Go Back   DisplayLink Forum > DisplayLink Graphics Technology > Linux and Open Source

Reply
 
Thread Tools Search this Thread Display Modes
Old 06-16-2023, 02:15 PM   #1
cl_swim
Junior Member
 
Join Date: Jun 2023
Posts: 1
Default Connecting to Monitor without EDID

Hello,

We're working with an ARM-based SoC without any display outputs, running Ubuntu 20.04. We need to connect a custom touch display via HDMI with a displaylink USB adapter.
Now the problem with that custom touch display is, it does not store any display information and therefore won't send anything over DDC.

We contacted the manufacturer of the display and got a testing model which does report EDID information.
Using the adapter we were able to connect to the testing model (working file) and grab the .edid file from /var/log/displaylink.

I was trying to connect the non-EDID display by using libevdi:
- getting the displaylink card with evdi_open()
- passing the content of the .edid file
- calling evdi_connect() to signal a connection to the linux drm

Unfortunately the drm refuses the connection. syslog tells me the following:
Code:
[  877.797540] evdi: [I] (card1) Connector state: connected
[  877.797577] Raw EDID:
[  877.797589]   00 00 00 00 08 60 29 01 5c 34 01 00 01 00 00 00
[  877.797596]   01 19 01 03 80 00 00 00 0a 00 00 00 00 00 00 00
[  877.797603]   00 00 00 00 00 00 01 01 01 01 01 01 01 01 01 01
[  877.797610]   01 01 01 01 01 01 aa 0a 20 42 30 e0 2c 10 10 0a
[  877.797617]   51 04 20 e0 31 00 00 18 00 00 00 fc 00 48 44 4d
[  877.797624]   49 20 44 49 53 50 4c 41 59 0a 00 00 00 10 00 00
[  877.797631]   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 10
[  877.797638]   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 24
[  877.797651] evdi evdi.0: [drm] DVI-I-1: EDID invalid.
[  877.797658] evdi: [I] (card1) Edid property set
[  877.980921] evdi: [I] (card1) Notifying mode changed: 800x600@60; bpp 32; pixel format XR24 little-endian (0x34325258)
[  877.980957] evdi: [I] (card1) Notifying display power state: on
[  888.080581] [drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CRTC:33:crtc-0] flip_done timed out
Is the EDID file the problem? How can it be invalid, if it comes from a display, that's working fine?
Is the problem something else? I am new to libevdi. If there is a way for me to quickly verify, if I can draw anything on the screen, that would be helpful.

Thanks in advance.
cl_swim is offline   Reply With Quote
Reply

Tags
drm, edid, hdmi, kernel

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 05:16 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.