what does "id_byte" of nandsim mean

Question

I want to use nandsim module to mount a ubifs file, the first step i modprobe nandsim, but i don't know the args of the commodline:sudo modprobe nandsim first_id_byte=0xec second_id_byte=0xd3 third_id_byte=0x10 fourth_id_byte=0x15. my options：

    sudo modprobe nandsim first_id_byte=0xec second_id_byte=0xd3 third_id_byte=0x10 fourth_id_byte=0x15
    sudo modprobe ubi mtd=0
    sudo ubidetach /dev/ubi_ctrl -m 0
    sudo ubiformat /dev/mtd0 -f appfs.ubifs -O 2048
    sudo ubiattach /dev/ubi_ctrl -m 0 -O 2048
    sudo mount -t ubifs ubi0 ./temp_ubi
    sudo umount temp_ubi