common/cmd_fdt.c

   1 /*
   2  * (C) Copyright 2007
   3  * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com
   4  * Based on code written by:
   5  *   Pantelis Antoniou <pantelis.antoniou@gmail.com> and
   6  *   Matthew McClintock <msm@freescale.com>
   7  *
   8  * See file CREDITS for list of people who contributed to this
   9  * project.
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License as
  13  * published by the Free Software Foundation; either version 2 of
  14  * the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  24  * MA 02111-1307 USA
  25  */
  26
  27 #include <common.h>
  28 #include <command.h>
  29 #include <linux/ctype.h>
  30 #include <linux/types.h>
  31 #include <asm/global_data.h>
  32 #include <fdt.h>
  33 #include <libfdt.h>
  34 #include <fdt_support.h>
  35
  36 #define MAX_LEVEL       32              /* how deeply nested we will go */
  37 #define SCRATCHPAD      1024            /* bytes of scratchpad memory */
  38
  39 /*
  40  * Global data (for the gd->bd)
  41  */
  42 DECLARE_GLOBAL_DATA_PTR;
  43
  44 static int fdt_valid(void);
  45 static int fdt_parse_prop(char *pathp, char *prop, char *newval,
  46         char *data, int *len);
  47 static int fdt_print(const char *pathp, char *prop, int depth);
  48
  49 /*
  50  * Flattened Device Tree command, see the help for parameter definitions.
  51  */
  52 int do_fdt (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
  53 {
  54         if (argc < 2) {
  55                 printf ("Usage:\n%s\n", cmdtp->usage);
  56                 return 1;
  57         }
  58
  59         /********************************************************************
  60          * Set the address of the fdt
  61          ********************************************************************/
  62         if (argv[1][0] == 'a') {
  63                 /*
  64                  * Set the address [and length] of the fdt.
  65                  */
  66                 fdt = (struct fdt_header *)simple_strtoul(argv[2], NULL, 16);
  67
  68                 if (!fdt_valid()) {
  69                         return 1;
  70                 }
  71
  72                 if (argc >= 4) {
  73                         int  len;
  74                         int  err;
  75                         /*
  76                          * Optional new length
  77                          */
  78                         len =  simple_strtoul(argv[3], NULL, 16);
  79                         if (len < fdt_totalsize(fdt)) {
  80                                 printf ("New length %d < existing length %d, "
  81                                         "ignoring.\n",
  82                                         len, fdt_totalsize(fdt));
  83                         } else {
  84                                 /*
  85                                  * Open in place with a new length.
  86                                  */
  87                                 err = fdt_open_into(fdt, fdt, len);
  88                                 if (err != 0) {
  89                                         printf ("libfdt fdt_open_into(): %s\n",
  90                                                 fdt_strerror(err));
  91                                 }
  92                         }
  93                 }
  94
  95         /********************************************************************
  96          * Move the fdt
  97          ********************************************************************/
  98         } else if ((argv[1][0] == 'm') && (argv[1][1] == 'o')) {
  99                 struct fdt_header *newaddr;
 100                 int  len;
 101                 int  err;
 102
 103                 if (argc < 4) {
 104                         printf ("Usage:\n%s\n", cmdtp->usage);
 105                         return 1;
 106                 }
 107
 108                 /*
 109                  * Set the address and length of the fdt.
 110                  */
 111                 fdt = (struct fdt_header *)simple_strtoul(argv[2], NULL, 16);
 112                 if (!fdt_valid()) {
 113                         return 1;
 114                 }
 115
 116                 newaddr = (struct fdt_header *)simple_strtoul(argv[3],NULL,16);
 117
 118                 /*
 119                  * If the user specifies a length, use that.  Otherwise use the
 120                  * current length.
 121                  */
 122                 if (argc <= 4) {
 123                         len = fdt_totalsize(fdt);
 124                 } else {
 125                         len = simple_strtoul(argv[4], NULL, 16);
 126                         if (len < fdt_totalsize(fdt)) {
 127                                 printf ("New length 0x%X < existing length "
 128                                         "0x%X, aborting.\n",
 129                                         len, fdt_totalsize(fdt));
 130                                 return 1;
 131                         }
 132                 }
 133
 134                 /*
 135                  * Copy to the new location.
