AFAIK, no. Loglevel is only define using -s or -d. Both enable debug mode
which exits after first connection. The next sane release will change -d
behavior, and "quit after first connection" will only be enabled if
explicitly set (-o|--once).
You could temporarily build from unstable source
root@raspberrypi:~:x86$ saned -d256
[saned] main: starting debug mode (level 256)
[saned] read_config: searching for config file
[saned] read_config: done reading config
[saned] saned (AF-indep+IPv6) from sane-backends 1.0.24 starting up
[saned] do_bindings: trying to get port for service
