This patch adds an fdt_parent_offset() function which returns an
offset to the parent node of a given node.  It also adds two helper
functions which are used to implement fdt_parent_offset() but are also
exported: fdt_supernode_atdepth_offset() which returns the ancestor of
a given node at a specified depth from the root of the tree, and
fdt_node_depth() which returns the depth of a given node.

Signed-off-by: David Gibson <[EMAIL PROTECTED]>

---
 libfdt/fdt_ro.c                  |   68 ++++++++++++++++++
 libfdt/libfdt.h                  |   10 ++
 tests/Makefile.tests             |    2 
 tests/parent_offset.c            |   90 ++++++++++++++++++++++++
 tests/run_tests.sh               |    2 
 tests/supernode_atdepth_offset.c |  144 +++++++++++++++++++++++++++++++++++++++
 6 files changed, 314 insertions(+), 2 deletions(-)

Index: dtc/libfdt/fdt_ro.c
===================================================================
--- dtc.orig/libfdt/fdt_ro.c    2007-08-29 14:28:32.000000000 +1000
+++ dtc/libfdt/fdt_ro.c 2007-08-30 14:28:35.000000000 +1000
@@ -349,3 +349,71 @@ int fdt_get_path(const void *fdt, int no
        buf[p] = '\0';
        return p;
 }
+
+int fdt_supernode_atdepth_offset(const void *fdt, int nodeoffset,
+                                int supernodedepth, int *nodedepth)
+{
+       int level = -1;
+       uint32_t tag;
+       int offset, nextoffset = 0;
+       int supernodeoffset = -FDT_ERR_INTERNAL;
+
+       CHECK_HEADER(fdt);
+
+       if (supernodedepth < 0)
+               return -FDT_ERR_NOTFOUND;
+
+       do {
+               offset = nextoffset;
+               tag = _fdt_next_tag(fdt, offset, &nextoffset);
+               switch (tag) {
+               case FDT_END:
+                       return -FDT_ERR_BADOFFSET;
+
+               case FDT_BEGIN_NODE:
+                       level++;
+                       if (level == supernodedepth)
+                               supernodeoffset = offset;
+                       break;
+
+               case FDT_END_NODE:
+                       level--;
+                       break;
+
+               case FDT_PROP:
+               case FDT_NOP:
+                       break;
+
+               default:
+                       return -FDT_ERR_BADSTRUCTURE;
+               }
+       } while (offset < nodeoffset);
+
+       if (nodedepth)
+               *nodedepth = level;
+
+       if (supernodedepth > level)
+               return -FDT_ERR_NOTFOUND;
+       return supernodeoffset;
+}
+
+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);
+}
Index: dtc/libfdt/libfdt.h
===================================================================
--- dtc.orig/libfdt/libfdt.h    2007-08-30 13:26:56.000000000 +1000
+++ dtc/libfdt/libfdt.h 2007-08-30 14:26:40.000000000 +1000
@@ -74,7 +74,10 @@
 #define FDT_ERR_BADSTRUCTURE   10
 #define FDT_ERR_BADLAYOUT      11
 
-#define FDT_ERR_MAX            11
+/* "Can't happen" error indicating a bug in libfdt */
+#define FDT_ERR_INTERNAL       12
+
+#define FDT_ERR_MAX            12
 
 #define fdt_get_header(fdt, field) \
        (fdt32_to_cpu(((const struct fdt_header *)(fdt))->field))
@@ -138,6 +141,11 @@ static inline void *fdt_getprop_w(void *
 
 int fdt_get_path(const void *fdt, int nodeoffset, char *buf, int buflen);
 
