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Implementing a Storport virtual miniport driver

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This page provides high-level implementation information for a Storport virtual miniport driver (VMiniport). The VMiniport interface is defined in storport.h.

Design considerations are unique to various VMiniports, so implementation specifics are not included here.

The VMiniport interface

This section lists the more prominent functions, callbacks, and structures that a VMiniport implements/uses. Some functions and callbacks are required; the optional callbacks are unique to a VMiniport's design.

  • DriverEntry, which is the first routine that the operating system calls after the VMiniport is loaded. This routine is required.

  • HW_INITIALIZATION_DATA, which is a Vminiport-allocated and initialized structure that the VMiniport passes to Storport during initialization. The VMiniport provides pointers to its callback functions in this structure.

    The following callback routines are required:

    The following callback routines are optional, though a VMiniport might have to implement some of them depending on its unique architecture:

    • HwInitializeTracing

    • HwCleanupTracing. This routine is required when HwInitializeTracing points to a callback routine; otherwise, this routine is optional, and is unique to a VMiniport.

    • HwProcessServiceRequest. This routine receives a "reverse-callback" IRP, which will be completed when the VMiniport updates the caller (such as a user-mode application or kernel-mode driver) or requires the caller to do something on the VMiniport's behalf.

    • HwCompleteServiceIrp. This routine is required when HwProcessServiceRequest points to a callback routine; otherwise, this routine is optional and is unique to a VMiniport.HwCompleteServiceIrp is called when the virtual adapter is being removed so that the VMiniport can complete any reverse-callback IRPs that might be pending.

    The VMiniport must also set the following members of the HW_INITIALIZATION_DATA structure:

    • Set HwInitializationDataSize to sizeof(HW_INITIALIZATION_DATA).

    • Set AdapterInterfaceType to Internal, which indicates to Storport that this is a virtual adapter.

    • Set HwBuildIo to NULL.

    The Vminiport driver sets other fields as needed. Unused fields must be set to zero.

  • PORT_CONFIGURATION_INFORMATION, which is a Storport-allocated structure. Storport initializes some PORT_CONFIGURATION_INFORMATION members and then passed it to the VMiniport's HwFindAdapter callback, where the VMiniport completes the initialization. Since this structure is pre-initialized by Storport, HWFindAdapter must not zero out the structure. A VMiniport must set VirtualDevice to TRUE.

VMiniport initialization

A VMiniport has three stages of initialization.

  • In the first stage, the VMiniport's DriverEntry routine calls StorPortInitialize with a pointer to its initialized HW_INITIALIZATION_DATA structure.

  • Storport calls the VMiniport's HwFindAdapter callback with a Storport-allocated and partially initialized PORT_CONFIGURATION_INFORMATION structure. The principal function of HwFindAdapter is to complete the initialization of PORT_CONFIGURATION_INFORMATION, including setting the VirtualDevice member to TRUE.

  • After HwFindAdapter successfully returns, Storport calls the VMiniport's HwInitialize callback to complete initialization of the VMiniport.

VMiniport I/O

Storport calls a VMiniport's HwStartIo callback to initiate an I/O request. In Storport, an I/O request is described using a SCSI_REQUEST_BLOCK or STORAGE_REQUEST_BLOCK (standard or extended SRB, respectively).

Unlike a physical miniport driver, Storport does not call HwBuildIo in a Vminiport prior to calling HwStartIo.

No locks are held prior to calling HwStartIo. The default queue depth for each logical unit that is exposed through the virtual miniport interface is 250.