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Old 02-15-2017, 03:01 PM   #1
seidler2547
Junior Member
 
Join Date: Feb 2017
Posts: 6
Smile Rotation working on DL-4300 USB3.0

Hi,

I just wanted to report that after a long time of trying, I finally got rotation working on my Generic DiplayLink DVI device that shows as 17e9:4300 in lsusb.

I use Arch Linux with Xorg 1.19.1 and the AUR packages for EVDI and DisplayLinkManager. The device was working fine but whenever I tried rotation, xrandr would accept the setting but it didn't actually do anything except confusing X itself.

I have a Intel graphics (i5-3317U, Intel® HD Graphics 4000), so I used xf86-video-intel for a long time, because even though modesetting is preferred now, I could never get it to work together with the modesetting driver that DisplayLink needs.

Now I have found a working configuration, and I believe the key is to disable DRI3 on the Intel modesetting driver, because DisplayLink doesn't support DRI3 (AFAIK) and so they don't play well together.

Despite all the stuff that one finds on the internet, I think that disabling DRI3 is done through
Code:
  Option      "PageFlip" "off"
and that is what worked in the end. Now I can have my two 1600x1200 screen rotated for a total of 2400x1600 screen estate. One is connected to the laptop HDMI, the other one to the USB DisplayLink.

Here is the relevant part of xorg.conf:

Code:
Section "Device"
  Identifier  "intel"
  Driver      "modesetting"
  Option      "kmsdev" "/dev/dri/card0"
  Option      "SWCursor" "on"
  Option      "PageFlip" "off"
  Option      "ShadowFB" "true"
EndSection

Section "Device"
  Identifier  "USB3"
  BusID       "USB"
  Driver      "modesetting"
  Option      "kmsdev" "/dev/dri/card1"
  Option       "ReportDamage" "on"
  Option       "SWCursor" "on"
  Option       "ShadowFB" "on"
EndSection
Important to note: it does not work the first time after login, but then when I log out and log in again, it works just fine.

[EDIT]
Forgot to say: the best thing about it is that I have no problems with partial screen updates anymore. Everything is working perfectly. Previously it would often not update parts of the screen until I went over them with the mouse cursor. I had worked around that by running a compositor (compton), but still I had lag sometimes. Now compton is not needed and the screen always updates everything just as it should.

I can also watch 1440p video on youtube spanning both monitors and it looks great, no lag on either screen. 4K is a bit too much for my little laptop CPU.
[/EDIT]

Hope that helps,

Stefan

Last edited by seidler2547; 02-15-2017 at 03:11 PM.
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