Video projector not detected anymore (under Xorg 1.18.4)

Christopher Barry christopher.barry at
Thu Nov 3 16:53:13 UTC 2016

On Thu, 3 Nov 2016 17:05:22 +0100
Philippe Dosch <Philippe.Dosch at> wrote:

>Le 03/11/2016 à 16:12, Łukasz Maśko a écrit :
>> Dnia czwartek, 3 listopada 2016 15:41:52 Philippe Dosch pisze:  
>>> Hi Folks,
>>> I'm assistant professor and I teach with the same video projectors
>>> since years (with each of the last three kubuntu releases on my
>>> laptop). I have a strange trouble since my last kubuntu update (2
>>> weeks ago). Now I'm under kubuntu 16.10, with a 1.18.4 Xorg
>>> server:  
>> Hello!
>> I have exactly the same problem and it lies in the kernel itself,
>> probably in i915 driver, not in X. The change was introuced in
>> kernel 4.7.0, the last of the 4.6.x line (4.6.7) works fine. The
>> changes deal with detection of external Display Port and as a result
>> I get first an error like this:
>> [drm:intel_dp_start_link_train [i915]] *ERROR* failed to update link
>> training  
>Hi Dnia,
>I have the same message several times at boot time (also found in
>dmesg). But in my case, my troubles are related to the VGA port, not
>the display port.
>> at the kernel start (visible in dmesg). And then this output is not
>> recognized anymore. I have filed a bug report
>I saw your post, but it is related to the display port and I don't
>know if the DP trouble makes some side effects with the VGA port.
>> Maybe you can confirm it or append yours so we make developers fix
>> this? I have no idea how to fix this myself. I'm just keeping kernel
>> 4.6.7 to use when I want to do my presentations.  
>It's an idea, maybe I could downgrade to a 4.6.x kernel to see what

It's probable that you already have the last kernel already installed
and selectable via GRUB. Do you see the GRUB menu on boot? If not, I
believe if you hold the shift key down just as soon as it's out of the
BIOS it will show the GRUB boot menu and you can select the previous


Christopher Barry

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