fw_device,
   - with most policies, it won't be necessary anymore to dig through
     child attributes.

The new attribute is called "units".  It contains space-separated tuples
of specifier_id and version of each present unit.  The delimiter within
tuples is a colon.  Specifier_id and version are printed as 0x%06x.

Here is an example of a node which implements an IPv4 unit and an IPv6
unit:  $ cat /sys/bus/firewire/devices/fw2/units
0x00005e:0x000001 0x00005e:0x000002

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
ƒnLu—+x