Man page 9 : pci_get_subsys

pci_get_subsys - begin or continue searching for a PCI device by vendor/subvendor/device/subdevice id

struct pci_dev * pci_get_subsys(unsigned int  vendor , unsigned int  device , unsigned int  ss_vendor , unsigned int  ss_device , struct pci_dev *  from );

vendor
    PCI vendor id to match, or PCI_ANY_ID to match all vendor ids

device
    PCI device id to match, or PCI_ANY_ID to match all device ids

ss_vendor
    PCI subsystem vendor id to match, or PCI_ANY_ID to match all vendor ids

ss_device
    PCI subsystem device id to match, or PCI_ANY_ID to match all device ids

from
    Previous PCI device found in search, or NULL for new search.

Iterates through the list of known PCI devices. If a PCI device is found with a matching vendor, device, ss_vendor and ss_device, a pointer to its device structure is returned, and the reference count to the device is incremented. Otherwise, NULL is returned. A new search is initiated by passing NULL as the from argument. Otherwise if from is not NULL, searches continue from next device on the global list. The reference count for from is always decremented if it is not NULL.