Here's an example script for your two-level case (with a section for subcommands of show
to show how it's done - you can just delete those three lines if they're not relevant to your case):
_foo()
{
local cur prev
cur=${COMP_WORDS[COMP_CWORD]}
prev=${COMP_WORDS[COMP_CWORD-1]}
case ${COMP_CWORD} in
1)
COMPREPLY=($(compgen -W "configure show" -- ${cur}))
;;
2)
case ${prev} in
configure)
COMPREPLY=($(compgen -W "CM DSP NPU" -- ${cur}))
;;
show)
COMPREPLY=($(compgen -W "some other args" -- ${cur}))
;;
esac
;;
*)
COMPREPLY=()
;;
esac
}
complete -F _foo foo
Hopefully it's fairly obvious from that example how you'd extend it to three-level commands etc., as well.