drivers/of/resolver.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Functions for dealing with DT resolution
   4  *
   5  * Copyright (C) 2012 Pantelis Antoniou <panto@antoniou-consulting.com>
   6  * Copyright (C) 2012 Texas Instruments Inc.
   7  */
   8
   9 #define pr_fmt(fmt)     "OF: resolver: " fmt
  10
  11 #include <linux/kernel.h>
  12 #include <linux/module.h>
  13 #include <linux/of.h>
  14 #include <linux/of_device.h>
  15 #include <linux/string.h>
  16 #include <linux/ctype.h>
  17 #include <linux/errno.h>
  18 #include <linux/slab.h>
  19
  20 #include "of_private.h"
  21
  22 static phandle live_tree_max_phandle(void)
  23 {
  24         struct device_node *node;
  25         phandle phandle;
  26         unsigned long flags;
  27
  28         raw_spin_lock_irqsave(&devtree_lock, flags);
  29         phandle = 0;
  30         for_each_of_allnodes(node) {
  31                 if (node->phandle != OF_PHANDLE_ILLEGAL &&
  32                                 node->phandle > phandle)
  33                         phandle = node->phandle;
  34         }
  35         raw_spin_unlock_irqrestore(&devtree_lock, flags);
  36
  37         return phandle;
  38 }
  39
  40 static void adjust_overlay_phandles(struct device_node *overlay,
  41                 int phandle_delta)
  42 {
  43         struct device_node *child;
  44         struct property *prop;
  45         phandle phandle;
  46
  47         /* adjust node's phandle in node */
  48         if (overlay->phandle != 0 && overlay->phandle != OF_PHANDLE_ILLEGAL)
  49                 overlay->phandle += phandle_delta;
  50
  51         /* copy adjusted phandle into *phandle properties */
  52         for_each_property_of_node(overlay, prop) {
  53
  54                 if (of_prop_cmp(prop->name, "phandle") &&
  55                     of_prop_cmp(prop->name, "linux,phandle"))
  56                         continue;
  57
  58                 if (prop->length < 4)
  59                         continue;
  60
  61                 phandle = be32_to_cpup(prop->value);
  62                 if (phandle == OF_PHANDLE_ILLEGAL)
  63                         continue;
  64
  65                 *(__be32 *)prop->value = cpu_to_be32(overlay->phandle);
  66         }
  67
  68         for_each_child_of_node(overlay, child)
  69                 adjust_overlay_phandles(child, phandle_delta);
  70 }
  71
  72 static int update_usages_of_a_phandle_reference(struct device_node *overlay,
  73                 struct property *prop_fixup, phandle phandle)
  74 {
  75         struct device_node *refnode;
  76         struct property *prop;
  77         char *value, *cur, *end, *node_path, *prop_name, *s;
  78         int offset, len;
  79         int err = 0;
  80
  81         value = kmemdup(prop_fixup->value, prop_fixup->length, GFP_KERNEL);
  82         if (!value)
  83                 return -ENOMEM;
  84
  85         /* prop_fixup contains a list of tuples of path:property_name:offset */
  86         end = value + prop_fixup->length;
  87         for (cur = value; cur < end; cur += len + 1) {
  88                 len = strlen(cur);
  89
  90                 node_path = cur;
  91                 s = strchr(cur, ':');
  92                 if (!s) {
  93                         err = -EINVAL;
  94                         goto err_fail;
  95                 }
  96                 *s++ = '\0';
  97
  98                 prop_name = s;
  99                 s = strchr(s, ':');
 100                 if (!s) {
 101                         err = -EINVAL;
 102                         goto err_fail;
 103                 }
 104                 *s++ = '\0';
 105
 106                 err = kstrtoint(s, 10, &offset);
 107                 if (err)
 108                         goto err_fail;
 109
 110                 refnode = __of_find_node_by_full_path(of_node_get(overlay), node_path);
 111                 if (!refnode)
 112                         continue;
 113
 114                 for_each_property_of_node(refnode, prop) {
 115                         if (!of_prop_cmp(prop->name, prop_name))
 116                                 break;
 117                 }
 118                 of_node_put(refnode);
 119
 120                 if (!prop) {
 121                         err = -ENOENT;
 122                         goto err_fail;
 123                 }
 124
 125                 if (offset < 0 || offset + sizeof(__be32) > prop->length) {
 126                         err = -EINVAL;
 127                         goto err_fail;
 128                 }
 129
 130                 *(__be32 *)(prop->value + offset) = cpu_to_be32(phandle);
 131         }
 132
 133 err_fail:
 134         kfree(value);
 135         return err;
 136 }
 137
 138 /* compare nodes taking into account that 'name' strips out the @ part */
 139 static int node_name_cmp(const struct device_node *dn1,
 140                 const struct device_node *dn2)
 141 {
 142         const char *n1 = kbasename(dn1->full_name);
 143         const char *n2 = kbasename(dn2->full_name);
 144
 145         return of_node_cmp(n1, n2);
 146 }
 147
 148 /*
 149  * Adjust the local phandle references by the given phandle delta.
