This tells the driver that a block-device file or character device is
+0 1 bLen 0dH (length of this request packet)
+2 1 bCmd 0eH (command code)
rStatus On exit, the driver must place a DevStatusWord here. Always
set the Done bit (bit 8). On an error, set the Done bit and
Notes: Only drivers capable of device Open/Close-processing need
DOS uses this request whenever an application closes a file or
device (fn 3eH). Drivers can use this in conjunction with
DvRq 0dH (Device Open) to help manage internal buffers.