modetest

List connectors and their available modes for a specific driver

$ modetest -M [driver] -c

$ sudo modetest -M [driver] -s [connector_id]:[1920]x[1080]

$ sudo modetest -M [i915]

$ sudo modetest -M [driver] -P [plane_id]@[crtc_id]:[WxH]+[X]+[Y]@[format]

$ modetest -M [driver] -v

modetest [-M module] [-c] [-e] [-p] [-f] [-s connector:mode] [-P plane] [-v]

modetest is a diagnostic tool for testing and debugging Kernel Mode Setting (KMS) functionality of Direct Rendering Manager (DRM) drivers. It enumerates DRM objects including connectors, encoders, CRTCs, and planes, and can set display modes directly.
The tool is part of libdrm and provides low-level access to the graphics subsystem for testing display configurations, pixel formats, and plane overlays. It displays an SMPTE color bar test pattern when setting modes.

-M _module_

Specify DRM driver module name (e.g., i915, amdgpu, nouveau, mgag200)

List connectors and their available modes

List encoders

List planes

List framebuffers

Set mode on connector (format: connector_id:WIDTHxHEIGHT[@refresh])

Test plane with specified configuration

Target specific CRTC (display controller)

Specify pixel format (e.g., XR24, BG24, ARGB8888)

Enable verbose output with detailed information

Display help message

Requires root privileges or membership in the render/video groups to access DRM devices. Running modetest on an active display can disrupt the current desktop environment (Xorg, Wayland), potentially causing blank screens or display corruption. Primarily intended for developers and diagnostic purposes.

modetest is part of the libdrm project, which provides the userspace library for interacting with the Linux kernel's Direct Rendering Manager. KMS was introduced in Linux kernel 2.6.29 (2009) to move display mode setting from userspace X servers into the kernel.

drm(7), xrandr(1), wlr-randr(1)