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

[Andrea Venturi]

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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