There is "45-ddcutil-usb.rules" udev rule coming with the package. Inside it there is a line: SUBSYSTEM=="usbmisc", KERNEL=="hiddev*", PROGRAM="/usr/local/bin/ddcutil chkusbmon $env{DEVNAME} -v", MODE="0660", GROUP="video" In gentoo (as well as in the most of linux distros) this path to program should be /usr/bin instead. Wrong path causes some error in dmesg: [ 1.909675] udevd[919]: failed to execute '/usr/local/bin/ddcutil' '/usr/local/bin/ddcutil chkusbmon /dev/usb/hiddev0 -v': No such file or directory Probably, this is an upstream bug, but it also can be solved on Gentoo side (correct rule file in FILESDIR or edited by sed inside of the ebuild). All current versions in portage tree (0.8.4 .. 0.8.1) seem to be affected.
Fixed in 0.9.5
