Android: CNSDK display-processor plug-in (libdxrp050_leia_cnsdk.so)

[leaiss]

Summary

Companion to displayxr-runtime PR #268, which splits the Android POC along the post-#263 plug-in boundary. The runtime side keeps the cross-cutting infrastructure (is_self_submitting vtable flag, vk_native Android plumbing, audit fixes); CNSDK + driver-side audit fixes live here.

Adds src/drv_leia_android/ as a sibling of the Windows src/drv_leia/, sharing the same plug-in entry contract (xrtPluginNegotiate) but selected at CMake configure time by if(WIN32) / elseif(ANDROID).

Source files (new src/drv_leia_android/)

File	Purpose
leia_cnsdk.{cpp,h}	CNSDK C-ABI wrapper. Core init (worker thread), interlacer lifecycle, atlas weave, face-tracking snapshot. Audit fixes: B2 (gamma format match), B4 (mm→m), B5 (camera-relative→display-relative), B10 (worker watchdog), B11 (interlacer fail-flag), B12 (device-config cache → also implicitly closes B9).
leia_display_processor_cnsdk.{cpp,h}	xrt_display_processor vtable wired to the wrapper. is_self_submitting=true, atlas-mode only (no per-tile blit — CNSDK splits the SBS atlas internally via set_interlace_view_texture_atlas), DXR_HW_DBG + DXR_ATRACE blocks gated on XRT_DEBUG_ANDROID_VERBOSE. Audit fixes: B7 (vkDeviceWaitIdle between weave + HUD record — masked on Android, future-proof), B8 (mono 1×1 passthrough), B14 (pause/resume from session begin/end).
leia_plugin_android.c	xrtPluginNegotiate entry point + xrt_plugin_iface vtable. Only create_dp_vk is non-NULL (no D3D/Metal/GL on Android). id = "leia-cnsdk". probe always succeeds (POC pattern — CNSDK device-config is async, so synchronous probing isn't possible at xrCreateInstance time). Minimal leia_android_hmd_create() with hardcoded Lume Pad 2 defaults; CNSDK metrics surface lazily via the DP's get_display_dimensions / get_display_pixel_info once the async core init completes.

Build wiring

• CMakeLists.txt (top-level): relax if(NOT WIN32) FATAL_ERROR to if(NOT WIN32 AND NOT ANDROID). Branch add_subdirectory between src/drv_leia (Windows) and src/drv_leia_android (Android). Skip the NSIS installer on Android — APK + jniLibs/ is the install path.
• src/drv_leia_android/CMakeLists.txt: find_package(CNSDK CONFIG REQUIRED) on CNSDK_ROOT env var or CMake var. Builds libdxrp050_leia_cnsdk.so, matching the runtime's plug-in filename convention (libdxrp<NNN>_<id>.so). Symbol-hidden except xrtPluginNegotiate.

Docs

• docs/cnsdk-android-calibration.md — moved from displayxr-runtime PR #271's docs/cnsdk-axis-calibration branch, with file-path refs rewritten to src/drv_leia_android/…. Three CNSDK convention assumptions (face axis signs/units, tile-to-eye mapping, UV vertical flip) with symptom→fix tables for on-device bring-up.

How this slots into the runtime APK (POC mode)

# 1. Build the plug-in standalone:
export CNSDK_ROOT=/path/to/cnsdk-android-0.7.28
cmake -S . -B build-android \
    -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake \
    -DANDROID_ABI=arm64-v8a \
    -DANDROID_PLATFORM=android-29 -G Ninja
cmake --build build-android --target dxrp050_leia_cnsdk

# 2. Drop the .so into the runtime APK's jniLibs/ tree:
cp build-android/src/drv_leia_android/libdxrp050_leia_cnsdk.so \
   <runtime-repo>/src/xrt/targets/openxr_android/src/main/jniLibs/arm64-v8a/

# 3. Build the runtime APK (PR #268 head):
./gradlew.bat :src:xrt:targets:openxr_android:assembleInProcessDebug

The runtime's target_plugin_loader.c Android branch (PR #309, commit c96c93ce8 on main) discovers the plug-in via dladdr-of-self + dirname enumeration at xrCreateInstance time. v2 multi-APK discovery (separate vendor APKs each shipping plug-ins) is tracked at runtime #310.

Status

• ✅ Compiles in the standalone repo against CNSDK 0.7.28 (host-side preflight).
• ⏳ Not yet wired into the runtime APK's Gradle (manual jniLibs/ drop per the README until multi-module Gradle integration lands — follow-up).
• ⏳ First hardware install gated on Lume Pad arrival. Bring-up plan: docs/getting-started/android-bringup-checklist.md in the runtime repo.

Test plan

• cmake -B build-android -DCMAKE_TOOLCHAIN_FILE=... configures cleanly with CNSDK_ROOT set.
• cmake --build build-android --target dxrp050_leia_cnsdk produces a .so whose only exported symbol is xrtPluginNegotiate (llvm-nm --defined-only --extern-only libdxrp050_leia_cnsdk.so).
• After dropping the .so into the runtime APK's jniLibs/arm64-v8a/, assembleInProcessDebug produces a single APK that contains both libopenxr_displayxr.so and libdxrp050_leia_cnsdk.so.
• On Lume Pad install: adb logcat | grep target_plugin_loader shows the loader discovering libdxrp050_leia_cnsdk.so and successfully calling xrtPluginNegotiate.
• Cube test app from displayxr-runtime PR #269 renders woven output (single first-light test from android-bringup-checklist.md Test A).

🤖 Generated with Claude Code

[leaiss]

@dfattal — reposting from the closed #5 (which was sourced from my fork; now consolidated to upstream branches). Same content. Android CNSDK plug-in stack #11 → #14 ready for review, CI green, end-to-end validated on Android-36 emulator up to xrCreateInstance -> XR_SUCCESS. Reviewing #14 alone effectively approves the whole stack since commit SHAs cascade.

[leaiss]

Rebased the whole Android stack (#11→#18) onto current main and force-pushed. Two reasons:

1. ABI major v2 (ADR-020). The stack was based on the old v1.4.1-pinned main; main now pins runtime v1.9.0 (ABI v2). The Android DP factory wired six optional vtable slots (is_self_submitting, on_pause/on_resume, eye positions, display dims/pixel info) but never set the new struct_size header — so under the v2 runtime, XRT_DP_HAS_SLOT would read every one as absent, silently regressing the self-submitting atlas path into a per-frame double-submit. Fixed by setting base.struct_size = sizeof(struct xrt_display_processor), mirroring the drv_leia (Windows) migration in a6c0d7d.
2. The rebase was otherwise clean (only the top-level CMakeLists.txt pin/guard overlapped; auto-merged).

Verified: builds clean against the v1.9.1 runtime headers (ABI v2) on the NDK r26 arm64-v8a toolchain — libdxrp050_leia_cnsdk.so links, DP TU compiles with 0 errors. Stack is MERGEABLE end-to-end again.