[PATCH v4 0/2] Attach DT nodes to existing PCI devices

[PATCH v4 0/2] Attach DT nodes to existing PCI devices

[Herve Codina]

Hi,

The commit 407d1a51921e ("PCI: Create device tree node for bridge")
creates of_node for PCI devices.

During the insertion handling of these new DT nodes done by of_platform,
new devices (struct device) are created. For each PCI devices a struct
device is already present (created and handled by the PCI core).

Creating a new device from a DT node leads to some kind of wrong struct
device duplication to represent the exact same PCI device.

This patch series first introduces device_{add,remove}_of_node() in
order to add or remove a newly created of_node to an already existing
device. Then it fixes the DT node creation for PCI devices to add or
remove the created node to the existing PCI device without any new
device creation.

Compared to the previous iteration:
  https://lore.kernel.org/lkml/20240325153919.199337-1-herve.codina@bootlin.com/
this v4 series does not create the of_node sysfs symlink.

Best regards,
Hervé

Changes v3 -> v4
  - Patch 1
    Remove the of_node sysfs symlink handling
    Update commit log

  - Patch 2
    Update commit log

Changes v2 -> v3
  - Patch 1
    No changes

  - Patch 2
    Rewrap commit log

Changes v1 -> v2
  - Patch 1
    Add 'Cc: stable@vger.kernel.org'

Herve Codina (2):
  driver core: Introduce device_{add,remove}_of_node()
  PCI: of: Attach created of_node to existing device

 drivers/base/core.c    | 52 ++++++++++++++++++++++++++++++++++++++++++
 drivers/pci/of.c       | 15 ++++++++++--
 include/linux/device.h |  2 ++
 3 files changed, 67 insertions(+), 2 deletions(-)

-- 
2.44.0

[PATCH v4 1/2] driver core: Introduce device_{add,remove}_of_node()

[Herve Codina]

An of_node can be set to a device using device_set_node().
This function cannot 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 if no of_node were 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().

Cc: stable@vger.kernel.org
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/base/core.c    | 52 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/device.h |  2 ++
 2 files changed, 54 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 521757408fc0..098ae335cb0a 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -5127,6 +5127,58 @@ 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
+ */
+void device_add_of_node(struct device *dev, struct device_node *of_node)
+{
+	if (!of_node)
+		return;
+
+	dev = get_device(dev);
+	if (!dev)
+		return;
+
+	if (WARN(dev->of_node, "%s: Cannot replace node %pOF with %pOF\n",
+		 dev_name(dev), dev->of_node, of_node))
+		goto end;
+
+	dev->of_node = of_node_get(of_node);
+
+	if (!dev->fwnode)
+		dev->fwnode = of_fwnode_handle(of_node);
+
+end:
+	put_device(dev);
+}
+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
diff --git a/include/linux/device.h b/include/linux/device.h
index 97c4b046c09d..1795121dee9a 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1127,6 +1127,8 @@ int device_offline(struct device *dev);
 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_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);
 void device_set_node(struct device *dev, struct fwnode_handle *fwnode);
 
-- 
2.44.0

[PATCH v4 2/2] PCI: of: Attach created of_node to existing device

[Herve Codina]

The commit 407d1a51921e ("PCI: Create device tree node for bridge")
creates of_node for PCI devices.

During the insertion handling of these new DT nodes done by of_platform,
new devices (struct device) are created. For each PCI devices a struct
device is already present (created and handled by the PCI core).
Having a second struct device to represent the exact same PCI device is
not correct.

On the of_node creation:
- tell the of_platform that there is no need to create a device for this
  node (OF_POPULATED flag),
- link this newly created of_node to the already present device,
- tell fwnode that the device attached to this of_node is ready using
  fwnode_dev_initialized().

On the of_node removal, revert the operations.

Fixes: 407d1a51921e ("PCI: Create device tree node for bridge")
Cc: stable@vger.kernel.org
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/pci/of.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index 51e3dd0ea5ab..5afd2731e876 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -615,7 +615,8 @@ void of_pci_remove_node(struct pci_dev *pdev)
 	np = pci_device_to_OF_node(pdev);
 	if (!np || !of_node_check_flag(np, OF_DYNAMIC))
 		return;
-	pdev->dev.of_node = NULL;
+
+	device_remove_of_node(&pdev->dev);
 
 	of_changeset_revert(np->data);
 	of_changeset_destroy(np->data);
@@ -668,12 +669,22 @@ void of_pci_make_dev_node(struct pci_dev *pdev)
 	if (ret)
 		goto out_free_node;
 
+	/*
+	 * This of_node will be added to an existing device.
+	 * Avoid any device creation and use the existing device
+	 */
+	of_node_set_flag(np, OF_POPULATED);
+	np->fwnode.dev = &pdev->dev;
+	fwnode_dev_initialized(&np->fwnode, true);
+
 	ret = of_changeset_apply(cset);
 	if (ret)
 		goto out_free_node;
 
 	np->data = cset;
-	pdev->dev.of_node = np;
+
+	/* Add the of_node to the existing device */
+	device_add_of_node(&pdev->dev, np);
 	kfree(name);
 
 	return;
-- 
2.44.0