If used with the -m command line parameter users can display all of the actively dmeventd monitored devices.
-{h/?} Show this help information
-m[r|u] List all currently active device mapper devices
        and their current status with dmeventd
        for registered (-r)/unregistered (-m) devices
            Syntax: dmevent_tool -m[u|r]
-a[r|u] Same as -m, but for devices with UUID only!
            Syntax: dmevent_tool -a[u|r]
-r      Register a device with dmeventd
            Syntax: dmevent_tool -r <device name> <path to DSO library>
            Example: dmevent_tool -r isw_abcdeh_Volume0 libdmraid-events.so
-u      Unregister a device with dmeventd
            Syntax: dmevent_tool -u <device name> [<path to DSO library>]
            Example: dmevent_tool -u isw_abcdefgh_Volume0
dmevent_tool -r is used to register a volume group device with dmeventd
    dmevent_tool -r isw_defeaigdde_Volume0_dmraid00 libdmraid-events.so
dmevent_tool -u is used to unregister a volume group from dmeventd
    dmevent_tool -u isw_defeaigdde_Volume0_dmraid00