linux-kernel - Re: [PATCH v1 1/1] PCI: of: Propagate firmware node

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Date:   Wed, 12 Apr 2023 11:02:53 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Pali Rohár <pali@...nel.org>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v1 1/1] PCI: of: Propagate firmware node

On Wed, Apr 12, 2023 at 04:15:20PM +0300, Andy Shevchenko wrote:
> Propagate firmware node by using a specific API call, i.e. device_set_node().

Can you add a line or two about *why* we should do this, e.g., is this
headed toward some goal?  Is it a simplification that's 100%
equivalent (doesn't seem so, see below)?

Seems like there's an underlying long-term effort to unify things from
OF and ACPI, which seems like a good thing, but at the moment it's a
little confusing to follow.  For instance pci_set_of_node() seems like
it ought to be sort of analogous to pci_set_acpi_fwnode(), but they
look nothing alike.

> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/pci/of.c | 19 +++++++------------
>  1 file changed, 7 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> index 196834ed44fe..4bba00dfbfc5 100644
> --- a/drivers/pci/of.c
> +++ b/drivers/pci/of.c
> @@ -18,19 +18,18 @@
>  #ifdef CONFIG_PCI
>  void pci_set_of_node(struct pci_dev *dev)
>  {
> +	struct device_node *node;
> +
>  	if (!dev->bus->dev.of_node)
>  		return;
> -	dev->dev.of_node = of_pci_find_child_device(dev->bus->dev.of_node,
> -						    dev->devfn);
> -	if (dev->dev.of_node)
> -		dev->dev.fwnode = &dev->dev.of_node->fwnode;
> +	node = of_pci_find_child_device(dev->bus->dev.of_node, dev->devfn);
> +	device_set_node(&dev->dev, of_fwnode_handle(node));

This doesn't seem 100% equivalent.  If of_pci_find_child_device()
returns NULL, the previous code doesn't set dev->dev.fwnode, but the
new code does.

>  }
>  
>  void pci_release_of_node(struct pci_dev *dev)
>  {
>  	of_node_put(dev->dev.of_node);
> -	dev->dev.of_node = NULL;
> -	dev->dev.fwnode = NULL;
> +	device_set_node(&dev->dev, NULL);
>  }
>  
>  void pci_set_bus_of_node(struct pci_bus *bus)
> @@ -45,17 +44,13 @@ void pci_set_bus_of_node(struct pci_bus *bus)
>  			bus->self->external_facing = true;
>  	}
>  
> -	bus->dev.of_node = node;
> -
> -	if (bus->dev.of_node)
> -		bus->dev.fwnode = &bus->dev.of_node->fwnode;
> +	device_set_node(&bus->dev, of_fwnode_handle(node));
>  }
>  
>  void pci_release_bus_of_node(struct pci_bus *bus)
>  {
>  	of_node_put(bus->dev.of_node);
> -	bus->dev.of_node = NULL;
> -	bus->dev.fwnode = NULL;
> +	device_set_node(&bus->dev, NULL);
>  }
>  
>  struct device_node * __weak pcibios_get_phb_of_node(struct pci_bus *bus)
> -- 
> 2.40.0.1.gaa8946217a0b
>