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The State Of Killing CONFIG_VT, Moving To User-Space

Free Software

Published on 09 July 2013 03:58 AM EDT
Written by Michael Larabel in Free Software
25 Comments

David Herrmann is a student developer and one of the kernel developers that has been on a mission to kill off CONFIG_VT, a.k.a. the VT console within the Linux kernel, and move it off to user-space. He's contributed to various projects to further his ideas and now he's written a new post to provide an update on this matter and his thoughts on the current situation of Linux system compositors.

For those interested in Linux graphics, system compositors, and low-level Linux technical reading, Thoughts on Linux System Compositors by David is worth reading. His blog post covers virtual terminals, systemd, current problems, logind, limitations, quirks, the Wayland System Compositor, the Kernel Log driver, and much more.

For those wanting to skip all of the low-level details, Herrmann concludes his post with:
While I was an enthusiastic advocate of the system-compositor idea, it did become pretty clear, that the performance penalty for input-event forwarding and the huge required kernel API extensions make it very unlikely that it will get accepted in the community. Furthermore, besides global keyboard handling, most technical concerns on the logind idea can be solved with quirks like wlsystemc and uvtd.

This post didn’t discuss or highlight the low-level technical concerns on kernel VTs, but I hope it explains why we get a lot more flexibility and possibilities by moving session handling into user-space. logind can be taught boot-splash awareness, emergency-handling or forced session-switching, which will be very unlikely to get implemented in kernel VTs.

But independent of how we implement it, moving VT handling to userspace and disabling CONFIG_VT still has one major advantage: it simplifies kernel programming a lot. And I know, nearly every DRM developer would be very happy to see this happen!

David Herrmann is the student developer currently working on DRM render nodes through the Google Summer of Code and he's also been responsible for SimpleDRM, FBLOG, and numerous other interesting open-source code contributions.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
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