The rom folders files kept the default core of each folder only, so a core the user picks in the frontend's menu was not known to read its sets there. Each folder now lists its offers: every <core> of every <emulator> in AmberELEC's es_systems.cfg (arcade: packages/ui/emulationstation/config/es_systems.cfg:116-150), every core of EmuELEC's es_systems.json, every add_emu_core of ROCKNIX's emulators package.mk with the device case it is written under (arcade: 218-229), and the emulator of every ES-DE <command>. A core written under every branch of a case is offered unconditionally. The ES-XML, ES-JSON, ELEC-conf and ES-DE setups are rescraped at their pins: archr, arkos, chaos, darkos, jelos, kolos, pan4elec, retrobat and unofficialos gain the same records and nothing else. A libretro core offered for a folder reads the sets it loads beside the game there, as the default one does. Manifests, roms folders gaining sets read beside the game: - AmberELEC: +215 (293.1 MB) in fbneo, arcade and mame, for MAME 2010, 2015, 2016 and 2003-Plus. 1 omission leaves. - EmuELEC: +291 (232.0 MB) in cps1, cps2, cps3, mame, fbneo and arcade, for MAME 2010 and 2003-Plus. 47 omissions leave. - ROCKNIX: +501 (538.7 MB) in fbneo, neogeo, cps1, cps2, cps3, arcade and mame, for MAME 2010, 2015 and 2003-Plus. 120 omissions leave. - EmuDeck: +306 (251.2 MB) in cps, cps1, cps2, cps3, arcade and mame, for MAME 2000, 2003, 2003-Plus and 2010. 92 omissions leave. Each omission that leaves was a set named as read outside the BIOS folder. RetroDECK and the other platforms do not change. No file leaves, and verify --all keeps its severity and status counts.
Platform Configs
How platform YAML files work and where subdirectory requirements come from.
Files
_registry.yml-- platform metadata (name, release pack, display order)_shared.yml-- shared file groups with canonical destinations<platform>.yml-- per-platform BIOS declarations- Inheritance:
lakka.ymlinheritsretroarch,retropie.ymlinheritsretroarch
Shared groups (_shared.yml)
The subdirectory a BIOS goes into is determined by the libretro core, not
the platform. NP2kai expects np2kai/BIOS.ROM whether you're on RetroArch,
Batocera, or Recalbox. Only base_destination varies (system/ vs bios/).
Shared groups define files with correct destinations once. Platforms
reference them via includes: [group_name] in their system definitions.
load_platform_config() in common.py resolves includes at load time,
deduplicating by filename.
When to use shared groups: whenever 2+ platforms share files that a core expects in a specific subdirectory. The group carries the correct destination so platforms can't drift.
For RetroArch specifically, libretro_scraper.py injects includes:
references and applies subdirectory prefixes via CORE_SUBDIR_MAP during
generation. Manual edits to retroarch.yml will be overwritten on next scrape.
Data directories (_data_dirs.yml)
Some cores need entire directory trees, not just individual BIOS files.
Dolphin needs dolphin-emu/Sys/ (GameSettings, DSP firmware, fonts),
PPSSPP needs PPSSPP/ (font assets, shaders), blueMSX needs Databases/
and Machines/ (machine configs).
These are defined in _data_dirs.yml as a central registry with upstream
source URLs. The pack generator auto-refreshes from upstream before building
(use --offline to skip). Data directories live in data/ (not bios/)
and are NOT indexed in database.json.
Adding a data directory:
- Add entry to
_data_dirs.ymlwith source URL, extraction path, cache location - Reference via
data_directories: [{ref: key, destination: path}]in platform systems - For scraper-generated platforms, add to
SYSTEM_DATA_DIRSin the scraper - Run
python scripts/refresh_data_dirs.py --key <name>to populate the cache
Subdirectory reference
Each entry documents where the requirement comes from. Check these source files to verify or update the paths.
| Core | Subdirectory | Source |
|---|---|---|
| NP2kai | np2kai/ |
libretro-np2kai/sdl/libretro.c |
| PX68k | keropi/ |
px68k/libretro/libretro.c |
| QUASI88 | quasi88/ |
quasi88/src/libretro.c |
| Kronos | kronos/ |
libretro-kronos/libretro/libretro.c |
| ep128emu | ep128emu/rom/ |
ep128emu-core/src/libretro.cpp |
| Flycast | dc/ |
flycast/shell/libretro/libretro.cpp |
| FBNeo NeoCD | neocd/ |
fbneo/src/burn/drv/neogeo/neo_run.cpp |
| Fuse | fuse/ |
fuse-libretro/fuse/settings.c |
| hatari | hatari/tos/ |
hatari/src/tos.c |
Full libretro docs: https://docs.libretro.com/library/<core>/
Adding a platform
- Create
platforms/<name>.yml - Set
base_destination(systemorbios),verification_mode,hash_type - Use
includes: [group]for systems with subdirectory requirements - Use
inherits: retroarchto share RetroArch's file set - Add platform-specific overrides in
overrides.systems - Test:
python scripts/verify.py --platform <name>
Adding a shared group
- Add the group to
_shared.ymlwith a source ref comment - Include: filename, destination with subdirectory prefix, required flag, hashes
- Reference via
includes: [group_name]in platform system definitions - For scraper-generated platforms, add the mapping in the scraper's
SYSTEM_SHARED_GROUPSdict so it persists across regeneration
Verification modes
| Platform | Mode | Native logic | Upstream source |
|---|---|---|---|
| RetroArch | existence | path_is_valid() -- file exists |
core_info.c |
| Lakka | existence | inherits RetroArch | idem |
| RetroPie | existence | inherits RetroArch | idem |
| Batocera | md5 | md5sum() + checkInsideZip() |
batocera-systems |
| RetroBat | md5 | MD5 check via JSON config | batocera-systems.json |
| EmuDeck | md5 | MD5 whitelist per system | checkBIOS.sh |
| Recalbox | md5 | multi-hash comma-separated | es_bios.xml + Bios.cpp |
| RetroDECK | md5 | MD5 per file via component manifests | api_data_processing.sh |
| RomM | md5 | size + any hash (MD5/SHA1/CRC32) | firmware.py |
| ROCKNIX | md5 | md5sum() + checkInsideZip() with altmd5 |
rocknix-systems |
| MiSTer FPGA | md5 | MD5 of the file at its destination | process_db_index_worker.py |
| BizHawk | sha1 | SHA1 per firmware entry | FirmwareDatabase.cs |