Arch Linux

nobleV

Member

Registered: 2014-06-06

Posts: 3

Issues related to HDMI and lightdm

Hello Archers,

I have the following setup:

Computer (Running Arch Linux)  --- HDMI --- Yamaha RX375 receiver (port HDMI1) --- Acer Projector

Computer:

Linux jugnu 4.1.6-1-ARCH #1 SMP PREEMPT Mon Aug 17 08:52:28 CEST 2015 x86_64 GNU/Linux
Lightdm 1.16.0
XFCE 4.12

Acer Projector: resolution 1280x720

With Yamaha receiver and projector already On, if I turn On the computer, there is no issue, I see the boot screen and am greeted with the lightdm gtk greeter. Since I am using the projector as an external monitor, I turn Off both projector and the receiver at the end of session. Next time when I try to use the system back again I get slapped in the face by 740x480 resolution and on top of that I just see a blank black screen. No login prompt/background or anything is shown.

I used to just restart the computer after the projector and receiver was On, and then I got a bit smarter and thought what if I can just restart the lighdm service via ssh? This solution works, but it is inconvenient for anyone else in the house to use.

So my question is: How can I obtain the output of login screen of the lightdm, after the HDMI devices were turned Off or essentially hot plugged back?

Any help on this topic is much appreciated.

Cheers,
Noble

Awebb

Member

Registered: 2010-05-06

Posts: 6,688

Re: Issues related to HDMI and lightdm

Have you tried another DM to see if it's just a lightdm problem? I have resolution problems with my Yamaha RX-V371 as well, the culprit is the TV providing a nonsensical EDID and not even fast enough for X to not crap its pants.

nobleV

Member

Registered: 2014-06-06

Posts: 3

Re: Issues related to HDMI and lightdm

Awebb,

Thank you for your reply. I have read this EDID nonsense making X crap its pants and tried to force the EDID as well using kms (which doesn't make any difference since I am able to always get the correct resolution on bootup). I recently tried GDM as well, with the same results.

It seems like the moment I restart the Yamaha receiver or the projector, the X lost track of the resolution capabilities of the connected device, which seems to piss him very badly. Upon starting both the receiver and the projector, I am sure the DM or X are receiving the EDID information, but they are likely to be pissed off and refuse to acknowledge this change. However when i restart the DM itself, it seems to like the newly received EDID.

I am very confused on this, isn't this turning On/Off similar to hotplugging? shouldn't the DM or X act upon it like they do on the externally attached monitor?

Please advise and guide,
Noble