Setting HDMI Resolution in Weston

Applicable Platforms

Applicable Platforms for this article are those that are running Weston with built-in HDMI interfaces:

• PICO-IMX6
• PICO-IMX8M
• EDM-IMX8M
• AXON-E-IMX8M-PLUS
• EDM-G-IMX8M-PLUS

Introduction

The following article describes a simple and quick way to set the screen resolution of your Weston GUI desktop without messing around with kernel display parameters.

Determining the modes supported by the display

Each HDMI display will be able to support different modes. A mode in this case refers to a resolution, display refresh frequencies, whether or not the display is interlaced, and so on. This information is referred to as Extended Display Identification Data (EDID) and stored on an EEPROM located on the monitor. This is read by the SOC over a dedicated (in some cases, not always) I2C bus called Display Data Channel (DDC).

DRM-based graphics frontends report the supported modes in sysfs:

$ cat /sys/class/drm/card0-HDMI-A-1/modes
1280x720
1920x1080
1920x1080
1280x720
720x576
720x480

Weston Desktop configuration file

The weston configuration file resides at the following location in your yocto/openembedded root filesystem.

/etc/xdg/weston/weston.ini

The content of the weston.ini looks like the following (this may vary with software versions and platform, so this might not look exactly like the file in your target system):

[core]
# i.MX: Disable idle timeout
idle-time=0
use-g2d=1
gbm-format=argb8888

[libinput]
touchscreen_calibrator=true

#[output]
#name=HDMI-A-1
#mode=1280x720@60
#transform=90

[output]
name=DSI-1
transform=90
mode=1280x720@60

[shell]
size=1920x1080

#[output]
#name=HDMI-A-2
#mode=off
#       WIDTHxHEIGHT    Resolution size width and height in pixels
#       off             Disables the output
#       preferred       Uses the preferred mode
#       current         Uses the current crt controller mode
#transform=90

[screen-share]
command=/usr/bin/weston --backend=rdp-backend.so --shell=fullscreen-shell.so --no-clients-resize

Modifying weston.ini

Uncomment the output section that includes the HDMI-A-1 from the weston configuration file, and configure the resolution in the mode line:

[output]
name=HDMI-A-1
mode=1920x1080@60
#transform=90

You will also need to set the correct name for your display card inorder for the output to take effect. To look for the correct device name, please examine your /var/log/weston.log file.

Restart Weston

You can restart weston by using systemctl:

$ systemctl restart weston