trusty (7) drm.7.gz

Provided by: libdrm-dev_2.4.67-1ubuntu0.14.04.2_amd64 bug

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 priviledged
       user-space processes which implement all the hardware abstraction layers. But more and more tasks where
       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 grapics 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 http://bugs.freedesktop.org under the "Mesa" product, with
       "Other" or "libdrm" as the component.

SEE ALSO

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