with version starting with 0.8.0 (and newer), upstream udev rules installed for certain devices which then owned by plugdev group. For example, if no openocd installed certain usb devices such as UART are owned by uucp crw-rw---- 1 root uucp 188, 2 dec 19 18:26 /dev/ttyUSB0 After installing openocd (and re-plugging) this now owned by plugdev group: crw-rw-r-- 1 root plugdev 188, 0 dec 19 18:41 /dev/ttyUSB0 If user not in plugdev group, then this device is not accessible. Suggestion is: ebuild should print message about users supposed to create and add themselves into plugdev group, somewhere in pkg_postinst.
also of note, plugdev isn't a default group in gentoo. fixed 0.8.0, 0.9.0, and 9999 added enewgroup and elog in pkg_postinst
