Intel

intel is the open source graphics driver for Intel GMA onboard graphics cards, starting with the Intel 810.

Hardware detection
To choose the right driver, first detect the graphics card. You can use lspci for this task:

This should show something like this:

Feature support

 * 1) A FOSS implementation is in development under the name Beignet

Kernel
You need to activate the following kernel options:

The legacy fbdev support is required since kernel 3.14.14 at least for i915 (CONFIG_DRM_I915_FBDEV=y). For hybrid Intel/AMD system, follow also the steps of radeon (opensource) or fglrx (closed binary) drivers.

Driver
Portage uses the  variable for enabling support for various graphics cards in packages. Setting  in  will pull in the correct video driver: (see the feature matrix)

"intel" is for and   resp. are for.

Check the USE flags of :

After setting this you want to update your system so the changes take effect:

VAAPI
Intel GMA X4500HD / G45 / GM45 and newer supports VAAPI hardware video acceleration.

xorg.conf
As xorg is not aware of i915 or i965 they will need to be addressed as Driver.

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.

Troubleshooting

 * Guide, how to report bugs upstream
 * Guide, how to report bugs upstream
 * Guide, how to report bugs upstream
 * Guide, how to report bugs upstream

KDM freezes
A workaround is to set TerminateServer=true in all sections of the file, which starts with X-.

Black screen
According to this Debian wiki, CONFIG_FRAMEBUFFER_CONSOLE must be set to y (aka built-in). Otherwise, it is possible to always have a black screen unless nomodeset is passed to the kernel, thus disabling KMS.

You can also try to pass acpi_osi="Linux" to the kernel line to try to solve this kind of issue

Brightness doesn't change with keyboard shortcuts
First, make sure your vendor compatibility is on in the kernel configuration, toshiba for toshiba and so on. If it is, or if you're sure that the brightness buttons are working, it's probably that your kernel can't detect where the brightness is. Luckily, this is easy enough to modify, as long as your kernel version is 3.13.x +. Simply add to your kernel command line.

External resources

 * X.Org Wiki