pci_find_capability — query for devices' capabilities
| int pci_find_capability ( | struct pci_dev * dev, | 
| int cap ); | 
   Tell if a device supports a given PCI capability.
   Returns the address of the requested capability structure within the
   device's PCI configuration space or 0 in case the device does not
   support it.  Possible values for cap:
   
   PCI_CAP_ID_PM           Power Management
   PCI_CAP_ID_AGP          Accelerated Graphics Port
   PCI_CAP_ID_VPD          Vital Product Data
   PCI_CAP_ID_SLOTID       Slot Identification
   PCI_CAP_ID_MSI          Message Signalled Interrupts
   PCI_CAP_ID_CHSWP        CompactPCI HotSwap
   PCI_CAP_ID_PCIX         PCI-X
   PCI_CAP_ID_EXP          PCI Express