emul_fb

A Linux userspace framebuffer emulator.

The emulator contains a kernel driver which creates a framebuffer device under /dev/fbX, where X is the next available frame buffer device.

It also creates a /dev/fb_view character device, which is used to notify the viewer (emul_fb) when the frame buffer content changes and needs to be redrawn.

Dependencies

The emulator uses SDL2 for the window showing the framebuffer content.

On Ubuntu the development dependencies can be installed with:

sudo apt-get install build-essential git make cmake autoconf automake libtool pkg-config libasound2-dev libpulse-dev libaudio-dev libjack-dev libx11-dev libxext-dev libxrandr-dev libxcursor-dev libxi-dev libxinerama-dev libxxf86vm-dev libxss-dev libgl1-mesa-dev libdbus-1-dev libudev-dev libgles2-mesa-dev libegl1-mesa-dev libibus-1.0-dev fcitx-libs-dev libsamplerate0-dev libsndio-dev libwayland-dev libxkbcommon-dev libdrm-dev libgbm-dev

sudo apt install libsdl2-2.0-0 libsdl2-dev

Build

The project is build using cmake version 3.16 or higher. Kitware has an apt repository if you Ubuntu version has an older version per default.

Best practice is to make an out of library build with cmake. Open a terminal and navigate into the source directory, then do:

mkdir build
cd build
cmake .. && make
sudo make install

Operation

The required kernel module must be installed before emul_fb can be invoked. In a terminal simply execute:

sudo modprobe vfb2
emul_fb

This will create a user accessible framebuffer device located at /dev/fbX and a viewer notification on /dev/fb_view.

Note: The kernel module can be loaded automatically at boot time, by entering its name in /etc/modules.

Test

Open another terminal and run the following command to fill the framebuffer with random pixel data, then start emul_fb to show the content:

cat /dev/urandom >> /dev/fbX
emul_fb