driver core: Introduce device_{add,remove}_of_node()

An of_node can be set to a device using device_set_node(), which does not
prevent any of_node and/or fwnode overwrites.

When adding an of_node on an already present device, the following
operations need to be done:

  - Attach the of_node only if no of_node is already attached

  - Attach the of_node as a fwnode if no fwnode were already attached

This is the purpose of device_add_of_node().  device_remove_of_node()
reverts the operations done by device_add_of_node().

Link: https://lore.kernel.org/r/20250224141356.36325-2-herve.codina@bootlin.com
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 63 insertions, 0 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 5a1f05198114..49eb5aaf19cc 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -5171,6 +5171,67 @@ void set_secondary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
 EXPORT_SYMBOL_GPL(set_secondary_fwnode);
 
 /**
+ * device_remove_of_node - Remove an of_node from a device
+ * @dev: device whose device tree node is being removed
+ */
+void device_remove_of_node(struct device *dev)
+{
+	dev = get_device(dev);
+	if (!dev)
+		return;
+
+	if (!dev->of_node)
+		goto end;
+
+	if (dev->fwnode == of_fwnode_handle(dev->of_node))
+		dev->fwnode = NULL;
+
+	of_node_put(dev->of_node);
+	dev->of_node = NULL;
+
+end:
+	put_device(dev);
+}
+EXPORT_SYMBOL_GPL(device_remove_of_node);
+
+/**
+ * device_add_of_node - Add an of_node to an existing device
+ * @dev: device whose device tree node is being added
+ * @of_node: of_node to add
+ *
+ * Return: 0 on success or error code on failure.
+ */
+int device_add_of_node(struct device *dev, struct device_node *of_node)
+{
+	int ret;
+
+	if (!of_node)
+		return -EINVAL;
+
+	dev = get_device(dev);
+	if (!dev)
+		return -EINVAL;
+
+	if (dev->of_node) {
+		dev_err(dev, "Cannot replace node %pOF with %pOF\n",
+			dev->of_node, of_node);
+		ret = -EBUSY;
+		goto end;
+	}
+
+	dev->of_node = of_node_get(of_node);
+
+	if (!dev->fwnode)
+		dev->fwnode = of_fwnode_handle(of_node);
+
+	ret = 0;
+end:
+	put_device(dev);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(device_add_of_node);
+
+/**
  * device_set_of_node_from_dev - reuse device-tree node of another device
  * @dev: device whose device-tree node is being set
  * @dev2: device whose device-tree node is being reused
diff --git a/include/linux/device.h b/include/linux/device.h
index 80a5b3268986..1244e5892292 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1191,6 +1191,8 @@ int device_online(struct device *dev);
 void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode);
 void set_secondary_fwnode(struct device *dev, struct fwnode_handle *fwnode);
 void device_set_node(struct device *dev, struct fwnode_handle *fwnode);
+int device_add_of_node(struct device *dev, struct device_node *of_node);
+void device_remove_of_node(struct device *dev);
 void device_set_of_node_from_dev(struct device *dev, const struct device *dev2);
 
 static inline struct device_node *dev_of_node(struct device *dev)