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189 lines
6.8 KiB
Markdown
189 lines
6.8 KiB
Markdown
Raspberry Pi
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============
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Requirements:
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Raspberry Pi OS (other Linux distros may work as well).
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In modern times, the Raspberry Pi works mostly like any other Linux device:
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for video, you can use X11, Wayland, or KMSDRM. For audio, you can use ALSA,
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PulseAudio, or PipeWire, etc. OpenGL, OpenGL ES, and Vulkan are known to work.
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There is a video backend in SDL called "rpi" that uses a deprecated Broadcom
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interface (named "dispmanx") to draw directly to the console without X11.
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Newer Raspberry Pi OS releases don't support this (and work fine with our
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"kmsdrm" backend for the same purposes, a standard Linux interface). Don't
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panic if you can't use this backend, or CMake says it can't find libraries it
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needs for this.
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SDL has, in past times, worked on the original Raspberry Pi and the RPi 2, but
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these devices are no longer targets we actively test; if they broke, please
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report bugs or send patches!
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The Raspberry Pi 3 and later (in 32-bit and 64-bit mode) are still known to
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work well at the time of this writing. The Raspberry Pi Zero and Zero 2 are
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also known to work well.
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## Documentation Out Of Date
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The rest of this document is likely out of date; a lot has changed in recent
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years in both SDL and the Raspberry Pi universe, and this document has not
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been updated to reflect those details. Take the rest of this information with
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a grain of salt!
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NEON
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----
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If your Pi has NEON support, make sure you add -mfpu=neon to your CFLAGS so
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that SDL will select some otherwise-disabled highly-optimized code. The
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original Pi and Pi Zero units don't have NEON; everything from the Pi2/PiZero2
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and later do.
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Cross compiling from x86 Linux
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------------------------------
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To cross compile SDL for Raspbian from your desktop machine, you'll need a
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Raspbian system root and the cross compilation tools. We'll assume these tools
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will be placed in /opt/rpi-tools
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sudo git clone --depth 1 https://github.com/raspberrypi/tools /opt/rpi-tools
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You'll also need a Raspbian binary image.
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Get it from: http://downloads.raspberrypi.org/raspbian_latest
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After unzipping, you'll get file with a name like: "<date>-wheezy-raspbian.img"
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Let's assume the sysroot will be built in /opt/rpi-sysroot.
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export SYSROOT=/opt/rpi-sysroot
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sudo kpartx -a -v <path_to_raspbian_image>.img
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sudo mount -o loop /dev/mapper/loop0p2 /mnt
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sudo cp -r /mnt $SYSROOT
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sudo apt-get install qemu binfmt-support qemu-user-static
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sudo cp /usr/bin/qemu-arm-static $SYSROOT/usr/bin
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sudo mount --bind /dev $SYSROOT/dev
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sudo mount --bind /proc $SYSROOT/proc
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sudo mount --bind /sys $SYSROOT/sys
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Now, before chrooting into the ARM sysroot, you'll need to apply a workaround,
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edit $SYSROOT/etc/ld.so.preload and comment out all lines in it.
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sudo chroot $SYSROOT
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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 libxss-dev
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exit
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sudo umount $SYSROOT/dev
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sudo umount $SYSROOT/proc
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sudo umount $SYSROOT/sys
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sudo umount /mnt
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There's one more fix required, as the libdl.so symlink uses an absolute path
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which doesn't quite work in our setup.
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sudo rm -rf $SYSROOT/usr/lib/arm-linux-gnueabihf/libdl.so
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sudo ln -s ../../../lib/arm-linux-gnueabihf/libdl.so.2 $SYSROOT/usr/lib/arm-linux-gnueabihf/libdl.so
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The final step is compiling SDL itself.
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export CC="/opt/rpi-tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf-gcc --sysroot=$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"
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cd <SDL SOURCE>
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mkdir -p build;cd build
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LDFLAGS="-L$SYSROOT/opt/vc/lib" ../configure --with-sysroot=$SYSROOT --host=arm-raspberry-linux-gnueabihf --prefix=$PWD/rpi-sdl3-installed --disable-pulseaudio --disable-esd
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make
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make install
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To be able to deploy this to /usr/local in the Raspbian system you need to fix up a few paths:
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perl -w -pi -e "s#$PWD/rpi-sdl3-installed#/usr/local#g;" ./rpi-sdl3-installed/lib/libSDL3.la ./rpi-sdl3-installed/lib/pkgconfig/sdl3.pc
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Apps don't work or poor video/audio performance
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-----------------------------------------------
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If you get sound problems, buffer underruns, etc, run "sudo rpi-update" to
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update the RPi's firmware. Note that doing so will fix these problems, but it
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will also render the CMA - Dynamic Memory Split functionality useless.
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Also, by default the Raspbian distro configures the GPU RAM at 64MB, this is too
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low in general, specially if a 1080p TV is hooked up.
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See here how to configure this setting: http://elinux.org/RPiconfig
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Using a fixed gpu_mem=128 is the best option (specially if you updated the
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firmware, using CMA probably won't work, at least it's the current case).
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No input
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--------
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Make sure you belong to the "input" group.
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sudo usermod -aG input `whoami`
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No HDMI Audio
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-------------
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If you notice that ALSA works but there's no audio over HDMI, try adding:
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hdmi_drive=2
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to your config.txt file and reboot.
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Reference: http://www.raspberrypi.org/phpBB3/viewtopic.php?t=5062
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Text Input API support
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----------------------
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The Text Input API is supported, with translation of scan codes done via the
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kernel symbol tables. For this to work, SDL needs access to a valid console.
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If you notice there's no SDL_EVENT_TEXT_INPUT message being emitted, double check that
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your app has read access to one of the following:
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* /proc/self/fd/0
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* /dev/tty
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* /dev/tty[0...6]
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* /dev/vc/0
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* /dev/console
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This is usually not a problem if you run from the physical terminal (as opposed
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to running from a pseudo terminal, such as via SSH). If running from a PTS, a
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quick workaround is to run your app as root or add yourself to the tty group,
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then re-login to the system.
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sudo usermod -aG tty `whoami`
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The keyboard layout used by SDL is the same as the one the kernel uses.
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To configure the layout on Raspbian:
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sudo dpkg-reconfigure keyboard-configuration
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To configure the locale, which controls which keys are interpreted as letters,
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this determining the CAPS LOCK behavior:
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sudo dpkg-reconfigure locales
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OpenGL problems
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---------------
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If you have desktop OpenGL headers installed at build time in your RPi or cross
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compilation environment, support for it will be built in. However, the chipset
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does not actually have support for it, which causes issues in certain SDL apps
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since the presence of OpenGL support supersedes the ES/ES2 variants.
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The workaround is to disable OpenGL at configuration time:
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./configure --disable-video-opengl
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Or if the application uses the Render functions, you can use the SDL_RENDER_DRIVER
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environment variable:
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export SDL_RENDER_DRIVER=opengles2
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Notes
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-----
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* When launching apps remotely (via SSH), SDL can prevent local keystrokes from
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leaking into the console only if it has root privileges. Launching apps locally
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does not suffer from this issue.
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