 136                  */
 137                 err = fdt_open_into(fdt, newaddr, len);
 138                 if (err != 0) {
 139                         printf ("libfdt fdt_open_into(): %s\n",
 140                                 fdt_strerror(err));
 141                         return 1;
 142                 }
 143                 fdt = newaddr;
 144
 145         /********************************************************************
 146          * Make a new node
 147          ********************************************************************/
 148         } else if ((argv[1][0] == 'm') && (argv[1][1] == 'k')) {
 149                 char *pathp;            /* path */
 150                 char *nodep;            /* new node to add */
 151                 int  nodeoffset;        /* node offset from libfdt */
 152                 int  err;
 153
 154                 /*
 155                  * Parameters: Node path, new node to be appended to the path.
 156                  */
 157                 if (argc < 4) {
 158                         printf ("Usage:\n%s\n", cmdtp->usage);
 159                         return 1;
 160                 }
 161
 162                 pathp = argv[2];
 163                 nodep = argv[3];
 164
 165                 nodeoffset = fdt_path_offset (fdt, pathp);
 166                 if (nodeoffset < 0) {
 167                         /*
 168                          * Not found or something else bad happened.
 169                          */
 170                         printf ("libfdt fdt_path_offset() returned %s\n",
 171                                 fdt_strerror(nodeoffset));
 172                         return 1;
 173                 }
 174                 err = fdt_add_subnode(fdt, nodeoffset, nodep);
 175                 if (err < 0) {
 176                         printf ("libfdt fdt_add_subnode(): %s\n",
 177                                 fdt_strerror(err));
 178                         return 1;
 179                 }
 180
 181         /********************************************************************
 182          * Set the value of a property in the fdt.
 183          ********************************************************************/
 184         } else if (argv[1][0] == 's') {
 185                 char *pathp;            /* path */
 186                 char *prop;             /* property */
 187                 char *newval;           /* value from the user (as a string) */
 188                 int  nodeoffset;        /* node offset from libfdt */
 189                 static char data[SCRATCHPAD];   /* storage for the property */
 190                 int  len;               /* new length of the property */
 191                 int  ret;               /* return value */
 192
 193                 /*
 194                  * Parameters: Node path, property, value.
 195                  */
 196                 if (argc < 5) {
 197                         printf ("Usage:\n%s\n", cmdtp->usage);
 198                         return 1;
 199                 }
 200
 201                 pathp  = argv[2];
 202                 prop   = argv[3];
 203                 newval = argv[4];
 204
 205                 nodeoffset = fdt_path_offset (fdt, pathp);
 206                 if (nodeoffset < 0) {
 207                         /*
 208                          * Not found or something else bad happened.
 209                          */
 210                         printf ("libfdt fdt_path_offset() returned %s\n",
 211                                 fdt_strerror(nodeoffset));
 212                         return 1;
 213                 }
 214                 ret = fdt_parse_prop(pathp, prop, newval, data, &len);
 215                 if (ret != 0)
 216                         return ret;
 217
 218                 ret = fdt_setprop(fdt, nodeoffset, prop, data, len);
 219                 if (ret < 0) {
 220                         printf ("libfdt fdt_setprop(): %s\n", fdt_strerror(ret));
 221                         return 1;
 222                 }
 223
 224         /********************************************************************
 225          * Print (recursive) / List (single level)
 226          ********************************************************************/
 227         } else if ((argv[1][0] == 'p') || (argv[1][0] == 'l')) {
 228                 int depth = MAX_LEVEL;  /* how deep to print */
 229                 char *pathp;            /* path */
 230                 char *prop;             /* property */
 231                 int  ret;               /* return value */
 232                 static char root[2] = "/";
 233
 234                 /*
 235                  * list is an alias for print, but limited to 1 level
 236                  */
 237                 if (argv[1][0] == 'l') {
 238                         depth = 1;
 239                 }
 240
 241                 /*
 242                  * Get the starting path.  The root node is an oddball,
 243                  * the offset is zero and has no name.
