Okay, I found it - one can select the number of stepper in the config-page.
Selecting 3 steppers gives me 4 GPIOs - just perfect !
EDIT: Does not seem to be as easy as expected. Get "Axis at limit" errors, even if there is nothing connected to the pin.
But the configuration is as expected:
halcmd: loadrt hm2_eth board_ip="192.168.1.121" config=" num_encoders=0 num_pwmgens=0 num_stepgens=3"
Note: Using POSIX realtime
hm2_eth: dlopen: /usr/lib/linuxcnc/modules/hm2_eth.so: undefined symbol: hm2_register
<stdin>:1: waitpid failed /usr/bin/rtapi_app hm2_eth
<stdin>:1: /usr/bin/rtapi_app exited without becoming ready
<stdin>:1: insmod for hm2_eth failed, returned -1
halcmd: loadrt hostmot2
Note: Using POSIX realtime
hm2: loading Mesa HostMot2 driver version 0.15
halcmd: loadrt hm2_eth board_ip="192.168.1.121" config=" num_encoders=0 num_pwmgens=0 num_stepgens=3"
hm2_eth: loading Mesa AnyIO HostMot2 ethernet driver version 0.2
hm2_eth: 192.168.1.121: INFO: Hardware address (MAC): 00:60:1b:13:06:39
hm2_eth: discovered 7I92
hm2/hm2_7i92.0: Low Level init 0.15
hm2/hm2_7i92.0: Smart Serial Firmware Version 43
hm2/hm2_7i92.0: 34 I/O Pins used:
hm2/hm2_7i92.0: IO Pin 000 (P2-01): StepGen #0, pin Direction (Output)
hm2/hm2_7i92.0: IO Pin 001 (P2-14): StepGen #0, pin Step (Output)
hm2/hm2_7i92.0: IO Pin 002 (P2-02): StepGen #1, pin Direction (Output)
hm2/hm2_7i92.0: IO Pin 003 (P2-15): StepGen #1, pin Step (Output)
hm2/hm2_7i92.0: IO Pin 004 (P2-03): StepGen #2, pin Direction (Output)
hm2/hm2_7i92.0: IO Pin 005 (P2-16): StepGen #2, pin Step (Output)
hm2/hm2_7i92.0: IO Pin 006 (P2-04): IOPort
hm2/hm2_7i92.0: IO Pin 007 (P2-17): IOPort
hm2/hm2_7i92.0: IO Pin 008 (P2-05): IOPort
hm2/hm2_7i92.0: IO Pin 009 (P2-06): IOPort
hm2/hm2_7i92.0: IO Pin 010 (P2-07): IOPort
hm2/hm2_7i92.0: IO Pin 011 (P2-08): IOPort
hm2/hm2_7i92.0: IO Pin 012 (P2-09): IOPort
hm2/hm2_7i92.0: IO Pin 013 (P2-10): IOPort
hm2/hm2_7i92.0: IO Pin 014 (P2-11): IOPort
hm2/hm2_7i92.0: IO Pin 015 (P2-12): IOPort
hm2/hm2_7i92.0: IO Pin 016 (P2-13): IOPort