Bug#787233: xserver-xorg-video-nouveau: (EE) [drm] KMS not enabled

[Sven Joachim <svenjoac@gmx.de>]

On 2015-05-30 08:56 +0200, Kingsley G. Morse Jr. wrote:

> Package: xserver-xorg-video-nouveau
> Version: 1:1.0.11-1+b1
> Severity: normal
>
> Dear Maintainer,
>
> Thanks for maintaining Debian's nouveau driver.
>
> It's great to have an open alternative.
>
> The main reason I'm writing is that a recent
>
>     $ aptitude full-upgrade
>
> and reboot, failed to run X.
>
> xorg's log file said something like
>
>     (EE) [drm] KMS not enabled
>
> My understanding is that KMS is an acronym for
> kernel mode switching, which is now code in the
> kernel for quickly switching between console and
> graphical video modes.
>
> Evidently X didn't think my kernel supported KMS.

That could have been because your installed nvidia packages blacklisted
the nouveau kernel module.  Running "update-alternatives --config glx"
and selecting the mesa alternative should change that, but you may have
to manually "modprobe nouveau" (or reboot, as you did).

Another possibility is that newer udev versions might be incompatible
with your old 3.0 kernel, causing modprobe to fail loading the nouveau
module.  Did you just upgrade to udev 220?

Cheers,
       Sven