 244                  */
 245                 if (argc == 2)
 246                         pathp = root;
 247                 else
 248                         pathp = argv[2];
 249                 if (argc > 3)
 250                         prop = argv[3];
 251                 else
 252                         prop = NULL;
 253
 254                 ret = fdt_print(pathp, prop, depth);
 255                 if (ret != 0)
 256                         return ret;
 257
 258         /********************************************************************
 259          * Remove a property/node
 260          ********************************************************************/
 261         } else if (argv[1][0] == 'r') {
 262                 int  nodeoffset;        /* node offset from libfdt */
 263                 int  err;
 264
 265                 /*
 266                  * Get the path.  The root node is an oddball, the offset
 267                  * is zero and has no name.
 268                  */
 269                 nodeoffset = fdt_path_offset (fdt, argv[2]);
 270                 if (nodeoffset < 0) {
 271                         /*
 272                          * Not found or something else bad happened.
 273                          */
 274                         printf ("libfdt fdt_path_offset() returned %s\n",
 275                                 fdt_strerror(nodeoffset));
 276                         return 1;
 277                 }
 278                 /*
 279                  * Do the delete.  A fourth parameter means delete a property,
 280                  * otherwise delete the node.
 281                  */
 282                 if (argc > 3) {
 283                         err = fdt_delprop(fdt, nodeoffset, argv[3]);
 284                         if (err < 0) {
 285                                 printf("libfdt fdt_delprop():  %s\n",
 286                                         fdt_strerror(err));
 287                                 return err;
 288                         }
 289                 } else {
 290                         err = fdt_del_node(fdt, nodeoffset);
 291                         if (err < 0) {
 292                                 printf("libfdt fdt_del_node():  %s\n",
 293                                         fdt_strerror(err));
 294                                 return err;
 295                         }
 296                 }
 297         }
 298 #ifdef CONFIG_OF_BOARD_SETUP
 299         /* Call the board-specific fixup routine */
 300         else if (argv[1][0] == 'b')
 301                 ft_board_setup(fdt, gd->bd);
 302 #endif
 303         /* Create a chosen node */
 304         else if (argv[1][0] == 'c')
 305                 fdt_chosen(fdt, 0, 0, 1);
 306
 307 #ifdef CONFIG_OF_HAS_UBOOT_ENV
 308         /* Create a u-boot-env node */
 309         else if (argv[1][0] == 'e')
 310                 fdt_env(fdt);
 311 #endif
 312 #ifdef CONFIG_OF_HAS_BD_T
 313         /* Create a bd_t node */
 314         else if (argv[1][0] == 'b')
 315                 fdt_bd_t(fdt);
 316 #endif
 317         else {
 318                 /* Unrecognized command */
 319                 printf ("Usage:\n%s\n", cmdtp->usage);
 320                 return 1;
 321         }
 322
 323         return 0;
 324 }
 325
 326 /****************************************************************************/
 327
 328 static int fdt_valid(void)
 329 {
 330         int  err;
 331
 332         if (fdt == NULL) {
 333                 printf ("The address of the fdt is invalid (NULL).\n");
 334                 return 0;
 335         }
 336
 337         err = fdt_check_header(fdt);
 338         if (err == 0)
 339                 return 1;       /* valid */
 340
 341         if (err < 0) {
 342                 printf("libfdt fdt_check_header(): %s", fdt_strerror(err));
 343                 /*
 344                  * Be more informative on bad version.
 345                  */
 346                 if (err == -FDT_ERR_BADVERSION) {
 347                         if (fdt_version(fdt) < FDT_FIRST_SUPPORTED_VERSION) {
 348                                 printf (" - too old, fdt $d < %d",
 349                                         fdt_version(fdt),
 350                                         FDT_FIRST_SUPPORTED_VERSION);
 351                                 fdt = NULL;
 352                         }
 353                         if (fdt_last_comp_version(fdt) > FDT_LAST_SUPPORTED_VERSION) {
 354                                 printf (" - too new, fdt $d > %d",
 355                                         fdt_version(fdt),
 356                                         FDT_LAST_SUPPORTED_VERSION);
 357                                 fdt = NULL;
 358                         }
 359                         return 0;
 360                 }
 361                 printf("\n");
 362                 return 0;
 363         }
 364         return 1;
 365 }
 366
 367 /****************************************************************************/
 368
 369 /*
 370  * Parse the user's input, partially heuristic.  Valid formats:
 371  * <00>         - hex byte
 372  * <0011>       - hex half word (16 bits)
 373  * <00112233>   - hex word (32 bits)
 374  *              - hex double words (64 bits) are not supported, must use
 375  *                      a byte stream instead.
