$ Linux Command

Development

modetest

Test DRM/KMS display modes on Linux.

drmkmsdisplaygpumodetest

Additional Notes

modetest is a utility for testing the Direct Rendering Manager (DRM) and Kernel Mode Setting (KMS) subsystems on Linux. It can enumerate display connectors, CRTCs, planes, and encoders, and it can set display modes for testing.

It is primarily used by developers working on graphics drivers, display servers (Wayland, Xorg), or embedded display systems. It can force a specific resolution, refresh rate, or display configuration to verify hardware functionality.

Syntax

modetest [options] [driver]

Parameters

  • driver: The DRM driver to use (e.g., i915, amdgpu, nouveau, virtio). If omitted, the first available driver is used.

Common Options

  • -M module: Specify the DRM driver module by name.
  • -e: Only enumerate (list) connectors, CRTCs, encoders, and planes.
  • -a: Atomic mode setting test.
  • -s connector:mode: Set a display mode on a connector (e.g., -s 32:1920x1080).
  • -P plane:format: Test a plane with a specific pixel format.
  • -v: Verbose output.
  • -D device: Use a specific DRM device (e.g., /dev/dri/card0).
  • -w: Wait for vertical blank before updating.

Examples

modetest -e

List all connectors, CRTCs, encoders, and planes.

modetest -M i915 -e

List display hardware for the Intel i915 driver.

modetest -s 32:1920x1080

Set connector 32 to 1920x1080 resolution.

modetest -v -D /dev/dri/card1

Show verbose information for the second DRM device.

Practical Notes

  • modetest is part of the libdrm utilities package. Install with apt install libdrm-utils or equivalent.
  • The connector, CRTC, and plane IDs are dynamic and can change. Run -e first to enumerate them.
  • Setting a mode with -s may change your display; use with caution on production systems.
  • For Wayland compositor or Xorg debugging, modetest provides raw DRM access that can help isolate driver issues.