[PATCH v4 6/6] of: unittest: cover /aliases updates from overlay apply/revert

[Abdurrahman Hussain]

Add overlay_alias.dtso plus of_unittest_overlay_alias() to cover the
"aliases inside an overlay" flow end-to-end.

The overlay has two fragments:

  fragment@0: target-path="" grafts a labeled node under target_base.
  fragment@1: target-path="/aliases" adds `testcase-alias99 =
              &<label>` at DT-root /aliases.

The runner applies the overlay with a non-NULL target_base via
of_overlay_fdt_apply() directly (rather than the overlay_data_apply()
wrapper, which always passes NULL), then asserts of_alias_get_id() on
the grafted node returns 99 after the apply and that
of_alias_get_highest_id() reports the stem gone after the revert,
with a matching precondition check before the apply.

The apply is wrapped in EXPECT_BEGIN/END for the "memory leak will
occur" warning that add_changeset_property() prints for any property
added to a node the overlay didn't create — /aliases here — matching
the other overlay tests that add properties to pre-existing nodes.

The grafted-node reference is dropped before of_overlay_remove():
overlay-created nodes must be back to refcount 1 when the changeset
is destroyed, or __of_changeset_entry_destroy() logs a leak error and
the node is never freed. The post-remove assertion therefore uses
of_alias_get_highest_id(), which is keyed by stem and needs no node
reference.

Exercises the three functional patches earlier in this series
together:

  * the reconfig notifier is what mutates aliases_lookup on
    apply/revert;
  * find_target()'s absolute-target-path handling is what lets
    fragment@1's target-path="/aliases" reach the DT root when
    target_base is non-NULL;
  * dup_and_fixup_symbol_prop()'s /aliases branch is what rewrites
    the fragment-internal alias value ("&<label>" -> fragment path)
    into the live-tree path that of_find_node_by_path() can resolve.

Any one of the three missing turns the middle assertion (get_id -> 99)
into -ENODEV.

The overlay is not added to the fdtoverlay static build test:
fdtoverlay has no target-base concept, so fragment@0's empty
target-path (meaning "the target base itself" at run time) cannot be
resolved statically.

Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@xxxxxxxxxx>
---
 drivers/of/unittest-data/Makefile           |  5 ++
 drivers/of/unittest-data/overlay_alias.dtso | 25 ++++++++++
 drivers/of/unittest.c                       | 73 +++++++++++++++++++++++++++++
 3 files changed, 103 insertions(+)

diff --git a/drivers/of/unittest-data/Makefile b/drivers/of/unittest-data/Makefile
index 01a966e39f23..fdfec5a7923b 100644
--- a/drivers/of/unittest-data/Makefile
+++ b/drivers/of/unittest-data/Makefile
@@ -22,6 +22,7 @@ obj-$(CONFIG_OF_OVERLAY) += overlay.dtbo.o \
 			    overlay_18.dtbo.o \
 			    overlay_19.dtbo.o \
 			    overlay_20.dtbo.o \
+			    overlay_alias.dtbo.o \
 			    overlay_bad_add_dup_node.dtbo.o \
 			    overlay_bad_add_dup_prop.dtbo.o \
 			    overlay_bad_phandle.dtbo.o \
@@ -66,6 +67,10 @@ DTC_FLAGS_testcases += -Wno-interrupts_property \
 #			  overlay_bad_add_dup_prop.dtbo \
 #			  overlay_bad_phandle.dtbo \
 #			  overlay_bad_symbol.dtbo \
+#
+# overlay_alias.dtbo needs a run-time target base for its empty target-path;
+# fdtoverlay has no equivalent, so it is also not included:
+#			  overlay_alias.dtbo \
 
