[RFC PATCH 05/15] libfdt: Introduce fdt_first_node()

Herve Codina
2026-02-10T17:34:29Z

In several places, libfdt assumes that a FDT_BEGIN_NODE tag is present
at the offset 0 of the structure block.

This assumption is not correct. Indeed, a FDT_NOP can be present at the
offset 0 and this is a legit case.

Introduce fdt_first_node() in order to get the offset of the first node
(first FDT_BEGIN_NODE tag) available in a fdt blob.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
libfdt/fdt.c | 25 +++++++++++++++++++++++++
libfdt/libfdt_internal.h | 1 +
2 files changed, 26 insertions(+)

diff --git a/libfdt/fdt.c b/libfdt/fdt.c
index 56d4dcb..676c7d7 100644
--- a/libfdt/fdt.c
+++ b/libfdt/fdt.c
@@ -252,6 +252,31 @@ int fdt_check_prop_offset_(const void *fdt, int offset)
return offset;
}

+int fdt_first_node(const void *fdt)
+{
+ int nextoffset = 0;
+ int offset;
+ uint32_t tag;
+
+ do {
+ offset = nextoffset;
+ tag = fdt_next_tag(fdt, offset, &nextoffset);
+ switch (tag) {
+ case FDT_END_NODE:
+ case FDT_PROP:
+ return -FDT_ERR_BADSTRUCTURE;
+
+ case FDT_BEGIN_NODE:
+ return offset;
+
+ default:
+ break;
+ }
+ } while (tag != FDT_END);
+
+ return (nextoffset < 0) ? nextoffset : -FDT_ERR_NOTFOUND;
+}
+
int fdt_next_node(const void *fdt, int offset, int *depth)
{
int nextoffset = 0;
diff --git a/libfdt/libfdt_internal.h b/libfdt/libfdt_internal.h
index 0e103ca..4c15264 100644
--- a/libfdt/libfdt_internal.h
+++ b/libfdt/libfdt_internal.h
@@ -32,6 +32,7 @@ static inline const char *fdt_find_string_(const char *strtab, int tabsize,
}

int fdt_node_end_offset_(void *fdt, int nodeoffset);
+int fdt_first_node(const void *fdt);

static inline const void *fdt_offset_ptr_(const void *fdt, int offset)
{
--
2.52.0