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Author SHA1 Message Date
claude-noether 15fc2aba14 kernel + daemon: H.264 B-frame display reorder fix (issue #6) 
H.264 streams with B-frames showed visibly pair-swapped output in
mpv / Firefox playback through the libva → daedalus_v4l2 path —
"frames went 2 1 4 3 6 5 instead of 1 2 3 4 5 6".  Reproduced in mpv
with --hwdec=vaapi-copy at 720p (bypassing Firefox's compositor),
confirming the bug was in this daemon pipeline, not downstream.

Root cause
----------
libavcodec's H.264 decoder internally reorders output to DISPLAY
order before returning from avcodec_receive_frame.  The daemon
previously called send_packet → receive_frame ONCE per REQ_DECODE
and shipped the resulting pixels in a RESP_FRAME tagged with the
SAME cookie.  For B-frames this is wrong: the frame returned from
receive_frame may belong to an EARLIER bitstream (libavcodec held
it for display-order release).  Cookie N's CAPTURE buffer therefore
got cookie N-2's pixels, while cookie N-2's CAPTURE buffer got
silently marked VB2_BUF_STATE_ERROR (the daemon returned
DAEDALUS_DECODE_NO_FRAME for the cookie whose pixels were held).

Fix shape
---------
Decouple kernel cookie identity (decode-order routing) from
libavcodec's display-ordered output.  Wire-protocol changes:

  REQ_DECODE  + __u64 src_pts        (= src_buf->vb2_buf.timestamp)
  RESP_FRAME  + __u32 flags          (HAS_PIXELS | SRC_CONSUMED)
              + __u64 output_src_pts (= frame->pts on drain)

PROTO_VERSION bumped 0 → 1.  Lock-step rebuild required.

Kernel
------
device_run now mirrors src_buf->vb2_buf.timestamp into req->src_pts
before sending REQ_DECODE, and stores it on the inflight item so
the completion path can stamp dst_buf.timestamp explicitly when
src/dst lifecycles decouple (V4L2_BUF_FLAG_TIMESTAMP_COPY's auto-
pairing no longer applies).

daedalus_complete_resp_frame splits into:

  HAS_PIXELS:    pack pixels into THIS cookie's CAPTURE buffer,
                 stamp dst timestamp from inflight->src_pts,
                 v4l2_m2m_buf_done(dst, DONE/ERROR).
                 No job_finish here.

  SRC_CONSUMED:  release the bound media_request, run
                 v4l2_m2m_buf_done(src) + v4l2_m2m_job_finish so
                 the scheduler can dispatch the next REQ.  dst_buf
                 may still be parked at this point.

Inflight entry is removed and freed only when BOTH src_buf and
dst_buf have been cleared.  Combined HAS_PIXELS|SRC_CONSUMED RESPs
(steady-state VP9/AV1 with no reorder lag) collapse to the prior
1:1 behaviour for free.

Daemon
------
daedalus_decoder_run_request split into three primitives:

  daedalus_decoder_submit       — set pkt->pts = req->src_pts,
                                  avcodec_send_packet.
  daedalus_decoder_drain_one    — avcodec_receive_frame, populate
                                  resp meta + output_src_pts (= the
                                  frame's pts, carried back from
                                  the bitstream that produced it).
  daedalus_decoder_pack_current — pack current AVFrame into the
                                  caller-mapped CAPTURE planes.

chardev_client maintains a small (src_pts → cookie, cached_req)
table indexed linearly (≤64 entries; bounded by V4L2 client buffer
pool depth).  On each REQ_DECODE:

  1. Register (src_pts → cookie) in the table.
  2. submit().
  3. Drain loop: for each frame returned, look up its owner cookie
     via pending_lookup(frame->pts), GET_DMABUF for THAT cookie,
     pack pixels, emit RESP_FRAME(owner_cookie, HAS_PIXELS,
     output_src_pts=frame->pts).  Combine with SRC_CONSUMED when
     owner_cookie equals the current REQ's cookie.
  4. If the current REQ's cookie wasn't drained inside the loop
     (libavcodec held the frame), emit a standalone SRC_CONSUMED
     RESP so the kernel runs job_finish + dispatches the next REQ;
     dst_buf for this cookie stays parked until a future drain
     produces its pixels.

VP9 / AV1 paths are unchanged in behaviour: one frame per REQ,
HAS_PIXELS|SRC_CONSUMED in one combined RESP.

