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Date:   Wed,  4 Nov 2020 15:23:47 -0800
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Subject: [PATCH v1 10/18] device property: Add fwnode_is_ancestor_of()
From:   Saravana Kannan <saravanak@google.com>
To:     "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Len Brown <lenb@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ard Biesheuvel <ardb@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Marc Zyngier <maz@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Cc:     Saravana Kannan <saravanak@google.com>,
        Tomi Valkeinen <tomi.valkeinen@ti.com>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Grygorii Strashko <grygorii.strashko@ti.com>,
        kernel-team@android.com, linux-acpi@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org,
        devicetree@vger.kernel.org
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Precedence: bulk

Add a helper function to check if a fwnode is an ancestor of another
fwnode. This will be useful for fw_devlink feature.

Signed-off-by: Saravana Kannan <saravanak@google.com>
---
 drivers/base/property.c  | 27 +++++++++++++++++++++++++++
 include/linux/property.h |  2 ++
 2 files changed, 29 insertions(+)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index 4c43d30145c6..2569ebd52e6b 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -660,6 +660,33 @@ struct fwnode_handle *fwnode_get_nth_parent(struct fwnode_handle *fwnode,
 }
 EXPORT_SYMBOL_GPL(fwnode_get_nth_parent);
 
+/**
+ * fwnode_is_ancestor_of - Test if @test_ancestor is ancestor of @test_child
+ * @test_ancestor: Firmware which is tested for being an ancestor
+ * @test_child: Firmware which is tested for being the child
+ *
+ * A node is considered an ancestor of itself too.
+ *
+ * Returns true if @test_ancestor is an ancestor of @test_child.
+ * Otherwise, returns false.
+ */
+bool fwnode_is_ancestor_of(struct fwnode_handle *test_ancestor,
+				  struct fwnode_handle *test_child)
+{
+	if (!test_ancestor)
+		return false;
+
+	fwnode_handle_get(test_child);
+	while (test_child) {
+		if (test_child == test_ancestor) {
+			fwnode_handle_put(test_child);
+			return true;
+		}
+		test_child = fwnode_get_next_parent(test_child);
+	}
+	return false;
+}
+
 /**
  * fwnode_get_next_child_node - Return the next child node handle for a node
  * @fwnode: Firmware node to find the next child node for.
diff --git a/include/linux/property.h b/include/linux/property.h
index 2d4542629d80..2e5eed3ddf1c 100644
--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -88,6 +88,8 @@ struct fwnode_handle *fwnode_get_next_parent(
 unsigned int fwnode_count_parents(const struct fwnode_handle *fwn);
 struct fwnode_handle *fwnode_get_nth_parent(struct fwnode_handle *fwn,
 					    unsigned int depth);
+bool fwnode_is_ancestor_of(struct fwnode_handle *test_ancestor,
+				  struct fwnode_handle *test_child);
 struct fwnode_handle *fwnode_get_next_child_node(
 	const struct fwnode_handle *fwnode, struct fwnode_handle *child);
 struct fwnode_handle *fwnode_get_next_available_child_node(
-- 
2.29.1.341.ge80a0c044ae-goog