Nov 20 02:35:20 pim udev[30422]: get_major_minor: found major = 81, minor = 0
Nov 20 02:35:20 pim udev[30422]: exec_callout: callout to /bin/echo -n xxx
Nov 20 02:35:20 pim udev[30422]: exec_callout: callout returned 'xxx'
Nov 20 02:35:20 pim udev[30422]: get_attr: kernel number appended: 0
The feature is really nice, but the maximum argument count is hard coded to 8.