fresnel-fourier/phase6_iter7_implementation.md

Iteration 7 — Phase 6 (implementation)

Single fork commit landed 2026-05-13. Build + install + Phase 7 verify pending fresnel uptime (offline at commit-push time).

Commit

SHA	Files	LOC	Summary
c106d95	src/request.c	+165 / -57	Refactor find_video_node_via_topology → find_decoder_video_node_via_topology (entity-function discrimination + link-graph walk). Two-pass find_codec_device for rkvdec preference.

Fork tip post-iter7-Phase-6: c106d95 (was 70196f8 at iter5b-β/iter6 close).

Phase 5 amendments incorporated

ID	Amendment	Where landed
CRIT-1	MEDIA_LNK_FL_INTERFACE_LINK link discrimination	find_decoder_video_node_via_topology data-link vs interface-link checks
CRIT-2	Check both source_id AND sink_id of each link	Both inner loops check both endpoints
IMP-1	Decoder-proc / encoder-proc distinction (algorithm safe by construction)	Confirmed correct; no additional code
IMP-2	MEDIA_ENT_F_PROC_VIDEO_DECODER set by rkvdec.c + hantro_drv.c	Confirmed at code level on boltzmann
IMP-3	2-call MEDIA_IOC_G_TOPOLOGY pattern	Replaces 3-call pattern in old find_video_node_via_topology
IMP-4	Two-pass fd open/close	for (pass = 0; pass < 2; pass++) outer loop
MIN-1	media_out from path preserved	Unchanged
MIN-2	Single-bit flag test for interface links	flags & MEDIA_LNK_FL_INTERFACE_LINK
MIN-3	Phase 7 MPEG-2/VP8 env-override mandatory	Phase 7 doc will enforce

All amendments mechanical; no structural plan changes.

Status

• Fork commit c106d95 on noether + gitea. Pushed via claude-noether SSH per feedback_gitea_as_claude_noether.md.
• Fresnel offline at commit time. Cannot syntax-check on noether (no va-api dev headers locally). Build error risk exists but is small — diff is mechanically derived from working code.
• Backend installed SHA on fresnel: unchanged from iter5b-β/iter6 close (2c6ff82c…). Will update post-build.

Phase 7 plan (pending fresnel uptime)

When fresnel returns:

1. Pull on fresnel: cd ~/src/libva-v4l2-request-fourier && git pull --ff-only origin master.
2. Build: ninja -C build. If syntax fails, report errors; fix via amend or new commit.
3. Install: sudo install -m 644 build/src/v4l2_request_drv_video.so /usr/lib/dri/v4l2_request_drv_video.so.
4. Capture new SHA256.
5. Phase 7 verification matrix:
   • C5 item 1: vainfo (no env override) lists H.264/HEVC/VP9 profiles (rkvdec).
   • C5 item 2: ffmpeg-vaapi HEVC fixture engages decoder (strace shows /dev/video opened).
   • C5 item 3 (mandatory per Phase 5 MIN-3): MPEG-2/VP8 with explicit env override still decode correctly.
   • C5 item 4: VP9 still PASS direct, MPEG-2 still PASS, no regression on Bugs 4/5/6 partial states.
   • C5 item 5: reboot fresnel; re-run vainfo + ffmpeg. Verify auto-detect repeats.
6. If 5 of 5 PASS: write Phase 7 verification doc; proceed to Phase 8 close.
7. If any fail: Phase 7 → Phase 4 loopback.

Risk register update

Risk	Status
Syntax/compile error from Edit-based refactor	UNTESTED — fresnel offline
Algorithm bug in link traversal	Mechanically verified against Phase 5 reviewer pseudocode
MEDIA_ENT_F_PROC_VIDEO_DECODER not set in kernel	Verified at code level (rkvdec.c:1382, hantro_drv.c)
Two-pass changes behavior on rkvdec-only systems	Same as single-pass (pass 1 picks rkvdec, pass 2 never fires)
Two-pass on hantro-only systems	Pass 1 finds nothing; pass 2 picks hantro-decoder (works)
Encoder mis-detection	Eliminated by construction (entity-function check excludes encoder-only paths)

Substrate state at Phase 6 close

• Fork tip c106d95 (iter7 Phase 6 commit).
• Backend installed: still iter5b-β/iter6 SHA 2c6ff82c…. To be updated when fresnel returns.
• Kernel linux-fresnel-fourier 7.0-1.
• Test fixtures unchanged.
• Phase 7 ready to execute once fresnel + build cycle complete.