linux-kernel - [PATCH v4 7/8] of/platform: Sanity check DT bindings before creating device links

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Message-Id: <20190708225624.119973-8-saravanak@google.com>
Date:   Mon,  8 Jul 2019 15:56:23 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     Saravana Kannan <saravanak@...gle.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        David Collins <collinsd@...eaurora.org>,
        kernel-team@...roid.com
Subject: [PATCH v4 7/8] of/platform: Sanity check DT bindings before creating
 device links

If a common DT binding is pointing to a child DT node of a particular
parent DT node, don't add device links for such DT references. This is
because, by definition, a child node can't be a functional dependency for
the parent node.

Signed-off-by: Saravana Kannan <saravanak@...gle.com>
---
 drivers/of/platform.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index dba962a0ee50..98414ba53b1f 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -512,6 +512,19 @@ int of_platform_default_populate(struct device_node *root,
 }
 EXPORT_SYMBOL_GPL(of_platform_default_populate);
 
+bool of_link_is_valid(struct device_node *con, struct device_node *sup)
+{
+	of_node_get(sup);
+	while (sup) {
+		if (sup == con) {
+			of_node_put(sup);
+			return false;
+		}
+		sup = of_get_next_parent(sup);
+	}
+	return true;
+}
+
 static int of_link_binding(struct device *dev,
 			   const char *binding, const char *cell)
 {
@@ -522,6 +535,10 @@ static int of_link_binding(struct device *dev,
 
 	while (!of_parse_phandle_with_args(dev->of_node, binding, cell, i,
 					   &sup_args)) {
+		if (!of_link_is_valid(dev->of_node, sup_args.np)) {
+			of_node_put(sup_args.np);
+			continue;
+		}
 		i++;
 		sup_dev = of_find_device_by_node(sup_args.np);
 		of_node_put(sup_args.np);
-- 
2.22.0.410.gd8fdbe21b5-goog