IOCTL_VVCR_QUERY_STATE (Windows CE 5.0)
This IOCTL permits the caller to iterate through the plugs pre-allocated by the driver due to registry settings.
Parameters
- hDevice
[in] Handle to the target object. To obtain a device handle, call the CreateFile function with a name dynamically obtained from the SetupDiEnumDeviceInterfaces function. - dwIoControlCode
[in] Set to IOCTL_VVCR_QUERY_STATE. This value identifies the target operation and the type of device on which to perform the operation. - lpInBuffer
[in] Unused. Set to NULL. - BufferSize
[in] Unused. Set to 0. - lpOutBuffer
[out] Pointer to a VVCR_QueryState_Response structure that will be filled if the command is successful. - nOutBufferSize
[out] Maximum size of the lpOutBuffer, which should be sizeof(VVCR_QueryState_Response). - lpBytesReturned
[out] Pointer to a DWORD that receives the actual count of bytes returned by the function in the output buffer. - lpOverlapped
[out] If not used, set to NULL. Otherwise, this should point to a completely filled out OVERLAPPED structure that contains a valid event. The event will be signaled when the I/O operation is complete.
Return Values
If the operation succeeds, the DeviceIoControl function returns a non-zero value. If the operation fails, DeviceIoControl returns zero. To obtain extended error information, call the GetLastError function. If the caller has supplied a plug index value greater than the number of plugs predefined, the API will return ERROR_NO_MORE_ITEMS, or STATUS_NO_MORE_ENTRIES if called from a WDM driver.
Remarks
Virtual subunits, or subunits for export, are available on the bus immediately after their drivers are activated. Core plugs for the subunit must be pre-allocated and ready at the time of startup. As an associated application would not necessarily be active at this time, the subunit driver allocates the necessary core plugs in advance.
This IOCTL detects these pre-allocated plugs and uses them. The plugs are valid for as long as the driver is loaded, which is at least as long as any application references the driver.
The application should not attempt to free or modify these plugs. It is acceptable to pass the plug handles returned as arguments to AVC_STREAM commands, such as IOCTL_STREAM_START_XMIT_SESSION or IOCTL_STREAM_START_RECV_SESSION.
The plugs are allocated and registered based on registry settings for the virtual VCR driver or interactive callbacks into the virtual VCR driver due to remote device connection requests.
Requirements
OS Versions: Windows CE .NET 4.0 and later.
Header: Avc_vvcr.h.
See Also
CreateFile | DeviceIoControl | IOCTL_STREAM_START_RECV_SESSION | IOCTL_STREAM_START_XMIT_SESSION | VVCR_QueryState_Response
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