Dear Maintainer, *** Reporter, please consider answering these questions, where appropriate *** * What led up to the situation? I think it happened after an important upgrade related to systemd a few months ago but I'm not fully sure. I'm now using systemd-logind. * What was the outcome of this action? Notice that I report the bug with a different kernel. The kernel on which the bug occurs is: Linux 3.16-2-amd64 Lightdm starts and instantly (maybe after 1/10 sec) shows a black screen. It is possible to login (I can see that the HDD light working) but the screen is still black. I'm reporting this for lightdm but I guess this is more general. Notice that when I use another kernel (3.14-2-amd64) the situation is a bit different: the screen is black but if I increase the luminosity of the screen then it suddenly works. * What outcome did you expect instead? To be able at least to increase the luminosity until it works. The best would be of course to have immediately a screen with display on.
control: tag -1 unreproducible moreinfo control: severity -1 important What am I supposed to do with that? LightDM doesn't control the screen brightness, so it's look completely unrelated to lightdm. Indeed. So why are you reporting against lightdm if it looks like a kernel regression? In any case, there's nothing I can do with the report, sorry. Regards,
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)
So something in your desktop environment handles the brightness and sets it to minimum? Ok. I assume your laptop needs something in userspace to handle the brightness keys, then? Because MATE handles the brightness keys. It's somehow related yeah. Brightness keys handling has been a mess these past years. It was once handled completely by the laptops embedded controller, then it was done by the kernel/ACPI, then by the driver, then by basically noone (since Windows 8 laptops), so it has to be done in userspace. Sure, but I'm not sure handling the brightness keys are really the role of a login screen. I'll forward this upstream but don't hold your breath. It might help to know which kind of laptop it is. Regards,
On Mon, Mar 30, 2015 at 12:18:20AM +0200, Thomas Goirand wrote: >> 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). > > So something in your desktop environment handles the brightness and > sets it to minimum? Yes, the screen saver. >> 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. > > I assume your laptop needs something in userspace to handle the > brightness keys, then? I believe my mate desktop is somehow handling this. >> 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. > >Because MATE handles the brightness keys. Yes, and lightdm should as well. >> 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... > > Sure, but I'm not sure handling the brightness keys are really the > role of a login screen. I'll forward this upstream but don't hold your > breath. If we can't handle the brightness keys, then just setting-up the brightness could be a quick and dirty fix-up. Here's a few way to do it on my laptop: # This needs root: echo 4792 > /sys/class/backlight/intel_backlight/brightness # This needs xbacklight to be installed, but this is from userland: xbacklight -inc 100% Do you know if the above can be set somewhere in the lightdm config as a hook script or something? If that is for *me* only, this type of hack is enough (but of course, a more generic / less dirty way to fix things for everyone else would be better...). >> 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. > >It might help to know which kind of laptop it is. My laptop is a Lenovo T440p. I have attached the output of dmidecode and lspci, if that helps. Cheers, Thomas Goirand (zigo)
That's not enough information. Also note that brightness is not DPMS. I have no idea about what MATE does, this is purely random guesses here. You might want to investigate more. I don't think that's the job of a login manager, actually (my opinion is that it was the kernel job, but they disagree). I've forwarded upstream, it's their call anyway. And you're back to handling manually everything, adding support for specific graphics cards and what not. Definitely not the role of a login manager. See /etc/lightdm/lightdm.conf (you can edit it, or put overrides in /etc/xdg/lightdm/lightdm.conf.d, remember to correctly set the section), for example: # display-setup-script = Script to run when starting a greeter session (runs as root) or: # greeter-setup-script = Script to run when starting a greeter (runs as root) So yes, that's a Windows 8 laptop which needs userspace handling for brightness keys. Regards,
I'm not sure how to collect the information that you need then. I'm well aware of it, and my screen isn't off using DPMS, it seems that my laptop just turns the LCD completely off when brightness is set to zero, as much as I can see. Correct. How? Well... I don't really care who's job it is, if at least it is possible to set the brightness whenever I need to type my password. You agree that this is a needed functionality, right? Thanks for the tips! I'll try. Ok. Thanks for your helpful replies so far. Thomas
I have no idea what your system is. I don't use MATE, so “screensaver” doesn't ring any bell for me. Ok. No idea, look at MATE documentation? I'm not interested in nitpicking. LightDM didn't touch the brightness to set it to zero, I don't think it should touch it at all. Anyway that's upstream call wether to implement this feature, so there's not much to discuss here anyway. Regards,