2 "\\#" [2 bytes id] [2 bytes length] [n bytes args] [2 byte crc] [dev:2 bytes length] [dev:n byte payload] [dev:2 byte crc] call function
4 If the host sends 0 bytes of arguments, the host-side crs may be omitted.
7 0x00: get device descriptor
8 returns the lzma-ed json-encoded device descriptor