USB_SUPERSPEED_ENDPOINT_COMPANION_DESCRIPTOR structure (usbspec.h)

The USB_SUPERSPEED_ENDPOINT_COMPANION_DESCRIPTOR structure is used by USB client drivers to retrieve a USB-defined SuperSpeed Endpoint Companion descriptor.

The members of this structure are described in the Universal Serial Bus 3.1 Specification available at USB Document Library. See section 9.6.7.

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 : 5;
      UCHAR SspCompanion : 1;
    } 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

bmAttributes.AsUchar

Specifies the length of the structures.

bmAttributes.Bulk

bmAttributes.Bulk.MaxStreams

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

bmAttributes.Bulk.Reserved1

Reserved. Do not use.

bmAttributes.Isochronous

bmAttributes.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.

bmAttributes.Isochronous.Reserved2

Reserved. Do not use.

bmAttributes.Isochronous.SspCompanion

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

See also

USB Structures