fdt: Add fdt_first/next_region() functions

These have been sent upstream but not accepted to libfdt. For now, bring
these into U-Boot to enable fdtgrep to operate. We will use fdtgrep to
cut device tree files down for SPL.

Signed-off-by: Simon Glass <sjg@chromium.org>

3 files changed, 731 insertions, 2 deletions

diff --git a/include/libfdt.h b/include/libfdt.h
index d0017d8865..e48c21aced 100644
--- a/include/libfdt.h
+++ b/include/libfdt.h
@@ -121,7 +121,12 @@
 	/* FDT_ERR_BADNCELLS: Device tree has a #address-cells, #size-cells
 	 * or similar property with a bad format or value */
 
-#define FDT_ERR_MAX		14
+#define FDT_ERR_TOODEEP		15
+	/* FDT_ERR_TOODEEP: The depth of a node has exceeded the internal
+	 * libfdt limit. This can happen if you have more than
+	 * FDT_MAX_DEPTH nested nodes. */
+
+#define FDT_ERR_MAX		15
 
 /**********************************************************************/
 /* Low-level functions (you probably don't need these)                */
@@ -1668,6 +1673,77 @@ struct fdt_region {
 	int size;
 };
 
+/*
+ * Flags for fdt_find_regions()
+ *
+ * Add a region for the string table (always the last region)
+ */
+#define FDT_REG_ADD_STRING_TAB		(1 << 0)
+
+/*
+ * Add all supernodes of a matching node/property, useful for creating a
+ * valid subset tree
+ */
+#define FDT_REG_SUPERNODES		(1 << 1)
+
+/* Add the FDT_BEGIN_NODE tags of subnodes, including their names */
+#define FDT_REG_DIRECT_SUBNODES	(1 << 2)
+
+/* Add all subnodes of a matching node */
+#define FDT_REG_ALL_SUBNODES		(1 << 3)
+
+/* Add a region for the mem_rsvmap table (always the first region) */
+#define FDT_REG_ADD_MEM_RSVMAP		(1 << 4)
+
+/* Indicates what an fdt part is (node, property, value) */
+#define FDT_IS_NODE			(1 << 0)
+#define FDT_IS_PROP			(1 << 1)
+#define FDT_IS_VALUE			(1 << 2)	/* not supported */
+#define FDT_IS_COMPAT			(1 << 3)	/* used internally */
+#define FDT_NODE_HAS_PROP		(1 << 4)	/* node contains prop */
+
+#define FDT_ANY_GLOBAL		(FDT_IS_NODE | FDT_IS_PROP | FDT_IS_VALUE | \
+					FDT_IS_COMPAT)
+#define FDT_IS_ANY			0x1f		/* all the above */
+
+/* We set a reasonable limit on the number of nested nodes */
+#define FDT_MAX_DEPTH			32
+
+/* Decribes what we want to include from the current tag */
+enum want_t {
+	WANT_NOTHING,
+	WANT_NODES_ONLY,		/* No properties */
+	WANT_NODES_AND_PROPS,		/* Everything for one level */
+	WANT_ALL_NODES_AND_PROPS	/* Everything for all levels */
+};
+
+/* Keeps track of the state at parent nodes */
+struct fdt_subnode_stack {
+	int offset;		/* Offset of node */
+	enum want_t want;	/* The 'want' value here */
+	int included;		/* 1 if we included this node, 0 if not */
+};
+
+struct fdt_region_ptrs {
+	int depth;			/* Current tree depth */
+	int done;			/* What we have completed scanning */
+	enum want_t want;		/* What we are currently including */
+	char *end;			/* Pointer to end of full node path */
+	int nextoffset;			/* Next node offset to check */
+};
+
+/* The state of our finding algortihm */
+struct fdt_region_state {
+	struct fdt_subnode_stack stack[FDT_MAX_DEPTH];	/* node stack */
+	struct fdt_region *region;	/* Contains list of regions found */
+	int count;			/* Numnber of regions found */
+	const void *fdt;		/* FDT blob */
+	int max_regions;		/* Maximum regions to find */
+	int can_merge;		/* 1 if we can merge with previous region */
+	int start;			/* Start position of current region */
+	struct fdt_region_ptrs ptrs;	/* Pointers for what we are up to */
+};
+
 /**
  * fdt_find_regions() - find regions in device tree
  *
@@ -1727,4 +1803,165 @@ int fdt_find_regions(const void *fdt, char * const inc[], int inc_count,
 		     struct fdt_region region[], int max_regions,
 		     char *path, int path_len, int add_string_tab);
 
+/**
+ * fdt_first_region() - find regions in device tree
+ *
+ * Given a nodes and properties to include and properties to exclude, find
+ * the regions of the device tree which describe those included parts.
