Alternative approach for a nested-xserver based video driver

Jamey Sharp jamey at
Wed Jun 4 09:16:03 PDT 2014

On Wed, Jun 04, 2014 at 09:07:22AM -0300, Laércio de Sousa wrote:
> Hello there!
> Some time ago I've wrotten asking for current status of xf86-video-nested
> development. I believe that, for a more robust single-card multiseat setup
> with systemd-logind, a "real" Xorg server with some kind of nested video
> driver works better than Xephyr, since it still lacks proper input
> hotplugging, for example.
> On the other hand, xf86-video-nested have received no relevant improvements
> for years, while Xephyr graphics support development is quite active.

Wow, I can't believe that capstone project was almost three years ago

> So I'm thinking on rewriting xf86-video-nested driver based on latest
> Xephyr code. A more ambicious idea is to identify and move all video
> related code that could be useful for both Xephyr and nested driver to a
> shared library, namely "libephyr", and link them against it. We could even
> rename xf86-video-nested to xf86-video-ephyr to reflect the new approach.
> I have absolutely no experience in writing video drivers for Xorg, but I'm
> open for learning. Any feedback from you will be welcome.

In my opinion, this would be great. One of my long-term goals is to have
only one X server implementation that anyone cares about, so being able
to replace both Xnest and Xephyr with Xorg+video-ephyr sounds good to
me. (And ideally, Xdmx would die in a fire.)

If I had my way, you wouldn't need to build a shared library, because
you'd just replace Xephyr. But practicality suggests that your shared
library plan is a better migration strategy.

I might suggest that you try hacking stuff into video-nested by
copy-paste before you try to figure out what shared library API you
need, though. It's much easier to make progress through incrementally
testable changes.

I hope this helps. :-)
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