_URB_OPEN_STATIC_STREAMS structure (usb.h)

The _URB_OPEN_STATIC_STREAMS structure is used by a USB client driver to open streams in the specified bulk endpoint.

To format the URB, call the UsbBuildOpenStaticStreamsRequest function.

Syntax

struct _URB_OPEN_STATIC_STREAMS {
  struct _URB_HEADER       Hdr;
  USBD_PIPE_HANDLE         PipeHandle;
  ULONG                    NumberOfStreams;
  USHORT                   StreamInfoVersion;
  USHORT                   StreamInfoSize;
  PUSBD_STREAM_INFORMATION Streams;
};

Members

Hdr

The _URB_HEADER structure that specifies the URB header information. Hdr.Function must be URB_FUNCTION_OPEN_STATIC_STREAMS, and Hdr.Length must be sizeof(_URB_OPEN_STATIC_STREAMS).

PipeHandle

An opaque handle for the pipe associated with the endpoint that supports the streams to open.

The client driver obtains PipeHandle from the URB_FUNCTION_SELECT_CONFIGURATION or URB_FUNCTION_SELECT_INTERFACE request.

NumberOfStreams

The number of streams to open. The NumberOfStreams value indicates the number of elements in the array pointed to by Streams. This value must be greater than zero and less than or equal to the maximum number of streams supported by the USB driver stack, the host controller, and the endpoint in the device. For more information, see Remarks.

StreamInfoVersion

Version of the USBD_STREAM_INFORMATION structure. Must be set to URB_OPEN_STATIC_STREAMS_VERSION_100; otherwise, the request fails and the URB status is USBD_STATUS_INVALID_PARAMETER.

StreamInfoSize

Size of the USBD_STREAM_INFORMATION structure. StreamInfoSize must be sizeof(USBD_STREAM_INFORMATION); otherwise, the request fails and the URB status is USBD_STATUS_INFO_LENGTH_MISMATCH.

Streams

Pointer to a caller-allocated, initialized array of USBD_STREAM_INFORMATION structures. The length of the array depends on the number of streams to open and must be the same as the NumberOfStreams value. For more information, see Remarks.

Remarks

To use streams (other than the default stream) in the endpoint for I/O operations, the client driver opens the required streams by sending an open-stream request (URB_FUNCTION_OPEN_STATIC_STREAMS) to the USB driver stack. For the request, the client driver must format the URB by initializing the _URB_OPEN_STATIC_STREAMS structure. To format the URB, call the UsbBuildOpenStaticStreamsRequest function.

The maximum number of streams that can be opened by a client driver, must be less than or equal to the maximum number of streams supported by the USB driver stack, the host controller, and the bulk endpoint. To get the maximum number of streams supported by the host controller, call USBD_QueryUsbCapability. The USB driver stack supports up to 255 streams. If the client driver requests more than 255 streams, USBD_QueryUsbCapability fails the request. To get the maximum number of streams supported by the endpoint, inspect the endpoint companion descriptor (see USB_SUPERSPEED_ENDPOINT_COMPANION_DESCRIPTOR in Usbspec.h).

For information about formatting the URB for the open-stream request and code example, see How to Open and Close Static Streams in a USB Bulk Endpoint.

When the client driver is finished using the streams, the driver can close all streams associated with a particular endpoint by sending a close-stream request. To send the request, the client driver must specify information about the endpoint in the _URB_PIPE_REQUEST structure. The Hdr member of _URB_PIPE_REQUEST must be URB_FUNCTION_CLOSE_STATIC_STREAMS; the PipeHandle member must be the handle to the endpoint that contains the streams in use.

Requirements

See also

How to Open and Close Static Streams in a USB Bulk Endpoint

URB

USB Structures

_URB_HEADER