Verified
--------
Builds clean cross-compiled on higgs against 6.18.29+rpt-rpi-2712
(Pi CM5).  Frame-size warning in device_run is pre-existing
(unchanged by this commit).
 2026-05-21 12:32:47 +02:00
marfrit 8c1d9960c4 DAEMON-PPS: synthesise H.264 SPS/PPS NAL units from V4L2 controls 
libva-v4l2-request-fourier (and any V4L2-stateless-API consumer)
passes H.264 SPS/PPS as separate V4L2_CID_STATELESS_H264_{SPS,PPS}
controls; only the slice NAL goes into the OUTPUT buffer.  This is
correct per the V4L2 stateless contract.  But libavcodec — which
the daedalus daemon uses for actual decode (Option γ) — wants a
self-contained AnnexB stream including SPS+PPS before any slice.
Result on higgs: "non-existing PPS 0 referenced" + decode_slice_
header errors on every H.264 frame, even after LIBVA-1 and -2
routing correctly delivered the request to the daemon.

Fix splits across kernel + daemon, keeping the kernel module as a
thin transport and putting the actual NAL encoding in userspace:

  include/daedalus_v4l2_proto.h:
    Add struct daedalus_h264_meta (the four v4l2_ctrl_h264_*
    structs the kernel collects) and DAEDALUS_REQ_FLAG_H264_META
    (set in req.flags when the meta block is present between the
    daedalus_req_decode prefix and the slice bitstream).

  kernel/daedalus_v4l2_main.c:
    Add daedalus_collect_h264_meta() — reads the H.264 ctrl values
    from the bound media_request via v4l2_ctrl_find +
    ctrl->p_cur.p_h264_*.  device_run() calls it on H.264 codec_id,
    copies the structs into the REQ_DECODE payload between the
    prefix and bitstream, and sets the flag.  Payload size is
    bounds-checked against DAEDALUS_PROTO_MAX_PAYLOAD so an over-
    sized slice + meta fails loud instead of truncating.

  daemon/src/bitstream_writer.{c,h}:
    New module — MSB-first bit packer with H.264 Exp-Golomb ue(v)
    and se(v) coding + rbsp_trailing_bits alignment.  Sticky
    overflow flag so callers can verify the output buffer wasn't
    truncated.

  daemon/src/h264_nal_synth.{c,h}:
    New module — turns v4l2_ctrl_h264_sps / v4l2_ctrl_h264_pps
    into AnnexB-framed NAL units per ITU-T H.264 7.3.2.1 / 7.3.2.2.
    Emits emulation prevention bytes (0x03 after every 00 00 in the
    EBSP) and the 4-byte start code (0x00000001).  Coverage matches
    what V4L2 stateless surface gives us: VUI parameters and full
    scaling matrices are NOT emitted (V4L2 doesn't carry them — the
    seq_scaling_matrix_present_flag is set to 0 and libavcodec uses
    flat defaults, which matches the de-facto behaviour of most
    H.264 streams libva-v4l2-request drives).

  daemon/src/decoder.c:
    daedalus_decoder_run_request() now takes an optional
    h264_meta parameter.  For codec_id == H264 with meta != NULL,
    synthesises SPS+PPS NAL units, allocates a combined
    [SPS][PPS][slice] buffer (+ AV_INPUT_BUFFER_PADDING_SIZE), and
    feeds that to avcodec_send_packet instead of the raw slice.
    VP9/AV1 path unchanged (frames are self-contained).  Cleanup
    now goes through a unified `out:` label so the assembled
    buffer is always freed on every exit (including the existing
    decoder_open_codec / no-frame / receive_frame failure paths).

  daemon/src/chardev_client.c:
    handle_req_decode() peels off the optional meta block when the
    flag is set, passes it through to the decoder, and updates
    the payload-length consistency check (now allows for an extra
    sizeof(daedalus_h264_meta) when the flag is on).

Build (boltzmann aarch64): clean compile of all daemon sources,
including bitstream_writer + h264_nal_synth + the refactored
decoder.c.  Kernel module compile to be verified via DKMS rebuild
on higgs in the marfrit-packages bump that follows.

Test plan: with this commit + a marfrit-packages daedalus pin
bump, higgs's ffmpeg -hwaccel vaapi -i h264_test.mp4 should
produce a successful decode (vs. the previous "non-existing PPS 0
referenced" failure).  The daemon log should show:
  decoder: opened h264 context
  decoder: h264 prepended SPS=NB PPS=MB slice=KB
  decoder: OK 320x240 fmt=0 (yuv420p) fnv1a=0x...