+ *
+ * The use for this function is twofold. Firstly it provides a convenient
+ * way of performing a structure-aware grep of the tree. For example it is
+ * possible to grep for a node and get all the properties associated with
+ * that node. Trees can be subsetted easily, by specifying the nodes that
+ * are required, and then writing out the regions returned by this function.
+ * This is useful for small resource-constrained systems, such as boot
+ * loaders, which want to use an FDT but do not need to know about all of
+ * it.
+ *
+ * Secondly it makes it easy to hash parts of the tree and detect changes.
+ * The intent is to get a list of regions which will be invariant provided
+ * those parts are invariant. For example, if you request a list of regions
+ * for all nodes but exclude the property "data", then you will get the
+ * same region contents regardless of any change to "data" properties.
+ *
+ * This function can be used to produce a byte-stream to send to a hashing
+ * function to verify that critical parts of the FDT have not changed.
+ * Note that semantically null changes in order could still cause false
+ * hash misses. Such reordering might happen if the tree is regenerated
+ * from source, and nodes are reordered (the bytes-stream will be emitted
+ * in a different order and mnay hash functions will detect this). However
+ * if an existing tree is modified using libfdt functions, such as
+ * fdt_add_subnode() and fdt_setprop(), then this problem is avoided.
+ *
+ * The nodes/properties to include/exclude are defined by a function
+ * provided by the caller. This function is called for each node and
+ * property, and must return:
+ *
+ *    0 - to exclude this part
+ *    1 - to include this part
+ *   -1 - for FDT_IS_PROP only: no information is available, so include
+ *		if its containing node is included
+ *
+ * The last case is only used to deal with properties. Often a property is
+ * included if its containing node is included - this is the case where
+ * -1 is returned.. However if the property is specifically required to be
+ * included/excluded, then 0 or 1 can be returned. Note that including a
+ * property when the FDT_REG_SUPERNODES flag is given will force its
+ * containing node to be included since it is not valid to have a property
+ * that is not in a node.
+ *
+ * Using the information provided, the inclusion of a node can be controlled
+ * either by a node name or its compatible string, or any other property
+ * that the function can determine.
+ *
+ * As an example, including node "/" means to include the root node and all
+ * root properties. A flag provides a way of also including supernodes (of
+ * which there is none for the root node), and another flag includes
+ * immediate subnodes, so in this case we would get the FDT_BEGIN_NODE and
+ * FDT_END_NODE of all subnodes of /.
+ *
+ * The subnode feature helps in a hashing situation since it prevents the
+ * root node from changing at all. Any change to non-excluded properties,
+ * names of subnodes or number of subnodes would be detected.
+ *
+ * When used with FITs this provides the ability to hash and sign parts of
+ * the FIT based on different configurations in the FIT. Then it is
+ * impossible to change anything about that configuration (include images
+ * attached to the configuration), but it may be possible to add new
+ * configurations, new images or new signatures within the existing
+ * framework.
+ *
+ * Adding new properties to a device tree may result in the string table
+ * being extended (if the new property names are different from those
+ * already added). This function can optionally include a region for
+ * the string table so that this can be part of the hash too. This is always
+ * the last region.
+ *
+ * The FDT also has a mem_rsvmap table which can also be included, and is
+ * always the first region if so.
+ *
+ * The device tree header is not included in the region list. Since the
+ * contents of the FDT are changing (shrinking, often), the caller will need
+ * to regenerate the header anyway.
+ *
+ * @fdt:	Device tree to check
+ * @h_include:	Function to call to determine whether to include a part or
+ *		not:
+ *
+ *		@priv: Private pointer as passed to fdt_find_regions()
+ *		@fdt: Pointer to FDT blob
+ *		@offset: Offset of this node / property
+ *		@type: Type of this part, FDT_IS_...
