_URB_OS_FEATURE_DESCRIPTOR_REQUEST structure

The _URB_OS_FEATURE_DESCRIPTOR_REQUEST structure is used by the USB hub driver to retrieve Microsoft OS Feature Descriptors from a USB device or an interface on a USB device.

Syntax

struct _URB_OS_FEATURE_DESCRIPTOR_REQUEST {
  _URB_HEADER  Hdr;
  ULONG       TransferBufferLength;
  PVOID       TransferBuffer;
  PMDL        TransferBufferMDL;
  struct URB  *UrbLink;
  UCHAR       Recipient;
  UCHAR       InterfaceNumber;
  UCHAR       MS_PageIndex;
  USHORT      MS_FeatureDescriptorIndex;
};

Members

Hdr

Pointer to a _URB_HEADER structure that specifies the URB header information. Hdr.Function must URB_FUNCTION_GET_MS_FEATURE_DESCRIPTOR. Hdr.Length must be sizeof(_URB_OS_FEATURE_DESCRIPTOR_REQUEST).

TransferBufferLength

Specifies the length, in bytes, of the buffer specified in TransferBuffer or described in TransferBufferMDL. The host controller driver returns the number of bytes read in this member. Current implementation of this function limits the maximum MS OS Feature Descriptor size to 4 Kilobytes.

TransferBuffer

Pointer to a resident buffer for the transfer or is NULL if an MDL is supplied in TransferBufferMDL.

TransferBufferMDL

Pointer to an MDL that describes a resident buffer or is NULL if a buffer is supplied in TransferBuffer. This MDL must be allocated from nonpaged pool.

UrbLink

Reserved. Do not use.

Recipient

Specifies whether the recipient is the USB device or an interface on the USB device. One of the following values must be specified:

• 0 indicates that the USB device is the recipient of the request.
• 1 indicates that a USB interface is the recipient of the request.
• 2 indicates that a USB endpoint is the recipient of the request.

InterfaceNumber

Indicates the interface number that is the recipient of the request, if the Recipient member value is 1. Must be set to 0 if the USB device is the recipient.

MS_PageIndex

Must be set to 0. Page index of the 64K page of the MS OS Feature Descriptor to be returned. Current implementation only supports a maximum descriptor size of 4K.

MS_FeatureDescriptorIndex

Index for MS OS Feature Descriptor to be requested.

Remarks

The reserved members of this structure must be treated as opaque and are reserved for system use.

Requirements

See also

URB

_URB_HEADER

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Build date: 2/28/2013