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rubenvb

Member

Registered: 2011-01-14

Posts: 104

How to start two X servers on different TTYs/GPUs, but same screen?

I have a Sony Vaio VPCZ1 model laptop, which comes with an Intel and NVIDIA GPU.
Both are connected to the laptop screen, but the HDMI port is only connected to the NVIDIA GPU.

I would like to be able to switch X servers by ctrl-alt-f{1,2} between an intel driven X and an NVIDIA driven X.

I have started from bumblebee's configuration and ended up with this minimal xorg.conf:

Section "Files"
    ModulePath "/usr/lib/nvidia/xorg,/usr/lib/xorg"
EndSection

Section "Device"
    Identifier  "DiscreteNvidia"
    Driver      "nvidia"
    BusID       "PCI:1:0:0"
EndSection

This gives me functional module loading but as I kind of expected "no screen found" when running the following command:

startx -- -conf xorg.conf -- :1

Xorg.1.log contents

[...]
[  8826.365] (--) NVIDIA(0): Valid display device(s) on GeForce GT 330M at PCI:1:0:0
[  8826.365] (--) NVIDIA(0):     CRT-0
[  8826.365] (--) NVIDIA(0):     DFP-0
[  8826.365] (--) NVIDIA(0):     DFP-1
[  8826.365] (--) NVIDIA(0):     DFP-2
[  8826.365] (--) NVIDIA(GPU-0): CRT-0: 400.0 MHz maximum pixel clock
[  8826.365] (--) NVIDIA(0): DFP-0: Internal TMDS
[  8826.365] (--) NVIDIA(GPU-0): DFP-0: 165.0 MHz maximum pixel clock
[  8826.365] (--) NVIDIA(0): DFP-1: Internal TMDS
[  8826.365] (--) NVIDIA(GPU-0): DFP-1: 165.0 MHz maximum pixel clock
[  8826.365] (--) NVIDIA(0): DFP-2: Internal DisplayPort
[  8826.365] (--) NVIDIA(GPU-0): DFP-2: 480.0 MHz maximum pixel clock
[  5824.415] (EE) NVIDIA(0): Failed to assign any connected display devices to X screen 0. 
[  5824.415] (EE) NVIDIA(0):     Set AllowEmptyInitialConfiguration if you want the server
[  5824.415] (EE) NVIDIA(0):     to start anyway
[  5824.427] (EE) NVIDIA(0): Failing initialization of X screen 0
[  5824.427] (II) UnloadModule: "nvidia"
[  5824.427] (II) UnloadSubModule: "wfb"
[  5824.427] (II) UnloadSubModule: "fb"
[  5824.427] (EE) Screen(s) found, but none have a usable configuration.
[  5824.427] (EE) 
Fatal server error:
[  5824.427] (EE) no screens found(EE) 

Is this at all possible (switching gpu by switching tty) or is it impossible to run two concurrent X servers simultaneously on the same screen?

What is the magic ingredient I am missing? I have looked throught the xorg.conf man pages but haven't found anything useful.
Thanks for any help!

Last edited by rubenvb (2015-07-07 20:12:09)

karol

Archivist

Registered: 2009-05-06

Posts: 25,440

Re: How to start two X servers on different TTYs/GPUs, but same screen?

Why do you want it?

rubenvb

Member

Registered: 2011-01-14

Posts: 104

Re: How to start two X servers on different TTYs/GPUs, but same screen?

I would like to at least have basic usage of the HDMI port which I can switch at runtime without a reboot, flicking a physical switch etc.

The first use case would be running kodi with nvidia vdpau and output over HDMI. I'd be happy with a solution that only works on HDMI, and not on the internal screen, if I'm honest.