The original article by Thomas Petazzoni can be found in his STM32MP1 blog.

Achtung

Ausgangsbasis sind die Vorarbeiten aus Lab 3
Bei Buildroot mit stm32mp157c-dk2.dts konfigurieren

Introduction

In Linux, both display controllers and GPUs are managed by a Linux kernel subsystem called DRM, for Direct Rendering Manager. The DRM drivers are located in drivers/gpu/drm in the Linux kernel source code. If the hardware also has a GPU in addition to the display controller, then the most significant part of handling the GPU is done in user-space libraries implementing OpenGL. In the open-source world, the de-facto standard OpenGL implementation is Mesa3D, which has support for a number of different GPUs. From a GPU driver perspective, the kernel mainly serves as a way for the user-space OpenGL library to allocate buffers and send commands to the GPU.

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In our case, we are going to use the Qt graphical toolkit, and on embedded Linux systems, it has four main display backends: eglfs (which requires an OpenGL/EGL graphics stack), linuxfb (which uses a simple legacy framebuffer interface), wayland (for Wayland, obviously) and xcb (for X.org). To keep things simple and because we don’t require OpenGL support, we will use the linuxfb backend.