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KernelModesetting
Contents
Kernel Mode Setting (KMS) provides faster mode switching for X and console. It also provides native-resolution VTs on some laptops and netbooks which, prior to this, would use some standard mode, e.g. 800×600 on a 1024×600 panel.
To enable, you need:
- a kernel image ≥ 2.6.29 (in Sid since 2009-04-04)
supported graphics card
Intel
i915
From xserver-xorg-video-intel version 2:2.9.1-2, KMS is enabled by default on Linux, by the way of the file /etc/modprobe.d/i915-kms.conf. So from Squeeze on, no hand modification should be necessary anymore.
Known bugs
- vbetool
Running this will cause X to fail to start up (black screen except for a static cursor at the top left, can't switch vt), and may cause other problems. (This is a kernel bug.) To avoid this, set SAVE_VBE_STATE=false in /etc/default/acpi-support.
- linux-2.6
- Do not load any framebuffer drivers other than inteldrmfb (which is provided by i915) if you enable KMS, else you will probably see hard lockups when trying to start X.
- If you launch your kernel with a vga=xxx option on the boot line, it will fail (black screen).
- 945GM
Enabling KMS on this chipset may cause a GPU crash: (link)
- 945GM and 82865G
In my system (HP/Compaq nx7300 with 945GM) enabling of KMS when loading the i915 module caused blank screen (seems not to be related to incorrect mode, rather the system got suspended or hibernated) when booting the system. Problem could be cured by changing of /etc/modprobe.d/i915-kms.conf to options i915 modeset=0. What's interesting, booting with acpi=off also cured the problem. The same problem occured in a desktop system with 82865G (link)
- i830, i845 and i855
Blacklisted for KMS as of linux-2.6 2.6.32-21 (package changelog).
ATI
radeon
From xserver-xorg-video-radeon version 1:6.12.192-2, KMS is enabled by default on Linux, by the way of the file /etc/modprobe.d/radeon-kms.conf. So from Squeeze on, no hand modification should be necessary anymore.
Known bugs
radeonhd Xorg driver (xserver-xorg-video-radeonhd)
Incompatible with KMS (575226).
Disabling
KMS is disabled at run time in Debian kernel images by default.1 It is enabled via modprobe configuration files provided by the xserver-xorg-video-intel and xserver-xorg-video-radeon packages.
To disable KMS use, either:
Boot with the nomodeset kernel command line parameter.
Edit /etc/modprobe.d/i915-kms.conf or /etc/modprobe.d/radeon-kms.conf accordingly.
Resources
KMS with the Intel GMA at the Gentoo Wiki