This has been bugging me for few days, the screen is either too bright or too dark and, yes, it’s all random. Accidentally I found a workaround tonight. Since I’ve been seeing people have all kinds of similar problem on the Internet, I’m simply posting this workaround that might help some others, and also hoping maybe someone can give some insight and provide a true solution to this. So, thanks in advance.
most Fn+X keys work, like volume control, but not Fn+Up/Down for brightness, even though the transparent window shows up when I adjust it (but with blank brightness level).
Checked /proc/acpi/video/OVGA/DD0X/brightness values, being <not supported> so the “echo -n X” method didn’t work for me. I realise some people are in the same case.
The brightness level changes by itself sometimes after logout then log back in. This gives me a blind idea how X window might be source of this problem…
Ctrl+Alt+F1 to get out of the X window session.
Based on prior screen brightness level, use the same Fn+Up/Down key to adjust the level, even you can’t see anything.
Ctrl+Alt+F7 to get back to the GUI, and the brightness is actually now changed. Tried a few times and it actually works pretty well.
Finally, I’m not an expert, but happy to provide any logs if anyone is interested.