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USB_SUPERSPEED_ENDPOINT_COMPANION_DESCRIPTOR structure

The USB_SUPERSPEED_ENDPOINT_COMPANION_DESCRIPTOR structure is used by USB client drivers to retrieve a USB-defined SuperSpeed Endpoint Companion descriptor. For more information, see section 9.6.7 and Table 9-20 in the official USB 3.0 specification.

Syntax


typedef struct _USB_SUPERSPEED_ENDPOINT_COMPANION_DESCRIPTOR {
  UCHAR  bLength;
  UCHAR  bDescriptorType;
  UCHAR  bMaxBurst;
  union {
    UCHAR  AsUchar;
    struct {
      UCHAR MaxStreams  :5;
      UCHAR Reserved1  :3;
    } Bulk;
    struct {
      UCHAR Mult  :2;
      UCHAR Reserved2  :6;
    } Isochronous;
  } bmAttributes;
  USHORT wBytesPerInterval;
} USB_SUPERSPEED_ENDPOINT_COMPANION_DESCRIPTOR, *PUSB_SUPERSPEED_ENDPOINT_COMPANION_DESCRIPTOR;

Members

bLength

Specifies the length, in bytes, of this descriptor.

bDescriptorType

Specifies the descriptor type. Must be set to USB_SUPERSPEED_ENDPOINT_COMPANION_DESCRIPTOR.

bMaxBurst

Specifies the maximum number of packets that the endpoint can send or receive as a part of a burst.

bmAttributes
AsUchar

Specifies the length of the structures.

Bulk
MaxStreams

Specifies the maximum number of streams supported by the bulk endpoint.

Reserved1

Reserved. Do not use.

Isochronous
Mult

Specifies a zero-based number that determines the maximum number of packets (bMaxBurst * (Mult + 1)) that can be sent to the endpoint within a service interval.

Reserved2

Reserved. Do not use.

wBytesPerInterval

Number of bytes per interval.

Remarks

A client driver that supports streams associated with a bulk endpoint, uses USB_SUPERSPEED_ENDPOINT_COMPANION_DESCRIPTOR to get the maximum number of streams supported by the endpoint. That information is required by the client driver in an open-streams request. In the request, the specified value for NumberOfStreams member of the _URB_OPEN_STATIC_STREAMS structure cannot exceed the MaxStreams value reported in USB_SUPERSPEED_ENDPOINT_COMPANION_DESCRIPTOR. For more information about opening streams, see How to Open and Close Static Streams in a USB Bulk Endpoint.

Requirements

Minimum supported client

Windows 8

Minimum supported server

None supported

Header

Usbspec.h (include Usbspec.h)

See also

USB Structures

 

 

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