FreeBSD 14, RPI CM3+ - how to use I2C?

From: Patrick M. Hausen <pmh_at_hausen.com>
Date: Thu, 21 Sep 2023 12:10:57 UTC 
Next topic with my TuringPi ...

The CM placed in slot 1 has got access to the management bus
of the TuringPi mainboard.

The documentation states that one should add these to config.txt:

dtoverlay=i2c1,pins_44_45
dtoverlay=i2c-rtc,mcp7940x

Source: https://docs.turingpi.com/docs/turing-pi1-cluster-management-bus-i2c

Did that, but

i2c -s

shows now output and

root@pi1:~ # i2c -a 0x57 -o 0xf2 -d r -c 1
i2c: ioctl(I2CRDWR) failed: Input/output error

root@pi1:~ # grep iic /var/run/dmesg.boot 
iichb0: <BCM2708/2835 BSC controller> mem 0x7e804000-0x7e804fff irq 20 on simplebus0
iicbus0: <OFW I2C bus> on iichb0
iic0: <I2C generic I/O> on iicbus0

Any hints on how to get this working?

Kind regards,
Patrick