[PATCH v8 1/5] driver core: platform: amend the API contract for fwnode setters

[Bartosz Golaszewski]

Calling platform_device_set_fwnode() (and by extension:
platform_device_set_of_node()) of platform_device_set_of_node_from_dev()
for a dynamically allocated platform device whose primary firmware node
is already assigned and is a software node leads to a resource leak as we
never perform the corresponding call to software_node_notify_remove(). As
there are currently no users for this special case - just disallow it and
warn loudly if it ever happens.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
---
 drivers/base/platform.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index a71015f1d915340aa01ebfae67196d4d7ccecba8..fb57d487a6c2aba799b4ca5ccd089006cf2d8bf6 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -707,7 +707,9 @@ EXPORT_SYMBOL_GPL(platform_device_add_data);
  *
  * Assign an OF node to this platform device. Internally keep track of the
  * reference count. Devices created with platform_device_alloc() must use this
- * function instead of assigning the node manually.
+ * function instead of assigning the node manually. This function must not be
+ * called for a platform device that already has a software node as its primary
+ * firmware node assigned.
  */
 void platform_device_set_of_node(struct platform_device *pdev,
 				 struct device_node *np)
@@ -723,11 +725,20 @@ EXPORT_SYMBOL_GPL(platform_device_set_of_node);
  *
  * Assign a firmware node to this platform device. Internally keep track of the
  * reference count. Devices created with platform_device_alloc() must use this
- * function instead of assigning the node manually.
+ * function instead of assigning the node manually. This function must not be
+ * called for a platform device that already has a software node as its primary
+ * firmware node assigned.
  */
 void platform_device_set_fwnode(struct platform_device *pdev,
 				struct fwnode_handle *fwnode)
 {
+	/*
+	 * If we call this function for a platform device whose primary
+	 * firmware node is a software node, we'll never end up calling the
+	 * symmetric software_node_notify_remove(). There are no users for this
+	 * right now in the tree so just disallow it.
+	 */
+	WARN_ON(is_software_node(dev_fwnode(&pdev->dev)));
 	fwnode_handle_put(pdev->dev.fwnode);
 	device_set_node(&pdev->dev, fwnode_handle_get(fwnode));
 }
@@ -739,11 +750,15 @@ EXPORT_SYMBOL_GPL(platform_device_set_fwnode);
  * @dev2: device whose OF node to reuse
  *
  * Reuses the OF node of another device in this platform device while
- * internally keeping track of reference counting.
+ * internally keeping track of reference counting. This function must not be
+ * called for a platform device that already has a software node as its primary
+ * firmware node assigned.
  */
 void platform_device_set_of_node_from_dev(struct platform_device *pdev,
 					  const struct device *dev2)
 {
+	/* See platform_device_set_fwnode(). */
+	WARN_ON(is_software_node(dev_fwnode(&pdev->dev)));
 	device_set_of_node_from_dev(&pdev->dev, dev2);
 	pdev->dev.fwnode = of_fwnode_handle(pdev->dev.of_node);
 }

-- 
2.47.3