URB
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_URB_BULK_OR_INTERRUPT_TRANSFER structure

The _URB_BULK_OR_INTERRUPT_TRANSFER structure is used by USB client drivers to send or receive data on a bulk pipe or on an interrupt pipe.

Syntax


struct _URB_BULK_OR_INTERRUPT_TRANSFER {
  struct URB_HEADER  Hdr;
  USBD_PIPE_HANDLE    PipeHandle;
  ULONG               TransferFlags;
  ULONG               TransferBufferLength;
  PVOID               TransferBuffer;
  PMDL                TransferBufferMDL;
  struct URB  *UrbLink;
  struct URB_HCD_AREA  hca;
};

Members

Hdr

Pointer to a _URB_HEADER structure that specifies the URB header information. Hdr.Function must be URB_FUNCTION_BULK_OR_INTERRUPT_TRANSFER, and Hdr.Length must be set to sizeof(_URB_BULK_OR_INTERRUPT_TRANSFER).

PipeHandle

Specifies an opaque handle to the bulk or interrupt pipe. The host controller driver returns this handle when the client driver selects the device configuration with a URB of type URB_FUNCTION_SELECT_CONFIGURATION or when the client driver changes the settings for an interface with a URB of type URB_FUNCTION_SELECT_INTERFACE.

TransferFlags

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

ValueMeaning
USBD_TRANSFER_DIRECTION_IN

Is set to request data from a device. To transfer data to a device, this flag must be clear.

USBD_TRANSFER_DIRECTION_OUT

Is set to transfer data to a device. Setting this flag is equivalent to clearing the USBD_TRANSFER_DIRECTION_IN flag.

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 wMaxPacketSize member of the USB_ENDPOINT_DESCRIPTOR structure (endpoint descriptor). When the host controller receives a packet shorter than wMaxPacketSize on a bulk or an interrupt endpoint, the host controller immediately stops requesting data from the endpoint and completes the transfer. If the USBD_SHORT_TRANSFER_OK flag is not set, the host controller completes the transfer with an error.

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

Note  On EHCI host controllers, USBD_SHORT_TRANSFER_OK is ignored for bulk and interrupt endpoints. Transfer of short packets on EHCI controllers does not result in an error condition.

On UHCI and OHCI host controllers, if USBD_SHORT_TRANSFER_OK is not set for a bulk or interrupt transfer, a short packet transfer halts the endpoint and an error code is returned for the transfer. The client driver must resume the endpoint by submitting a URB_FUNCTION_SYNC_RESET_PIPE_AND_CLEAR_STALL request before submitting a transfer request to the endpoint.

 

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.

Remarks

Drivers can use the UsbBuildInterruptOrBulkTransferRequest service routine to format this URB. Buffers specified in TransferBuffer or described in TransferBufferMDL must be nonpageable.

In an URB, both TransferBuffer and TransferBufferMDL parameters can be non-NULL values, at the same time. In that case, the transfer buffer and the MDL pointed to TransferBuffer and TransferBufferMDL must point to the same buffer.

The USB bus driver processes this URB at DISPATCH_LEVEL.

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

Requirements

Header

Usb.h (include Usb.h)

See also

URB
_URB_HEADER
USB Structures

 

 

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