Description of the statusfd mechanism:

Applications can now ask scdaemon to be notified about certain events
(card inserted/removed) on a specified file descriptor.

This is how it works:

Run gpg-agent in daemon mode.
Figure out scdaemons socket:


moritz@pink:~/g10/hacks/gnupg-mo/build/scd$ gpg-connect-agent 
SCD GETINFO socket_name
D /tmp/gpg-QZRVNr/S.scdaemon
OK

Connect to scdaemon and register a status file descriptor:

moritz@pink:~/g10/hacks/gnupg-mo/build/scd$ gpg-connect-agent -S /tmp/gpg-QZRVNr/S.scdaemon
/sendfd /tmp/scd-events w
STATUSFD
OK
moritz@pink:~/g10/hacks/gnupg-mo/build/scd$ 


Watch the log file as you remove/insert the smartcard:

moritz@pink:~/g10/hacks/gnupg-mo/build/scd$ tail -f /tmp/scd-events 
CARD REMOVED
CARD INSERTED
CARD REMOVED
CARD INSERTED
^C
moritz@pink:~/g10/hacks/gnupg-mo/build/scd$ 

That's it for now.