drivers/of/resolver.c

   1 /*
   2  * Functions for dealing with DT resolution
   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: resolver: " 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/slab.h>
  22
  23 #include "of_private.h"
  24
  25 /* illegal phandle value (set when unresolved) */
  26 #define OF_PHANDLE_ILLEGAL      0xdeadbeef
  27
  28 static phandle live_tree_max_phandle(void)
  29 {
  30         struct device_node *node;
  31         phandle phandle;
  32         unsigned long flags;
  33
  34         raw_spin_lock_irqsave(&devtree_lock, flags);
  35         phandle = 0;
  36         for_each_of_allnodes(node) {
  37                 if (node->phandle != OF_PHANDLE_ILLEGAL &&
  38                                 node->phandle > phandle)
  39                         phandle = node->phandle;
  40         }
  41         raw_spin_unlock_irqrestore(&devtree_lock, flags);
  42
  43         return phandle;
  44 }
  45
  46 static void adjust_overlay_phandles(struct device_node *overlay,
  47                 int phandle_delta)
  48 {
  49         struct device_node *child;
  50         struct property *prop;
  51         phandle phandle;
  52
  53         /* adjust node's phandle in node */
  54         if (overlay->phandle != 0 && overlay->phandle != OF_PHANDLE_ILLEGAL)
  55                 overlay->phandle += phandle_delta;
  56
  57         /* copy adjusted phandle into *phandle properties */
  58         for_each_property_of_node(overlay, prop) {
  59
  60                 if (of_prop_cmp(prop->name, "phandle") &&
  61                     of_prop_cmp(prop->name, "linux,phandle"))
  62                         continue;
  63
  64                 if (prop->length < 4)
  65                         continue;
  66
  67                 phandle = be32_to_cpup(prop->value);
  68                 if (phandle == OF_PHANDLE_ILLEGAL)
  69                         continue;
  70
  71                 *(__be32 *)prop->value = cpu_to_be32(overlay->phandle);
  72         }
  73
  74         for_each_child_of_node(overlay, child)
  75                 adjust_overlay_phandles(child, phandle_delta);
  76 }
  77
  78 static int update_usages_of_a_phandle_reference(struct device_node *overlay,
  79                 struct property *prop_fixup, phandle phandle)
  80 {
  81         struct device_node *refnode;
  82         struct property *prop;
  83         char *value, *cur, *end, *node_path, *prop_name, *s;
  84         int offset, len;
  85         int err = 0;
  86
  87         value = kmalloc(prop_fixup->length, GFP_KERNEL);
  88         if (!value)
  89                 return -ENOMEM;
  90         memcpy(value, prop_fixup->value, prop_fixup->length);
  91
  92         /* prop_fixup contains a list of tuples of path:property_name:offset */
  93         end = value + prop_fixup->length;
  94         for (cur = value; cur < end; cur += len + 1) {
  95                 len = strlen(cur);
  96
  97                 node_path = cur;
  98                 s = strchr(cur, ':');
  99                 if (!s) {
 100                         err = -EINVAL;
 101                         goto err_fail;
 102                 }
 103                 *s++ = '\0';
 104
 105                 prop_name = s;
 106                 s = strchr(s, ':');
 107                 if (!s) {
 108                         err = -EINVAL;
 109                         goto err_fail;
 110                 }
 111                 *s++ = '\0';
 112
 113                 err = kstrtoint(s, 10, &offset);
 114                 if (err)
 115                         goto err_fail;
 116
 117                 refnode = __of_find_node_by_full_path(of_node_get(overlay), node_path);
 118                 if (!refnode)
 119                         continue;
 120
 121                 for_each_property_of_node(refnode, prop) {
 122                         if (!of_prop_cmp(prop->name, prop_name))
 123                                 break;
 124                 }
 125                 of_node_put(refnode);
 126
 127                 if (!prop) {
 128                         err = -ENOENT;
 129                         goto err_fail;
 130                 }
 131
 132                 *(__be32 *)(prop->value + offset) = cpu_to_be32(phandle);
 133         }
 134
 135 err_fail:
 136         kfree(value);
 137         return err;
 138 }
 139
 140 /* compare nodes taking into account that 'name' strips out the @ part */
 141 static int node_name_cmp(const struct device_node *dn1,
 142                 const struct device_node *dn2)
 143 {
 144         const char *n1 = kbasename(dn1->full_name);
 145         const char *n2 = kbasename(dn2->full_name);
 146
 147         return of_node_cmp(n1, n2);
 148 }
 149
 150 /*
 151  * Adjust the local phandle references by the given phandle delta.