+ *		@data: Pointer to data (node name, property name, compatible
+ *			string, value (not yet supported)
+ *		@size: Size of data, or 0 if none
+ *		@return 0 to exclude, 1 to include, -1 if no information is
+ *		available
+ * @priv:	Private pointer passed to h_include
+ * @region:	Returns list of regions, sorted by offset
+ * @max_regions: Maximum length of region list
+ * @path:	Pointer to a temporary string for the function to use for
+ *		building path names
+ * @path_len:	Length of path, must be large enough to hold the longest
+ *		path in the tree
+ * @flags:	Various flags that control the region algortihm, see
+ *		FDT_REG_...
+ * @return number of regions in list. If this is >max_regions then the
+ * region array was exhausted. You should increase max_regions and try
+ * the call again. Only the first max_regions elements are available in the
+ * array.
+ *
+ * On error a -ve value is return, which can be:
+ *
+ *	-FDT_ERR_BADSTRUCTURE (too deep or more END tags than BEGIN tags
+ *	-FDT_ERR_BADLAYOUT
+ *	-FDT_ERR_NOSPACE (path area is too small)
+ */
+int fdt_first_region(const void *fdt,
+		int (*h_include)(void *priv, const void *fdt, int offset,
+				 int type, const char *data, int size),
+		void *priv, struct fdt_region *region,
+		char *path, int path_len, int flags,
+		struct fdt_region_state *info);
+
+/** fdt_next_region() - find next region
+ *
+ * See fdt_first_region() for full description. This function finds the
+ * next region according to the provided parameters, which must be the same
+ * as passed to fdt_first_region().
+ *
+ * This function can additionally return -FDT_ERR_NOTFOUND when there are no
+ * more regions
+ */
+int fdt_next_region(const void *fdt,
+		int (*h_include)(void *priv, const void *fdt, int offset,
+				 int type, const char *data, int size),
+		void *priv, struct fdt_region *region,
+		char *path, int path_len, int flags,
+		struct fdt_region_state *info);
+
+/**
+ * fdt_add_alias_regions() - find aliases that point to existing regions
+ *
+ * Once a device tree grep is complete some of the nodes will be present
+ * and some will have been dropped. This function checks all the alias nodes
+ * to figure out which points point to nodes which are still present. These
+ * aliases need to be kept, along with the nodes they reference.
+ *
+ * Given a list of regions function finds the aliases that still apply and
+ * adds more regions to the list for these. This function is called after
+ * fdt_next_region() has finished returning regions and requires the same
+ * state.
+ *
+ * @fdt:	Device tree file to reference
+ * @region:	List of regions that will be kept
+ * @count:	Number of regions
+ * @max_regions: Number of entries that can fit in @region
+ * @info:	Region state as returned from fdt_next_region()
+ * @return new number of regions in @region (i.e. count + the number added)
+ * or -FDT_ERR_NOSPACE if there was not enough space.
+ */
+int fdt_add_alias_regions(const void *fdt, struct fdt_region *region, int count,
+			  int max_regions, struct fdt_region_state *info);
+
 #endif /* _LIBFDT_H */
diff --git a/lib/libfdt/Makefile b/lib/libfdt/Makefile
index 2f5413f90d..934d6142c3 100644
--- a/lib/libfdt/Makefile
+++ b/lib/libfdt/Makefile
@@ -6,4 +6,4 @@
 #
 
 obj-y += fdt.o fdt_ro.o fdt_rw.o fdt_strerror.o fdt_sw.o fdt_wip.o \
-	fdt_empty_tree.o fdt_addresses.o
+	fdt_empty_tree.o fdt_addresses.o fdt_region.o
diff --git a/lib/libfdt/fdt_region.c b/lib/libfdt/fdt_region.c
new file mode 100644
index 0000000000..9fea775a97
--- /dev/null
+++ b/lib/libfdt/fdt_region.c
@@ -0,0 +1,492 @@
+/*
+ * libfdt - Flat Device Tree manipulation
+ * Copyright (C) 2013 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ * SPDX-License-Identifier:	GPL-2.0+ BSD-2-Clause
+ */
+
+#include "libfdt_env.h"
+
+#ifndef USE_HOSTCC
+#include <fdt.h>
+#include <libfdt.h>
+#else
+#include "fdt_host.h"
+#endif
+
+#include "libfdt_internal.h"
+
+/**
+ * fdt_add_region() - Add a new region to our list
+ *
+ * The region is added if there is space, but in any case we increment the
+ * count. If permitted, and the new region overlaps the last one, we merge
+ * them.
