[PATCH v2 1/2] driver core: Introduce device_{add,remove}_of_node()

[PATCH v2 1/2] driver core: Introduce device_{add,remove}_of_node()

[Herve Codina]

An of_node can be duplicated from an existing device using
device_set_of_node_from_dev() or initialized using device_set_node()
In both cases, these functions have to be called before the device_add()
call in order to have the of_node link created in the device sysfs
directory. Further more, these 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
- Create the of_node sysfs link if needed

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    | 74 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/device.h |  2 ++
 2 files changed, 76 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 2926f3b1f868..ac026187ac6a 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -5046,6 +5046,80 @@ 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;
+
+	sysfs_remove_link(&dev->kobj, "of_node");
+
+	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)
+{
+	int ret;
+
+	if (!of_node)
+		return;
+
+	dev = get_device(dev);
+	if (!dev)
+		return;
+
+	if (dev->of_node) {
+		dev_warn(dev, "Replace node %pOF with %pOF\n", dev->of_node, of_node);
+		device_remove_of_node(dev);
+	}
+
+	dev->of_node = of_node_get(of_node);
+
+	if (!dev->fwnode)
+		dev->fwnode = of_fwnode_handle(of_node);
+
+	if (!dev->p) {
+		/*
+		 * device_add() was not previously called.
+		 * The of_node link will be created when device_add() is called.
+		 */
+		goto end;
+	}
+
+	/*
+	 * device_add() was previously called and so the of_node link was not
+	 * created by device_add_class_symlinks().
+	 * Create this link now.
+	 */
+	ret = sysfs_create_link(&dev->kobj, of_node_kobj(of_node), "of_node");
+	if (ret)
+		dev_warn(dev, "Error %d creating of_node link\n", ret);
+
+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 d7a72a8749ea..2b093e62907a 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1128,6 +1128,8 @@ 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);
 
-- 
2.42.0

[PATCH v2 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 and tell fwnode that the
device attached to this of_node is ready (fwnode_dev_initialized()).

With this fix, the of_node are available in the sysfs device tree:
/sys/devices/platform/soc/d0070000.pcie/
+ of_node -> .../devicetree/base/soc/pcie@d0070000
+ pci0000:00
  + 0000:00:00.0
    + of_node -> .../devicetree/base/soc/pcie@d0070000/pci@0,0
    + 0000:01:00.0
      + of_node -> .../devicetree/base/soc/pcie@d0070000/pci@0,0/dev@0,0

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;
-- 
2.42.0

Re: [PATCH v2 2/2] PCI: of: Attach created of_node to existing device

[Bjorn Helgaas]

On Thu, Nov 30, 2023 at 05:56:59PM +0100, Herve Codina wrote:
> 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.

Can you rewrap this or, if you intend multiple paragraphs, add blank
lines between them?

> 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 and tell fwnode that the
> device attached to this of_node is ready (fwnode_dev_initialized()).
> 
> With this fix, the of_node are available in the sysfs device tree:
> /sys/devices/platform/soc/d0070000.pcie/
> + of_node -> .../devicetree/base/soc/pcie@d0070000
> + pci0000:00
>   + 0000:00:00.0
>     + of_node -> .../devicetree/base/soc/pcie@d0070000/pci@0,0
>     + 0000:01:00.0
>       + of_node -> .../devicetree/base/soc/pcie@d0070000/pci@0,0/dev@0,0
> 
> 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;
> -- 
> 2.42.0
>