 150  *
 151  * Subtree @local_fixups, which is overlay node __local_fixups__,
 152  * mirrors the fragment node structure at the root of the overlay.
 153  *
 154  * For each property in the fragments that contains a phandle reference,
 155  * @local_fixups has a property of the same name that contains a list
 156  * of offsets of the phandle reference(s) within the respective property
 157  * value(s).  The values at these offsets will be fixed up.
 158  */
 159 static int adjust_local_phandle_references(struct device_node *local_fixups,
 160                 struct device_node *overlay, int phandle_delta)
 161 {
 162         struct device_node *child, *overlay_child;
 163         struct property *prop_fix, *prop;
 164         int err, i, count;
 165         unsigned int off;
 166
 167         if (!local_fixups)
 168                 return 0;
 169
 170         for_each_property_of_node(local_fixups, prop_fix) {
 171
 172                 /* skip properties added automatically */
 173                 if (!of_prop_cmp(prop_fix->name, "name") ||
 174                     !of_prop_cmp(prop_fix->name, "phandle") ||
 175                     !of_prop_cmp(prop_fix->name, "linux,phandle"))
 176                         continue;
 177
 178                 if ((prop_fix->length % 4) != 0 || prop_fix->length == 0)
 179                         return -EINVAL;
 180                 count = prop_fix->length / sizeof(__be32);
 181
 182                 for_each_property_of_node(overlay, prop) {
 183                         if (!of_prop_cmp(prop->name, prop_fix->name))
 184                                 break;
 185                 }
 186
 187                 if (!prop)
 188                         return -EINVAL;
 189
 190                 for (i = 0; i < count; i++) {
 191                         off = be32_to_cpu(((__be32 *)prop_fix->value)[i]);
 192                         if ((off + 4) > prop->length)
 193                                 return -EINVAL;
 194
 195                         be32_add_cpu(prop->value + off, phandle_delta);
 196                 }
 197         }
 198
 199         /*
 200          * These nested loops recurse down two subtrees in parallel, where the
 201          * node names in the two subtrees match.
 202          *
 203          * The roots of the subtrees are the overlay's __local_fixups__ node
 204          * and the overlay's root node.
 205          */
 206         for_each_child_of_node(local_fixups, child) {
 207
 208                 for_each_child_of_node(overlay, overlay_child)
 209                         if (!node_name_cmp(child, overlay_child))
 210                                 break;
 211
 212                 if (!overlay_child)
 213                         return -EINVAL;
 214
 215                 err = adjust_local_phandle_references(child, overlay_child,
 216                                 phandle_delta);
 217                 if (err)
 218                         return err;
 219         }
 220
 221         return 0;
 222 }
 223
 224 /**
 225  * of_resolve_phandles - Relocate and resolve overlay against live tree
 226  *
 227  * @overlay:    Pointer to devicetree overlay to relocate and resolve
 228  *
 229  * Modify (relocate) values of local phandles in @overlay to a range that
 230  * does not conflict with the live expanded devicetree.  Update references
 231  * to the local phandles in @overlay.  Update (resolve) phandle references
 232  * in @overlay that refer to the live expanded devicetree.
