The configuration files in “/etc/X11/” are where you would start. Before EDID existed there was no such thing as “hotplug” to configure monitors. Most monitors simply provided a number of “standard” resolutions, and those would work out of the box…but seldom were those resolutions the best the monitor could do…so in that case you’d either directly or indirectly edit the “/etc/X11/” files.
Indirectly meant a program could be used to select known monitors from a database (the driver disk shipped with the monitor), and the program would do the editing. Directly means getting out an editor and typing in the edits by hand. This latter is what you will have to do. If you have EDID, then the edits still take place, but they only take place in RAM and occur as a hotplug event doing the edits.
Take a look at the existing “/etc/X11/xorg.conf”. When Jetsons are first flashed this is a very minimal file because it expects everything else to be automatically filled in from the monitor’s EDID data upon plugin. You’re going to have a steep learning curve, as what you will need to do is learn about this file’s syntax. You will find there are “sections” which are interchangeable, and that one section may refer to another. Within this particular file consider that the JTX1 has two video output possibilities…one is the HDMI connector, the other is the eDP/DSI…the syntax of the file (regardless of whether it is in the file or from a hotplug EDID event) will typically be to disable the non-HDMI output and add content for the HDMI-related sections.
I think the “Device” you are interested in is the one which allows “AllowEmptyInitialConfiguration”…meaning the server will start even if no configuration is found…a case where the server will end up in some fallback standard mode (this is the set of standard modes from the original days of 15-pin D-sub VGA monitors). In your case the fallback mode is not what you want, so even if this mode works, you’d still have to add your own Monitor section describing the modelines (detailed timing descriptors…at edidreader.com see Descriptor 1 and Descriptor 2). Once you have your Monitor set you’ll probably bind this Monitor to a Screen or other layout section (I don’t know which sections, I have not edited one of these by hand in a very very long time).
Btw, modelines are simpler on digital panels; on analog they had a number of extra timings. You’ll still need to be able to create the modelines in the correct syntax (edidreader.com provides human formatting, you need to reverse this into a file edit). See:
There is also a program you can run on Linux called “cvt”. This is to calculate VESA modelines.
The xorg.conf man page is here:
One thing I suggest is to find what seems to be the simplest possible example of each section you might be interested in via a web search, and then find out how to modify it for your case. Test it and see if “/var/log/Xorg.0.log” produces an error on boot. If not, then you’ve progressed. Once you get your Monitor section associated with the display things should either work or be close to working.