On Arch Linux, the brightness control slider takes a second to apply once adjusted. On NixOS, the transition is instantaneous, with some visual irregularities—the bottom panel which is blurred and gray, becomes very white. My assumption is that on NixOS, instead of using my monitor’s brightness controls, it’s doing some gamma adjustment instead. How can I get it to control my monitor’s actual brightness?
Fixed by adding hardware.i2c.enable = true; and “i2c” to extraGroups.
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Adding your user to the “i2c” group shouldn’t be necessary. If it is, it means there’s a problem in the i2c module.
It is necessary, otherwise I have Permission Denied errors for /dev/i2c-* (shows in journalctl -b) and the brightness slider won’t be accessible in KDE Plasma - Display Configuration.
Well, then the udev rules are broken. You should be given access to these devices once you log in. I’ll have to look into this.
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There have been some changes in systemd v258 regarding uaccess, but our rules look still correct.
So, I just tested with a DDC display and everything seems to work fine.
Setting hardware.i2c.enable = true only, when logging on a local seat, my user is added automatically to the i2c and the users is directly given access to /dev/i2c-* with the uaccess ACL. Instead, if I log in remotely, I’m not in the i2c group, which confirms the rules are working.