Man page 9 : pci_enable_obff

pci_enable_obff - enable optimized buffer flush/fill

int pci_enable_obff(struct pci_dev *  dev , enum pci_obff_signal_type  type );

dev
    PCI device

type
    type of signaling to use

Try to enable type OBFF signaling on dev. It will try using WAKE# signaling if possible, falling back to message signaling only if WAKE# isnAqt supported. type should indicate whether the PCIe link be brought out of L0s or L1 to send the message. It should be either PCI_EXP_OBFF_SIGNAL_ALWAYS or PCI_OBFF_SIGNAL_L0.

If your device can benefit from receiving all messages, even at the power cost of bringing the link back up from a low power state, use PCI_EXP_OBFF_SIGNAL_ALWAYS. Otherwise, use PCI_OBFF_SIGNAL_L0 (the preferred type).

Zero on success, appropriate error number on failure.