Screen U4919DW not fully recognised on Ubuntu 20.04

[valls]

Hi,

I have a problem with a specific screen model that i have to use.

Our computers use for now Ubuntu 20.04.

- One is connected to a single screen U4919DW
- Another one is connected to 4 screens, including one U4919DW

For both computers xrandr is not able to retrieve the correct screen size in millimetre.

```
opid24@tesla:~$ xrandr
[...]
DP-2 connected primary 5120x1440+344+1080
(normal left inverted right x axis y axis) 1mm x 1mm
[...]
```

See the "1mm x 1mm" while it should be something like "1200mm x 340mm"

We are able to reach the EDID via nvidia-settings, and here it is:

```
        00ffffffffffff0010ac0da14c4e4630
        17200104b57822783eee91a3544c9926
        0f5054a54b00714f81008180a940d1c0
        0101010101011a6800a0f0381f403020
        3a00ae514100001a000000ff0043434c
        4e5848330a2020202020000000fc0044
        656c6c20553439313944570a000000fd
        00185619732f010a20202020202002db
        020310b14b900504030201141f12135a
        cd4600a0a0381f4030203a00ae514100
        001a0000000000000000000000000000
        00000000000000000000000000000000
        00000000000000000000000000000000
        00000000000000000000000000000000
        00000000000000000000000000000000
        000000000000000000000000000000d0
        701279030001000ccd2e2a0d0014a005
        1078ff9903012833b70088ff139f002f
        801f009f05280002000900545a0008ff
        139f002f801f009f0514000200090000
        00000000000000000000000000000000
        00000000000000000000000000000000
        00000000000000000000000000000000
        00000000000000000000000000006e90
```

We have tried to decode this EDID with:

- `pyedid`, and it returns the right size
- but `parse-edid` fails (from `read-edid` package)

I understand xrandr is not responsible for reading/parsing such information, but i don't really know which component is responsible of that in the graphic software stack.

At this level i am stuck.

Do you have any idea how to debug that deeper?

Do you know for example which component is responsible of feeding xrandr?

So what maybe we could check if this component is able to read/parse/propagate properly the EDID information?

Thanks in advance.