firmware/tools/python-packages/README.md

The Python packages Moonraker and klippy need, cross-built for mipsel

The second half of phase 6. tools/python/ builds the interpreter; this builds what runs on it. Not yet wired into bin/patch.sh -- see "What is left" at the bottom. build.sh is the measurement harness, preserved here because it is where the findings live, exactly as tools/supervisor/ is for s6.

Everything below was run in the printer replica on the real rootfs.squashfs, not read off a project page. test/integration/printer/case-pyext.sh is that run, kept.

What builds

19 packages, 12 mipsel extension modules, from a 56-second clean build in one throwaway debian:bookworm. Every .so is gated at e_flags=0x70001407, nan2008/o32/mips32r2 -- shared objects carry EF_MIPS_PIC, so they read …07 where an executable reads …05.

Native: cffi, greenlet, lmdb, markupsafe, streaming-form-data, tornado speedups, pillow. Pure: jinja2, distro, inotify-simple, libnacl, dbus-next, preprocess-cancellation, pyserial, pyserial-asyncio, pycparser, smart_open, setuptools.

The list is deliberately not moonraker-requirements.txt, which installs every optional component's dependencies. It is the closure of what the enabled component set imports -- moonraker.conf's sections plus CORE_COMPONENTS -- plus klippy's. So no apprise, ldap3, paho-mqtt, zeroconf or python-periphery. msgspec and uvloop are skipped on purpose: Moonraker guards both with contextlib.suppress(ImportError) and falls back to the stdlib, measured.

The method

No crossenv. The staged interpreter already carries _sysconfigdata__linux_mipsel-linux-gnu, so exporting _PYTHON_SYSCONFIGDATA_NAME at an x86-64 build-python of the same 3.13.7 makes setuptools answer every question for the target. The stage is bind-mounted at /usr/data/anvil so INCLUDEPY resolves unmodified. Plus the gcc-wrapper trick from tools/python/build.sh, which is what gets -EL -mnan=2008 onto the link lines.

What fought back, and what it cost

• greenlet was the expected blocker, for an unexpected reason. The MIPS stack-switching assembly was never a problem. greenlet 3.x is C++ and writes its PyTypeObjects as designated initializers, which gcc 7.2 accepts only in declaration order with no gaps:

  sorry, unimplemented: non-trivial designated initializers not supported
  

  The exact rule was probed rather than assumed: in-order contiguous is fine, a trailing gap is fine, an interior or leading gap is refused. fill-designators.py writes the skipped fields back as explicit zeros, taking field order from the target's own headers and refusing to guess when a designator is not in them. 55 fields across two files, semantically a no-op -- static storage duration, those fields were already zero -- and the result switches out and back, in order, on the printer.

• pip silently downloaded x86-64 manylinux wheels for cffi, greenlet and tornado on the first run. Three wrong-architecture .so files sailed straight through the build and only the ABI gate caught them. --no-binary :all: is mandatory here, not caution.

• lmdb chose its cffi backend and produced a py3-none-any wheel with mdb.c inside -- which is phase 6's recorded trap rebuilt from scratch: on the printer that path tries to invoke a compiler that does not exist. LMDB_FORCE_CPYTHON=1 fixes it. Note LMDB_FORCE_CFFI=0 makes it worse: the variable is tested for presence, so "0" selects cffi.

• pillow 10.3.0 cannot be built by any 3.13, cross or not: its setup.py does exec(...) then reads locals()["__version__"], which PEP 667 broke. 11.0.0 is the first version that works.

• streaming-form-data 1.13.0 (Moonraker's pin) ships pregenerated Cython C calling the 4-argument _PyLong_AsByteArray, which grew a fifth parameter in 3.13. 1.19.1 instead, which then wants smart_open at module scope.

What it proves

Beyond "it imports", which proves very little on its own:

• cffi does cdef + dlopen + call through libm -- klippy's exact ABI-mode usage.
• cffi dlopens the printer's own /usr/prog/klipper/klippy/chelper/c_helper.so, resolves stepcompress_alloc, steppersync_alloc and itersolve_generate_steps, and calls one. That is phase 7's central question -- whether a Python we built can drive FlashForge's C helper -- answered yes, and it is the reason the interpreter had to be glibc and not musl.
• lmdb writes and a second process reads back.
• pillow decodes, resizes and re-encodes a PNG: the real thumbnail path.
• all 16 Moonraker components import on 3.13, the list taken from CORE_COMPONENTS + moonraker.conf rather than written down here.
• zero /usr/prog libraries mapped, with every extension imported.
• Negative control: move the tree aside and every third-party import fails.

Size

13.5MB built, 2.9MB gzipped, 1073 files; 18.2MB on the printer once __pycache__ exists. With the interpreter, about 50MB.

setuptools/pkg_resources are 4.9MB of that -- 36% -- and are not needed at runtime: measured, with them removed lmdb still loads its CPython extension and all 16 components still import. The phase-6 trap was the lmdb egg's cffi fallback, and installing lmdb as a wheel removes it. Dropping them is a size decision, not a correctness one.

