README-raspberrypi.txt
author Gabriel Jacobo <gabomdq@gmail.com>
Sat, 12 Oct 2013 16:29:34 -0300
changeset 7808 627f256b0e56
parent 7806 03e6aaea8347
child 7809 fd53b2b2a205
permissions -rw-r--r--
Fixes X11 video backend compilation when no GL is available For example, in our Raspberry Pi sysroot.

================================================================================
SDL2 for Raspberry Pi
================================================================================

Requirements:

Raspbian (other Linux distros may work as well).

================================================================================
 Features
================================================================================

* Works without X11
* Hardware accelerated OpenGL ES 2.x
* Sound via ALSA
* Input (mouse/keyboard/joystick) via EVDEV
* Hotplugging of input devices via UDEV

================================================================================
 Raspbian Build Dependencies
================================================================================

sudo apt-get install libudev-dev libasound2-dev libdbus-1-dev

You also need the VideoCore binary stuff that ships in /opt/vc for EGL and 
OpenGL ES 2.x, it usually comes pre installed, but in any case:
    
sudo apt-get install libraspberrypi0 libraspberrypi-bin libraspberrypi-dev

================================================================================
 Cross compiling from x86 Linux
================================================================================

To cross compile SDL for Raspbian from your desktop machine, you'll need a
Raspbian system root and the cross compilation tools. We'll assume these tools
will be placed in /opt/rpi-tools

    sudo git clone --depth 1 https://github.com/raspberrypi/tools /opt/rpi-tools

You'll also need a Rasbian binary image.
Get it from: http://downloads.raspberrypi.org/raspbian_latest 
After unzipping, you'll get file with a name like: <date>-wheezy-raspbian.img
Let's assume the sysroot will be built in /opt/rpi-sysroot.

    export SYSROOT=/opt/rpi-sysroot
    sudo kpartx -a -v <path_to_raspbian_image>.img
    sudo mount -o loop /dev/mapper/loop0p2 /mnt
    sudo cp -r /mnt $SYSROOT
    sudo apt-get install qemu binfmt-support qemu-user-static
    sudo cp /usr/bin/qemu-arm-static $SYSROOT/usr/bin
    sudo mount --bind /dev $SYSROOT/dev
    sudo mount --bind /proc $SYSROOT/proc
    sudo mount --bind /sys $SYSROOT/sys

Now, before chrooting into the ARM sysroot, you'll need to apply a workaround,
edit $SYSROOT/etc/ld.so.preload and comment out all lines in it.

    sudo chroot $SYSROOT
    apt-get install libudev-dev libasound2-dev libdbus-1-dev libraspberrypi0 libraspberrypi-bin libraspberrypi-dev libx11-dev libxext-dev libxrandr-dev libxcursor-dev libxi-dev libxinerama-dev libxxf86vm-dev libxss-dev
    exit
    sudo umount $SYSROOT/dev
    sudo umount $SYSROOT/proc
    sudo umount $SYSROOT/sys
    sudo umount /mnt

The final step is compiling SDL itself.

    export CC="/opt/rpi-tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf-gcc --sysroot=$SYSROOT -I$SYSROOT/opt/vc/include -I$SYSROOT/usr/include -I$SYSROOT/opt/vc/include/interface/vcos/pthreads -I$SYSROOT/opt/vc/include/interface/vmcs_host/linux"
    cd <SDL SOURCE>
    mkdir -p build;cd build
    ../configure --with-sysroot=$SYSROOT --host=arm-raspberry-linux-gnueabihf --prefix=$PWD/rpi-sdl2-installed --disable-pulseaudio --disable-esd
    make
    make install

To be able to deploy this to /usr/local in the Raspbian system you need to fix up a few paths:
    
    perl -w -pi -e "s#$PWD/rpi-sdl2-installed#/usr/local#g;" ./rpi-sdl2-installed/lib/libSDL2.la ./rpi-sdl2-installed/lib/pkgconfig/sdl2.pc ./rpi-sdl2-installed/bin/sdl2-config
    
================================================================================
 Apps don't work or poor video/audio performance
================================================================================

If you get sound problems, buffer underruns, etc, run "sudo rpi-update" to 
update the RPi's firmware. Note that doing so will fix these problems, but it
will also render the CMA - Dynamic Memory Split functionality useless.

Also, by default the Raspbian distro configures the GPU RAM at 64MB, this is too
low in general, specially if a 1080p TV is hooked up.

See here how to configure this setting: http://elinux.org/RPiconfig

Using a fixed gpu_mem=128 is the best option (specially if you updated the 
firmware, using CMA probably won't work, at least it's the current case).

================================================================================
 No input
================================================================================

Make sure you belong to the "input" group.

    sudo usermod -aG input `whoami`

================================================================================
 No HDMI Audio
================================================================================

If you notice that ALSA works but there's no audio over HDMI, try adding:
    
    hdmi_drive=2
    
to your config.txt file and reboot.

Reference: http://www.raspberrypi.org/phpBB3/viewtopic.php?t=5062

================================================================================
 Text Input API support
================================================================================

The Text Input API is supported, with translation of scan codes done via the
kernel symbol tables. For this to work, SDL needs access to a valid console.
If you notice there's no SDL_TEXTINPUT message being emmited, double check that
your app has read access to one of the following:
    
* /proc/self/fd/0
* /dev/tty
* /dev/tty[0...6]
* /dev/vc/0
* /dev/console

This is usually not a problem if you run from the physical terminal (as opposed
to running from a pseudo terminal, such as via SSH). If running from a PTS, a 
quick workaround is to run your app as root or add yourself to the tty group,
then re login to the system.

   sudo usermod -aG tty `whoami`
    
The keyboard layout used by SDL is the same as the one the kernel uses.
To configure the layout on Raspbian:
    
    sudo dpkg-reconfigure keyboard-configuration
    
To configure the locale, which controls which keys are interpreted as letters,
this determining the CAPS LOCK behavior:

    sudo dpkg-reconfigure locales

================================================================================
 Notes
================================================================================

* Input events from the keyboard leak through to the console