[Interest] issues with Qt 5.9.3 with eglfs QPA_Platform on DRM/KMS kernel on Arm32/Mali HW

[Laszlo Agocs]

Hi,

No immediate ideas unfortunately, but it could well be that widgets (raster windows) do not behave as well in this regard as pure OpenGL windows (Qt Quick and friends). The multi-head work in the past was focused on the latter.

Please create a bug report at https://bugreports.qt.io

Best regards,
Laszlo

From: Interest <interest-bounces+laszlo.agocs=qt.io at qt-project.org> On Behalf Of Andrea Venturi
Sent: mandag 19. mars 2018 12.32
To: interest at qt-project.org
Subject: Re: [Interest] issues with Qt 5.9.3 with eglfs QPA_Platform on DRM/KMS kernel on Arm32/Mali HW


hello,

i put together a small code snippet for QtCreator, to better showcase the issue i see in my dual-head setup with a Qt widget app running through EGLFS on a libMali.so/DRM/KMS setup on Allwinner A20 mainline based OS:

 https://github.com/aventuri/widgetMultiScreen

the outcome is the wrong display of the two (yellow and red) rectangles with the code above only on the ext HDMI diplay. see:

https://drive.google.com/open?id=1tGJxoBzBNn_wEhCi5mnI5a5zLSKIrAwX

the puzzling issue is that if i comment out the w2.show() line:

https://github.com/aventuri/widgetMultiScreen/blob/master/main.cpp#L3

i can see (correctly) a single yellow screen on the primary LCD display.

can someone point me toward better debugging? is a GDB step by step approach the best one?  the Qt stack is that huge..


On 03/09/2018 02:42 PM, Laszlo Agocs wrote:

Hi,

eglfs_mali is for Mali userspace drivers (https://developer.arm.com/products/software/mali-drivers/user-space) marked as fbdev. This is from the time when there were only two options, fbdev and x11.

When having the wayland variants in place, use eglfs_kms instead. When in doubt, try running weston first. If it comes up correctly, eglfs_kms is the right choice. This has been tested with an Asus Tinkerboard (Rockchip RK3288) a while ago. I don’t have experience with other Mali-based boards.

We do have multi-screen support with DRM, yes. The fbdev and other backends have none or very limited capabilities in this regard. The way forward is to use eglfs_kms (or eglfs_kms_egldevice when on NVIDIA) whenever possible.

Best regards,
Laszlo

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