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