love-mmiyoo

LÖVE 11.5 runtime for the Miyoo Mini / Mini+ (OnionOS) — a device with no GPU.

The whole OpenGL pipeline is served in software by glsoft (glsoft/core.c), a purpose-built rasterizer loaded through SDL_VIDEO_GL_DRIVER into a custom SDL2 whose dummy video driver gained GL hooks (patches/sdl2-dummy-gl.patch). Drawing goes straight to /dev/fb0; input comes from /dev/input/event0 (the Miyoo's gpio_keys) via SDL's evdev path, delivered to games as keyboard events.

Born inside the Balatro-on-Miyoo port effort and extracted here as the reusable part: any LÖVE 11.x game enters the device through this same door. It has shipped two games so far — Balatro and gen1recomp.

Grab love-mmiyoo-runtime-<version>.tar.gz from Releases. Contents:

love # launcher stub
lib/liblove-11.5.so # LÖVE 11.5 (patched: see patches/love-keep-context.patch)
lib/libSDL2-2.0.so.0 # SDL 2.28.5 (patched: dummy-GL hooks, evdev w/o udev)
lib/libglsoft.so # the software GL renderer
lib/... # LuaJIT, OpenAL, ALSA, ogg/vorbis, theora, freetype, ...
share/alsa/ # ALSA config (the Onion rootfs has no /usr/share/alsa)

19 shared libraries, ~4.4 MB compressed. glibc & friends come from the device (Onion ships glibc 2.28; the toolchain matches it by construction).

See example/launch.sh (annotated) and example/Game.port. The short version:

DIR=/mnt/SDCARD/Roms/PORTS/Games/YourGame
export LD_LIBRARY_PATH=$DIR/runtime/lib:${LD_LIBRARY_PATH:-/lib:/config/lib:/mnt/SDCARD/miyoo/lib}
unset LD_PRELOAD # libpadsp hooks fb0 AND audio; we use neither
export SDL_VIDEODRIVER=evdev # the patched dummy driver's polling name
export SDL_EVDEV_DEVICES="2:/dev/input/event0"
export SDL_VIDEO_GL_DRIVER=$DIR/runtime/lib/libglsoft.so
export SDL_DUMMY_MODE=640x480 # the fake desktop the dummy driver reports
export GLSOFT_FB=/dev/fb0 GLSOFT_FILTER=nearest GLSOFT_KEEP_CONTEXT=1
export ALSA_CONFIG_PATH=$DIR/runtime/share/alsa/alsa.conf
export ALSA_CONFIG_DIR=$DIR/runtime/share/alsa
export ALSOFT_CONF=$DIR/alsoft.conf # 48 kHz — the only rate the hw accepts
. /mnt/SDCARD/.tmp_update/script/stop_audioserver.sh # NEVER killall audioserver
$DIR/runtime/love $DIR/game

Hard-won rules encoded there (each one cost a debugging round on the device):

• Prefix LD_LIBRARY_PATH, never replace it — Onion launches ports with LD_PRELOAD=libpadsp.so and /config/lib in the path; replacing the variable kills the dynamic loader before LÖVE even starts.
• SDL_VIDEODRIVER=evdev, not dummy — same driver, but only this name polls input.
• Stop the audioserver with Onion's own script — it preserves volume through /proc/mi_modules; a bare killall leaves the MI_AO device unusable until reboot.
• OpenAL at 48 kHz (example/alsoft.conf) — the hardware accepts only 8/16/32/48 kHz S16; OpenAL's default 44.1 kHz fails context creation.
• .port files need GameDir= and GameDataFile= — Onion's "Import ports" validates against them and renames the shortcut to .notfound otherwise.
• Test scripts that inject input need SDL_EVDEV_GRAB=1, or the frozen MainUI replays your keys when it wakes.

Custom shaders become passthrough. glsoft implements the fixed pipeline LÖVE uses (Texel(tex, uv) * VertexColor * ConstantColor), parses GLSL only to extract uniforms, and runs every custom shader as that same passthrough. Games whose correctness depends on shaders need those effects disabled or reimplemented; games that only decorate with them run fine, flat. Canvas/FBO render-to-texture is supported; stencil is accepted and ignored.

Measured throughput on the Mini+ (Cortex-A7 ×ばつ1.2 GHz): solid fill 137 Mpx/s, opaque solid color 54.7, translucent 19.4, nearest-texture 10.5 — plus ~2.7 μs per triangle and ~0.57 μs per raster line of fixed overhead. Budget accordingly: one full-screen 640x480 pass ≈ 20 ms on the texture path.

Requires Docker (the image is arm32v7/debian:buster, run emulated — matching the device's glibc 2.28 exactly):

make toolchain # build the armhf image
make sdl2 # SDL 2.28.5 + dummy-GL patch
make love-build # LÖVE 11.5 against that SDL2 (+ keep-context patch)
make glsoft # the rasterizer (regenerates glsoft_gen.c and verifies enums)
make love-package # -> third_party/runtime.tar.gz
make love-verify # ldd in a CLEAN container; fails on any missing lib

glsoft, the build scripts and everything original here: MIT (see LICENSE). The runtime tarball redistributes third-party libraries — versions, sources and licenses in THIRD_PARTY.md. LÖVE and SDL are zlib; the exact patches applied to each are in patches/.