drm(4) - NetBSD Manual Pages

DRM(4)                  NetBSD Kernel Interfaces Manual                 DRM(4)


NAME

     drm -- Direct Rendering Manager -- display configuration and graphics
     rendering acceleration


SYNOPSIS

   Kernel mode-setting drivers
     amdgpu*                at pci? dev ? function ?
     i915drmkms*            at pci? dev ? function ?
     nouveau*               at pci? dev ? function ?
     radeon*                at pci? dev ? function ?
     rkdrm*                 at fdt? pass 5
     sunxidrm*              at fdt? pass 5
     tegradrm*              at fdt? pass 5

   Legacy user mode-setting options and drivers
     options                DRM_LEGACY
     viadrmums*             at drm?

   Options
     options        DRM_MAX_RESOLUTION_HORIZONTAL=integer
     options        DRM_MAX_RESOLUTION_VERTICAL=integer


DESCRIPTION

     The Direct Rendering Manager is part of the Direct Rendering Infrastruc-
     ture for supporting display configuration and hardware acceleration for
     graphics rendering and other computation on a graphics processing unit
     (GPU).

     drm drivers come in two generations:

     Kernel mode-setting (KMS)
                   Modern drivers that query and control display configuration
                   in the kernel via ioctl(2) commands exposed to userland.

                   The /dev/dri/render* device nodes provide access to graph-
                   ics buffers and command stream submission for rendering.
                   The /dev/dri/card* device nodes additionally provide access
                   to the display configuration.

                   KMS drivers provided as modules must generally be loaded by
                   the bootloader, configured in boot.cfg(8), and cannot be
                   loaded dynamically.

     User mode-setting (UMS)
                   Legacy drivers that rely on userland support code that
                   accesses device registers in the X(7) server to query and
                   control display configuration.  The kernel may be unable to
                   recover if the display server crashes, or the device is
                   suspended or resumed.

                   The kernel driver and /dev/dri/card* interfaces only manage
                   buffers mapped in the GPU address space.  Display configu-
                   ration from userland requires the INSECURE option (see
                   options(4)) to allow userland access to device registers.

                   The DRM_LEGACY option allows legacy UMS drivers to be
                   loaded as modules (see module(7)).

     The drm drivers provide support for the following graphics devices:

           amdgpu      Newer AMD graphics devices.

           i915drmkms  Intel integrated graphics devices from the i915 series
                       onward.  (Some i8xx support is included but not well-
                       maintained.  i7xx is not supported.)

           nouveau     NVIDIA graphics devices.

           radeon      Older AMD (including formerly ATI) Radeon graphics
                       devices.

           viadrmums (legacy UMS)
                       VIA graphics devices.

     With some drivers (at least radeon(4)), in some cases the driver does not
     choose the resolution correctly.  The options
     DRM_MAX_RESOLUTION_HORIZONTAL and DRM_MAX_RESOLUTION_VERTICAL allow lim-
     iting the maximum resolution in X and Y direction.

     X(7) will attempt to create the device nodes automatically and use drm
     automatically.  To create a device node manually:

           mkdir -p /dev/dri
           mknod /dev/dri/card0 c 180 0
           chgrp wheel /dev/dri/card0
           chmod 0660 /dev/dri/card0

     Debugging output can be enabled and disabled by setting flag bits in the
     sysctl(8) node hw.drm2.__drm_debug.  Various other knobs may be available
     under hw.drm2.


FILES

     /dev/dri/render*  Provides access to graphics buffers and command stream
                       submission for rendering.  Generally unprivileged.

     /dev/dri/card*    In addition to everything provided by /dev/dri/render*,
                       provides access to change the display configuration.
                       Usually privileged.


CODE REFERENCES

     The drm subsystem and drivers mostly live under sys/external/bsd/drm2,
     with various Linux API shims in sys/external/bsd/common and some individ-
     ual drm drivers scattered elsewhere in the tree.


SEE ALSO

     Xorg(1), agp(4), xorg.conf(5), X(7)

     Direct Rendering Infrastructure:
           https://dri.freedesktop.org/


HISTORY

     drm was first available for Linux and later ported to FreeBSD and NetBSD.
     The port to NetBSD was redone after the introduction of KMS.

     The first generation of drm drivers appeared in NetBSD 5.0.  The second
     generation of drm with KMS appeared in NetBSD 7.0.


AUTHORS

     Too many to list.

     Work on the NetBSD port was contributed by: Anonymous, Nia Alarie, Eric
     Anholt, Rafal Boni, Taylor R Campbell, Mihai Chelaru, David Brownlee,
     Jaromír Doleek, Matthias Drochner, Christoph Egger, FUKAUMI Naoki, Paul
     Goyette, matthew green, Yorick Hardy, Nick Hudson, Martin Husemann, Arto
     Huusko, Thomas Klausner, Jonathan Kollasch, Tonnerre Lombard, Jared
     McNeill, Jeremy Morse, Kimihiro Nonaka, Tobias Nygren, Rin Okuyama, Maya
     Rashish, Erik Reid, Masanobu SAITOH, Blair Sadewitz, Chuck Silvers,
     Nathanial Sloss, Jörg Sonnenberger, Grégoire Sutre, Matt Thomas, Izumi
     Tsutsui, Patrick Welche, and Christos Zoulas.


CAVEATS

     drm is large and complicated and has no shortage of bugs.  On systems
     where graphics is not important, you may wish to use userconf(4) to dis-
     able the special-purpose drm drivers for your graphics device and fall
     back to vga(4) or genfb(4) with the default display configuration pro-
     vided by firmware.

     drm is not `Digital Rights Management' and does not deprive you of agency
     over your own computer, except insofar as the code base is difficult to
     maintain.

NetBSD 10.99                   October 21, 2023                   NetBSD 10.99