The412Banner
f86b64b18e
It only checks the schemes an apk's own minSdk requires, so at 26 it reported v1 as false while the JAR signature was sitting in META-INF the whole time. The file check beside it says the same thing a second way.
SteamDeck
Valve's native aarch64 Linux Steam client, running on an Android phone or handheld: a glibc rootfs under proot, gamescope as a Wayland client of an in-app Vulkan compositor, Xwayland and Zink for the client's CEF, and the device's Turnip driver underneath. There is no Wine here, and no x86 translation for the client itself — it is ARM code running as ARM code. Windows games it launches go through Valve's own ARM64 Proton build, which is where FEX comes in.
One screen, one button: install the runtime, press Play, Big Picture comes up.
How it fits together
Android app (this repo)
├── libbannerwayland.so Wayland compositor, presents into the activity's Surface (Vulkan/Turnip)
├── PulseAudio 13 + AAudio the guest's audio server, on a socket bound into the session
├── fake-evdev rings a physical pad, republished as /dev/input/eventN for the client
└── proot ── linuxfs (~790 MB, downloaded once)
├── gamescope ── Xwayland ── Zink
└── Steam (steamrtarm64, fetched from Valve on first run) ── Proton ARM64 ── FEX
The runtime image is the one published for Bannerlator (linuxfs.json in
The412Banner/winlator-contents); this app installs and updates it from that catalog. No Valve
software is redistributed — the client is fetched from Valve's own manifest on the device at
first use.
Building
Nothing is built locally. Push, and the Build APK workflow produces steamdeck-apk, a
debug-signed arm64 apk. It cross-compiles the two glibc preloads the session needs
(libfakeinput.so, libblsession.so) from the sources in this repo before the app build, so
those can never drift from what ships.
If Bannerlator is already installed
The runtime image is the same one Bannerlator installs, so on a device that already has it the 790 MB download can be skipped entirely — copy it across with root, once, before the first launch:
su -c 'cp -a /data/data/com.tencent.ig/files/linuxfs /data/data/com.steamdeck.launcher/files/ \
&& chown -R $(stat -c %u /data/data/com.steamdeck.launcher/files) \
/data/data/com.steamdeck.launcher/files/linuxfs \
&& chcon -R u:object_r:app_data_file:s0 /data/data/com.steamdeck.launcher/files/linuxfs'
The two runtimes are independent after that: each app has its own Steam install, its own login and its own games.
Controls
A physical controller is republished into the session as a synthetic Xbox 360 pad, which is the identity SDL and Steam have a mapping for. With nothing attached, an on-screen pad appears — d-pad, A/B/X/Y, shoulders, select/start and the Steam button — writing into the same rings, so the client sees one pad either way. Connect a controller and the on-screen one disappears; unplug it and it comes back. Anywhere the controls are not is a touchpad: touch moves the pointer and a tap clicks, which is how the client's own on-screen keyboard is used to sign in.
Background and foreground
A session belongs to a foreground service, not to the activity, so leaving Big Picture does not end it: the process stays at perceptible priority, a partial wake lock keeps the CPU from dropping the guest's threads, and a high-performance WiFi lock keeps a backgrounded download from being throttled to nothing. Back puts the app away and leaves Steam running; the (silent) notification brings it back. A session ends only when you say so — the notification's Stop session action — or when the app is swiped out of recents.
Device switches
Files in /sdcard/Download, for a device that cannot be reached with a debugger:
| File | Effect |
|---|---|
steamdeck-no-pad |
Turns the controller feature off entirely (a true baseline) |
steamdeck-pad-log |
Traces every interposer call into the session log |
steamdeck-driver |
a7xx, a8xx or system — overrides the Turnip build the compositor loads |
steamdeck-osc |
always or never — pins the on-screen controls instead of following what is attached |
Session logs land in /sdcard/Download/SteamDeck/.
Authors
- The412Banner — the app, the Wayland compositor, the runtime plumbing and the Steam session.
- maxjivi05 (Max) — the gamescope runtime this is built on: the proot session, the session shim, the fake-evdev interposer and the controller work, from WinNative.
Lineage and licence
GPL-3.0. The gamescope runtime, the session shim and the fake-evdev interposer come from maxjivi05's WinNative work and from Bannerlator, both GPL-3.0; the Wayland compositor and the runtime plumbing are Bannerlator's. Valve, Steam and Proton are Valve Corporation's; this project is not affiliated with Valve.