linux_kernel/scripts/dtc/libfdt/fdt_ro.c

/*
 * libfdt - Flat Device Tree manipulation
 * Copyright (C) 2006 David Gibson, IBM Corporation.
 *
 * libfdt is dual licensed: you can use it either under the terms of
 * the GPL, or the BSD license, at your option.
 *
 *  a) This library is free software; you can redistribute it and/or
 *     modify it under the terms of the GNU General Public License as
 *     published by the Free Software Foundation; either version 2 of the
 *     License, or (at your option) any later version.
 *
 *     This library is distributed in the hope that it will be useful,
 *     but WITHOUT ANY WARRANTY; without even the implied warranty of
 *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *     GNU General Public License for more details.
 *
 *     You should have received a copy of the GNU General Public
 *     License along with this library; if not, write to the Free
 *     Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
 *     MA 02110-1301 USA
 *
 * Alternatively,
 *
 *  b) Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *     1. Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *     2. Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 *     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 *     CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 *     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 *     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 *     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 *     CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 *     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 *     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 *     HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *     CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 *     OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 *     EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include "libfdt_env.h"

#include <fdt.h>
#include <libfdt.h>

#include "libfdt_internal.h"

static int fdt_nodename_eq_(const void *fdt, int offset,
			    const char *s, int len)
{
	int olen;
	const char *p = fdt_get_name(fdt, offset, &olen);

	if (!p || olen < len)
		/* short match */
		return 0;

	if (memcmp(p, s, len) != 0)
		return 0;

	if (p[len] == '\0')
		return 1;
	else if (!memchr(s, '@', len) && (p[len] == '@'))
		return 1;
	else
		return 0;
}

const char *fdt_get_string(const void *fdt, int stroffset, int *lenp)
{
	uint32_t absoffset = stroffset + fdt_off_dt_strings(fdt);
	size_t len;
	int err;
	const char *s, *n;

	err = fdt_ro_probe_(fdt);
	if (err != 0)
		goto fail;

	err = -FDT_ERR_BADOFFSET;
	if (absoffset >= fdt_totalsize(fdt))
		goto fail;
	len = fdt_totalsize(fdt) - absoffset;

	if (fdt_magic(fdt) == FDT_MAGIC) {
		if (stroffset < 0)
			goto fail;
		if (fdt_version(fdt) >= 17) {
			if (stroffset >= fdt_size_dt_strings(fdt))
				goto fail;
			if ((fdt_size_dt_strings(fdt) - stroffset) < len)
				len = fdt_size_dt_strings(fdt) - stroffset;
		}
	} else if (fdt_magic(fdt) == FDT_SW_MAGIC) {
		if ((stroffset >= 0)
		    || (stroffset < -fdt_size_dt_strings(fdt)))
			goto fail;
		if ((-stroffset) < len)
			len = -stroffset;
	} else {
		err = -FDT_ERR_INTERNAL;
		goto fail;
	}

	s = (const char *)fdt + absoffset;
	n = memchr(s, '\0', len);
	if (!n) {
		/* missing terminating NULL */
		err = -FDT_ERR_TRUNCATED;
		goto fail;
	}

	if (lenp)
		*lenp = n - s;
	return s;

fail:
	if (lenp)
		*lenp = err;
	return NULL;
}

const char *fdt_string(const void *fdt, int stroffset)
{
	return fdt_get_string(fdt, stroffset, NULL);
}

static int fdt_string_eq_(const void *fdt, int stroffset,
			  const char *s, int len)
{
	int slen;
	const char *p = fdt_get_string(fdt, stroffset, &slen);

	return p && (slen == len) && (memcmp(p, s, len) == 0);
}

uint32_t fdt_get_max_phandle(const void *fdt)
{
	uint32_t max_phandle = 0;
	int offset;

	for (offset = fdt_next_node(fdt, -1, NULL);;
	     offset = fdt_next_node(fdt, offset, NULL)) {
		uint32_t phandle;

		if (offset == -FDT_ERR_NOTFOUND)
			return max_phandle;

		if (offset < 0)
			return (uint32_t)-1;

