On Tue, 14 Oct 2014 17:12:08 jeremy@visser.name said,

ITYM fourth kernel.

X.org borders on an entire operating system.

Not any more really, the low level functions of all modern drivers are now in the Linux Kernel (Note 1), so the xserver increasingly stays in user mode. Even the closed src AMD/ATI driver (Note 2) is currently being rewriten to pass all the lowlevel functions to the kernel. Note 1: This was started quite some time back, the Xserver GPU drivers being divided into 2 parts, a low level driver in the kernel specfic to a Graphics card and a largely common high level driver within Mesa DRI. This was done as it was found the high level functions for most cards even from different manufacturers was virtually identical and dividing the drivers into low and hgh level saved much programming effort. Note 2: AMD is doing this to allow a greater effort to be put in to the open source driver. Basicly from a month or so ago, all low level driver work for both the open and closed src drivers use the same code base. The ultimate goal being that when AMD releases a new GPU the open source driver will be availible from day one. Lindsay