Nixpkgs: ati_unfree: doesn't work with some display managers

[vcunat]

Data so far:

• OK: lightdm;
• KO: kdm, gdm.

For details see https://github.com/NixOS/nixpkgs/issues/9903#issuecomment-223483656

[cleverca22]

related, a few months ago, i found that ati_unfree 'worked' with slim+xfce, but the instant i enabled dual-monitor, it segfaulted X and left the gpu in a bad state

attempting to restart X caused the kernel to hang solid

and then upon rebooting, slim worked fine, i logged in, and xfce restored the monitor state, crashing it again!

[domenkozar]

cc @ocharles

[ocharles]

Thanks @domenkozar, this was exactly my problem. I'm now using ati_unfree with lightdm successfully. In the meantime, could we perhaps just throw an exception if someone tries to build a configuration.nix with ati_unfree and KDM or GDM?

[adelbertc]

Unsure if related, but prior to using ati_unfree I had services.xserver.enable = true; with XMonad enabled as my window manager. Seemed to be working fine, then I set:

nixpkgs.config.allowUnfree = true;

services.xserver.videoDrivers = [ "ati_unfree" ]

did a nixos-rebuild switch followed by a reboot, and now X doesn't seem to want to start anymore, I just get dropped into a shell as if X was never enabled.

Any ideas?

[jerith666]

Are you using a display manager? Do you see the same stack trace as in https://github.com/NixOS/nixpkgs/issues/9903#issuecomment-223483656?

[davidak]

Linux 4.9, LightDM and Xfce works, but performance is very bad. https://github.com/NixOS/nixpkgs/issues/49726#issuecomment-485301170

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