run Xorg rootless without any input devices (or even tty?)

[Youssef GHORBAL]

Hello,

	I have a special use case in an HPC environement when we want to run Xorg for 3D acceleration purposes only (basically creating GL contexts)
	It's what VirtualGL[0] uses to render (server side) GL accelerated apps.

	When a user is allocated a slot on an HPC compute node with a GPU card, we expect it to be able to run an Xorg (under his identity) bound to the GPU card allocated to him.
		
	I think the rootless Xorg topic was alread discussed elsewhere in different distrib channels (Arch, Ubuntu etc) but it was always under the assumtion that we needed a fullly featured Xorg (with displays, input devices, etc) whereas in my use case I just want an Xorg screen for GLX.

	For now, I can't run Xorg without handing it a tty, so I have to preallocate a tty for a user (and manage the permissions on it) and since Xorg is not able to access input devices I have this message (but Xorg starts neverthelss):

	xf86EnableIOPorts: failed to set IOPL for I/O (Operation not permitted)

	My questions would be:
	- Is there any way/trick to avoid allocating a tty for Xorg (and thus avoid managing tty allocations and permissions)? (maybe this does'nt make sense at all)
	- Is there any way/trick to avoid Xorg to probe for any input devices at all?

	Thank you for your help.

Youssef Ghorbal

[0] https://virtualgl.org/vgldoc/2_2_1/x11transport.png