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#1 2016-09-20 19:38:12

Nicky726
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From: Czech Republic
Registered: 2008-02-15
Posts: 142
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[SOLVED] Some projectors connected over VGA not detected

I've been hit by a weird problem. I connect my HP EliteBook 820 to several projectors during lectures over VGA and this term there are some, which are not detected. The xrandr just shows (as is the case when nothing is plugged in):

Screen 0: minimum 8 x 8, current 1366 x 768, maximum 32767 x 32767
eDP1 connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 280mm x 160mm
   1366x768      59.99*+  40.00  
   1280x720      60.00  
   1024x768      60.00  
   1024x576      60.00  
   960x540       60.00  
   800x600       60.32    56.25  
   864x486       60.00  
   640x480       59.94  
   720x405       60.00  
   680x384       60.00  
   640x360       60.00  
DP1 disconnected (normal left inverted right x axis y axis)
DP2 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

The projector is connected to output designated as DP2. I had no trouble in May at the same place (though I cannot rule off a hardware change), and I do not have trouble currently with other projectors or VGA monitors, only with some. Peculiarly, a colegue of mine using also Arch Linux on a similar laptop was able to successfully connect to one of the devices in question (in his case using a hotkey on notebook to switch screen, while I normally use a xrandr command. Note though, that the hot key is not working for me either). Since I am at the place in question only once a week, would you suggest some steps to try to help solving the issue? Also, the technical support is not exactly Linux-aware, and I am not sure if I can rule out software problem.

Last edited by Nicky726 (2016-12-06 20:23:58)


"Although the masters make the rules
For the wise men and the fools
I got nothing, Ma, to live up to."

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#2 2016-09-21 16:41:49

Ticonderogafr
Member
Registered: 2016-09-21
Posts: 1

Re: [SOLVED] Some projectors connected over VGA not detected

I have the same problem and as a teacher I need VGA output so I downgraded my kernel to 4.6.3-1 to fix the VGA output

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#3 2016-09-22 06:01:15

Nicky726
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From: Czech Republic
Registered: 2008-02-15
Posts: 142
Website

Re: [SOLVED] Some projectors connected over VGA not detected

Thankx for suggestion, I'll give it a try next Tuesday. Luckily, I have the old kernels in cache.


"Although the masters make the rules
For the wise men and the fools
I got nothing, Ma, to live up to."

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#4 2016-09-24 03:07:13

guoxh
Member
Registered: 2016-09-24
Posts: 1

Re: [SOLVED] Some projectors connected over VGA not detected

I had the same problem. Now I have install the lts kernel and it is solved. Thanks Ticonderogafr. I did not realize that this is a kernel issue.

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#5 2016-09-28 06:40:12

Nicky726
Member
From: Czech Republic
Registered: 2008-02-15
Posts: 142
Website

Re: [SOLVED] Some projectors connected over VGA not detected

OK, I gave it a try with LTS kernel and the projectors in question were detected, so it indeed seems to be a kernel issue.


"Although the masters make the rules
For the wise men and the fools
I got nothing, Ma, to live up to."

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#6 2016-10-06 14:35:33

rochus
Member
Registered: 2007-02-14
Posts: 86

Re: [SOLVED] Some projectors connected over VGA not detected

Any news in here what the issue actually is? I seem to have the same problem (external displays are not detected on my T450s), but I would like to stick to the default kernel.

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#7 2016-10-13 21:22:12

Nicky726
Member
From: Czech Republic
Registered: 2008-02-15
Posts: 142
Website

Re: [SOLVED] Some projectors connected over VGA not detected

Not really, it may be Broadwell specific (my laptop), as with Haswell laptop the projectors in question were detected. I do not quite know how to debug it and have only limited time for experiments due to lessons schedulle.


"Although the masters make the rules
For the wise men and the fools
I got nothing, Ma, to live up to."

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#8 2016-10-18 10:47:51

rochus
Member
Registered: 2007-02-14
Posts: 86

Re: [SOLVED] Some projectors connected over VGA not detected

I guess this and this refers to the issue, let's see.

Last edited by rochus (2016-10-18 10:57:43)

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#9 2016-10-30 21:56:50

titaniumbones
Member
Registered: 2013-12-20
Posts: 52

Re: [SOLVED] Some projectors connected over VGA not detected

Just noting that I have the same issue on both a thinkpad t440 and an T460s.  I'll try the lts when I'm in the appropriate classroom -- hopefully it will work, though it will be nice to have the fixes in the Arch kernel when it comes.

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#10 2016-12-02 17:22:24

Logos1024
Member
Registered: 2016-12-02
Posts: 2

Re: [SOLVED] Some projectors connected over VGA not detected

I have a Lenovo ThinkPad T450 and have the same issues with a Samsung TV and a projector at work. A Dell monitor works just fine. xrandr shows DP2 as disconnected. I'm not sure what diagnostics could be useful here, but I have time to try something if anyone has a suggestion.

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#11 2016-12-04 19:11:21

titaniumbones
Member
Registered: 2013-12-20
Posts: 52

Re: [SOLVED] Some projectors connected over VGA not detected

Updating to a pretty recent 4.8 kernel *seems* to have fixed the issues for me at least:

Linux ansul 4.8.11-1-ARCH #1 SMP PREEMPT Sun Nov 27 09:26:14 CET 2016 x86_64 GNU/Linux

Also, reverting to LTS definitely solved the issue.  This is on a T460. Interested to hear if either solution works for you.

Last edited by titaniumbones (2016-12-04 19:12:28)

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#12 2016-12-06 20:23:23

Nicky726
Member
From: Czech Republic
Registered: 2008-02-15
Posts: 142
Website

Re: [SOLVED] Some projectors connected over VGA not detected

I confirm, that the projectors in question from my original post were today correctly detected with Linux 4.8.11-1, so I mark this solved.


"Although the masters make the rules
For the wise men and the fools
I got nothing, Ma, to live up to."

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#13 2016-12-06 22:29:36

Logos1024
Member
Registered: 2016-12-02
Posts: 2

Re: [SOLVED] Some projectors connected over VGA not detected

Just updated to Linux ansul 4.8.11-1-ARCH #1 SMP PREEMPT Sun Nov 27 09:26:14 CET 2016 x86_64 GNU/Linux, I can confirm it also solved the problem for me.

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