+ *
+ * @info: State information
+ * @offset: Start offset of region
+ * @size: Size of region
+ */
+static int fdt_add_region(struct fdt_region_state *info, int offset, int size)
+{
+	struct fdt_region *reg;
+
+	reg = info->region ? &info->region[info->count - 1] : NULL;
+	if (info->can_merge && info->count &&
+	    info->count <= info->max_regions &&
+	    reg && offset <= reg->offset + reg->size) {
+		reg->size = offset + size - reg->offset;
+	} else if (info->count++ < info->max_regions) {
+		if (reg) {
+			reg++;
+			reg->offset = offset;
+			reg->size = size;
+		}
+	} else {
+		return -1;
+	}
+
+	return 0;
+}
+
+static int region_list_contains_offset(struct fdt_region_state *info,
+				       const void *fdt, int target)
+{
+	struct fdt_region *reg;
+	int num;
+
+	target += fdt_off_dt_struct(fdt);
+	for (reg = info->region, num = 0; num < info->count; reg++, num++) {
+		if (target >= reg->offset && target < reg->offset + reg->size)
+			return 1;
+	}
+
+	return 0;
+}
+
+int fdt_add_alias_regions(const void *fdt, struct fdt_region *region, int count,
+			  int max_regions, struct fdt_region_state *info)
+{
+	int base = fdt_off_dt_struct(fdt);
+	int node, node_end, offset;
+	int did_alias_header;
+
+	node = fdt_subnode_offset(fdt, 0, "aliases");
+	if (node < 0)
+		return -FDT_ERR_NOTFOUND;
+
+	/* The aliases node must come before the others */
+	node_end = fdt_next_subnode(fdt, node);
+	if (node_end <= 0)
+		return -FDT_ERR_BADLAYOUT;
+	node_end -= sizeof(fdt32_t);
+
+	did_alias_header = 0;
+	info->region = region;
+	info->count = count;
+	info->can_merge = 0;
+	info->max_regions = max_regions;
+
+	for (offset = fdt_first_property_offset(fdt, node);
+	     offset >= 0;
+	     offset = fdt_next_property_offset(fdt, offset)) {
+		const struct fdt_property *prop;
+		const char *name;
+		int target, next;
+
+		prop = fdt_get_property_by_offset(fdt, offset, NULL);
+		name = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
+		target = fdt_path_offset(fdt, name);
+		if (!region_list_contains_offset(info, fdt, target))
+			continue;
+		next = fdt_next_property_offset(fdt, offset);
+		if (next < 0)
+			next = node_end - sizeof(fdt32_t);
+
+		if (!did_alias_header) {
+			fdt_add_region(info, base + node, 12);
+			did_alias_header = 1;
+		}
+		fdt_add_region(info, base + offset, next - offset);
+	}
+
+	/* Add the 'end' tag */
+	if (did_alias_header)
+		fdt_add_region(info, base + node_end, sizeof(fdt32_t));
+
+	return info->count < max_regions ? info->count : -FDT_ERR_NOSPACE;
+}
+
+/**
+ * fdt_include_supernodes() - Include supernodes required by this node
+ *
+ * When we decided to include a node or property which is not at the top
+ * level, this function forces the inclusion of higher level nodes. For
+ * example, given this tree:
+ *
+ * / {
+ *     testing {
+ *     }
+ * }
+ *
+ * If we decide to include testing then we need the root node to have a valid
+ * tree. This function adds those regions.
+ *
+ * @info: State information
+ * @depth: Current stack depth
+ */
+static int fdt_include_supernodes(struct fdt_region_state *info, int depth)
+{
+	int base = fdt_off_dt_struct(info->fdt);
+	int start, stop_at;
+	int i;
+
+	/*
+	 * Work down the stack looking for supernodes that we didn't include.
