On Fri, Aug 17, 2018 at 04:17:19PM +0800, Jiecheng Wu wrote: > Function dpc_probe() defined in drivers/pci/pcie/dpc.c calls > pci_find_ext_capability(). Function pci_find_ext_capability() returns > the address of the requested extended capability structure within the > device's PCI configuration space or 0 if the device does not support > it. The return value of this function should be checked against 0. dpc_probe will not get called if the capability doesn't exist. The capability existing is the criteria for PCIE_PORT_SERVICE_DPC flag, which is required to call dpc_probe.