 376  * [00 11 22 .. nn] - byte stream
 377  * "string"     - If the the value doesn't start with "<" or "[", it is
 378  *                      treated as a string.  Note that the quotes are
 379  *                      stripped by the parser before we get the string.
 380  */
 381 static int fdt_parse_prop(char *pathp, char *prop, char *newval,
 382         char *data, int *len)
 383 {
 384         char *cp;               /* temporary char pointer */
 385         unsigned long tmp;      /* holds converted values */
 386
 387         if (*newval == '<') {
 388                 /*
 389                  * Bigger values than bytes.
 390                  */
 391                 *len = 0;
 392                 newval++;
 393                 while ((*newval != '>') && (*newval != '\0')) {
 394                         cp = newval;
 395                         tmp = simple_strtoul(cp, &newval, 16);
 396                         if ((newval - cp) <= 2) {
 397                                 *data = tmp & 0xFF;
 398                                 data  += 1;
 399                                 *len += 1;
 400                         } else if ((newval - cp) <= 4) {
 401                                 *(uint16_t *)data = __cpu_to_be16(tmp);
 402                                 data  += 2;
 403                                 *len += 2;
 404                         } else if ((newval - cp) <= 8) {
 405                                 *(uint32_t *)data = __cpu_to_be32(tmp);
 406                                 data  += 4;
 407                                 *len += 4;
 408                         } else {
 409                                 printf("Sorry, I could not convert \"%s\"\n",
 410                                         cp);
 411                                 return 1;
 412                         }
 413                         while (*newval == ' ')
 414                                 newval++;
 415                 }
 416                 if (*newval != '>') {
 417                         printf("Unexpected character '%c'\n", *newval);
 418                         return 1;
 419                 }
 420         } else if (*newval == '[') {
 421                 /*
 422                  * Byte stream.  Convert the values.
 423                  */
 424                 *len = 0;
 425                 newval++;
 426                 while ((*newval != ']') && (*newval != '\0')) {
 427                         tmp = simple_strtoul(newval, &newval, 16);
 428                         *data++ = tmp & 0xFF;
 429                         *len    = *len + 1;
 430                         while (*newval == ' ')
 431                                 newval++;
 432                 }
 433                 if (*newval != ']') {
 434                         printf("Unexpected character '%c'\n", *newval);
 435                         return 1;
 436                 }
 437         } else {
 438                 /*
 439                  * Assume it is a string.  Copy it into our data area for
 440                  * convenience (including the terminating '\0').
 441                  */
 442                 *len = strlen(newval) + 1;
 443                 strcpy(data, newval);
 444         }
 445         return 0;
 446 }
 447
 448 /****************************************************************************/
 449
 450 /*
 451  * Heuristic to guess if this is a string or concatenated strings.
 452  */
 453
 454 static int is_printable_string(const void *data, int len)
 455 {
 456         const char *s = data;
 457
 458         /* zero length is not */
 459         if (len == 0)
 460                 return 0;
 461
 462         /* must terminate with zero */
 463         if (s[len - 1] != '\0')
 464                 return 0;
 465
 466         /* printable or a null byte (concatenated strings) */
 467         while (((*s == '\0') || isprint(*s)) && (len > 0)) {
 468                 /*
 469                  * If we see a null, there are three possibilities:
 470                  * 1) If len == 1, it is the end of the string, printable
 471                  * 2) Next character also a null, not printable.
 472                  * 3) Next character not a null, continue to check.
 473                  */
 474                 if (s[0] == '\0') {
 475                         if (len == 1)
 476                                 return 1;
 477                         if (s[1] == '\0')
 478                                 return 0;
 479                 }
 480                 s++;
 481                 len--;
 482         }
 483
 484         /* Not the null termination, or not done yet: not printable */
 485         if (*s != '\0' || (len != 0))
 486                 return 0;
 487
 488         return 1;
 489 }
 490
 491
 492 /*
 493  * Print the property in the best format, a heuristic guess.  Print as
 494  * a string, concatenated strings, a byte, word, double word, or (if all
 495  * else fails) it is printed as a stream of bytes.
