IOCTL_SERIAL_SET_FIFO_CONTROL control code
The IOCTL_SERIAL_SET_FIFO_CONTROL request sets the FIFO control register (FCR). Serial does not verify the specified FIFO control information.
The AssociatedIrp.SystemBuffer member points to a client-allocated ULONG that is used to input FIFO control information.
The Parameters.DeviceIoControl.InputBufferLength is set to the size, in bytes, of a ULONG.
The Information member is set to zero.
The Status member is set to one of the Generic Status Values for Serial Device Control Requests.