Phase 33 platform plan

Phase 33 — platform.amiga_info() step plan

Companion to the Phase 33 design block in Amiga port design. That section answers what and why; this file is the step-by-step ship plan — how to chunk the work into landable PRs.

Phase 33 ships six tiny C accessors on amiga.* and a frozen platform.py that wraps them with the CPython-shaped API:

>>> import platform
>>> platform.system()
'AmigaOS'
>>> platform.machine()
'68020'
>>> platform.amiga_info()
'CPU: 68020 | FPU: 68881 | Chipset: AGA | Kickstart: 45.57 | Chip: 1856KB | Fast: 14336KB'

Modelled on OoZe1911's port for surface compatibility — anything written against their platform should run unchanged on ours.

Phasing overview

Step 1: amiga.* CPU/FPU/chipset/kickstart/mem accessors
                                          ↓
                              Step 2: frozen platform.py + docs/smoke

#	Step	Output	On-target smoke
1	Six new C entries in modamiga.c: amiga.cpu(), amiga.fpu(), amiga.chipset(), amiga.kickstart(), amiga.chipmem(), amiga.fastmem(). Each is a one-shot probe into SysBase->AttnFlags, GfxBase->ChipRevBits0, or AvailMem.	New entries in amiga_module_globals_table.	From the REPL: amiga.cpu(), amiga.fpu(), etc. return the expected strings/ints under Amiberry.
2	Frozen platform.py (under ports/amiga/modules/) exposing CPython's system() / machine() / processor() / version() / release() / python_implementation() / python_version() / platform() / node() plus the amiga_info() convenience. Docs flip + vamos arg-shape test.	New module; docs/amiga.md Phase 33 → ✅, docs/amiga-testing.md gains a short platform subsection.	import platform; platform.amiga_info() returns the expected formatted string.

Each step is small (~80 LOC C, ~50 LOC Python frozen).

---

Step 1 — Six amiga.* accessors

Deliverables

• amiga.cpu() → str. Reads SysBase->AttnFlags, picks the highest CPU bit set (AFF_68060 > AFF_68040 > AFF_68030 > AFF_68020 > AFF_68010 > else "68000").
• amiga.fpu() → str. Same flags: AFF_FPU40 ("68040"), AFF_68882 ("68882"), AFF_68881 ("68881"), else "none".
• amiga.chipset() → str. Reads GfxBase->ChipRevBits0 (opens graphics.library v36 lazily; cached). "AGA" if GFXG_AGA set, "ECS" if GFXG_ECS_DENISE or GFXG_ECS_AGNUS, "OCS" otherwise.
• amiga.kickstart() → str. Formats SysBase->LibNode.lib_Version and lib_Revision as "VV.RR". (Tuple form is already available via the existing amiga.os_version(); this is the string convenience.)
• amiga.chipmem() → int. AvailMem(MEMF_CHIP) — currently free bytes, not total. Matches OoZe1911's semantics for surface compatibility.
• amiga.fastmem() → int. AvailMem(MEMF_FAST) — same caveat.

graphics.library lifecycle

amiga.chipset() is the only one that needs a new library open. Lazy global pattern matches Phase 30 / 32:

static struct GfxBase *GfxBaseAccessor = NULL;

static void amiga_gfx_ensure_open(void) {
    if (GfxBaseAccessor == NULL) {
        GfxBaseAccessor = (struct GfxBase *)OpenLibrary(
            (CONST_STRPTR)"graphics.library", 36);
        if (GfxBaseAccessor == NULL) {
            mp_raise_OSError(MP_ENOENT);
        }
    }
}

Closed in a new amiga_gfx_close() wired into main.c's shutdown path (matches amiga_asl_close / amiga_intuition_close).

Verification

REPL on target:

>>> import amiga
>>> amiga.cpu(), amiga.fpu(), amiga.chipset(), amiga.kickstart()
('68020', '68881', 'AGA', '45.57')
>>> amiga.chipmem(), amiga.fastmem()
(1900544, 14680064)

Vamos check: vamos's emulated CPU/FPU bits surface via SysBase->AttnFlags, so these all return something; the test just confirms the shape.

---

Step 2 — Frozen platform.py + docs/smoke

Deliverables

• ports/amiga/modules/platform.py — frozen module exposing:
  • system() → "AmigaOS"
  • machine() → amiga.cpu()
  • processor() → amiga.cpu()
  • version() → "Kickstart " + amiga.kickstart()
  • release() → amiga.kickstart()
  • python_implementation() → "MicroPython"
  • python_version() → sys.implementation.version formatted
  • platform() → "AmigaOS-<kickstart>-<cpu>-MicroPython_<pyver>"
  • node() → "Amiga" (no NodeName concept on AmigaOS)
  • amiga_info() → the formatted single-line dump
• tests/ports/amiga/test_platform_smoke.py — vamos-runnable:
  • platform.system() returns "AmigaOS"
  • platform.machine() is a str
  • platform.amiga_info() returns a str containing all six fields
• docs/amiga.md Phase 33 → ✅, "Status — done" block with the full accessor / module-function matrix.
• docs/amiga-testing.md short platform subsection.

Variant gating

All three shipped variants include the accessors + the frozen module — there's nothing per-variant to gate. Per-variant text-segment growth: ~600 bytes.

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Cross-cutting concerns

• "Currently free" vs "total" memory. OoZe1911's port reports AvailMem(MEMF_*) which is current free, not installed total. Matches user mental model ("how much do I have right now") and matches their port exactly so surface compatibility is preserved. Document the semantics.
• CPU/FPU detection via AttnFlags. Reflects what AmigaOS detected at boot, which can differ from compile-time CPU targeting (a standard binary built for -m68020 -msoft-float running on a 68040 reports "68040" / "68040").
• Latin-1 strings. Hard-coded chipset names are ASCII; CPU / FPU strings are ASCII. No codec concerns.
• No caching. Strings are cheap to recompute; memory values shift continuously so caching would be wrong. chipset opens graphics.library lazily (cached for the process lifetime), but the chipset bits themselves are re-read every call.

---

Out-of-scope items reaffirmed

• Full CPython platform parity (uname(), linux_distribution, mac_ver, etc.) — not meaningful on AmigaOS.
• Reporting installed memory totals (separate from currently free) — would need walking the memory list manually.
• Per-CPU feature flags (MMU, cache state) — not user-facing enough to be worth the surface.
• Reporting graphics modes / monitor / RTG board details — out of scope; that's an Intuition / graphics.library deeper dive best left to a future phase.