Is Wayland going to replace X?

The interwebs are full this morning of reports on Mark Shuttleworth’s announcement that someday he’d like to use Wayland instead of Xorg as Ubuntu’s primary display driver.

My favorite so far is Ryan Paul’s Ars Technica article for this dead-on estimate of the amount of effort it would take to completely replace X11:

Although the Linux ecosystem would benefit greatly from a lighter and more easily extensible alternative, a concerted effort to displace X11 on the Linux desktop hasn’t really emerged yet because the task of bringing drivers, third-party software, and all of the other layers of the stack into alignment with such a move would be prohibitively cumbersome. Like, in the sense that using only your toes to build a full-scale replica of the Statue of Liberty out of toothpicks is prohibitively cumbersome.

And that’s the important point - despite what some of the sensationalist headlines are saying, Ubuntu is not dropping X. They’re not even sure when it would be possible to start shipping Wayland - the announcement from Mark Shuttleworth was that this is the direction they want to go in hopes that a show of support will help get more people working on Wayland (which has mostly been a single person effort) in order to make it a usable solution in a year or more.

Even once they start shipping Wayland, since most applications will still be written for X, they’ll have to include an X server which now has to share the graphics devices with Wayland. (The Wayland site has architecture diagrams showing how this works.) Sure, their Unity desktop (the Ubuntu replacement for GNOME 3.0’s gnome-shell) will be written to Wayland, but more widespread adoption depends on how many other platforms also adopt Wayland, since then the creators of other applications will have to decide if its worth the effort of porting just for those distros when they can do nothing and continue to work on all X11 platforms, including those running Wayland.

One of the challenges in widespread Wayland adoption, especially on non-Linux kernels, is that Wayland requires a kernel Direct Rendering Module (DRM) with Kernel Modesetting Support (KMS) for every graphics device.

That’s especially challenging in Solaris, where even in the latest OpenSolaris and Solaris Express releases, we only have DRM drivers for Intel and ATI Radeon graphics (and the Radeon one currently doesn’t work, but that’s fixable).

That leaves these non-EOL graphics devices with no DRM/KMS support in Solaris:

  • AST (service processor/remote KVM in Sun servers)
  • ATI Rage and Mach64
  • Cirrus
  • Matrox
  • Nvidia
  • VIA Unichrome
  • Trident
  • VESA (fallback for hardware without specific driver support)
  • VirtualBox
  • VMWare
  • Sun XVR-50/100/300 (OEM ATI Radeon series, but with separate driver)
  • Sun XVR-2500
  • Sun Ray

Of course, that’s the list of devices Oracle is supporting in Solaris - other distros/forks from the OpenSolaris code base, such as OpenIndiana or Belenix, may choose to support more or less, but I’ve not yet seen any sign of them porting DRM drivers on their own.

For some of those, support could be provided by porting the existing open source dual-BSD/GPL-licensed DRM code - others require creating drivers where there are none.

Nvidia appears on their list since we ship their driver, which has their own kernel/driver architecture instead of DRI. Getting DRI/KMS support for nvidia either requires them to rearchitect their driver or moving from their driver to the open source / reverse engineered Nouveau project.

From Owain Ainsworth’s talk at this year’s X Developer Summit, we know that work is in progress to port KMS support to the BSD DRI, but again, that’s not yet done, though the BSDs do have a lot more of the device-specific DRM modules already ported than Solaris did.

So Xorg is in little danger of disappearing overnight - our desktop architecture continues to evolve, as it has over many years, and Wayland may play an increasingly larger role in it, or may end up an interesting side note, like Xgl before it, but either way it will be an evolutionary process, not a big bang flag day sudden change.

Comments:

Thanks for the technical explanation, which sounds entirely reasonable, but I'm not finding the "X is no danger of becoming irrelevant because we're going to keep shipping it in OpenSolaris" argument to be exceedingly persuasive.

Posted by Chris on November 05, 2010 at 07:29 AM PDT #

STFU.

X needs to die, and I hope it dies.

Wayland is the future.

Posted by Diego on November 05, 2010 at 07:31 AM PDT #

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