When creating a consumer/supplier relationship between devices it's
essential to make sure they aren't supplying each other creating a
circular dependency.
Introduce a new function to check if such circular dependency exists
between two device nodes and use it in of_link_to_phandle().
Fixes: a3e1d1a7f5fc ("of: property: Add functional dependency link from DT bindings")
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
---
NOTE:
I feel of_link_is_circular() is a little dense, and could benefit from
some abstraction/refactoring. That said, I'd rather get some feedback,
before spending time on it.
drivers/of/property.c | 50 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 50 insertions(+)
diff --git a/drivers/of/property.c b/drivers/of/property.c
index 2c7978ef22be1..74a5190408c3b 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1171,6 +1171,44 @@ static const struct supplier_bindings of_supplier_bindings[] = {
{}
};
+/**
+ * of_link_is_circular - Make sure potential link isn't circular
+ *
+ * @sup_np: Supplier device
+ * @con_np: Consumer device
+ *
+ * This function checks if @sup_np's properties contain a reference to @con_np.
+ *
+ * Will return true if there's a circular dependency and false otherwise.
+ */
+static bool of_link_is_circular(struct device_node *sup_np,
+ struct device_node *con_np)
+{
+ const struct supplier_bindings *s = of_supplier_bindings;
+ struct device_node *tmp;
+ bool matched = false;
+ struct property *p;
+ int i = 0;
+
+ for_each_property_of_node(sup_np, p) {
+ while (!matched && s->parse_prop) {
+ while ((tmp = s->parse_prop(sup_np, p->name, i))) {
+ matched = true;
+ i++;
+
+ if (tmp == con_np)
+ return true;
+ }
+ i = 0;
+ s++;
+ }
+ s = of_supplier_bindings;
+ matched = false;
+ }
+
+ return false;
+}
+
/**
* of_link_to_phandle - Add device link to supplier from supplier phandle
* @dev: consumer device
@@ -1216,6 +1254,18 @@ static int of_link_to_phandle(struct device *dev, struct device_node *sup_np,
return -ENODEV;
}
+ /*
+ * It is possible for consumer device nodes to also supply the device
+ * node they are consuming from. Creating an unwarranted circular
+ * dependency.
+ */
+ if (of_link_is_circular(sup_np, dev->of_node)) {
+ dev_dbg(dev, "Not linking to %pOFP - Circular dependency\n",
+ sup_np);
+ of_node_put(sup_np);
+ return -ENODEV;
+ }
+
/*
* Don't allow linking a device node as a consumer of one of its
* descendant nodes. By definition, a child node can't be a functional
--
2.26.0
