[PATCH v3 10/15] libfdt: Introduce fdt_ptr_offset_()

[Herve Codina <herve.codina@bootlin.com>]

libfdt provides internal helpers to convert an offset to a pointer but
nothing to do the reverse operation.

Introduce the fdt_ptr_offset_() internal helper to convert a pointer to
an offset.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
---
 libfdt/libfdt_internal.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libfdt/libfdt_internal.h b/libfdt/libfdt_internal.h
index f2e30ce8..3c83d9a7 100644
--- a/libfdt/libfdt_internal.h
+++ b/libfdt/libfdt_internal.h
@@ -46,6 +46,11 @@ static inline void *fdt_offset_ptr_w_(void *fdt, int offset)
 	return (void *)(uintptr_t)fdt_offset_ptr_(fdt, offset);
 }
 
+static inline int fdt_ptr_offset_(const void *fdt, const void *ptr)
+{
+	return (const char *)ptr - (const char *)fdt_offset_ptr_(fdt, 0);
+}
+
 static inline const struct fdt_reserve_entry *fdt_mem_rsv_(const void *fdt, int n)
 {
 	const struct fdt_reserve_entry *rsv_table =
-- 
2.55.0