Hi. On Thu, Jun 27, 2019 at 10:24:51AM -0500, David Wright wrote: > That has led to finding these lines in systemd's journal: ... > Jun 27 09:47:06 west systemd-backlight[615]: [0;1;31mFailed to write system > 'brightness' attribute: Input/output error[0m ... > which suggests there's something wrong with the backlight.
Hardly. More likely there's something wrong with the appropriate kernel facility. Basically what this systemd unit tries to do is to write a saved value to /sys/class/backlight/intel_backlight/brightness. Kernel responds to this with EIO, which is unusual for the laptop (to be expected for the desktop as there's no backlight there). It may be possible to workaround this with certain knobs of i915 kernel module (enable_dpcd_backlight or invert_brightness), I'd try the latter first. I.e. try adding "i915.invert_brightness=1" or "i915.enable_dpcd_backlight=1" to the kernel's commandline. Reco