+	 * The algortihm here is actually pretty simple, since we know that
+	 * no previous subnode had to include these nodes, or if it did, we
+	 * marked them as included (on the stack) already.
+	 */
+	for (i = 0; i <= depth; i++) {
+		if (!info->stack[i].included) {
+			start = info->stack[i].offset;
+
+			/* Add the FDT_BEGIN_NODE tag of this supernode */
+			fdt_next_tag(info->fdt, start, &stop_at);
+			if (fdt_add_region(info, base + start, stop_at - start))
+				return -1;
+
+			/* Remember that this supernode is now included */
+			info->stack[i].included = 1;
+			info->can_merge = 1;
+		}
+
+		/* Force (later) generation of the FDT_END_NODE tag */
+		if (!info->stack[i].want)
+			info->stack[i].want = WANT_NODES_ONLY;
+	}
+
+	return 0;
+}
+
+enum {
+	FDT_DONE_NOTHING,
+	FDT_DONE_MEM_RSVMAP,
+	FDT_DONE_STRUCT,
+	FDT_DONE_END,
+	FDT_DONE_STRINGS,
+	FDT_DONE_ALL,
+};
+
+int fdt_first_region(const void *fdt,
+		int (*h_include)(void *priv, const void *fdt, int offset,
+				 int type, const char *data, int size),
+		void *priv, struct fdt_region *region,
+		char *path, int path_len, int flags,
+		struct fdt_region_state *info)
+{
+	struct fdt_region_ptrs *p = &info->ptrs;
+
+	/* Set up our state */
+	info->fdt = fdt;
+	info->can_merge = 1;
+	info->max_regions = 1;
+	info->start = -1;
+	p->want = WANT_NOTHING;
+	p->end = path;
+	*p->end = '\0';
+	p->nextoffset = 0;
+	p->depth = -1;
+	p->done = FDT_DONE_NOTHING;
+
+	return fdt_next_region(fdt, h_include, priv, region,
+			       path, path_len, flags, info);
+}
+
+/*
+ * Theory of operation
+ *
+ *
+ *
+
+Note: in this description 'included' means that a node (or other part of
+the tree) should be included in the region list, i.e. it will have a region
+which covers its part of the tree.
+
+This function maintains some state from the last time it is called. It
+checks the next part of the tree that it is supposed to look at
+(p.nextoffset) to see if that should be included or not. When it finds
+something to include, it sets info->start to its offset. This marks the
+start of the region we want to include.
+
+Once info->start is set to the start (i.e. not -1), we continue scanning
+until we find something that we don't want included. This will be the end
+of a region. At this point we can close off the region and add it to the
+list. So we do so, and reset info->start to -1.
+
+One complication here is that we want to merge regions. So when we come to
+add another region later, we may in fact merge it with the previous one if
+one ends where the other starts.
+
+The function fdt_add_region() will return -1 if it fails to add the region,
+because we already have a region ready to be returned, and the new one
+cannot be merged in with it. In this case, we must return the region we
+found, and wait for another call to this function. When it comes, we will
+repeat the processing of the tag and again try to add a region. This time it
+will succeed.
+
+The current state of the pointers (stack, offset, etc.) is maintained in
+a ptrs member. At the start of every loop iteration we make a copy of it.
+The copy is then updated as the tag is processed. Only if we get to the end
+of the loop iteration (and successfully call fdt_add_region() if we need
+to) can we commit the changes we have made to these pointers. For example,
+if we see an FDT_END_NODE tag we will decrement the depth value. But if we
+need to add a region for this tag (let's say because the previous tag is
+included and this FDT_END_NODE tag is not included) then we will only commit
+the result if we were able to add the region. That allows us to retry again
+next time.
+
+We keep track of a variable called 'want' which tells us what we want to
+include when there is no specific information provided by the h_include
+function for a particular property. This basically handles the inclusion of
+properties which are pulled in by virtue of the node they are in. So if you
+include a node, its properties are also included. In this case 'want' will
+be WANT_NODES_AND_PROPS. The FDT_REG_DIRECT_SUBNODES feature also makes use
+of 'want'. While we are inside the subnode, 'want' will be set to
+WANT_NODES_ONLY, so that only the subnode's FDT_BEGIN_NODE and FDT_END_NODE
+tags will be included, and properties will be skipped. If WANT_NOTHING is
+selected, then we will just rely on what the h_include() function tells us.
