Janet v1 verdict was AMEND with 1 structural BLOCKER (Q5) + 3
implementation-time risks (F1-F3).
Q5 (BLOCKER) empirically confirmed on ampere: RK3588 has THREE
hantro-vpu instances (legacy MPEG2/VP8 at /dev/video2, encoder at
/dev/video3, vpu981 AV1 at /dev/video4). Current backend's 2-device
fd model (rkvdec + hantro) is "RK3399-shaped knowledge" per its own
comment — silently picks the wrong hantro on RK3588.
v2 fix: add third device slot (video_fd_vpu981 + media_fd_vpu981),
discriminate by V4L2_PIX_FMT_AV1_FRAME capability (not driver name),
extend request_device_kind_for_profile with 'a' kind for VAProfile-
AV1Profile0, extend cap_pool pair-of-flags layout per iter38 pattern.
Q1 amendment: tile_group_entry DYNAMIC_ARRAY size = sizeof * MAX(N,1);
add _Static_assert for kernel uAPI drift catch.
Q2 amendment: VIDIOC_QUERY_EXT_CTRL probe at context init for film_grain
availability; gate per-frame send on the flag.
Q3 PROCEED: per-frame SEQUENCE send (no caching).
Q4 PROCEED: ignore VAOpaqueAV1 (codec_store_buffer has default fallback).
Q6 PROCEED: V4L2_REQUEST_MAX_PROFILES=11 exactly full with AV1; add
comment for future bumps.
F1-F3 implementation risks catalogued for Phase 2 code review:
- mi_col/row_starts sentinel (silent corruption on multi-tile)
- superres_denom AV1_SUPERRES_NUM=8 default offset
- loop_restoration_size[] USES_LR flag gating
File estimate up from 800 to 880 LoC (added vpu981 scaffolding).
Phase 0 test vectors were single-tile (208×208 + 352×288); Phase 3
verification must include multi-tile 1080p+ AV1 to exercise F1.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