		phandle = fdt_get_phandle(fdt, offset);
		if (phandle == (uint32_t)-1)
			continue;

		if (phandle > max_phandle)
			max_phandle = phandle;
	}

	return 0;
}

static const struct fdt_reserve_entry *fdt_mem_rsv(const void *fdt, int n)
{
	int offset = n * sizeof(struct fdt_reserve_entry);
	int absoffset = fdt_off_mem_rsvmap(fdt) + offset;

	if (absoffset < fdt_off_mem_rsvmap(fdt))
		return NULL;
	if (absoffset > fdt_totalsize(fdt) - sizeof(struct fdt_reserve_entry))
		return NULL;
	return fdt_mem_rsv_(fdt, n);
}

int fdt_get_mem_rsv(const void *fdt, int n, uint64_t *address, uint64_t *size)
{
	const struct fdt_reserve_entry *re;

	FDT_RO_PROBE(fdt);
	re = fdt_mem_rsv(fdt, n);
	if (!re)
		return -FDT_ERR_BADOFFSET;

	*address = fdt64_ld(&re->address);
	*size = fdt64_ld(&re->size);
	return 0;
}

int fdt_num_mem_rsv(const void *fdt)
{
	int i;
	const struct fdt_reserve_entry *re;

	for (i = 0; (re = fdt_mem_rsv(fdt, i)) != NULL; i++) {
		if (fdt64_ld(&re->size) == 0)
			return i;
	}
	return -FDT_ERR_TRUNCATED;
}

static int nextprop_(const void *fdt, int offset)
{
	uint32_t tag;
	int nextoffset;

	do {
		tag = fdt_next_tag(fdt, offset, &nextoffset);

		switch (tag) {
		case FDT_END:
			if (nextoffset >= 0)
				return -FDT_ERR_BADSTRUCTURE;
			else
				return nextoffset;

		case FDT_PROP:
			return offset;
		}
		offset = nextoffset;
	} while (tag == FDT_NOP);

	return -FDT_ERR_NOTFOUND;
}

int fdt_subnode_offset_namelen(const void *fdt, int offset,
			       const char *name, int namelen)
{
	int depth;

	FDT_RO_PROBE(fdt);

	for (depth = 0;
	     (offset >= 0) && (depth >= 0);
	     offset = fdt_next_node(fdt, offset, &depth))
		if ((depth == 1)
		    && fdt_nodename_eq_(fdt, offset, name, namelen))
			return offset;

	if (depth < 0)
		return -FDT_ERR_NOTFOUND;
	return offset; /* error */
}

int fdt_subnode_offset(const void *fdt, int parentoffset,
		       const char *name)
{
	return fdt_subnode_offset_namelen(fdt, parentoffset, name, strlen(name));
}

int fdt_path_offset_namelen(const void *fdt, const char *path, int namelen)
{
	const char *end = path + namelen;
	const char *p = path;
	int offset = 0;

	FDT_RO_PROBE(fdt);

	/* see if we have an alias */
	if (*path != '/') {
		const char *q = memchr(path, '/', end - p);

		if (!q)
			q = end;

		p = fdt_get_alias_namelen(fdt, p, q - p);
		if (!p)
			return -FDT_ERR_BADPATH;
		offset = fdt_path_offset(fdt, p);

		p = q;
	}

	while (p < end) {
		const char *q;

		while (*p == '/') {
			p++;
			if (p == end)
				return offset;
		}
		q = memchr(p, '/', end - p);
		if (! q)
			q = end;

		offset = fdt_subnode_offset_namelen(fdt, offset, p, q-p);
		if (offset < 0)
			return offset;

		p = q;
	}

	return offset;
}

int fdt_path_offset(const void *fdt, const char *path)
{
	return fdt_path_offset_namelen(fdt, path, strlen(path));
}

const char *fdt_get_name(const void *fdt, int nodeoffset, int *len)
{
	const struct fdt_node_header *nh = fdt_offset_ptr_(fdt, nodeoffset);
	const char *nameptr;
	int err;

	if (((err = fdt_ro_probe_(fdt)) != 0)
	    || ((err = fdt_check_node_offset_(fdt, nodeoffset)) < 0))
			goto fail;