VP9 / AV1 behaviour unchanged — they don't carry meta and the
existing per-frame self-describing path still applies.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
 2026-05-20 17:35:24 +02:00
marfrit c7f6fb90cb Phase 8.6: dmabuf + AV1 + H.264 + stateless controls 
Removes the Phase 8.5 64 KiB frame-size cap by exporting CAPTURE
buffers as dmabuf-fds the daemon mmaps and writes pixels into
directly. Adds AV1 + H.264 codec support, V4L2 stateless control
registration, and the compliance polish that brings the driver
to 47/48 v4l2-compliance pass.

Protocol (include/daedalus_v4l2_proto.h):
- struct daedalus_req_decode grew capture-buffer metadata
  (width/height/pix_fmt/num_planes + per-plane size+stride).
- New DAEDALUS_IOC_GET_DMABUF ioctl on the chardev: daemon
  asks for a per-plane dmabuf fd, kernel calls vb2_core_expbuf
  in daemon task context so the fd lands in the daemon's table.

Kernel m2m driver (kernel/daedalus_v4l2_main.c):
- Both queues switched to vb2_dma_contig_memops. OUTPUT was
  vmalloc in 8.5; the switch is needed because vmalloc doesn't
  honour V4L2_MEMORY_FLAG_NON_COHERENT and v4l2-compliance's
  REQBUFS test rejected the driver because of it. We still
  read bitstream via vb2_plane_vaddr (dma_contig gives a
  kernel virtual address just like vmalloc did).
- dma_coerce_mask_and_coherent(DMA_BIT_MASK(32)) in probe.
- queue_setup populates alloc_devs[plane] = &pdev->dev for
  both queues; allow_cache_hints=1 on both.
- daedalus_export_capture_dmabuf(cookie, plane, flags, *fd):
  walks inflight list, calls vb2_core_expbuf on the CAPTURE
  buffer in the caller's (daemon's) task context.
- device_run fills the new REQ_DECODE capture fields from
  ctx->dst_fmt and maps ctx->src_fmt.pixelformat to
  DAEDALUS_CODEC_VP9 / _AV1 / _H264 (was hard-wired to VP9).
- daedalus_complete_resp_frame handles both the 8.5 inline
  path (kept for debugging) and the 8.6 dmabuf path (pixels
  already in CAPTURE buffer, just set payload from metadata).
- enum_fmt advertises all 3 OUTPUT formats (VP9F, AV1F, S264).
- try_fmt preserves userspace colorspace fields instead of
  overwriting with REC709 defaults (fixes 8.5 compliance fail).
- s_fmt propagates OUTPUT colorspace → CAPTURE (stateless
  decoder round-trip test at v4l2-test-formats.cpp:958).
- 12 V4L2 stateless controls registered per open (VP9_FRAME,
  VP9_COMPRESSED_HDR, H264_SPS/PPS/SCALING/PRED_WEIGHTS/
  SLICE_PARAMS/DECODE_PARAMS, AV1_FRAME/SEQUENCE/
  TILE_GROUP_ENTRY/FILM_GRAIN). Daemon ignores values (FFmpeg
  re-parses); registration is what makes libva-v4l2-request
  see us.

Kernel chardev (kernel/daedalus_v4l2_chardev.c):
- New unlocked_ioctl dispatching DAEDALUS_IOC_GET_DMABUF to
  daedalus_export_capture_dmabuf.
- debugfs test_decode cookies unified with the m2m cookie
  allocator via shared daedalus_next_cookie() — kills the
  Phase 8.5 namespace collision.

Daemon (daemon/src/...):
- New dmabuf_capture.{c,h}: GET_DMABUF + mmap each plane on
  REQ_DECODE; munmap + close on completion. O_RDWR | O_CLOEXEC
  is essential — vb2_core_expbuf extracts O_ACCMODE from flags
  and exports read-only by default (caught on first run; mmap
  -EACCES on PROT_WRITE).
- decoder.{c,h}: lazily opens AV1 + H.264 AVCodecContexts in
  addition to VP9 (dropped the -ENOSYS stubs). pack_nv12_to_planes
  writes Y line-by-line into planes[0] with planes[0].stride;
  interleaves Cb/Cr into planes[1] with planes[1].stride.
- chardev_client.c handle_req_decode: opens dmabuf planes,
  runs decode (pixels land in CAPTURE buffer directly), closes
  planes, sends metadata-only RESP_FRAME. No wire-pixel
  allocation.

Test harness (tools/test_m2m_decode.c):
- Optional 5th arg `codec` (vp9 | av1 | h264). Same client
  drives all three codecs.

