Man page 9 : pci_get_slot

pci_get_slot - locate PCI device for a given PCI slot

struct pci_dev * pci_get_slot(struct pci_bus *  bus , unsigned int  devfn );

bus
    PCI bus on which desired PCI device resides

devfn
    encodes number of PCI slot in which the desired PCI device resides and the logical device number within that slot in case of multi-function devices.

Given a PCI bus and slot/function number, the desired PCI device is located in the list of PCI devices. If the device is found, its reference count is increased and this function returns a pointer to its data structure. The caller must decrement the reference count by calling pci_dev_put. If no device is found, NULL is returned.