+
+Using 'want' we work out 'include', which tells us whether this current tag
+should be included or not. As you can imagine, if the value of 'include'
+changes, that means we are on a boundary between nodes to include and nodes
+to exclude. At this point we either close off a previous region and add it
+to the list, or mark the start of a new region.
+
+Apart from the nodes, we have mem_rsvmap, the FDT_END tag and the string
+list. Each of these dealt with as a whole (i.e. we create a region for each
+if it is to be included). For mem_rsvmap we don't allow it to merge with
+the first struct region. For the stringlist we don't allow it to merge with
+the last struct region (which contains at minimum the FDT_END tag).
+*/
+int fdt_next_region(const void *fdt,
+		int (*h_include)(void *priv, const void *fdt, int offset,
+				 int type, const char *data, int size),
+		void *priv, struct fdt_region *region,
+		char *path, int path_len, int flags,
+		struct fdt_region_state *info)
+{
+	int base = fdt_off_dt_struct(fdt);
+	int last_node = 0;
+	const char *str;
+
+	info->region = region;
+	info->count = 0;
+	if (info->ptrs.done < FDT_DONE_MEM_RSVMAP &&
+	    (flags & FDT_REG_ADD_MEM_RSVMAP)) {
+		/* Add the memory reserve map into its own region */
+		if (fdt_add_region(info, fdt_off_mem_rsvmap(fdt),
+				   fdt_off_dt_struct(fdt) -
+				   fdt_off_mem_rsvmap(fdt)))
+			return 0;
+		info->can_merge = 0;	/* Don't allow merging with this */
+		info->ptrs.done = FDT_DONE_MEM_RSVMAP;
+	}
+
+	/*
+	 * Work through the tags one by one, deciding whether each needs to
+	 * be included or not. We set the variable 'include' to indicate our
+	 * decision. 'want' is used to track what we want to include - it
+	 * allows us to pick up all the properties (and/or subnode tags) of
+	 * a node.
+	 */
+	while (info->ptrs.done < FDT_DONE_STRUCT) {
+		const struct fdt_property *prop;
+		struct fdt_region_ptrs p;
+		const char *name;
+		int include = 0;
+		int stop_at = 0;
+		uint32_t tag;
+		int offset;
+		int val;
+		int len;
+
+		/*
+		 * Make a copy of our pointers. If we make it to the end of
+		 * this block then we will commit them back to info->ptrs.
+		 * Otherwise we can try again from the same starting state
+		 * next time we are called.
+		 */
+		p = info->ptrs;
+
+		/*
+		 * Find the tag, and the offset of the next one. If we need to
+		 * stop including tags, then by default we stop *after*
+		 * including the current tag
+		 */
+		offset = p.nextoffset;
+		tag = fdt_next_tag(fdt, offset, &p.nextoffset);
+		stop_at = p.nextoffset;
+
+		switch (tag) {
+		case FDT_PROP:
+			stop_at = offset;
+			prop = fdt_get_property_by_offset(fdt, offset, NULL);
+			str = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
+			val = h_include(priv, fdt, last_node, FDT_IS_PROP, str,
+					    strlen(str) + 1);
+			if (val == -1) {
+				include = p.want >= WANT_NODES_AND_PROPS;
+			} else {
+				include = val;
+				/*
+				 * Make sure we include the } for this block.
+				 * It might be more correct to have this done
+				 * by the call to fdt_include_supernodes() in
+				 * the case where it adds the node we are
+				 * currently in, but this is equivalent.
