claude-noether
f10a26d883
Hard reboot observed on higgs (Pi CM5) during the first mpv vaapi-copy playback against the freshly-deployed r28+g79256dc stack — kernel panic, no persistent journal, no recoverable trace. Bug introduced by the daedalus-v4l2#6 reorder fix (#7). Cause ----- The new completion path runs `v4l2_m2m_job_finish` on SRC_CONSUMED even when the dst_buf is still parked (waiting for a future HAS_PIXELS). job_finish moves the m2m_ctx back to IDLE, the scheduler dispatches the next device_run — which calls `v4l2_m2m_next_dst_buf`, which returns the head of the CAPTURE ready-queue, which is STILL the parked dst_buf because we never removed it. Two inflight entries now reference the same vb2_buffer; the later HAS_PIXELS triggers `v4l2_m2m_dst_buf_remove_by_buf` on a vb2_buffer whose list_head is no longer linked to that queue, and `list_del()` smashes the next/prev pointers of whatever ELSE was at those addresses. Fix --- Take both src and dst off `m2m_ctx`'s rdy_queue at device_run — as soon as `v4l2_m2m_next_*_buf` has peeked them and all early-exit validation has passed. After that, the daemon owns both halves exclusively via the inflight item; the m2m scheduler can't re-issue them on the next device_run. Completion path drops the redundant `_remove_by_buf` calls — list is already detached, so `buf_done` alone is correct. Matches the amphion `vdec.c`/`venc.c` pattern (which also claims at device_run for the same reason: amphion's encode pipeline parks output buffers across multiple frames waiting for the codec to finish, structurally the same as our H.264 B-frame DPB parking). `fail_buf_error` learns about the new `claimed` flag and skips the `v4l2_m2m_*_buf_remove` calls when the buffers have already been removed by-buf at device_run. Verified -------- Builds clean against 6.18.29+rpt-rpi-2712. Field test pending — deploy via marfrit-packages bump in lock-step with the daemon (which doesn't need to change for this fix; PROTO_VERSION stays at 1).
daedalus-v4l2
V4L2 stateless decoder for the Raspberry Pi 5 / CM5, backed by the
daedalus-fourier kernel library (VP9 + AV1 CDEF + H.264 video
decode kernels on VideoCore VII compute + ARM NEON).
Status: scaffold (2026-05-18). Architecture locked per daedalus-fourier session memory; implementation not yet begun.
What this is
Sibling repo to daedalus-fourier (the kernel library; cycles 1-9 closed).
A two-piece userspace + kernel-module stack that exposes a V4L2
stateless decoder interface (/dev/videoNN) so that
libva-v4l2-request-fourier → firefox-fourier /
chromium-fourier can drive it the same way they drive existing
hardware-decode pipelines on Pi 5 / RK3588.
+-----------------------------------------------------------+
| firefox-fourier / chromium-fourier (existing) |
+-----------------------------------------------------------+
| VA-API |
+-----------------------------------------------------------+
| libva-v4l2-request-fourier (existing, sibling project) |
+-----------------------------------------------------------+
| V4L2 stateless ioctl uAPI |
+-----------------------------------------------------------+
| daedalus-v4l2 kernel module (`kernel/`) |
| - registers /dev/videoNN |
| - parses V4L2 stateless ioctls (VP9/AV1/H.264 controls) |
| - forwards bitstream + controls to userspace daemon |
| via chardev or netlink |
+-----------------------------------------------------------+
| daedalus-v4l2 userspace daemon (`daemon/`) |
| - takes bitstream blobs + per-slice controls |
| - drives FFmpeg parsers via dlopen (Option γ) |
| - dispatches per-block ops via daedalus-fourier |
| public API (daedalus_dispatch_*) |
| - posts decoded frames back to kernel module |
+-----------------------------------------------------------+
| daedalus-fourier kernel library (sibling project) |
| - exports include/daedalus.h public API |
| - per-kernel CPU NEON + opportunistic V3D QPU dispatch |
| - 9 closed cycles across VP9, AV1 CDEF, H.264 |
+-----------------------------------------------------------+
| V3D 7.1 (Mesa userspace v3dv) + ARM NEON (BCM2712) |
+-----------------------------------------------------------+
Why this architecture (Option B + γ + sibling)
Locked by user 2026-05-18 from 3 options in
daedalus-fourier/docs/phase8_scoping.md:
- Option B over A (userspace v4l2loopback): real
/dev/videoNN, proper DRM PRIME / dmabuf for browser zero-copy. - Option γ: dlopen FFmpeg as parser at runtime. No vendoring, fastest to v1.
- Sibling repo: per
project_consumer_targetconvention, V4L2-side work lives outside daedalus-fourier so the kernel-library has a clean API boundary.
Status
Initial scaffold only. See docs/architecture.md for the
deeper design and docs/roadmap.md for the
sub-phase breakdown.
Repo layout
kernel/— Linux kernel module (V4L2 device registration + ioctl handling + userspace chardev bridge). Out-of-tree.daemon/— userspace decoder daemon (linkslibdaedalus_core.afrom sibling daedalus-fourier; uses dlopen for FFmpeg parser).include/— shared headers between kernel and daemon.docs/— architecture + roadmap.
License
Kernel module: GPLv2 (required for kernel-tree compatibility). Userspace daemon: BSD-2-Clause (matches daedalus-fourier).