Submits an arbitrary NVMe IO command and returns the applicable
results. This may be the simply the command’s result and status, or may
also include a buffer if the command returns one. This command does no
interpretation of the opcodes or options.
The <device> parameter is mandatory and may be either the NVMe character
device (ex: /dev/nvme0), or a namespace block device (ex: /dev/nvme0n1).
On success, the returned structure (if applicable) may be returned in
one of several ways depending on the option flags; the structure may
printed by the program as a hex dump, or may be returned as a raw buffer
printed to stdout for another program to parse.