 233  *
 234  * Phandle values in the live tree are in the range of
 235  * 1 .. live_tree_max_phandle().  The range of phandle values in the overlay
 236  * also begin with at 1.  Adjust the phandle values in the overlay to begin
 237  * at live_tree_max_phandle() + 1.  Update references to the phandles to
 238  * the adjusted phandle values.
 239  *
 240  * The name of each property in the "__fixups__" node in the overlay matches
 241  * the name of a symbol (a label) in the live tree.  The values of each
 242  * property in the "__fixups__" node is a list of the property values in the
 243  * overlay that need to be updated to contain the phandle reference
 244  * corresponding to that symbol in the live tree.  Update the references in
 245  * the overlay with the phandle values in the live tree.
 246  *
 247  * @overlay must be detached.
 248  *
 249  * Resolving and applying @overlay to the live expanded devicetree must be
 250  * protected by a mechanism to ensure that multiple overlays are processed
 251  * in a single threaded manner so that multiple overlays will not relocate
 252  * phandles to overlapping ranges.  The mechanism to enforce this is not
 253  * yet implemented.
 254  *
 255  * Return: %0 on success or a negative error value on error.
 256  */
 257 int of_resolve_phandles(struct device_node *overlay)
 258 {
 259         struct device_node *child, *local_fixups, *refnode;
 260         struct device_node *tree_symbols, *overlay_fixups;
 261         struct property *prop;
 262         const char *refpath;
 263         phandle phandle, phandle_delta;
 264         int err;
 265
 266         tree_symbols = NULL;
 267
 268         if (!overlay) {
 269                 pr_err("null overlay\n");
 270                 err = -EINVAL;
 271                 goto out;
 272         }
 273
 274         if (!of_node_check_flag(overlay, OF_DETACHED)) {
 275                 pr_err("overlay not detached\n");
 276                 err = -EINVAL;
 277                 goto out;
 278         }
 279
 280         phandle_delta = live_tree_max_phandle() + 1;
 281         adjust_overlay_phandles(overlay, phandle_delta);
 282
 283         for_each_child_of_node(overlay, local_fixups)
 284                 if (of_node_name_eq(local_fixups, "__local_fixups__"))
 285                         break;
 286
 287         err = adjust_local_phandle_references(local_fixups, overlay, phandle_delta);
 288         if (err)
 289                 goto out;
 290
 291         overlay_fixups = NULL;
 292
 293         for_each_child_of_node(overlay, child) {
 294                 if (of_node_name_eq(child, "__fixups__"))
 295                         overlay_fixups = child;
 296         }
 297
 298         if (!overlay_fixups) {
 299                 err = 0;
 300                 goto out;
 301         }
 302
 303         tree_symbols = of_find_node_by_path("/__symbols__");
 304         if (!tree_symbols) {
 305                 pr_err("no symbols in root of device tree.\n");
 306                 err = -EINVAL;
 307                 goto out;
 308         }
 309
 310         for_each_property_of_node(overlay_fixups, prop) {
 311
 312                 /* skip properties added automatically */
 313                 if (!of_prop_cmp(prop->name, "name"))
 314                         continue;
 315
 316                 err = of_property_read_string(tree_symbols,
 317                                 prop->name, &refpath);
 318                 if (err)
 319                         goto out;
 320
 321                 refnode = of_find_node_by_path(refpath);
 322                 if (!refnode) {
 323                         err = -ENOENT;
 324                         goto out;
 325                 }
 326
 327                 phandle = refnode->phandle;
 328                 of_node_put(refnode);
 329
 330                 err = update_usages_of_a_phandle_reference(overlay, prop, phandle);
 331                 if (err)
 332                         break;
 333         }
 334
 335 out:
 336         if (err)
 337                 pr_err("overlay phandle fixup failed: %d\n", err);
 338         of_node_put(tree_symbols);
 339
 340         return err;
 341 }
 342 EXPORT_SYMBOL_GPL(of_resolve_phandles);