 152  *
 153  * Subtree @local_fixups, which is overlay node __local_fixups__,
 154  * mirrors the fragment node structure at the root of the overlay.
 155  *
 156  * For each property in the fragments that contains a phandle reference,
 157  * @local_fixups has a property of the same name that contains a list
 158  * of offsets of the phandle reference(s) within the respective property
 159  * value(s).  The values at these offsets will be fixed up.
 160  */
 161 static int adjust_local_phandle_references(struct device_node *local_fixups,
 162                 struct device_node *overlay, int phandle_delta)
 163 {
 164         struct device_node *child, *overlay_child;
 165         struct property *prop_fix, *prop;
 166         int err, i, count;
 167         unsigned int off;
 168         phandle phandle;
 169
 170         if (!local_fixups)
 171                 return 0;
 172
 173         for_each_property_of_node(local_fixups, prop_fix) {
 174
 175                 /* skip properties added automatically */
 176                 if (!of_prop_cmp(prop_fix->name, "name") ||
 177                     !of_prop_cmp(prop_fix->name, "phandle") ||
 178                     !of_prop_cmp(prop_fix->name, "linux,phandle"))
 179                         continue;
 180
 181                 if ((prop_fix->length % 4) != 0 || prop_fix->length == 0)
 182                         return -EINVAL;
 183                 count = prop_fix->length / sizeof(__be32);
 184
 185                 for_each_property_of_node(overlay, prop) {
 186                         if (!of_prop_cmp(prop->name, prop_fix->name))
 187                                 break;
 188                 }
 189
 190                 if (!prop)
 191                         return -EINVAL;
 192
 193                 for (i = 0; i < count; i++) {
 194                         off = be32_to_cpu(((__be32 *)prop_fix->value)[i]);
 195                         if ((off + 4) > prop->length)
 196                                 return -EINVAL;
 197
 198                         phandle = be32_to_cpu(*(__be32 *)(prop->value + off));
 199                         phandle += phandle_delta;
 200                         *(__be32 *)(prop->value + off) = cpu_to_be32(phandle);
 201                 }
 202         }
 203
 204         /*
 205          * These nested loops recurse down two subtrees in parallel, where the
 206          * node names in the two subtrees match.
 207          *
 208          * The roots of the subtrees are the overlay's __local_fixups__ node
 209          * and the overlay's root node.
 210          */
 211         for_each_child_of_node(local_fixups, child) {
 212
 213                 for_each_child_of_node(overlay, overlay_child)
 214                         if (!node_name_cmp(child, overlay_child))
 215                                 break;
 216
 217                 if (!overlay_child)
 218                         return -EINVAL;
 219
 220                 err = adjust_local_phandle_references(child, overlay_child,
 221                                 phandle_delta);
 222                 if (err)
 223                         return err;
 224         }
 225
 226         return 0;
 227 }
 228
 229 /**
 230  * of_resolve_phandles - Relocate and resolve overlay against live tree
 231  *
 232  * @overlay:    Pointer to devicetree overlay to relocate and resolve
 233  *
 234  * Modify (relocate) values of local phandles in @overlay to a range that
 235  * does not conflict with the live expanded devicetree.  Update references
 236  * to the local phandles in @overlay.  Update (resolve) phandle references
 237  * in @overlay that refer to the live expanded devicetree.