+int fdt_supernode_atdepth_offset(const void *fdt, int nodeoffset,
+                                int supernodedepth, int *nodedepth);
+int fdt_node_depth(const void *fdt, int nodeoffset);
+int fdt_parent_offset(const void *fdt, int nodeoffset);
+
 /* Write-in-place functions */
 int fdt_setprop_inplace(void *fdt, int nodeoffset, const char *name,
                        const void *val, int len);
Index: dtc/tests/Makefile.tests
===================================================================
--- dtc.orig/tests/Makefile.tests       2007-08-30 13:43:53.000000000 +1000
+++ dtc/tests/Makefile.tests    2007-08-30 14:17:07.000000000 +1000
@@ -1,5 +1,5 @@
 LIB_TESTS_L = root_node find_property subnode_offset path_offset \
-       get_name getprop get_path \
+       get_name getprop get_path supernode_atdepth_offset parent_offset \
        notfound \
        setprop_inplace nop_property nop_node \
        sw_tree1 \
Index: dtc/tests/run_tests.sh
===================================================================
--- dtc.orig/tests/run_tests.sh 2007-08-30 13:44:15.000000000 +1000
+++ dtc/tests/run_tests.sh      2007-08-30 14:17:14.000000000 +1000
@@ -38,6 +38,8 @@ tree1_tests () {
     run_test get_name $TREE
     run_test getprop $TREE
     run_test get_path $TREE
+    run_test supernode_atdepth_offset $TREE
+    run_test parent_offset $TREE
     run_test notfound $TREE
 
