From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: saravanak@google.com,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
devicetree@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
Frank Rowand <frowand.list@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
linux-kernel@vger.kernel.org
Subject: [PATCH 4/4] of: property: Avoid linking devices with circular dependencies
Date: Wed, 15 Apr 2020 17:05:49 +0200 [thread overview]
Message-ID: <20200415150550.28156-5-nsaenzjulienne@suse.de> (raw)
In-Reply-To: <20200415150550.28156-1-nsaenzjulienne@suse.de>
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@suse.de>
---
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
next prev parent reply other threads:[~2020-04-15 15:06 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 15:05 [PATCH 0/4] of: property: fw_devlink misc fixes Nicolas Saenz Julienne
2020-04-15 15:05 ` [PATCH 1/4] of: property: Fix create device links for all child-supplier dependencies Nicolas Saenz Julienne
2020-04-15 18:20 ` Saravana Kannan
2020-04-15 18:22 ` Saravana Kannan
2020-04-16 11:32 ` Nicolas Saenz Julienne
2020-04-15 15:05 ` [PATCH 2/4] of: property: Do not link to disabled devices Nicolas Saenz Julienne
2020-04-15 18:30 ` Saravana Kannan
2020-04-16 11:37 ` Nicolas Saenz Julienne
2020-04-16 20:56 ` Saravana Kannan
2020-04-15 15:05 ` [PATCH 3/4] of: property: Move of_link_to_phandle() Nicolas Saenz Julienne
2020-04-15 15:05 ` Nicolas Saenz Julienne [this message]
2020-04-15 18:52 ` [PATCH 4/4] of: property: Avoid linking devices with circular dependencies Saravana Kannan
2020-04-16 16:01 ` Nicolas Saenz Julienne
2020-04-16 20:57 ` Saravana Kannan
2020-04-16 20:58 ` [PATCH v1] of: property: Don't retry device_link_add() upon failure Saravana Kannan
2020-04-17 16:50 ` Nicolas Saenz Julienne
2020-04-17 18:16 ` Rob Herring
2020-04-17 20:30 ` Saravana Kannan
2020-04-28 17:11 ` Rob Herring
2020-04-15 18:17 ` [PATCH 0/4] of: property: fw_devlink misc fixes Saravana Kannan
2020-04-16 11:02 ` Nicolas Saenz Julienne
2020-04-16 20:56 ` Saravana Kannan
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