+				 */
+				if ((flags & FDT_REG_SUPERNODES) && val &&
+				    !p.want)
+					p.want = WANT_NODES_ONLY;
+			}
+
+			/* Value grepping is not yet supported */
+			break;
+
+		case FDT_NOP:
+			include = p.want >= WANT_NODES_AND_PROPS;
+			stop_at = offset;
+			break;
+
+		case FDT_BEGIN_NODE:
+			last_node = offset;
+			p.depth++;
+			if (p.depth == FDT_MAX_DEPTH)
+				return -FDT_ERR_TOODEEP;
+			name = fdt_get_name(fdt, offset, &len);
+			if (p.end - path + 2 + len >= path_len)
+				return -FDT_ERR_NOSPACE;
+
+			/* Build the full path of this node */
+			if (p.end != path + 1)
+				*p.end++ = '/';
+			strcpy(p.end, name);
+			p.end += len;
+			info->stack[p.depth].want = p.want;
+			info->stack[p.depth].offset = offset;
+
+			/*
+			 * If we are not intending to include this node unless
+			 * it matches, make sure we stop *before* its tag.
+			 */
+			if (p.want == WANT_NODES_ONLY ||
+			    !(flags & (FDT_REG_DIRECT_SUBNODES |
+				       FDT_REG_ALL_SUBNODES))) {
+				stop_at = offset;
+				p.want = WANT_NOTHING;
+			}
+			val = h_include(priv, fdt, offset, FDT_IS_NODE, path,
+					p.end - path + 1);
+
+			/* Include this if requested */
+			if (val) {
+				p.want = (flags & FDT_REG_ALL_SUBNODES) ?
+					WANT_ALL_NODES_AND_PROPS :
+					WANT_NODES_AND_PROPS;
+			}
+
+			/* If not requested, decay our 'p.want' value */
+			else if (p.want) {
+				if (p.want != WANT_ALL_NODES_AND_PROPS)
+					p.want--;
+
+			/* Not including this tag, so stop now */
+			} else {
+				stop_at = offset;
+			}
+
+			/*
+			 * Decide whether to include this tag, and update our
+			 * stack with the state for this node
+			 */
+			include = p.want;
+			info->stack[p.depth].included = include;
+			break;
+
+		case FDT_END_NODE:
+			include = p.want;
+			if (p.depth < 0)
+				return -FDT_ERR_BADSTRUCTURE;
+
+			/*
+			 * If we don't want this node, stop right away, unless
+			 * we are including subnodes
+			 */
+			if (!p.want && !(flags & FDT_REG_DIRECT_SUBNODES))
+				stop_at = offset;
+			p.want = info->stack[p.depth].want;
+			p.depth--;
+			while (p.end > path && *--p.end != '/')
+				;
+			*p.end = '\0';
+			break;
+
+		case FDT_END:
+			/* We always include the end tag */
+			include = 1;
+			p.done = FDT_DONE_STRUCT;
+			break;
+		}
+
+		/* If this tag is to be included, mark it as region start */
+		if (include && info->start == -1) {
+			/* Include any supernodes required by this one */
+			if (flags & FDT_REG_SUPERNODES) {
+				if (fdt_include_supernodes(info, p.depth))
+					return 0;
+			}
+			info->start = offset;
+		}
+
+		/*
+		 * If this tag is not to be included, finish up the current
+		 * region.
+		 */
+		if (!include && info->start != -1) {
+			if (fdt_add_region(info, base + info->start,
+					   stop_at - info->start))
+				return 0;
+			info->start = -1;
+			info->can_merge = 1;
+		}
+
+		/* If we have made it this far, we can commit our pointers */
+		info->ptrs = p;
+	}
+
+	/* Add a region for the END tag and a separate one for string table */
+	if (info->ptrs.done < FDT_DONE_END) {
+		if (info->ptrs.nextoffset != fdt_size_dt_struct(fdt))
+			return -FDT_ERR_BADSTRUCTURE;
+
+		if (fdt_add_region(info, base + info->start,
+				   info->ptrs.nextoffset - info->start))
+			return 0;
+		info->ptrs.done++;
+	}
+	if (info->ptrs.done < FDT_DONE_STRINGS) {
+		if (flags & FDT_REG_ADD_STRING_TAB) {
+			info->can_merge = 0;
+			if (fdt_off_dt_strings(fdt) <
+			    base + info->ptrs.nextoffset)
+				return -FDT_ERR_BADLAYOUT;
+			if (fdt_add_region(info, fdt_off_dt_strings(fdt),
+					   fdt_size_dt_strings(fdt)))
+				return 0;
+		}
+		info->ptrs.done++;
+	}
+
+	return info->count > 0 ? 0 : -FDT_ERR_NOTFOUND;
+}