Hi Yves-Alexis, I have experienced the same issue as described by Fabien.
What happens is, if I leave my laptop unused for a (very) long period of time idle, it goes into darkness (slowly fades out, then full screen black). When I want to wake-up my latop, I just press any key. This wakes up the laptop, but it does *not* set the screen brightness back to normal.
Increasing the brightness on the lightdm password prompt doesn't work. However, if I just type my password (blankly, hoping it works...), then I get to X (using the mate Desktop in my case), then brightness control works, and I can see the screen again.
Before I knew this trick, I thought my laptop was crashed. So I just powered off, then on again. But then when lightdm gets back, it sets the brightness to zero again (meaning screen is off in my case), and I can see nothing. The only way is again, to type my login and password blanking (without any control to see if I typed correctly), then when X start, I can set the brightness again.
I can confirm that the issue is in lightdm, because gdm doesn't have this issue. I'm also using systemd. I'm using the Nouveau driver (and probably also the intel i915 since my laptop has 2 cards). I'm not sure this is related to video board and driver, but I thought it was a good info.
I believe that the best way to fix it, is to make sure that the brightness controls are *always* working in lightdm. If I get back to lightdm with a black screen, I don't really mind if I can fix that by increasing the brightness...
If I may help to debug the issue in any way, let me know. I'd be happy to do whatever you propose to debug the issue or test some fixes.
Cheers, Thomas Goirand (zigo) -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