	nameptr = nh->name;

	if (fdt_version(fdt) < 0x10) {
		/*
		 * For old FDT versions, match the naming conventions of V16:
		 * give only the leaf name (after all /). The actual tree
		 * contents are loosely checked.
		 */
		const char *leaf;
		leaf = strrchr(nameptr, '/');
		if (leaf == NULL) {
			err = -FDT_ERR_BADSTRUCTURE;
			goto fail;
		}
		nameptr = leaf+1;
	}

	if (len)
		*len = strlen(nameptr);

	return nameptr;

 fail:
	if (len)
		*len = err;
	return NULL;
}

int fdt_first_property_offset(const void *fdt, int nodeoffset)
{
	int offset;

	if ((offset = fdt_check_node_offset_(fdt, nodeoffset)) < 0)
		return offset;

	return nextprop_(fdt, offset);
}

int fdt_next_property_offset(const void *fdt, int offset)
{
	if ((offset = fdt_check_prop_offset_(fdt, offset)) < 0)
		return offset;

	return nextprop_(fdt, offset);
}

static const struct fdt_property *fdt_get_property_by_offset_(const void *fdt,
						              int offset,
						              int *lenp)
{
	int err;
	const struct fdt_property *prop;

	if ((err = fdt_check_prop_offset_(fdt, offset)) < 0) {
		if (lenp)
			*lenp = err;
		return NULL;
	}

	prop = fdt_offset_ptr_(fdt, offset);

	if (lenp)
		*lenp = fdt32_ld(&prop->len);

	return prop;
}

const struct fdt_property *fdt_get_property_by_offset(const void *fdt,
						      int offset,
						      int *lenp)
{
	/* Prior to version 16, properties may need realignment
	 * and this API does not work. fdt_getprop_*() will, however. */

	if (fdt_version(fdt) < 0x10) {
		if (lenp)
			*lenp = -FDT_ERR_BADVERSION;
		return NULL;
	}

	return fdt_get_property_by_offset_(fdt, offset, lenp);
}

static const struct fdt_property *fdt_get_property_namelen_(const void *fdt,
						            int offset,
						            const char *name,
						            int namelen,
							    int *lenp,
							    int *poffset)
{
	for (offset = fdt_first_property_offset(fdt, offset);
	     (offset >= 0);
	     (offset = fdt_next_property_offset(fdt, offset))) {
		const struct fdt_property *prop;

		if (!(prop = fdt_get_property_by_offset_(fdt, offset, lenp))) {
			offset = -FDT_ERR_INTERNAL;
			break;
		}
		if (fdt_string_eq_(fdt, fdt32_ld(&prop->nameoff),
				   name, namelen)) {
			if (poffset)
				*poffset = offset;
			return prop;
		}
	}

	if (lenp)
		*lenp = offset;
	return NULL;
}


const struct fdt_property *fdt_get_property_namelen(const void *fdt,
						    int offset,
						    const char *name,
						    int namelen, int *lenp)
{
	/* Prior to version 16, properties may need realignment
	 * and this API does not work. fdt_getprop_*() will, however. */
	if (fdt_version(fdt) < 0x10) {
		if (lenp)
			*lenp = -FDT_ERR_BADVERSION;
		return NULL;
	}

	return fdt_get_property_namelen_(fdt, offset, name, namelen, lenp,
					 NULL);
}


const struct fdt_property *fdt_get_property(const void *fdt,
					    int nodeoffset,
					    const char *name, int *lenp)
{
	return fdt_get_property_namelen(fdt, nodeoffset, name,
					strlen(name), lenp);
}

const void *fdt_getprop_namelen(const void *fdt, int nodeoffset,
				const char *name, int namelen, int *lenp)
{
	int poffset;
	const struct fdt_property *prop;

	prop = fdt_get_property_namelen_(fdt, nodeoffset, name, namelen, lenp,
					 &poffset);
	if (!prop)
		return NULL;

