idr_remove(&ov_idr, id);
 506         of_changeset_destroy(&ov->cset);
 507         kfree(ov);
 508
 509         err = 0;
 510
 511 out:
 512         mutex_unlock(&of_mutex);
 513
 514         return err;
 515 }
 516 EXPORT_SYMBOL_GPL(of_overlay_destroy);
 517
 518 /**
 519  * of_overlay_destroy_all() - Removes all overlays from the system
 520  *
 521  * Removes all overlays from the system in the correct order.
 522  *
 523  * Returns 0 on success, or a negative error number
 524  */
 525 int of_overlay_destroy_all(void)
 526 {
 527         struct of_overlay *ov, *ovn;
 528
 529         mutex_lock(&of_mutex);
 530
 531         /* the tail of list is guaranteed to be safe to remove */
 532         list_for_each_entry_safe_reverse(ov, ovn, &ov_list, node) {
 533                 list_del(&ov->node);
 534                 __of_changeset_revert(&ov->cset);
 535                 of_free_overlay_info(ov);
 536                 idr_remove(&ov_idr, ov->id);
 537                 kfree(ov);
 538         }
 539
 540         mutex_unlock(&of_mutex);
 541
 542         return 0;
 543 }
 544 EXPORT_SYMBOL_GPL(of_overlay_destroy_all);