 496  */
 497 static void print_data(const void *data, int len)
 498 {
 499         int j;
 500         const u8 *s;
 501
 502         /* no data, don't print */
 503         if (len == 0)
 504                 return;
 505
 506         /*
 507          * It is a string, but it may have multiple strings (embedded '\0's).
 508          */
 509         if (is_printable_string(data, len)) {
 510                 puts("\"");
 511                 j = 0;
 512                 while (j < len) {
 513                         if (j > 0)
 514                                 puts("\", \"");
 515                         puts(data);
 516                         j    += strlen(data) + 1;
 517                         data += strlen(data) + 1;
 518                 }
 519                 puts("\"");
 520                 return;
 521         }
 522
 523         switch (len) {
 524         case 1:  /* byte */
 525                 printf("<%02x>", (*(u8 *) data) & 0xff);
 526                 break;
 527         case 2:  /* half-word */
 528                 printf("<%04x>", be16_to_cpu(*(u16 *) data) & 0xffff);
 529                 break;
 530         case 4:  /* word */
 531                 printf("<%08x>", be32_to_cpu(*(u32 *) data) & 0xffffffffU);
 532                 break;
 533         case 8:  /* double-word */
 534 #if __WORDSIZE == 64
 535                 printf("<%016llx>", be64_to_cpu(*(uint64_t *) data));
 536 #else
 537                 printf("<%08x ", be32_to_cpu(*(u32 *) data) & 0xffffffffU);
 538                 data += 4;
 539                 printf("%08x>", be32_to_cpu(*(u32 *) data) & 0xffffffffU);
 540 #endif
 541                 break;
 542         default:                /* anything else... hexdump */
 543                 printf("[");
 544                 for (j = 0, s = data; j < len; j++)
 545                         printf("%02x%s", s[j], j < len - 1 ? " " : "");
 546                 printf("]");
 547
 548                 break;
 549         }
 550 }
 551
 552 /****************************************************************************/
 553
 554 /*
 555  * Recursively print (a portion of) the fdt.  The depth parameter
 556  * determines how deeply nested the fdt is printed.
 557  */
 558 static int fdt_print(const char *pathp, char *prop, int depth)
 559 {
 560         static int offstack[MAX_LEVEL];
 561         static char tabs[MAX_LEVEL+1] =
 562                 "\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t"
 563                 "\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t";
 564         const void *nodep;      /* property node pointer */
 565         int  nodeoffset;        /* node offset from libfdt */
 566         int  nextoffset;        /* next node offset from libfdt */
 567         uint32_t tag;           /* tag */
 568         int  len;               /* length of the property */
 569         int  level = 0;         /* keep track of nesting level */
 570         const struct fdt_property *prop1;
 571
 572         nodeoffset = fdt_path_offset (fdt, pathp);
 573         if (nodeoffset < 0) {
 574                 /*
 575                  * Not found or something else bad happened.
 576                  */
 577                 printf ("libfdt fdt_path_offset() returned %s\n",
 578                         fdt_strerror(nodeoffset));
 579                 return 1;
 580         }
 581         /*
 582          * The user passed in a property as well as node path.
 583          * Print only the given property and then return.
 584          */
 585         if (prop) {
 586                 nodep = fdt_getprop (fdt, nodeoffset, prop, &len);
 587                 if (len == 0) {
 588                         /* no property value */
 589                         printf("%s %s\n", pathp, prop);
 590                         return 0;
 591                 } else if (len > 0) {
 592                         printf("%s=", prop);
 593                         print_data (nodep, len);
 594                         printf("\n");
 595                         return 0;
 596                 } else {
 597                         printf ("libfdt fdt_getprop(): %s\n",
 598                                 fdt_strerror(len));
 599                         return 1;
 600                 }
 601         }
 602
 603         /*
 604          * The user passed in a node path and no property,
 605          * print the node and all subnodes.