     # Write-in-place tests
Index: dtc/tests/supernode_atdepth_offset.c
===================================================================
--- /dev/null   1970-01-01 00:00:00.000000000 +0000
+++ dtc/tests/supernode_atdepth_offset.c        2007-08-30 13:51:45.000000000 
+1000
@@ -0,0 +1,144 @@
+/*
+ * libfdt - Flat Device Tree manipulation
+ *     Testcase for fdt_supernode_atdepth_offset()
+ * Copyright (C) 2006 David Gibson, IBM Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser 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
+ */
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+#include <fdt.h>
+#include <libfdt.h>
+
+#include "tests.h"
+#include "testdata.h"
+
+int path_depth(const char *path)
+{
+       const char *p;
+       int depth = 0;
+
+       if (path[0] != '/')
+               TEST_BUG();
+
+       if (strcmp(path, "/") == 0)
+               return 0;
+       for (p = path; *p; p++)
+               if (*p == '/')
+                       depth++;
+
+       /* Special case for path == "/" */
+       if (p == (path + 1))
+               return 0;
+       else
+               return depth;
+}
+
+int path_prefix(const char *path, int depth)
+{
+       const char *p;
+       int i;
+
+       if (path[0] != '/')
+               TEST_BUG();
+
+       if (depth == 0)
+               return 1;
+
+       p = path;
+       for (i = 0; i < depth; i++)
+               p = strchrnul(p+1, '/');
+
+       return p - path;
+}
+
+void check_supernode_atdepth(struct fdt_header *fdt, const char *path,
+                            int depth)
+{
+       int pdepth = path_depth(path);
+       char *superpath;
+       int nodeoffset, supernodeoffset, superpathoffset;
+       int nodedepth;
+
+       superpath = strndupa(path, path_prefix(path, depth));
+       verbose_printf("Path %s (%d), depth %d, supernode is %s\n",
+                      path, pdepth, depth, superpath);
+
+       nodeoffset = fdt_path_offset(fdt, path);
+       if (nodeoffset < 0)
+               FAIL("fdt_path_offset(%s): %s", path, fdt_strerror(nodeoffset));
+       superpathoffset = fdt_path_offset(fdt, superpath);
+       if (superpathoffset < 0)
+               FAIL("fdt_path_offset(%s): %s", superpath,
+                    fdt_strerror(superpathoffset));
+
+       supernodeoffset = fdt_supernode_atdepth_offset(fdt, nodeoffset,
+                                                      depth, &nodedepth);
+       if (supernodeoffset < 0)
+               FAIL("fdt_supernode_atdepth_offset(): %s",
+                    fdt_strerror(supernodeoffset));
+
+       if (supernodeoffset != superpathoffset)
+               FAIL("fdt_supernode_atdepth_offset() returns %d instead of %d",
+                    supernodeoffset, superpathoffset);
+
+       if (nodedepth != pdepth)
+               FAIL("fdt_supernode_atdept_offset() returns node depth %d "
+                    "instead of %d", nodedepth, pdepth);
+}
+
+void check_supernode_overdepth(struct fdt_header *fdt, const char *path)
+{
+       int pdepth = path_depth(path);
+       int nodeoffset, err;
+
+       nodeoffset = fdt_path_offset(fdt, path);
+       if (nodeoffset < 0)
+               FAIL("fdt_path_offset(%s): %s", path, fdt_strerror(nodeoffset));
+
+       err = fdt_supernode_atdepth_offset(fdt, nodeoffset, pdepth + 1, NULL);
+       if (err != -FDT_ERR_NOTFOUND)
+               FAIL("fdt_supernode_atdept_offset(%s, %d) returns %d instead "
+                    "of FDT_ERR_NOTFOUND", path, pdepth+1, err);
+}
+
+void check_path(struct fdt_header *fdt, const char *path)
+{
+       int i;
+
+       for (i = 0; i <= path_depth(path); i++)
+               check_supernode_atdepth(fdt, path, i);
+       check_supernode_overdepth(fdt, path);
+}
+int main(int argc, char *argv[])
+{
+       void *fdt;
+
+       test_init(argc, argv);
+       fdt = load_blob_arg(argc, argv);
+
+       check_path(fdt, "/");
+       check_path(fdt, "/subnode1");
+       check_path(fdt, "/subnode2");
+       check_path(fdt, "/subnode1/subsubnode");
+       check_path(fdt, "/subnode2/subsubnode");
+
+       PASS();
+}
Index: dtc/tests/parent_offset.c
===================================================================
--- /dev/null   1970-01-01 00:00:00.000000000 +0000
+++ dtc/tests/parent_offset.c   2007-08-30 14:21:10.000000000 +1000
@@ -0,0 +1,90 @@
+/*
+ * libfdt - Flat Device Tree manipulation
+ *     Testcase for fdt_parent_offset()
+ * Copyright (C) 2006 David Gibson, IBM Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser 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
+ */
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+#include <fdt.h>
+#include <libfdt.h>
+
+#include "tests.h"
+#include "testdata.h"
+
+int path_parent_len(const char *path)
+{
+       const char *p = strrchr(path, '/');
+
+       if (!p)
+               TEST_BUG();
+       if (p == path)
+               return 1;
+       else
+               return p - path;
+}
+
+void check_path(struct fdt_header *fdt, const char *path)
+{
+       char *parentpath;
+       int nodeoffset, parentoffset, parentpathoffset;
+
+       parentpath = strndupa(path, path_parent_len(path));
+
+       verbose_printf("Path: \"%s\"\tParent: \"%s\"\n", path, parentpath);
+
+       nodeoffset = fdt_path_offset(fdt, path);
+       if (nodeoffset < 0)
+               FAIL("fdt_path_offset(%s): %s", path, fdt_strerror(nodeoffset));
+
+       parentpathoffset = fdt_path_offset(fdt, parentpath);
+       if (parentpathoffset < 0)
+               FAIL("fdt_path_offset(%s): %s", parentpath,
+                    fdt_strerror(parentpathoffset));
+
+       parentoffset = fdt_parent_offset(fdt, nodeoffset);
+       if (parentoffset < 0)
+               FAIL("fdt_parent_offset(): %s", fdt_strerror(parentoffset));
+
+       if (parentoffset != parentpathoffset)
+               FAIL("fdt_parent_offset() returns %d instead of %d",
+                    parentoffset, parentpathoffset);
+}
+
+int main(int argc, char *argv[])
+{
+       void *fdt;
+       int err;
+
+       test_init(argc, argv);
+       fdt = load_blob_arg(argc, argv);
+
+       check_path(fdt, "/subnode1");
+       check_path(fdt, "/subnode2");
+       check_path(fdt, "/subnode1/subsubnode");
+       check_path(fdt, "/subnode2/subsubnode");
+       err = fdt_parent_offset(fdt, 0);
+       if (err != -FDT_ERR_NOTFOUND)
+               FAIL("fdt_parent_offset(/) returns %d instead of "
+                    "-FDT_ERR_NOTFOUND", err);
+
+       PASS();
+}
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