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

["Kingsley G. Morse Jr." <kingsley@loaner.com>]

On 05/30/15 09:58, Sven Joachim wrote:
> 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.

Hi Sven,

Thanks for your prompt thoughts.

> 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).

Yes, I seem to recall also wondering if the
nouveau kernel module had been blacklisted, and
checking two ways.

If I recall correctly, 

    one way was the lsmod command, and 
    
    both tests indicated it was loaded.

> Another possibility is that newer udev versions might be incompatible
> with your old 3.0 kernel, causing modprobe to fail loading the nouveau
> module.

However, I think I may be aware of some evidence
related to your second theory: incompatible udev
and kernel versions.

Soon after trying to upgrade the Linux kernel from
3.0 to 4.0, my computer hung after booting with

    /scripts/init-top/udev: line 14: can't create /sys/kernel/uevent_helper: Permission denied
    Gave up waiting for root device.  Common problems:
     - Boot args (cat /proc/cmdline)
       - Check rootdelay= (did the system wait long enough?)
       - Check root= (did the system wait for the right device?)
     - Missing modules (cat /proc/modules: ls/dev)
    ALERT!  /dev/disk/by-uuid/a9792df8-2513-4185-bb81-589f5f9d508d does not exist.
    Dropping to a shell!

    modprobe: module ehci-orion not found in modules.dep

    BusyBox v1.22.1 [...]
    Enter 'help' for a list of built-in commands.

    (initramfs)

This happened with the following versions

    udev:                           204-5
    initramfs-tools:                0.114
    sysv-rc:                        2.88dsf-43
    linux-image-4.0.0-1-686-pae:    4.0.2-1

> Did you just upgrade to udev 220?

An

    $ aptitude full-upgrade

to version 215-18 of udev and 4.0 of the kernel
seems to have fixed it.

So, that's what I think I know.


On a related note, my testing suggests that
version 215-18 of udev needs version 4.0 of the
kernel to work.

I can imagine that adding a dependency header
indicating this might also be helpful.

If you happen to have any insights into whether
this would be a good bug to report or not, please
enlighten me.

Thanks,
Kingsley

> Cheers,
>        Sven

-- 
Time is the fire in which we all burn.