nouveau is the open source driver for nVidia graphics cards.
You need to activate the following kernel options:
Portage uses the variable VIDEO_CARDS for enabling support for various graphics cards in packages. Setting VIDEO_CARDS to nouveau will pull in the correct driver:
After setting this you want to update your system so the changes take effect:
If you have the USE flag acl enabled globally and are using ConsoleKit (i.e you're using a Desktop profile) permissions to video cards will be handled automatically. You can check the permissions using getfacl:
A broader solution is to add the user you want to be able to access the video card to the video group:
Note that you will still be able to run X without permission to the DRI subsystem, but usually not with acceleration enabled.
The X server is designed to work out-of-the-box, with no need to manually edit X.Org's configuration files. It should detect and configure devices such as displays, keyboards, and mice.
However, the main configuration file of the X server is the xorg.conf.
Multi Monitor Problems
If you're having problems with freezing with possible EDID probes when using dual monitors/displays, try adding "video=VGA-1:e" or "video=VGA-1:d" (enable or disable respectively) to your grub.cfg/grub2.cfg command line options, substituting the name of your monitor listed within dmesg or /var/log/Xorg.0.log. (ie. CRT-1, VGA-1, LVDS-1, DVI-1, ...)
I have a Dell Inspiron 8100 laptop with a connected external display connected via the laptop's external VGA port. My current command line is: "video=LVDS-1:1280x1024@60 video=VGA-1:1280x1024@60". Think the EDID (DRM) probe on the external VGA connected display is still causing freezing during nouveau/drm load, but at least it's usable if the display is connected after grub is loaded and prior to the nouveau/drm modules loading. And with the prior mentioned command line LVDS/VGA resolutions, the displays are cloned and centered with somewhat correct resolutions for cloned displays.