Re: [PATCH 1/3] PCI: use pci_is_root_bus() to check whether it is a root bus

[Bjorn Helgaas <bhelgaas@google.com>]

[+cc Kenji, Alex]

On Fri, Sep 06, 2013 at 09:45:56AM +0800, Wei Yang wrote:
> In __pci_bus_size_bridges() we check whether a pci bus is a root
> bus by testing bus->self. As indicated by commit 79af72d7
> ("PCI: pci_is_root_bus helper"), bus->self == NULL is not a proper
> way to check the pci root bus.
> 
> This patch changes it to pci_is_root_bus() to check whether it is
> a root bus.

I think this is a good change, even if only on the grounds of
consistency.

Did you trip over a case where a root bus has bus->self != NULL?
I'd like to know more details about the case where:

  (bus->parent == NULL) && (bus->self != NULL)

I'm sure that situation exists, or Kenji and Alex would not have
made the change in 79af72d7, but I don't know the details.

I'd like to know the details so I can recognize similar problems
elsewhere.

> Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
> ---
>  drivers/pci/setup-bus.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 520210f..989de3c 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -1134,7 +1134,7 @@ void __ref __pci_bus_size_bridges(struct pci_bus *bus,
>  	}
>  
>  	/* The root bus? */
> -	if (!bus->self)
> +	if (pci_is_root_bus(bus))
>  		return;
>  
>  	switch (bus->self->class >> 8) {
> -- 
> 1.7.1
>