Kernel mode-setting is more flexible and allows displaying of an error in the case of a fatal error in the kernel, even when using a user-space display server.
User-space mode setting would require superuser privileges for direct hardware access, so kernel-based mode setting removes the need for superuser privileges for the user-space graphics server.
Atomic mode setting
Atomic mode setting means setting the output modes of a single graphics device. Collecting the video mode, encoder and connector setup over the whole graphics card into a single operation avoids flicker. Either the whole set succeeds, or it fails.
The Linux kernel got the prerequisite for kernel-based mode setting by accepting Intel's GEM in version 2.6.28, released in December 2008. This will be[dated info] replaced by Tungstens Graphics TTM (Translation Table Maps) memory manager which supports the GEM API. TTM was developed for the free and open-source drivers for Radeon and S3 Graphics graphic chipsets (see Free and open-source graphics device driver). Support for Intel GMA graphic chipsets was accepted in version 2.6.29, which was released on March 23, 2009. Support for pre-R600 ATI Radeon graphics cards was accepted in version 2.6.31, which was released on September 9, 2009. Support for R600 and R700 was in development within DRM and was merged in version 2.6.32. Support for Evergreen (R800) was merged in version 2.6.34. As Nvidia did not release all the needed documentation for its graphics chip, development proceeded under the nouveau project, which uses reverse engineering to build a working open-source driver for Nvidia cards. Nouveau was accepted in version 2.6.33 of the kernel, which was released on December 10, 2009. Kernel-based mode setting is not only supported by the nouveau driver, it is required. Wayland compositors (e.g. Weston) and kmscon depend on kernel mode setting via ioctl.
OpenBSD has kernel-based mode setting support for Intel and Radeon GPUs. Starting with version 5.4 of OpenBSD, support for Intel GPUs is available. With the release of version 5.5, the implementation has been extended to add support for Radeon chipsets as well.
|This section is outdated. (August 2014)|
- At the Linux Plumbers Conference 2013, it was suggested to split GEM and KMS.
- There is the Atomic Display Framework; it was presented by Google's Android-Team at the Linux Plumbers Conference 2013.
- There is the Common Display Framework.
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