[PATCH RFC 3/4] of/overlay: rewrite /aliases path values to live-tree paths

[Abdurrahman Hussain]

/aliases entries added by an overlay reference labeled nodes inside
the overlay via '&label' in the .dtso. dtc renders those references
as string paths at compile time, but the paths encode the overlay's
internal fragment layout (e.g. "/fragment@1/__overlay__/fpga@0/i2c@40000")
rather than the location where the node will live after apply.

Currently only /__symbols__ has its property values rewritten from
overlay-internal paths to live-tree paths by dup_and_fixup_symbol_prop().
/aliases values fall through the plain __of_prop_dup() path and are
copied byte-for-byte, so of_find_node_by_path() on such a value returns
NULL, of_alias_get_id() reports -ENODEV — and the reconfig notifier
added earlier in this series sees uninterpretable paths and can't
populate aliases_lookup for overlay-declared aliases.

The values in /aliases follow the same textual convention as
/__symbols__, so we can reuse the existing rewriter. Detect the
/aliases target node and route its properties through
dup_and_fixup_symbol_prop() as well. Fall back to a raw dup when the
value is not a rewritable fragment path (legacy string aliases like
"ttyS0" that some out-of-tree code writes verbatim).

Signed-off-by: Abdurrahman Hussain <abdurrahman@xxxxxxxxxx>
---
 drivers/of/overlay.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index 654a70d5cb07..338786cef17a 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -350,6 +350,19 @@ static int add_changeset_property(struct overlay_changeset *ovcs,
 		if (prop)
 			return -EINVAL;
 		new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
+	} else if (target->np->parent &&
+		   of_node_is_root(target->np->parent) &&
+		   of_node_name_eq(target->np, "aliases")) {
+		/*
+		 * /aliases property values are string paths in the same
+		 * "/fragment@N/__overlay__/..." form as /__symbols__.
+		 * Rewrite them to live-tree paths so of_alias_get_id() can
+		 * resolve them; fall back to a raw dup for non-fragment
+		 * values (e.g. legacy string aliases like "ttyS0").
+		 */
+		new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
+		if (!new_prop)
+			new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
 	} else {
 		new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
 	}

-- 
2.54.0