On Wed, Jul 01, 2020 at 09:53:51AM +0800, Yicong Yang wrote:
> > static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
> > {
> > - struct pci_dev *bridge = pci_upstream_bridge(dev);
> > -
> > - while (bridge) {
> > - if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
> > - return bridge;
> > - bridge = pci_upstream_bridge(bridge);
> > + while (dev) {
> > + if (pci_is_pcie(dev) &&
> > + pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
> > + return dev;
> > + dev = pci_upstream_bridge(dev);
> > }
> >
>
> We may have some problems here, as after pcie_find_root_port() called, *dev will
> be either root port or NULL but users may want it unchanged. One such usage is
> in acpi_pci_bridge_d3(), drivers/pci/pci-acpi.c, *dev is used as origin
> after called this.
>
> So we should use a temporary point to *dev rather than directly modify it.
dev is already a copy of what is passed by the caller so it does not
matter if it gets changed here. You would need to pass it through struct
pci_dev **dev in order to modify the passed pointer.
