Rootless X [LWN.net]

Rootless X

Posted Jul 16, 2009 9:45 UTC (Thu) by mjthayer (guest, #39183)
Parent article: Rootless X

Can some person wiser than me enlighten me as to why KMS for Nouveau is so complicated? I would have thought that modesetting would be trivial compared to the rest of the stuff they are doing, and the 3D stuff (at least the privileged bits) is all done in-kernel anyway AFAIK. I actually thought that Fedora was now doing KMS with Nouveau.

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Rootless X

Posted Jul 16, 2009 19:38 UTC (Thu) by jlokier (guest, #52227) [Link]

At least in other video card drivers I've looked at, and some I've worked on (not in Linux), modesetting is pretty complicated stuff because it involves so many hardware-specific quirks, tables full of obscure numbers, and probably touches more hardware registers than any other feature including 3D acceleration.

That's not to say the rest is easy, but modesetting is usually more complicated than you'd think, for something which sounds so trivial.

Also it tends to require more hardware-specific hacks. At least with 3D rendering, you can see if it works and then it's likely to work the same on all boards with the same generation GPU. The same can't be said for modesetting.

Finally, modesetting is very important, but it's not as much fun as rendering.

Rootless X

Posted Jul 19, 2009 18:29 UTC (Sun) by rahulsundaram (subscriber, #21946) [Link]

Fedora 11 supports Nouveau with KMS but you have to pass a boot option

http://fedoraproject.org/wiki/Features/NouveauModesetting

Fedora 12 likely will have it on by default since Red Hat hired Ben Skeggs, one of the primary developers during the last release cycle to support development.