libfdt: Add fdt_parent_offset() and supporting functions
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 <david@gibson.dropbear.id.au>
diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index 0e9deb5..dc4a596 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -349,3 +349,71 @@
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);
+}