Re: [PATCH] PCI: allow pci_resize_resource() to be used on devices on the root bus

[Ard Biesheuvel <ardb@kernel.org>]

On Tue, 21 Apr 2020 at 18:43, Christian König <christian.koenig@amd.com> wrote:
>
> Am 21.04.20 um 18:22 schrieb Ard Biesheuvel:
> > When resizing a BAR, pci_reassign_bridge_resources() is invoked to
> > bring the bridge windows of parent bridges in line with the new BAR
> > assignment.
> >
> > This assumes that the device whose BAR is being resized lives on a
> > subordinate bus, but this is not necessarily the case. A device may
> > live on the root bus, in which case dev->bus->self is NULL, and
> > passing a NULL pci_dev pointer to pci_reassign_bridge_resources()
> > will cause it to crash.
> >
> > So let's make the call to pci_reassign_bridge_resources() conditional
> > on whether dev->bus->self is non-NULL in the first place.
> >
> > Fixes: 8bb705e3e79d84e7 ("PCI: Add pci_resize_resource() for resizing BARs")
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>
> Sounds like it makes sense, patch is
> Reviewed-by: Christian König <christian.koenig@amd.com>.

Thanks Christian.

>
> May I ask where you found that condition?
>

In this particular case, it was on an ARM board with funky PCIe IP
that does not expose a root port in its bus hierarchy.

But in the general case, PCIe endpoints can be integrated into the
root complex, in which case they appear on the root bus, and there is
no reason such endpoints shouldn't be allowed to have resizable BARs.