Format of USB4DOS Host Controller request packet:
Offset	Size	Description	)
 00h	WORD	command number
 02h	WORD	(ret) major status
 04h	WORD	(ret) minor status
 06h	DWORD	-> callback function
 0Ah 25 BYTEs	data for command (varies by command number)
 23h 12 BYTEs	reserved for future use