Direct Rendering Manager
The Direct Rendering Manager (abbreviated to DRM) is a hardware - specific kernel module ( driver), who is also without an X server such as X.org server access to the memory (DMA, AGP ) granted the graphics card. In addition, the DRM ensures that the defined security rules are respected and that accesses are managed at the hardware. DRM is part of the Direct Rendering Infrastructure (DRI ).
What does the DRM
The DRM supports the DRI in three ways:
- It is an instance granted access only to the mechanisms, if the instance is connected to the X server ( xauth ).
- A direct rendering instance will only have access to the memory if they access to / dev / drm? has. The access rights can be changed only by root (this is generally about the X server configuration file).
- In addition, such DRI instance only to the memory access, if the server allows. The server can also only allow read access.
Development
Just as the Direct Rendering Infrastructure itself, are also subject to a continuous development of its components.
- Linux kernel version 3.11 from September 2, 2013 included major changes to the DRM.
- In the Linux kernel 3:12 freedreno was taken
- Were the graphics capabilities of the DRM and the KMS ( kernel mode setting ), see mode setting, separated
- Was an experimental implementation of " Render Nodes" integrated in the Direct Rendering Manager.
The new Render Nodes applications can have more than one node in the Linux kernel on graphic units, access to several. Previously was allowed to make only one application, such as the Display Server, KMS, and only with root privileges. Render Nodes provide an API that can do with the userspace non- privileged GPU commands, such as for GPGPU.