On Tue, Jun 21, 2016 at 07:58:08PM +0800, wangyijing wrote:

Hi Bjorn, use devm_request_resource() for host bridge resource is cool,
what about do the similar change for x86, now we request host bridge resource
in pci_acpi_root_add_resources() in x86, and we would release the host bridge
resource when host bridge device refcount reach 0. This logic may introduce issue,
E.g.
If we try to remove a pci host bridge, but there is a child pci device which refcount
cannot decrease to 0 after remove the device, in this case, its parent pci_bus and
parent device, all their refcount cannot reach to 0, the result is pci host bridge
refcount can not reach 0, so its .release_fn() won't be called, and host bridge
resouces can not release. If we want to add the pci host bridge again, all pci devices
can not work because the resource is conflict with the old.

devm resource would be released when the driver detach, this is better than what we do now, I think.

I'm not going to convert pci_root.c to use devm right now.  That might
be a good thing, but this current series is mostly trivial.  I think
changing pci_root.c would not be trivial, so that looks like a project
all by itself.

I don't quite follow the example of removing a host bridge while a
child PCI device refcount is non-zero.  That sounds like an invalid
scenario regardless of whether the resources are released by a
.release_fn() or by devm.

Bjorn