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_URB_CONTROL_VENDOR_OR_CLASS_REQUEST structure (usb.h)

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The _URB_CONTROL_VENDOR_OR_CLASS_REQUEST structure is used by USB client drivers to issue a vendor or class-specific command to a device, interface, endpoint, or other device-defined target.

Syntax

struct _URB_CONTROL_VENDOR_OR_CLASS_REQUEST {
  struct _URB_HEADER   Hdr;
  PVOID                Reserved;
  ULONG                TransferFlags;
  ULONG                TransferBufferLength;
  PVOID                TransferBuffer;
  PMDL                 TransferBufferMDL;
  struct _URB          *UrbLink;
  struct _URB_HCD_AREA hca;
  UCHAR                RequestTypeReservedBits;
  UCHAR                Request;
  USHORT               Value;
  USHORT               Index;
  USHORT               Reserved1;
};

Members

Hdr

Pointer to a _URB_HEADER structure that specifies the URB header information. Hdr.Function must be one of URB_FUNCTION_CLASS_XXX or URB_FUNCTION_VENDOR_XXX GET_STATUS, and Hdr.Length must be sizeof(_URB_CONTROL_VENDOR_OR_CLASS_REQUEST).

Reserved

TransferFlags

Specifies zero, one, or a combination of the following flags:

Value Meaning
USBD_TRANSFER_DIRECTION_IN
 Is set to request data from a device. To transfer data to a device, this flag must be clear. The flag must be set if the pipe is an interrupt transfer pipe.
USBD_SHORT_TRANSFER_OK
 Is set to direct the host controller not to return an error when it receives a packet from the device that is shorter than the maximum packet size for the endpoint. The maximum packet size for the endpoint is reported in the bMaxPacketSize0 member of the USB_DEVICE_DESCRIPTOR structure (device descriptor) for the default control endpoint. For a non-default control endpoint, maximum packet size is set in the wMaxPacketSize member of the USB_ENDPOINT_DESCRIPTOR structure (endpoint descriptor).

When the host controller receives a packet whose length is shorter than the wMaxPacketSize value on a control endpoint, the behavior is as follows depending on the type of host controller:

  • On EHCI host controllers, the host controller proceeds immediately to the status phase of the control transfer. The transfer completes successfully, regardless of whether USBD_SHORT_TRANSFER_OK is set.
  • On UHCI and OHCI host controllers, if USBD_SHORT_TRANSFER_OK is set, the host controller proceeds to the status phase. If USBD_SHORT_TRANSFER_OK is not set, the host controller abandons the data and status phases of the control transfer and the transfer completes with an error.

This flag should not be set unless USBD_TRANSFER_DIRECTION_IN is also set.

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 sent to or read from the pipe in this member.

TransferBuffer

Pointer to a resident buffer for the transfer or is NULL if an MDL is supplied in TransferBufferMDL. The contents of this buffer depend on the value of TransferFlags. If USBD_TRANSFER_DIRECTION_IN is specified this buffer will contain data read from the device on return from the host controller driver. Otherwise, this buffer contains driver-supplied data for transfer to the device.

TransferBufferMDL

Pointer to an MDL that describes a resident buffer or is NULL if a buffer is supplied in TransferBuffer. The contents of the buffer depend on the value of TransferFlags. If USBD_TRANSFER_DIRECTION_IN is specified, the described buffer will contain data read from the device on return from the host controller driver. Otherwise, the buffer contains driver-supplied data for transfer to the device. This MDL must be allocated from nonpaged pool.

UrbLink

Reserved. Do not use.

hca

Reserved. Do not use.

RequestTypeReservedBits

Reserved. Do not use.

Request

Specifies the USB or vendor-defined request code for the device, interface, endpoint, or other device-defined target.

Value

Specifies a value, specific to Request, that becomes part of the USB-defined setup packet for the target. This value is defined by the creator of the code used in Request.

Index

Specifies the device-defined index, returned by a successful configuration request, if the request is for an endpoint or interface. Otherwise, Index must be zero.

Reserved1

Reserved. Do not use.

Remarks

Drivers can use the UsbBuildVendorRequest service routine format this URB.

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

Requirements

Requirement Value
Header usb.h (include Usb.h)

See also

URB

USB Structures

_URB_HEADER