libfdt: Add phandle generation helper

The new fdt_generate_phandle() function can be used to generate a new,
unused phandle given a specific device tree blob. The implementation is
somewhat naive in that it simply walks the entire device tree to find
the highest phandle value and then returns a phandle value one higher
than that. A more clever implementation might try to find holes in the
current set of phandle values and fill them. But this implementation is
relatively simple and works reliably.

Also add a test that validates that phandles generated by this new API
are indeed unique.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Message-Id: <20190326153302.17109-3-thierry.reding@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 5 insertions, 0 deletions

diff --git a/tests/references.dts b/tests/references.dts
index f783e8b..b390639 100644
--- a/tests/references.dts
+++ b/tests/references.dts
@@ -33,4 +33,9 @@
 		linux,phandle = <&n5>;
 		phandle = <&n5>;
 	};
+
+	node6 {
+		linux,phandle = <0xfffffffe>;
+		phandle = <0xfffffffe>;
+	};
 };