Mode setting

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Mode setting is the setting up of the screen resolution and color depth mode for a computer graphics card.

Modern mode setting software supports multiple monitors ("multi-head") and hot plugging.

Contents

Location [edit]

Mode setting can be done in kernel space (Kernel Mode Setting or KMS) or in user space (User-space Mode Setting, UMS).

Doing mode setting in kernel-space 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 have needed superuser privileges for direct hardware access, so kernel-based mode setting increases security because the user-space graphics server does not need superuser privileges.

Implementation [edit]

Microsoft Windows versions that are NT-based use kernel mode setting. The kernel error display made possible by kernel mode setting is known as the Blue Screen of Death.

The Linux kernel got the prerequisite for kernel-based mode setting by accepting GEM in version 2.6.28, released in December 2008.[1] This will be replaced by a TTM (Translation Table Maps) memory manager which supports the GEM API.[2] TTM was developed for the ATI Radeon driver and VIA S3 Graphics chipsets.[3] Support for Intel GMA graphic cards has been accepted in version 2.6.29 which was released on March 23, 2009.[4] Support for pre-R600 ATI Radeon graphics cards has been accepted in version 2.6.31 which was released on September 9, 2009.[5] Support for R600 and R700 was in development within DRM and has been merged in version 2.6.32.[6] Support for Evergreen (R800) has been merged in version 2.6.34. As Nvidia did not release all the needed documentation for its graphics chip, the development is under the nouveau project which uses reverse engineering to get it to work. Nouveau has been accepted in version 2.6.33 of the kernel which was released on December 10, 2009. This will allow to use kernel-based mode setting for Nvidia cards with this driver. Weston and kmscon depend on kernel mode setting.

FreeBSD has support for both kernel-based mode setting and GEM for later generations of Intel GPUs (IronLake, SandyBridge, and IvyBridge) starting with version 9.1.[7]

OpenBSD, which has a strong focus on security, is interested in getting kernel-based mode setting in order to run X without superuser privileges.[8] Support for kernel-based mode setting for later generations of Intel GPUs was added to OpenBSD in March 2013 (so should be available starting with the 5.4 release).[9]

See also [edit]

References [edit]

  1. ^ "Linux 2 6 28". Linux Kernel Newbies. Retrieved 2013-02-14. 
  2. ^ Larabel, Michael (2008-08-26). "A GEM-ified TTM Manager For Radeon". Phoronix. Retrieved 2013-02-14. 
  3. ^ Larabel, Michael (2009-06-10). "TTM Memory Manager Gets Ready For Release". Phoronix. Retrieved 2013-02-14. 
  4. ^ "Linux 2 6 29". Linux Kernel Newbies. Retrieved 2013-02-14. 
  5. ^ "Linux 2 6 31". Linux Kernel Newbies. 2009-09-09. Retrieved 2013-02-14. 
  6. ^ Larabel, Michael (2009-09-30). "AMD R600/700 2D Performance: Open vs. Closed Drivers". Phoronix. Retrieved 2013-02-14. 
  7. ^ "FreeBSD 9.1-RELEASE Release Notes". FreeBSD Foundation. 30 December 2012. 
  8. ^ Larabel, Michael (February 25, 2009). "Gallium3D, EGL Now Buildable On FreeBSD". Phoronix. Retrieved 2013-02-14. 
  9. ^ Larabel, Michael (March 18, 2013). "Intel KMS/DRM Driver Readied For OpenBSD". Phoronix. Retrieved 2013-04-03. 

External links [edit]

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