	/* Handle realignment */
	if (fdt_version(fdt) < 0x10 && (poffset + sizeof(*prop)) % 8 &&
	    fdt32_ld(&prop->len) >= 8)
		return prop->data + 4;
	return prop->data;
}

const void *fdt_getprop_by_offset(const void *fdt, int offset,
				  const char **namep, int *lenp)
{
	const struct fdt_property *prop;

	prop = fdt_get_property_by_offset_(fdt, offset, lenp);
	if (!prop)
		return NULL;
	if (namep) {
		const char *name;
		int namelen;
		name = fdt_get_string(fdt, fdt32_ld(&prop->nameoff),
				      &namelen);
		if (!name) {
			if (lenp)
				*lenp = namelen;
			return NULL;
		}
		*namep = name;
	}

	/* Handle realignment */
	if (fdt_version(fdt) < 0x10 && (offset + sizeof(*prop)) % 8 &&
	    fdt32_ld(&prop->len) >= 8)
		return prop->data + 4;
	return prop->data;
}

const void *fdt_getprop(const void *fdt, int nodeoffset,
			const char *name, int *lenp)
{
	return fdt_getprop_namelen(fdt, nodeoffset, name, strlen(name), lenp);
}

uint32_t fdt_get_phandle(const void *fdt, int nodeoffset)
{
	const fdt32_t *php;
	int len;

	/* FIXME: This is a bit sub-optimal, since we potentially scan
	 * over all the properties twice. */
	php = fdt_getprop(fdt, nodeoffset, "phandle", &len);
	if (!php || (len != sizeof(*php))) {
		php = fdt_getprop(fdt, nodeoffset, "linux,phandle", &len);
		if (!php || (len != sizeof(*php)))
			return 0;
	}

	return fdt32_ld(php);
}

const char *fdt_get_alias_namelen(const void *fdt,
				  const char *name, int namelen)
{
	int aliasoffset;

	aliasoffset = fdt_path_offset(fdt, "/aliases");
	if (aliasoffset < 0)
		return NULL;

	return fdt_getprop_namelen(fdt, aliasoffset, name, namelen, NULL);
}

const char *fdt_get_alias(const void *fdt, const char *name)
{
	return fdt_get_alias_namelen(fdt, name, strlen(name));
}

int fdt_get_path(const void *fdt, int nodeoffset, char *buf, int buflen)
{
	int pdepth = 0, p = 0;
	int offset, depth, namelen;
	const char *name;

	FDT_RO_PROBE(fdt);

	if (buflen < 2)
		return -FDT_ERR_NOSPACE;

	for (offset = 0, depth = 0;
	     (offset >= 0) && (offset <= nodeoffset);
	     offset = fdt_next_node(fdt, offset, &depth)) {
		while (pdepth > depth) {
			do {
				p--;
			} while (buf[p-1] != '/');
			pdepth--;
		}

		if (pdepth >= depth) {
			name = fdt_get_name(fdt, offset, &namelen);
			if (!name)
				return namelen;
			if ((p + namelen + 1) <= buflen) {
				memcpy(buf + p, name, namelen);
				p += namelen;
				buf[p++] = '/';
				pdepth++;
			}
		}

		if (offset == nodeoffset) {
			if (pdepth < (depth + 1))
				return -FDT_ERR_NOSPACE;

			if (p > 1) /* special case so that root path is "/", not "" */
				p--;
			buf[p] = '\0';
			return 0;
		}
	}

	if ((offset == -FDT_ERR_NOTFOUND) || (offset >= 0))
		return -FDT_ERR_BADOFFSET;
	else if (offset == -FDT_ERR_BADOFFSET)
		return -FDT_ERR_BADSTRUCTURE;

	return offset; /* error from fdt_next_node() */
}

int fdt_supernode_atdepth_offset(const void *fdt, int nodeoffset,
				 int supernodedepth, int *nodedepth)
{
	int offset, depth;
	int supernodeoffset = -FDT_ERR_INTERNAL;

