Phase 2 source-read found iter4-B1 conflates two sub-bugs:
- B1a: walk picks encoder when it should pick decoder. SMALL FIX
(~100-150 LOC). Add MEDIA_ENT_F_PROC_VIDEO_DECODER entity check
in find_video_node_via_topology; two-pass prefer rkvdec.
- B1b: multi-decoder routing (rkvdec for H.264/HEVC/VP9 + hantro
for MPEG-2/VP8 from one backend instance). Bigger arch fix
~200-400 LOC. DEFERRED.
iter7 ships B1a. Phase 1 criteria amended:
- Auto-detect always picks a decoder, never an encoder.
- Prefer rkvdec over hantro (rkvdec serves 3 of 5 codecs).
- 2 reboots verify stability.
- vainfo lists rkvdec's 3 codecs minimum.
- No regression on iter5b-β / iter6 state.
Phase 6 will use MEDIA_IOC_G_TOPOLOGY's entities+links arrays to
match V4L node entities to decoder-proc entities. Two-pass walk:
pass-1 rkvdec only, pass-2 any decoder.
Empirical baseline: on 2026-05-12 boot, /dev/media0=rkvdec (only
decoder), /dev/media1=hantro-vpu (encoder AND decoder both inside),
/dev/media2=uvc. Fix must skip encoder when accepting media1.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
