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Setting the Parameters of a NIC Switch

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An overlying driver can change the parameters for a NIC switch that has been created on a network adapter that supports single root I/O virtualization (SR-IOV). The driver issues an object identifier (OID) set request of OID_NIC_SWITCH_PARAMETERS to change these parameters. Only the miniport driver for the PCI Express (PCIe) Physical Function (PF) of the SR-IOV adapter handles this OID set request.

Before the overlying driver issues this OID set request, it must initialize an NDIS_NIC_SWITCH_PARAMETERS structure with the parameters to be changed on the NIC switch. The driver then initializes an NDIS_OID_REQUEST structure for the OID request, and sets the InformationBuffer member to a pointer of the NDIS_NIC_SWITCH_PARAMETERS structure.

Only a limited subset of configuration parameters for a NIC switch can be changed. The overlying driver specifies the parameter to change by setting the following members of the NDIS_NIC_SWITCH_PARAMETERS structure:

  • The SwitchId member is set to the identifier of the NIC switch whose parameters will be changed.

    Note  Starting with Windows Server 2012, the SR-IOV interface supports only one NIC switch on the network adapter. This switch is known as the default NIC switch. The SwitchId member must be set to NDIS_DEFAULT_SWITCH_ID.

  • The appropriate NDIS_NIC_SWITCH_PARAMETERS_Xxx_CHANGED flags are set in the Flags member. Members of the NDIS_NIC_SWITCH_PARAMETERS structure can only be changed if a corresponding NDIS_NIC_SWITCH_PARAMETERS_Xxx_CHANGED flag is defined in Ntddndis.h.

  • The members of the NDIS_NIC_SWITCH_PARAMETERS structure, which correspond to the NDIS_NIC_SWITCH_PARAMETERS_Xxx_CHANGED flags set in the Flags member, are set with the NIC switch configuration parameters that are to be changed.

    Note  Starting with Windows Server 2012, only the SwitchName member of the NDIS_NIC_SWITCH_PARAMETERS structure can be changed through an OID set request of OID_NIC_SWITCH_PARAMETERS.

The PF miniport driver must follow these guidelines when it receives the OID set request of OID_NIC_SWITCH_PARAMETERS

  • If the PF miniport driver can apply the changes without requiring a reinitialization of the network adapter, the driver applies the changes to the hardware and completes the OID request with NDIS_STATUS_SUCCESS.

    If this status code is returned, NDIS updates the NIC switch configuration information in the registry.

  • If the PF miniport driver requires a reinitialization of the network adapter to apply the changes, the driver completes the OID request with NDIS_STATUS_REINIT_REQUIRED.

    If this status code is returned, NDIS also updates the NIC switch configuration information in the registry. However, the overlying driver that issued the OID set request must reinitialize the network adapter so that the changes can take effect.

    Note  PF miniport drivers that support static NIC creation and configuration can return NDIS_STATUS_REINIT_REQUIRED to make sure that the adapter is reinitialized for the new parameters to take effect.

  • If the PF miniport driver cannot apply the changes requested in the OID, it must fail the OID and return the appropriate NDIS_STATUS_Xxx code.

    In this case, NDIS does not update the NIC switch configuration information in the registry.