	FDT_RO_PROBE(fdt);

	if (supernodedepth < 0)
		return -FDT_ERR_NOTFOUND;

	for (offset = 0, depth = 0;
	     (offset >= 0) && (offset <= nodeoffset);
	     offset = fdt_next_node(fdt, offset, &depth)) {
		if (depth == supernodedepth)
			supernodeoffset = offset;

		if (offset == nodeoffset) {
			if (nodedepth)
				*nodedepth = depth;

			if (supernodedepth > depth)
				return -FDT_ERR_NOTFOUND;
			else
				return supernodeoffset;
		}
	}

	if ((offset == -FDT_ERR_NOTFOUND) || (offset >= 0))
		return -FDT_ERR_BADOFFSET;
	else if (offset == -FDT_ERR_BADOFFSET)
		return -FDT_ERR_BADSTRUCTURE;

	return offset; /* error from fdt_next_node() */
}

int fdt_node_depth(const void *fdt, int nodeoffset)
{
	int nodedepth;
	int err;

	err = fdt_supernode_atdepth_offset(fdt, nodeoffset, 0, &nodedepth);
	if (err)
		return (err < 0) ? err : -FDT_ERR_INTERNAL;
	return nodedepth;
}

int fdt_parent_offset(const void *fdt, int nodeoffset)
{
	int nodedepth = fdt_node_depth(fdt, nodeoffset);

	if (nodedepth < 0)
		return nodedepth;
	return fdt_supernode_atdepth_offset(fdt, nodeoffset,
					    nodedepth - 1, NULL);
}

int fdt_node_offset_by_prop_value(const void *fdt, int startoffset,
				  const char *propname,
				  const void *propval, int proplen)
{
	int offset;
	const void *val;
	int len;

	FDT_RO_PROBE(fdt);

	/* FIXME: The algorithm here is pretty horrible: we scan each
	 * property of a node in fdt_getprop(), then if that didn't
	 * find what we want, we scan over them again making our way
	 * to the next node.  Still it's the easiest to implement
	 * approach; performance can come later. */
	for (offset = fdt_next_node(fdt, startoffset, NULL);
	     offset >= 0;
	     offset = fdt_next_node(fdt, offset, NULL)) {
		val = fdt_getprop(fdt, offset, propname, &len);
		if (val && (len == proplen)
		    && (memcmp(val, propval, len) == 0))
			return offset;
	}

	return offset; /* error from fdt_next_node() */
}

int fdt_node_offset_by_phandle(const void *fdt, uint32_t phandle)
{
	int offset;

	if ((phandle == 0) || (phandle == -1))
		return -FDT_ERR_BADPHANDLE;

	FDT_RO_PROBE(fdt);

	/* FIXME: The algorithm here is pretty horrible: we
	 * potentially scan each property of a node in
	 * fdt_get_phandle(), then if that didn't find what
	 * we want, we scan over them again making our way to the next
	 * node.  Still it's the easiest to implement approach;
	 * performance can come later. */
	for (offset = fdt_next_node(fdt, -1, NULL);
	     offset >= 0;
	     offset = fdt_next_node(fdt, offset, NULL)) {
		if (fdt_get_phandle(fdt, offset) == phandle)
			return offset;
	}

	return offset; /* error from fdt_next_node() */
}

int fdt_stringlist_contains(const char *strlist, int listlen, const char *str)
{
	int len = strlen(str);
	const char *p;

	while (listlen >= len) {
		if (memcmp(str, strlist, len+1) == 0)
			return 1;
		p = memchr(strlist, '\0', listlen);
		if (!p)
			return 0; /* malformed strlist.. */
		listlen -= (p-strlist) + 1;
		strlist = p + 1;
	}
	return 0;
}

int fdt_stringlist_count(const void *fdt, int nodeoffset, const char *property)
{
	const char *list, *end;
	int length, count = 0;

	list = fdt_getprop(fdt, nodeoffset, property, &length);
	if (!list)
		return length;

	end = list + length;

	while (list < end) {
		length = strnlen(list, end - list) + 1;

		/* Abort if the last string isn't properly NUL-terminated. */
		if (list + length > end)
			return -FDT_ERR_BADVALUE;

		list += length;
		count++;
	}

	return count;
}

int fdt_stringlist_search(const void *fdt, int nodeoffset, const char *property,
			  const char *string)
{
	int length, len, idx = 0;
	const char *list, *end;

	list = fdt_getprop(fdt, nodeoffset, property, &length);
	if (!list)
		return length;

	len = strlen(string) + 1;
	end = list + length;

	while (list < end) {
		length = strnlen(list, end - list) + 1;

