[RFC PATCH 04/15] libfdt: fdt_rw: Introduce fdt_downgrade_version()

Herve Codina
2026-02-10T17:34:27Z

Current code perform a version downgrade at one place only, the end of
fdt_rw_probe_().

In order to offer a finer grain and choose to downgrade or not depending
on the exact writes done, introduce fdt_downgrade_version() to perform
the downgrade operation.

The modification doesn't introduce any functional changes.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
libfdt/fdt_rw.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/libfdt/fdt_rw.c b/libfdt/fdt_rw.c
index 7475caf..90ea14e 100644
--- a/libfdt/fdt_rw.c
+++ b/libfdt/fdt_rw.c
@@ -22,6 +22,12 @@ static int fdt_blocks_misordered_(const void *fdt,
(fdt_off_dt_strings(fdt) + fdt_size_dt_strings(fdt)));
}

+static void fdt_downgrade_version(void *fdt)
+{
+ if (!can_assume(LATEST) && fdt_version(fdt) > FDT_LAST_SUPPORTED_VERSION)
+ fdt_set_version(fdt, FDT_LAST_SUPPORTED_VERSION);
+}
+
static int fdt_rw_probe_(void *fdt)
{
if (can_assume(VALID_DTB))
@@ -33,9 +39,8 @@ static int fdt_rw_probe_(void *fdt)
if (fdt_blocks_misordered_(fdt, sizeof(struct fdt_reserve_entry),
fdt_size_dt_struct(fdt)))
return -FDT_ERR_BADLAYOUT;
- if (!can_assume(LATEST) && fdt_version(fdt) > 17)
- fdt_set_version(fdt, 17);

+ fdt_downgrade_version(fdt);
return 0;
}

--
2.52.0