NAME

       drm - Direct Rendering Manager

SYNOPSIS

       #include <xf86drm.h>

DESCRIPTION

       The Direct Rendering Manager (DRM) is a framework to manage Graphics Processing Units
       (GPUs). It is designed to support the needs of complex graphics devices, usually
       containing programmable pipelines well suited to 3D graphics acceleration. Furthermore, it
       is responsible for memory management, interrupt handling and DMA to provide a uniform
       interface to applications.

       In earlier days, the kernel framework was solely used to provide raw hardware access to
       privileged user-space processes which implement all the hardware abstraction layers. But
       more and more tasks were moved into the kernel. All these interfaces are based on ioctl(2)
       commands on the DRM character device. The libdrm library provides wrappers for these
       system-calls and many helpers to simplify the API.

       When a GPU is detected, the DRM system loads a driver for the detected hardware type. Each
       connected GPU is then presented to user-space via a character-device that is usually
       available as /dev/dri/card0 and can be accessed with open(2) and close(2). However, it
       still depends on the graphics driver which interfaces are available on these devices. If
       an interface is not available, the syscalls will fail with EINVAL.

   Authentication
       All DRM devices provide authentication mechanisms. Only a DRM-Master is allowed to perform
       mode-setting or modify core state and only one user can be DRM-Master at a time. See
       drmSetMaster(3) for information on how to become DRM-Master and what the limitations are.
       Other DRM users can be authenticated to the DRM-Master via drmAuthMagic(3) so they can
       perform buffer allocations and rendering.

   Mode-Setting
       Managing connected monitors and displays and changing the current modes is called
       Mode-Setting. This is restricted to the current DRM-Master. Historically, this was
       implemented in user-space, but new DRM drivers implement a kernel interface to perform
       mode-setting called Kernel Mode Setting (KMS). If your hardware-driver supports it, you
       can use the KMS API provided by DRM. This includes allocating framebuffers, selecting
       modes and managing CRTCs and encoders. See drm-kms(7) for more.

   Memory Management
       The most sophisticated tasks for GPUs today is managing memory objects. Textures,
       framebuffers, command-buffers and all other kinds of commands for the GPU have to be
       stored in memory. The DRM driver takes care of managing all memory objects, flushing
       caches, synchronizing access and providing CPU access to GPU memory. All memory management
       is hardware driver dependent. However, two generic frameworks are available that are used
       by most DRM drivers. These are the Translation Table Manager (TTM) and the Graphics
       Execution Manager (GEM). They provide generic APIs to create, destroy and access buffers
       from user-space. However, there are still many differences between the drivers so
       driver-depedent code is still needed. Many helpers are provided in libgbm (Graphics Buffer
       Manager) from the mesa-project. For more information on DRM memory-management, see drm-
       memory(7).

REPORTING BUGS

       Bugs in this manual should be reported to
       https://bugs.freedesktop.org/enter_bug.cgi?product=DRI&component=libdrm under the "DRI"
       product, component "libdrm"

SEE ALSO

       drm-kms(7), drm-memory(7), drmSetMaster(3), drmAuthMagic(3), drmAvailable(3), drmOpen(3)