		/* Abort if the last string isn't properly NUL-terminated. */
		if (list + length > end)
			return -FDT_ERR_BADVALUE;

		if (length == len && memcmp(list, string, length) == 0)
			return idx;

		list += length;
		idx++;
	}

	return -FDT_ERR_NOTFOUND;
}

const char *fdt_stringlist_get(const void *fdt, int nodeoffset,
			       const char *property, int idx,
			       int *lenp)
{
	const char *list, *end;
	int length;

	list = fdt_getprop(fdt, nodeoffset, property, &length);
	if (!list) {
		if (lenp)
			*lenp = length;

		return NULL;
	}

	end = list + length;

	while (list < end) {
		length = strnlen(list, end - list) + 1;

		/* Abort if the last string isn't properly NUL-terminated. */
		if (list + length > end) {
			if (lenp)
				*lenp = -FDT_ERR_BADVALUE;

			return NULL;
		}

		if (idx == 0) {
			if (lenp)
				*lenp = length - 1;

			return list;
		}

		list += length;
		idx--;
	}

	if (lenp)
		*lenp = -FDT_ERR_NOTFOUND;

	return NULL;
}

int fdt_node_check_compatible(const void *fdt, int nodeoffset,
			      const char *compatible)
{
	const void *prop;
	int len;

	prop = fdt_getprop(fdt, nodeoffset, "compatible", &len);
	if (!prop)
		return len;

	return !fdt_stringlist_contains(prop, len, compatible);
}

int fdt_node_offset_by_compatible(const void *fdt, int startoffset,
				  const char *compatible)
{
	int offset, err;

	FDT_RO_PROBE(fdt);

	/* FIXME: The algorithm here is pretty horrible: we scan each
	 * property of a node in fdt_node_check_compatible(), then if
	 * that didn't find what we want, we scan over them again
	 * making our way to the next node.  Still it's the easiest to
	 * implement approach; performance can come later. */
	for (offset = fdt_next_node(fdt, startoffset, NULL);
	     offset >= 0;
	     offset = fdt_next_node(fdt, offset, NULL)) {
		err = fdt_node_check_compatible(fdt, offset, compatible);
		if ((err < 0) && (err != -FDT_ERR_NOTFOUND))
			return err;
		else if (err == 0)
			return offset;
	}

	return offset; /* error from fdt_next_node() */
}

int fdt_check_full(const void *fdt, size_t bufsize)
{
	int err;
	int num_memrsv;
	int offset, nextoffset = 0;
	uint32_t tag;
	unsigned depth = 0;
	const void *prop;
	const char *propname;

	if (bufsize < FDT_V1_SIZE)
		return -FDT_ERR_TRUNCATED;
	err = fdt_check_header(fdt);
	if (err != 0)
		return err;
	if (bufsize < fdt_totalsize(fdt))
		return -FDT_ERR_TRUNCATED;

	num_memrsv = fdt_num_mem_rsv(fdt);
	if (num_memrsv < 0)
		return num_memrsv;

	while (1) {
		offset = nextoffset;
		tag = fdt_next_tag(fdt, offset, &nextoffset);

		if (nextoffset < 0)
			return nextoffset;

		switch (tag) {
		case FDT_NOP:
			break;

		case FDT_END:
			if (depth != 0)
				return -FDT_ERR_BADSTRUCTURE;
			return 0;

		case FDT_BEGIN_NODE:
			depth++;
			if (depth > INT_MAX)
				return -FDT_ERR_BADSTRUCTURE;
			break;

		case FDT_END_NODE:
			if (depth == 0)
				return -FDT_ERR_BADSTRUCTURE;
			depth--;
			break;

		case FDT_PROP:
			prop = fdt_getprop_by_offset(fdt, offset, &propname,
						     &err);
			if (!prop)
				return err;
			break;

		default:
			return -FDT_ERR_INTERNAL;
		}
	}
}