 606          */
 607         offstack[0] = nodeoffset;
 608
 609         while(level >= 0) {
 610                 tag = fdt_next_tag(fdt, nodeoffset, &nextoffset);
 611                 switch(tag) {
 612                 case FDT_BEGIN_NODE:
 613                         pathp = fdt_offset_ptr(fdt, nodeoffset, 1);
 614                         if(level <= depth)
 615                                 printf("%s%s {\n",
 616                                         &tabs[MAX_LEVEL - level], pathp);
 617                         level++;
 618                         offstack[level] = nodeoffset;
 619                         if (level >= MAX_LEVEL) {
 620                                 printf("Aaaiii <splat> nested too deep. "
 621                                         "Aborting.\n");
 622                                 return 1;
 623                         }
 624                         break;
 625                 case FDT_END_NODE:
 626                         level--;
 627                         if(level <= depth)
 628                                 printf("%s};\n", &tabs[MAX_LEVEL - level]);
 629                         if (level == 0) {
 630                                 level = -1;             /* exit the loop */
 631                         }
 632                         break;
 633                 case FDT_PROP:
 634                         prop1 = fdt_offset_ptr(fdt, nodeoffset, sizeof(*prop1));
 635                         pathp = fdt_string(fdt, fdt32_to_cpu(prop1->nameoff));
 636                         nodep = fdt_getprop (fdt, offstack[level], pathp, &len);
 637                         if (len < 0) {
 638                                 printf ("libfdt fdt_getprop(): %s\n",
 639                                         fdt_strerror(len));
 640                                 return 1;
 641                         } else if (len == 0) {
 642                                 /* the property has no value */
 643                                 if(level <= depth)
 644                                         printf("%s%s;\n",
 645                                                 &tabs[MAX_LEVEL - level],
 646                                                 pathp);
 647                         } else {
 648                                 if(level <= depth) {
 649                                         printf("%s%s=",
 650                                                 &tabs[MAX_LEVEL - level],
 651                                                 pathp);
 652                                         print_data (nodep, len);
 653                                         printf(";\n");
 654                                 }
 655                         }
 656                         break;
 657                 case FDT_NOP:
 658                         break;
 659                 case FDT_END:
 660                         return 1;
 661                 default:
 662                         if(level <= depth)
 663                                 printf("Unknown tag 0x%08X\n", tag);
 664                         return 1;
 665                 }
 666                 nodeoffset = nextoffset;
 667         }
 668         return 0;
 669 }
 670
 671 /********************************************************************/
 672
 673 U_BOOT_CMD(
 674         fdt,    5,      0,      do_fdt,
 675         "fdt     - flattened device tree utility commands\n",
 676             "addr   <addr> [<length>]        - Set the fdt location to <addr>\n"
 677 #ifdef CONFIG_OF_BOARD_SETUP
 678         "fdt boardsetup                      - Do board-specific set up\n"
 679 #endif
 680         "fdt move   <fdt> <newaddr> <length> - Copy the fdt to <addr>\n"
 681         "fdt print  <path> [<prop>]          - Recursive print starting at <path>\n"
 682         "fdt list   <path> [<prop>]          - Print one level starting at <path>\n"
 683         "fdt set    <path> <prop> [<val>]    - Set <property> [to <val>]\n"
 684         "fdt mknode <path> <node>            - Create a new node after <path>\n"
 685         "fdt rm     <path> [<prop>]          - Delete the node or <property>\n"
 686         "fdt chosen - Add/update the /chosen branch in the tree\n"
 687 #ifdef CONFIG_OF_HAS_UBOOT_ENV
 688         "fdt env    - Add/replace the /u-boot-env branch in the tree\n"
 689 #endif
 690 #ifdef CONFIG_OF_HAS_BD_T
 691         "fdt bd_t   - Add/replace the /bd_t branch in the tree\n"
 692 #endif
 693         "Hints:\n"
 694         " If the property you are setting/printing has a '#' character or spaces,\n"
 695         "     you MUST escape it with a \\ character or quote it with \".\n"
 696         "Examples: fdt print /               # print the whole tree\n"
 697         "          fdt print /cpus \"#address-cells\"\n"
 698         "          fdt set   /cpus \"#address-cells\" \"[00 00 00 01]\"\n"
 699 );