Also note that upstream bug 106 ( https://github.com/haikarainen/light/issues/106) claims that the udev rule "ACTION" should be "change" rather than "add". I am not proficient with udev rules but I did not observe a problem leaving the "ACTION" as "add" either on the backports kernel or the regular stable kernel. Perhaps someone else can speak to the significance of "add" vs "change" in the "ACTION" match clause of the udev rules.
On Sat, 13 Nov 2021 18:06:26 -0500 Alexander Necheff <neche...@gmail.com> wrote: > Package: light > Version: 1.2.2-2 > > Executing light commands that would modify the backlight brightness, for > example setting the brightness to 10%: > ~$ light -S 10 > do not work when run as a non-root user, even if that user is a member of > the "video" group. The upstream author suggests "video" membership is the > intended mechanism to grant non-root users the necessary privilege to > modify backlight settings. su'ing to root and then executing the same > commands successfully modifies the backlight brightness. > > Looking at the upstream git repo there is a udev rule included as part of > the source distribution: > https://github.com/haikarainen/light/blob/master/90-backlight.rules > Manually copying these rules into /etc/udev/rules.d/ allowed my > unpriviledged user to modify the backlight brightness on the condition that > I was a member of the "video" group. > This seems more attractive than manually making /usr/bin/light SUID. > > Currently running Bullseye 11.1, kernel 5.14.9-2~bpo11+1, glibc > 2.31-13+deb11u2. > For hardware, I'm using a Framework laptop which appears to use > /sys/class/backlight/intel_backlight/ for getting and setting backlight > options.
