Direct use of SDL with kms / drm

[Adrian1]

Hello,

I use SDL with X11 for now but I want to use it directly with kms/drm kernel driver. I run basic_splash_drm and it works.

I don't know how to configure sdl to work together with kms/drm, somebody use it in this way ?

Regards,

Adrian

[AntonioST]

You need to configure libsdl2 with option

--enable-video-kmsdrm

because kmsdrm is not enabled by default. Then you also need to disable the unsupported OpenGL, otherwise libsdl2 fails to detect OpenGLES and OpenGLES2

--disable-video-opengl

With the two flags above, drmkms is already working, but libsdl2 detects the GPU of STM32MP1xx as Vivante, and try to use an internal driver that does not work with STM32MP1xx. To skip this auto-detection, you can either specify the preferred video driver in the libsdl2 specific global variable, before running your application:

export SDL_VIDEODRIVER=kmsdrm

or disable the Vivante driver at libsdl2 configuration time, adding:

--disable-video-vivante

[Redoy]

Hi AntonioST

i have also facing same problem. i have compile binary with STM32CUBE IDE and run on STM32mp2_EVK board. 
work fine with WAYLAND as configuration 1. but

with Configuration 2 (SDL2 and KMSDRM) not work, nothing display. 
i try with export SDL_VIDEODRIVER=kmsdrm bot not work.
try to getCurrentVideoDriver = offscreen. 

maybe kmsdrm is not enabled. 

i follow this (STM32MP LVGL ) tutorial and want to drive Configuration 2 setup. 

what i have already achived:

configuration 1: success no issue 

configuration 2 : nothing display ( i preferred this)

configuration 3: work but touch not work correclty.

can you please help me to resolve the problem.

Thanks.

[Khaled-ELGHA]

Hello @AntonioST 

Thank you for your answer

I was able to make the SDL2 library works with KMSDRM with kernel 5.15 Kirkston but with kernel 6.6 Scarthgap it doesn't work. I also configured the kmsdrm to work as mentioned but in the .bbappend file since I am using Yocto. I can see from the log.configure that the kmsdrm is on but the application which was working with 5.15 is still not able to run with 6.6. However, KMSCube is working means KMSDRM is working from the kernel point of view. The messages that I got when debug are below:

INFO: video driver in use is: (null)
INFO: video driver 0: wayland
INFO: video driver 1: KMSDRM
INFO: video driver 2: (null)
INFO: video driver 3: (null)
INFO: Failed to initialize SDL: No available video device

Even if I specify the driver to be kmdrm I see the following

INFO: video driver in use is: (null)
INFO: video driver 0: wayland
INFO: video driver 1: KMSDRM
INFO: video driver 2: (null)
INFO: video driver 3: (null)
INFO: Failed to initialize SDL: kmsdrm not available

I don't know why it is still unavailable?

from the "log.do_configure" of Yocto I can see this:

-- SDL_KMSDRM (Wanted: ON): ON
-- SDL_KMSDRM_SHARED (Wanted: ON): ON

in the build folder of "libsdl2" I can see also this in the "CMakeCache.txt" file:

//Use KMS DRM video driver
SDL_KMSDRM:BOOL=ON

//Dynamically load KMS DRM support
SDL_KMSDRM_SHARED:BOOL=ON

I edited the bbappend by adding those two lines to switch the offscreen off and to make sure that the KMSDRM is working

EXTRA_OECMAKE += " \
-DSDL_VIVANTE=OFF \
-DSDL_OPENGL=OFF \
-DSDL_KMSDRM=ON \
-DSDL_OFFSCREEN=OFF \
"

What else can I do? any suggestions?
Thanks in advance