 238  *
 239  * Phandle values in the live tree are in the range of
 240  * 1 .. live_tree_max_phandle().  The range of phandle values in the overlay
 241  * also begin with at 1.  Adjust the phandle values in the overlay to begin
 242  * at live_tree_max_phandle() + 1.  Update references to the phandles to
 243  * the adjusted phandle values.
 244  *
 245  * The name of each property in the "__fixups__" node in the overlay matches
 246  * the name of a symbol (a label) in the live tree.  The values of each
 247  * property in the "__fixups__" node is a list of the property values in the
 248  * overlay that need to be updated to contain the phandle reference
 249  * corresponding to that symbol in the live tree.  Update the references in
 250  * the overlay with the phandle values in the live tree.
 251  *
 252  * @overlay must be detached.
 253  *
 254  * Resolving and applying @overlay to the live expanded devicetree must be
 255  * protected by a mechanism to ensure that multiple overlays are processed
 256  * in a single threaded manner so that multiple overlays will not relocate
 257  * phandles to overlapping ranges.  The mechanism to enforce this is not
 258  * yet implemented.
 259  *
 260  * Return: %0 on success or a negative error value on error.
 261  */
 262 int of_resolve_phandles(struct device_node *overlay)
 263 {
 264         struct device_node *child, *local_fixups, *refnode;
 265         struct device_node *tree_symbols, *overlay_fixups;
 266         struct property *prop;
 267         const char *refpath;
 268         phandle phandle, phandle_delta;
 269         int err;
 270
 271         tree_symbols = NULL;
 272
 273         if (!overlay) {
 274                 pr_err("null overlay\n");
 275                 err = -EINVAL;
 276                 goto out;
 277         }
 278         if (!of_node_check_flag(overlay, OF_DETACHED)) {
 279                 pr_err("overlay not detached\n");
 280                 err = -EINVAL;
 281                 goto out;
 282         }
 283
 284         phandle_delta = live_tree_max_phandle() + 1;
 285         adjust_overlay_phandles(overlay, phandle_delta);
 286
 287         for_each_child_of_node(overlay, local_fixups)
 288                 if (!of_node_cmp(local_fixups->name, "__local_fixups__"))
 289                         break;
 290
 291         err = adjust_local_phandle_references(local_fixups, overlay, phandle_delta);
 292         if (err)
 293                 goto out;
 294
 295         overlay_fixups = NULL;
 296
 297         for_each_child_of_node(overlay, child) {
 298                 if (!of_node_cmp(child->name, "__fixups__"))
 299                         overlay_fixups = child;
 300         }
 301
 302         if (!overlay_fixups) {
 303                 err = 0;
 304                 goto out;
 305         }
 306
 307         tree_symbols = of_find_node_by_path("/__symbols__");
 308         if (!tree_symbols) {
 309                 pr_err("no symbols in root of device tree.\n");
 310                 err = -EINVAL;
 311                 goto out;
 312         }
 313
 314         for_each_property_of_node(overlay_fixups, prop) {
 315
 316                 /* skip properties added automatically */
 317                 if (!of_prop_cmp(prop->name, "name"))
 318                         continue;
 319
 320                 err = of_property_read_string(tree_symbols,
 321                                 prop->name, &refpath);
 322                 if (err)
 323                         goto out;
 324
 325                 refnode = of_find_node_by_path(refpath);
 326                 if (!refnode) {
 327                         err = -ENOENT;
 328                         goto out;
 329                 }
 330
 331                 phandle = refnode->phandle;
 332                 of_node_put(refnode);
 333
 334                 err = update_usages_of_a_phandle_reference(overlay, prop, phandle);
 335                 if (err)
 336                         break;
 337         }
 338
 339 out:
 340         if (err)
 341                 pr_err("overlay phandle fixup failed: %d\n", err);
 342         of_node_put(tree_symbols);
 343
 344         return err;
 345 }
 346 EXPORT_SYMBOL_GPL(of_resolve_phandles);