modetest

diagnostic tool for testing and debugging Kernel Mode Setting functionality

TLDR

List connectors and their available modes for a specific driver

$ modetest -M [driver] -c

List all DRM objects (connectors, encoders, CRTCs, planes)

$ modetest -M [i915]

Set resolution of a connector

$ sudo modetest -M [driver] -s [connector_id]:[1920x1080]

Test a specific plane with format

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

Set a DRM property on an object

$ sudo modetest -M [driver] -w [obj_id]:[prop_name]:[value]

Use atomic mode setting with a connector

$ sudo modetest -M [driver] -a -s [connector_id]:[1920x1080]

SYNOPSIS

modetest [-M module] [-D device] [-c] [-e] [-f] [-p] [-s connector:mode] [-P plane] [-a] [-C] [-w prop] [-v] [-d]

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. When no query or test options are given, it dumps all available DRM information. It displays an SMPTE color bar test pattern when setting modes.

PARAMETERS

-M _module_

Use the given DRM driver module (e.g., i915, amdgpu, nouveau)

-D _device_

Use the given DRM device node

-c

List connectors and their available modes

-e

List encoders

-f

List framebuffers

-p

List CRTCs and planes

-s _connector_id[,connector_id][@crtc_id]:mode[-vrefresh][@format]_

Set a mode on one or more connectors

**-P planeid@crtcid:WxH[+X+Y][*scale][@format]**

Test a plane with specified configuration

-C

Test hardware cursor

-v

Test vsynced page flipping

-w _obj_id:prop_name:value_

Set a property on a DRM object

-a

Use atomic mode setting API

-F _pattern1,pattern2_

Specify fill patterns for test image

-d

Drop DRM master after mode set

CAVEATS

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.

HISTORY

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.