Could not open DRM (NV) device

bandito_embedded

Hi everyone,

I'm trying to run a Qt example and I face the following issue :

root@bandito:/home/Qt# ./animation -platform eglfs
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/var/volatile/tmp/runtime-root'
Could not open DRM (NV) device
Aborted

Can anyone help me figure out what's wrong?

Here are my environment variables :

QT_QPA_FB_DRM=1
QT_QPA_EGLFS_KMS_ATOMIC=1
QT_QPA_EGLFS_INTEGRATION=eglfs_kms_egldevice
QT_QPA_EGLFS_FB=/dev/dri/card0
QT_QPA_EGLFS_ALWAYS_SET_MODE=1

SGaist

Hi and welcome to devnet,

Are you running your code on an embedded device ?
Does it have any other graphics system running like an a X server or wayland ?

bandito_embedded

Hi @SGaist ,
Yes, I'm running my app on an embedded device.
I'm not using XServer nor Wayland.

I'have noticed that I missed an option during the confirguration of Qt.
Among egldeviceintegration libraries, there is only :

eglfs_kms_egldevice
eglfs_emu

It seems that I should have enabled gbm. But I need to dig deep to understand how the linux graphical stack works to put everything together.

bandito_embedded

Okay, I was able to solve the issue by adding gbm ( Generic Buffer Management ) among the configurations options passed to the configure script of Qt.
This allowed me to obtain among the egl device integrations shared libraries :

After that, setting up QT_QPA_EGLFS_KMS_CONFIG environment variables to my .json configuration file,
I was able to run my application properly.

I probably need to spend more time understanding the linux graphical stack to put everything together in my mind, but for now the application is running and I can continue the development.

Hope it helps someone.
Bye Bye !

SGaist

Nice ! Thanks for sharing the findings :-)