OpenEmbedded / Yocto software layer for RetroArch and libretro cores

This layer provides RetroArch front-end and libretro cores emulators recipes for use with OpenEmbedded and/or Yocto.

Building

You can test this layer and distro (retro) with reference build environment on your host computer

user@localhost:~$ git clone --recursive https://github.com/dev-0x7C6/retro-build-environment.git
user@localhost:~$ cd retro-build-environment
user@localhost:~$ source source.me
user@localhost:~$ MACHINE="raspberrypi4" bitbake retro-image-full

Images

Image (recipe name)	Retroarch	Libretro cores	Shaders	Titles	Cheats	Themes	Overlays
retro-image-full	✔️	✔️	✔️	✔️	✔️	✔️	✔️
retro-image-standard	✔️	✔️	✔️	✔️
retro-image-minimal	✔️	✔️	✔️

Recomendation: retro-image-full

Tested platforms

Machine	Layer	Build against	Runtime testing	Notice
cubietruck	meta-sunxi	Often	Rarely	Unable to run kms with lima(mesa)
intel-core2-32	meta-intel	Often	Sometimes	As pendrive dongle
intel-corei7-64	meta-intel	Often	Sometimes	As pendrive dongle
orange-pi-pc	meta-sunxi	Often	Rarely	---
raspberrypi3-64	meta-raspberrypi	Often	Sometimes	---
raspberrypi3	meta-raspberrypi	Often	Sometimes	---
raspberrypi4-64	meta-raspberrypi	Always	Often	---
raspberrypi4	meta-raspberrypi	Always	Often	---
rock-pi-4a	meta-rockchip	Often	None	Thanks to @MarkusVolk for sending patches

Distro features

Meta-retro introduced a collection of switches that can be set by DISTRO_FEATURES in local.conf or distro.conf

RetroArch and system features:

• retroarch-automount - added extra automounting in /var/run/media
• retroarch-autostart - enabling systemd RetroArch startup as main graphics.target
• retroarch-online - compile RetroArch with online capabilities
• retroarch-updater - compile RetroArch with update capabilities

Graphical capabilities:

• retroarch-gles - enable for OpenGLES 2.0 support in retroarch and libretro cores
• retroarch-gles3 - enable for OpenGLES 3.0 support in retroarch and libretro cores
• retroarch-opengl - enable for OpenGL >= 2.0 support in retroarch and libretro cores
• vulkan - enable for Vulkan support in retroarch and libretro cores

Customizable variables

There is a collection of variables that can be set in local.conf or distro.conf:

Default drivers

• RETROARCH_DEFAULT_INPUT_DRIVER - default is udev
• RETROARCH_DEFAULT_JOYPAD_DRIVER - default is udev
• RETROARCH_DEFAULT_VIDEO_DRIVER - default is gl
• RETROARCH_DEFAULT_VIDEO_CONTEXT - default is kms-egl
• RETROARCH_DEFAULT_AUDIO_DRIVER - default is pulseaudio or alsathread
• RETROARCH_DEFAULT_RESAMPLER_DRIVER - default is sinc
• RETROARCH_DEFAULT_MENU_DRIVER - default is ozone

Configuration

• RETROARCH_CONFIG_FULLSCREEN - default is true, go for fullscreen mode, this respects initial resolutions (tested with rpi4)
• RETROARCH_CONFIG_THREADED_VIDEO - default is true, use another thread for renderer
• RETROARCH_CONFIG_AUDIO_LATENCY - default is 256, stock value is 64, I got better performance with higher values on rpi platforms

Video settings

• RETROARCH_CONFIG_FONT_SIZE

Themes

• RETROARCH_CONFIG_XMB_SHADOWS
• RETROARCH_CONFIG_XMB_THEME_COLOR
• RETROARCH_CONFIG_XMB_THEME_INDEX

For more information see file: retroarch.inc

Layer dependencies

Layer	Sublayer	Required	Software	Recommended BSPs
openembedded-core	meta	✔️	✔️
meta-openembedded	meta-oe	✔️	✔️
↪️	meta-multimedia	✔️	✔️
↪️	meta-python	✔️	✔️
↪️	meta-networking	✔️	✔️
meta-qt5	.	✔️	✔️
meta-kodi	.		✔️
meta-raspberrypi	.		✔️	✔️
meta-raspberrypi-extras	.		✔️	✔️
meta-intel	.		✔️	✔️
meta-rockchip	.		✔️	✔️

Patches

Please submit patches against the dev-0x7C6/meta-retro layer by pull requests.

Adding the meta-retro layer to your build

In order to use this layer, you need to make the build system aware of it.

Assuming the meta-retro layer exists at the top-level of your yocto build tree, you can add it to the build system by adding the location of the meta-retro layer to bblayers.conf, along with any other layers needed. e.g.:

BBLAYERS ?= " \
  /path/to/yocto/meta \
  /path/to/yocto/meta-yocto \
  /path/to/yocto/meta-yocto-bsp \
  /path/to/yocto/meta-retro \
"