Re: [PATCH v8 2/5] PCI: of: Use device_{add,remove}_of_node() to attach of_node to existing device

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Feb 24, 2025 at 03:13:52PM +0100, Herve Codina wrote:
> The commit 407d1a51921e ("PCI: Create device tree node for bridge")
> creates of_node for PCI devices. The newly created of_node is attached
> to an existing device. This is done setting directly pdev->dev.of_node
> in the code.
> 
> Even if pdev->dev.of_node cannot be previously set, this doesn't handle
> the fwnode field of the struct device. Indeed, this field needs to be
> set if it hasn't already been set.
> 
> device_{add,remove}_of_node() have been introduced to handle this case.

I guess another way to say this is:

  - If dev->of_node has already been set, it is an error and we want
    to do nothing.  The error is impossible in this case because
    of_pci_make_dev_node() returns early if dev->of_node has been set.

  - Otherwise, we want to set dev->of_node (just as we previously
    did), and

  - if dev->fwnode has not been set, we want to set that too.

So the whole point of this is to set dev->fwnode, which we didn't do
before.  But has np->fwnode been set to anything?  Maybe it's buried
somewhere inside of_changeset_create_node(), but I didn't see it.

I can't tell if this actually *does* anything.  And if it does, all
the above is basically C code translated into English, so it doesn't
tell us *why* this is useful, which is what I try to put in the merge
commit log.

> Use them instead of the direct setting.
> 
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>
> Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
> ---
>  drivers/pci/of.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> index 7a806f5c0d20..fb5e6da1ead0 100644
> --- a/drivers/pci/of.c
> +++ b/drivers/pci/of.c
> @@ -653,8 +653,8 @@ 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);
>  	of_node_put(np);
> @@ -711,11 +711,18 @@ void of_pci_make_dev_node(struct pci_dev *pdev)
>  		goto out_free_node;
>  
>  	np->data = cset;
> -	pdev->dev.of_node = np;
> +
> +	ret = device_add_of_node(&pdev->dev, np);
> +	if (ret)
> +		goto out_revert_cset;
> +
>  	kfree(name);
>  
>  	return;
>  
> +out_revert_cset:
> +	np->data = NULL;
> +	of_changeset_revert(cset);
>  out_free_node:
>  	of_node_put(np);
>  out_destroy_cset:
> -- 
> 2.48.1
>