GNOME Bugzilla – Bug 623102
gdm can't set the right resolution when loading matroxfb
Last modified: 2010-06-29 22:45:11 UTC
gdm works right just after ubuntu installation, showing welcome screen at 1280x1024 without any xorg.conf. But when I edit boot modules in order to load framebuffer support (matroxfb module, my video card is a matrox g550) it can't do the same, showing bad resolution or even unsupported frequencies (monitor goes blank). The workaround is to create a /etc/X11/xorg.conf with a `modelines' statement (I really thought this wouldn't be needed anymore), with two modes: the first is "1280x960", used by gdm (the desktop area is still 1280x1024, so I have to discover the whole of it moving my mouse), this way I can see the screen. Without this setting, gdm tries to set 1280x1024 selecting a bad/wrong frequency and the monitor shuts off => I don't get a welcome screen. Please note that gdm itself works: if I enter my login (blind typing) I can get in, and have a working xorg session (and xorg DOES set a valid frequency). The second mode is "1280x1024", used by xorg. In fact, when this is missing, xorg keeps using 1280x960 which appears a bit distorced (my flat panel's native resolution is 1280x1024). Is this really a bug? Or am I missing some setting? What can I do to make gdm show the resolution I want (even with matroxfb loaded)? I'm using: Linux LucidHome 2.6.32-22-generic #36-Ubuntu SMP Thu Jun 3 22:02:19 UTC 2010 i686 GNU/Linux with gnome 2.30.2, xorg X server 1.7.6.
This sounds like an X bug. GDM doesn't set the resolution of the monitor. It runs gnome-settings-daemon which set the resolution of the monitor if you have a saved configuration, but you presumably don't in your case. It sounds like X is getting things wrong out of the box and you have to fix it by overriding the defaults. You probably need to file this in freedesktop.org
I will, thank you very much.