Specifies the buffered I/O method, which is typically used for transferring small amounts of data per request. Most I/O control codes for device and intermediate drivers use this TransferType value.

Specifies the direct I/O method, which is typically used for reading or writing large amounts of data, using DMA or PIO, that must be transferred quickly. Specify METHOD_IN_DIRECT if the caller of DeviceIoControl or IoBuildDeviceIoControlRequest will pass data to the driver.

Specifies neither buffered nor direct I/O. The I/O manager does not provide any system buffers or MDLs. The IRP supplies the user-mode virtual addresses of the input and output buffers that were specified to DeviceIoControl or IoBuildDeviceIoControlRequest, without validating or mapping them.

Specifies the direct I/O method, which is typically used for reading or writing large amounts of data, using DMA or PIO, that must be transferred quickly. Specify METHOD_OUT_DIRECT if the caller of DeviceIoControl or IoBuildDeviceIoControlRequest will receive data from the driver.