ARM VGF Backend on Android

[tmayoff-hh]

I'm writing a conan recipe for executorch and want to add support for ARM VGF, but am running into issues.

I'm getting a bunch of undefined symbols:

error: undefined symbol: mlsdk::vgflib::CreateHeaderDecoder(void const*, unsigned long, unsigned long)

The python wheel only seems to include linux/macos libraries. Do I need to build those for android manually? Does executorch provide a method to use an external version from the one the CMake tries to use.

Also is there any list of supported android devices for this backend as well?

[omni-front]

You need to build the ARM VGF libraries for Android manually since they're not included in the Python wheel.

cmake -DCMAKE_TOOLCHAIN_FILE=<path-to-ndk>/build/cmake/android.toolchain.cmake \
      -DANDROID_ABI=arm64-v8a \
      -DANDROID_PLATFORM=android-21 \
      -S <source-dir> -B <build-dir>

This approach explicitly sets up the Android environment using NDK, which should help you resolve the undefined symbols issue.

[tmayoff-hh]

Does this also override the version of VGF lib CMake looks for? Correct me if I'm wrong but the CMake only looks for VGF in the examples folder or the pip package

  if(EXISTS
     "${EXECUTORCH_ROOT}/examples/arm/arm-scratch/ml-sdk-for-vulkan-manifest/"
  )
    message(STATUS "libvgf sourced from local scratch tree")

    # Legacy layout: libvgf sourced from local scratch tree
    set(LIBVGF_PATH
        "${EXECUTORCH_ROOT}/examples/arm/arm-scratch/ml-sdk-for-vulkan-manifest/sw/vgf-lib/"
    )
    set(LIBVGF_STATIC "${LIBVGF_PATH}/build/src/libvgf.a")
  else()
    message(STATUS "libvgf installed from pip package")

[omni-front]

The CMake script doesn't inherently override the VGF version it's looking for. You'll need to specify the correct VGF path or version in your CMake configuration to ensure it picks up the right one from your local setup, not just from the default search directories.