RaspberryPi2EGLFS

A modern guide for cross-compiling Qt 5.6 for HW accelerated OpenGL with eglfs on Raspbian Jessie.

Note that this is not intended for running desktop-style, windowed Qt apps under X11, but rather for the real embedded/device creation use case where the Qt app runs fullscreen on top of dispmanx/EGL using the Broadcom drivers.

1. Get the latest image from https://downloads.raspberrypi.org/raspbian_latest

2. Unzip and write it to a memory card. Replace ... with the SD card device (check dmesg).

sudo dd if=2015-09-24-raspbian-jessie.img of=... bs=4M

3. Boot it up, run raspi-config, change it to boot to the console instead of X, change the GPU memory to 256 MB, install a bunch of development files (for simplicity we use build-dep, not everything is really needed, but it is easier this way), and prepare our target directory:

sudo raspi-config

sudo nano /etc/apt/sources.list

and uncomment the deb-src line.

sudo apt-get update
sudo apt-get build-dep qt4-x11
sudo apt-get build-dep libqt5gui5
sudo apt-get install libudev-dev libinput-dev libts-dev

sudo mkdir /usr/local/qt5pi
sudo chown pi:pi /usr/local/qt5pi

4. Back on the host PC, create our working directory and get a toolchain:

mkdir ~/raspi
cd ~/raspi
git clone https://github.com/raspberrypi/tools

5. Create a sysroot. Using rsync we can properly keep things synchronized in the future as well. Replace IP with the address of the Pi.

mkdir sysroot sysroot/usr sysroot/opt
rsync -avz pi@IP:/lib sysroot
rsync -avz pi@IP:/usr/include sysroot/usr
rsync -avz pi@IP:/usr/lib sysroot/usr
rsync -avz pi@IP:/opt/vc sysroot/opt

6. Adjust symlinks to be relative. Instead of the old fixQualifiedLibraryPaths get a script that works:

wget https://raw.githubusercontent.com/riscv/riscv-poky/master/scripts/sysroot-relativelinks.py
chmod +x sysroot-relativelinks.py
./sysroot-relativelinks.py sysroot

7. Get qtbase (note that Qt 5.6 is not yet released and is work in progress) and configure Qt. The target directory is /usr/local/qt5pi on the Pi, the host tools like qmake will go to ~/raspi/qt5, while make install will target ~/raspi/qt5pi (this is what we will sync to the device).

git clone git://code.qt.io/qt/qtbase.git -b 5.6
cd qtbase
./configure -release -opengl es2 -device linux-rasp-pi2-g++ -device-option CROSS_COMPILE=~/raspi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf- -sysroot ~/raspi/sysroot -opensource -confirm-license -make libs -prefix /usr/local/qt5pi -extprefix ~/raspi/qt5pi -hostprefix ~/raspi/qt5 -v
make
make install

8. Deploy to the device. We simply sync everything from ~/raspi/qt5pi to the prefix we configured above.

rsync -avz qt5pi pi@IP:/usr/local

9. Build an example:

cd qtbase/examples/opengl/qopenglwidget
~/raspi/qt5/bin/qmake
make
scp qopenglwidget pi@IP:/home/pi

10. On the device, let the linker find the Qt libs:

echo /usr/local/qt5pi/lib | sudo tee /etc/ld.so.conf.d/qt5pi.conf
sudo ldconfig

11. Still on the device, fix the EGL/GLES library nonsense:

The device may have the Mesa version of libEGL and libGLESv2 in /usr/lib/arm-linux-gnueabihf, resulting Qt apps picking these instead of the real thing from /opt/vc/lib. This may be fine for X11 desktop apps not caring about OpenGL performance but is totally useless for windowing system-less, fullscreen embedded apps.

sudo rm /usr/lib/arm-linux-gnueabihf/libEGL.so.1.0.0 /usr/lib/arm-linux-gnueabihf/libGLESv2.so.2.0.0
sudo ln -s /opt/vc/lib/libEGL.so /usr/lib/arm-linux-gnueabihf/libEGL.so.1.0.0
sudo ln -s /opt/vc/lib/libGLESv2.so /usr/lib/arm-linux-gnueabihf/libGLESv2.so.2.0.0

You may want to save the originals somewhere, just in case.

12. Run qopenglwidget we deployed to /home/pi. At this point it should just work at fullscreen with 60 FPS and mouse and keyboard support.

13. Build other Qt modules as desired, the steps are the same always:

~/raspi/qt5/bin/qmake -r
make
make install

then deploy the new files by running

rsync -avz qt5pi pi@IP:/usr/local

in ~/raspi