Comment 40 for bug 398026

Oded, I also get a complaint that i915.modeset=0 is an unknown boot option when adding it to the kernel command line. It still disables KMS, though.

The reason that you cannot remove i915 while the system is running is that the module is responsible for _all_ modesetting on the system, not only for X. This is one of its advantages - all the mode setting is coordinated from one piece of code. On my computer the VT fonts are different when KMS is enabled. One easy (but probably not standard) way of recognizing if KMS is used is to look at the display names in the output of xrandr and Xorg.0.log. UMS (Userland mode setting) uses names like LVDS, VGA, VGA-1, etc. but KMS uses LVDS1, VGA1, etc. There's probably something in dmesg output that gives away KMS as well.

Even if you don't see any difference with UMS (i.e. KMS disabled), Xorg.0.log and the xrandr output for that case may be useful for someone who knows what to look for.