Moonraker SERVES on 3.13 -- settled, not assumed

Importing is not serving, so it was run. test/integration/printer/case-moonraker313.sh starts Moonraker on the exact command line payload/etc/s6/moonraker/run execs, only with our interpreter, against the mod's own assets/moonraker.conf:

• bound :7125 in 3s, /proc/PID/cmdline confirming our interpreter and our entry point
• GET /server/info 200 with 23 components loaded and 0 failed; /machine/system_info (a different component, reading this box's /proc) reports cpu: mips, python 3.13.7 [GCC 7.2.0]
• the database really works: POST wrote a namespace, GET read it back, the namespace appears beside Moonraker's own, and data.mdb is 147456 bytes on disk -- through lmdb/cpython.cpython-313-mipsel-linux-gnu.so, not the compile-at-import cffi fallback
• alive and still answering 120 seconds later, zero tracebacks in its log, and SIGTERM released the port in 2s
• the running process maps 0 libraries under /usr/prog, with LD_LIBRARY_PATH completely unset -- not merely purged of /usr/prog
• negative controls: nothing on :7125 beforehand, and with site-packages moved aside it never binds

What is still unproven is endurance and integration, not capability: no real hardware, no live klippy attached (klippy_connected=False throughout, so the klippy_apis paths loaded but were never exercised), no upload through streaming_form_data, no websocket client, and it has not been run through S62moonraker under s6 on 3.13 -- the entry point was driven directly, on purpose, so that a failure would be the interpreter and not an init script.

libsodium: built into the prefix, and it costs anvil-env.sh nothing

build-libsodium.sh cross-builds libsodium 1.0.20 with the Ingenic toolchain (24s), gated at 0x70001407 nan2008/o32/mips32r2, SONAME libsodium.so.26, needing only libpthread, libc and the loader. 406KB stripped, into $MODDIR/lib.

It does not need a new LD_LIBRARY_PATH entry, which is the pleasant part. libnacl's third fallback is __file__[0:__file__.find("lib")+3] + "/libsodium.so", and __file__ is $MODDIR/lib/python3.13/site-packages/libnacl/__init__.py, so it resolves $MODDIR/lib/libsodium.so by absolute path -- measured working with LD_LIBRARY_PATH unset entirely. Worth writing down that this works because the prefix happens to contain the string lib; a prefix without it would break silently. Adding $MODDIR/lib to the path also works and is the belt-and-braces option, but it would put our libraries in front of everything for every mod process, which is the kind of entry this file's own history argues against.

It computes as well as loads: sodium_version_string() is 1.0.20, its BLAKE2b-256 matches CPython's own _blake2 on the same kernel, and libnacl.sign.Signer/Verifier -- the exact ed25519 pair authorization.py imports -- signs, verifies and rejects a tampered message. With it, /usr/prog/libsodium/lib can come off ANVIL_LIBS, though only as part of the same one-line FF_PYTHON switch, since 3.8's libnacl still needs it.

What is left before FF_PYTHON can switch

Capability is settled -- Moonraker serves, the database works, libsodium is ours. What is left is packaging and integration:

1. Wire into bin/patch.sh. The blocker is that section 5c's trim deletes include/ and lib/python3.13/config-3.13-* and then removes the staging tree, and the package build needs both. Cleanest fix is to run the package build inside 5c against the untrimmed stage BEFORE the trim, rather than caching a second tree. Add a step for libsodium, a step to stage the 19 packages into lib/python3.13/site-packages/, and move every pin into versions.env with sha256s.
2. Extend the ABI gate's reach. It walks $PY_BUILD/bin and $PY_BUILD/lib -- the build cache, not the payload -- so libsodium and the twelve extension .so files staged straight into $MOD_PAYLOAD would bypass it. No logic change needed, the two-word DYN -> 0x70001407 rule already covers them; only coverage.
3. Run it through S62moonraker under s6 on 3.13. The entry point was driven directly on purpose, so the s6 readiness and restart machinery is still gated only against 3.8.
4. Then the switch itself: FF_PYTHON in anvil-env.sh, and /usr/prog/libsodium/lib off ANVIL_LIBS in the same commit.
5. klippy is not blocked by packages: cffi, greenlet, jinja2, markupsafe and pyserial all build, and c_helper.so binds. numpy is the only gap, wanted solely by extras/stepper_resonance_tester.py, which Klipper loads on demand. numpy on 3.13 means numpy >= 2.1 and a Meson cross-file, and that genuinely is a multi-day rabbit hole. It costs input-shaper calibration, not printing.

Unverified: no real hardware, replica only; nothing has run under sustained load; and the greenlet designator patch is a no-op by argument plus a working switch test, not by upstream blessing.