 apply_static_overlay_1 := overlay_0.dtbo \
 			  overlay_1.dtbo \
diff --git a/drivers/of/unittest-data/overlay_alias.dtso b/drivers/of/unittest-data/overlay_alias.dtso
new file mode 100644
index 000000000000..17e02d1940f6
--- /dev/null
+++ b/drivers/of/unittest-data/overlay_alias.dtso
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/dts-v1/;
+/plugin/;
+
+/*
+ * overlay_alias - declare an /aliases entry that points, via label, at a
+ * node grafted under the run-time target base (empty target-path).
+ */
+
+/ {
+	fragment@0 {
+		target-path = "";
+		__overlay__ {
+			testcase_target: alias-target {
+			};
+		};
+	};
+
+	fragment@1 {
+		target-path = "/aliases";
+		__overlay__ {
+			testcase-alias99 = &testcase_target;
+		};
+	};
+};
diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
index e255f54f4d76..2f5e4056efae 100644
--- a/drivers/of/unittest.c
+++ b/drivers/of/unittest.c
@@ -3475,6 +3475,77 @@ static struct notifier_block of_nb = {
 	.notifier_call = of_notify,
 };
 
+/* created by cmd_wrap_S_dtbo in scripts/Makefile.dtbs */
+extern uint8_t __dtbo_overlay_alias_begin[];
+extern uint8_t __dtbo_overlay_alias_end[];
+
+static void __init of_unittest_overlay_alias(void)
+{
+	const char *base_path =
+		"/testcase-data/overlay-node/test-bus/test-unittest100";
+	const char *target_path =
+		"/testcase-data/overlay-node/test-bus/test-unittest100/alias-target";
+	u32 size = __dtbo_overlay_alias_end - __dtbo_overlay_alias_begin;
+	struct device_node *base, *target;
+	int ovcs_id = 0;
+	int id, ret;
+
+	base = of_find_node_by_path(base_path);
+	if (!base) {
+		unittest(0, "could not find alias target base %s\n", base_path);
+		return;
+	}
+
+	id = of_alias_get_highest_id("testcase-alias");
+	if (id != -ENODEV) {
+		unittest(0, "unexpected testcase-alias%d before overlay apply\n",
+			 id);
+		goto out_put_base;
+	}
+
+	EXPECT_BEGIN(KERN_INFO,
+		     "OF: overlay: WARNING: memory leak will occur if overlay removed, property: /aliases/testcase-alias99");
+
+	ret = of_overlay_fdt_apply(__dtbo_overlay_alias_begin, size,
+				   &ovcs_id, base);
+
+	EXPECT_END(KERN_INFO,
+		   "OF: overlay: WARNING: memory leak will occur if overlay removed, property: /aliases/testcase-alias99");
+
+	if (ret < 0) {
+		unittest(0, "overlay_alias apply failed, ret = %d\n", ret);
+		if (ovcs_id)
+			of_overlay_remove(&ovcs_id);
+		goto out_put_base;
+	}
+
+	target = of_find_node_by_path(target_path);
+	if (!target) {
+		unittest(0, "could not find grafted target %s\n", target_path);
+	} else {
+		id = of_alias_get_id(target, "testcase-alias");
+		unittest(id == 99,
+			 "of_alias_get_id() = %d after overlay apply, expected 99\n",
+			 id);
+		/* changeset destroy expects overlay nodes back at refcount 1 */
+		of_node_put(target);
+	}
+
+	ret = of_overlay_remove(&ovcs_id);
+	if (ret) {
+		unittest(0, "overlay_alias remove failed, ret = %d\n", ret);
+		goto out_put_base;
+	}
+
+	id = of_alias_get_highest_id("testcase-alias");
+	unittest(id == -ENODEV,
+		 "of_alias_get_highest_id() = %d after overlay remove, expected -ENODEV\n",
+		 id);
+
+out_put_base:
+	of_node_put(base);
+}
+
 static void __init of_unittest_overlay_notify(void)
 {
 	int ovcs_id;
@@ -3649,6 +3720,8 @@ static void __init of_unittest_overlay(void)
 
 	of_unittest_overlay_gpio();
 
+	of_unittest_overlay_alias();
+
 	of_unittest_remove_tracked_overlays();
 
 	of_unittest_overlay_notify();

-- 
2.54.0