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>

1 files changed, 238 insertions, 1 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 */