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

[Herve Codina]

On Fri, 28 Feb 2025 14:58:55 -0600
Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:

> 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.

np->fwnode can be set by ACPI. We are at the frontier between ACPI and
device-tree.

The ofnode is created and filled from an already existing device. This
device can be created from information provided by the ACPI world.
In that case, np->fwnode is set to and ACPI fwnode.

Best regards,
Hervé