Posts: 106
Joined: Tue Jun 25, 2019 12:10 pm

Dual Seat Acceleration on One GPU/Single DRM Layer RPi 4

Sun Aug 25, 2019 5:24 pm

This tread is being created to foster and track the support of a dual seat accelerated displays on the RPi 4 over it's single GPU/DRM layer.

This feature would enable new use cases on a single RPi4 such as dual screen arcade cabinets, dual seat 3D accelerated stations for undeserved areas of the world, and virtual reality.

Here are some references from other topics:

Why is doesn't work (limitation of the Linux DRM model - two devices share the single DRM layer):
https://www.raspberrypi.org/forums/view ... 7#p1521768

Who is trying to get it work to work (kernel graphics maintainer Dave Airlie):
https://www.raspberrypi.org/forums/view ... 7#p1521786
Two X servers one graphics card (2010): (https://airlied.livejournal.com/72187.html
xlease (developed for Virtual Reality)
https://www.raspberrypi.org/forums/view ... 7#p1521797

Other ideas and solutions:
Half working solutions:
NON-accelerated dual seat RPi4 (https://www.raspberrypi.org/forums/view ... 5#p1508148)

Hacks that do not work on the RPi:
Multi-Seat Gaming Guide (https://www.reddit.com/r/archlinux/comm ... ing_guide/)
-VirtualGL (https://virtualgl.org/About/Background)
-VirtualGL does NOT support GLES (RPi uses GLES, funding required for feature request - https://github.com/VirtualGL/virtualgl/issues/66)

Doesn't allow true multi seat, but works with some games and utilities:
Crude-Pseudo Multi Seat with xinput (https://wiki.archlinux.org/index.php/Multi-pointer_X)

Xinput is crude and only allows for two users on one desktop. It doesn't not play well with 3D games due to X and window focus.

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Posts: 4547
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Re: Dual Seat Acceleration on One GPU/Single DRM Layer RPi 4

Mon Aug 26, 2019 2:07 am

Just installed OpenScenegraph on my Gentoo64 last night.
Been reading up on it, more applications than just Flightgear ;)
Still trying to get my head around what to use two 21:9 curved wide screens for :D

Pi4's do OpenGL quite well now.
WebGL is not bad and Docker now works.
14+ servers on one Pi4B4, thin multiseat clients.
That's one classroom of 28 kids with 15 Pi's.

I pretty sure RPF are very, very interested in two seat usage as it aligns with their mission.
Is dual screen/seat support already in Mesa?
I don't even know if it runs on PC's.
Google Multiseat?

Userful - Brazil, hmm are blue Pi's still being made?
Are there blue Pi4's in the wild?
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

Posts: 2327
Joined: Tue Jul 02, 2019 2:28 pm

Re: Dual Seat Acceleration on One GPU/Single DRM Layer RPi 4

Mon Aug 26, 2019 3:08 am

Gavinmc42 wrote:
Mon Aug 26, 2019 2:07 am
Are there blue Pi4's in the wild?
Not yet. No Anatel certification for the 4B on https://www.raspberrypi.org/documentati ... formity.md

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