Verification on hertz (Pi 5, 6.12.75+rpt-rpi-2712):

Bit-exact end-to-end vs `ffmpeg -pix_fmt nv12`:
  VP9   1920x1080  3,110,400 bytes  MATCH
  AV1     128x96      18,432 bytes  MATCH
  H.264   128x96      18,432 bytes  MATCH

VP9 1080p went through the full dmabuf path with no chardev
payload bloat — the same chardev that capped at 64 KiB in 8.5
now ferries metadata only and lets the daemon mmap+write a
3.1 MB frame directly into the V4L2 client's buffer.

v4l2-compliance:
  Phase 8.1: 44/48
  Phase 8.5: 44/48 (different fails after m2m landed)
  Phase 8.6: 47/48
  Only remaining: VIDIOC_(TRY_)DECODER_CMD (needs media
  controller — explicitly Phase 8.7 work).

11 standard compound controls visible:
  vp9_frame_decode_parameters, vp9_probabilities_updates,
  h264_sequence_parameter_set, h264_picture_parameter_set,
  h264_scaling_matrix, h264_prediction_weight_table,
  h264_slice_parameters, h264_decode_parameters,
  av1_sequence_parameters, av1_frame_parameters,
  av1_film_grain (av1_tile_group_entry refused by hdl->error
  on this kernel — skipped silently).

Clean SIGTERM + rmmod, no oops/WARN.

Roadmap update (docs/roadmap.md):
- Phase 8.6 marked closed with the closure-doc reference.
- Phase 8.7 reshaped to (1) media controller, (2) perf +
  daedalus_dispatch_* substitution, (3) HDR/10-bit, (4)
  long-form multi-frame streaming.

Per correctness-before-speed:
- Real V4L2 dmabuf via vb2_core_expbuf (not a sideband
  fd-passing hack).
- O_RDWR access mode threaded through correctly.
- Strict pixel-byte comparison against ffmpeg, not "looks
  right" eyeballing.
- Each compliance edge documented with the underlying test
  source-line + the fix.
- All resource paths cleaned (munmap + close per plane on
  every exit, including error paths).

Phase 8.7 next: media controller binding (closes last
compliance fail), per-frame profiling, QPU dispatch
substitution targeting 30fps@1080p from
30fps-floor-is-fine memory.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
 2026-05-18 16:16:06 +00:00
marfrit 2a449632b9 Phase 8.4: daemon ↔ kernel decode round-trip (VP9 end-to-end) 
Wires the Phase 8.3 FFmpeg loader through the Phase 8.2 chardev
bridge: kernel injects REQ_DECODE carrying a raw VP9 access unit,
daemon hands the bitstream to libavcodec via dlopen, sends
RESP_FRAME back with a content-dependent FNV-1a digest of the
decoded YUV planes. Pure CPU decode for now — Phase 8.5 swaps in
dmabuf + QPU dispatch.

Protocol (include/daedalus_v4l2_proto.h):
- New REQ_DECODE (kernel→daemon) and RESP_FRAME (daemon→kernel)
  message types, with fixed-size payload structs.
- New DAEDALUS_CODEC_VP9/AV1/H264 enum (wire-stable so 8.6's
  AV1+H.264 work doesn't move existing values).
- New DAEDALUS_DECODE_* status enum (OK / NO_FRAME / ERR_OPEN /
  ERR_SEND / ERR_RECV / ERR_CODEC).
- Converted the prior `enum daedalus_msg_type` to #defines —
  high-bit values exceed INT_MAX and tripped -Wpedantic on
  userspace; kernel uABI headers use the same idiom.

Kernel (kernel/daedalus_v4l2_chardev.c):
- New debugfs entry /sys/kernel/debug/daedalus_v4l2/test_decode:
  writing raw bitstream bytes wraps them in a REQ_DECODE
  (codec=VP9 for Phase 8.4) and enqueues with an
  auto-incrementing cookie.
- daedalus_chardev_write learned RESP_FRAME: parses the payload
  and emits a single pr_info line with decode metadata. Keeps
  existing PONG handling on the default arm.

Daemon (daemon/src/...):
- chardev_client.{c,h} — opens /dev/daedalus-v4l2, blocking read
  loop, single-buffer write() responses (kernel chardev has only
  .write, not .write_iter, so writev lands as -EINVAL —
  discovered the hard way during first run).
- decoder.{c,h} — lazily-opened AVCodecContext per codec, shared
  AVPacket/AVFrame pair, descriptor-driven plane walker
  (av_pix_fmt_desc_get) so the same hash path covers YUV420P,
  YUV422P, YUV444P, GBRP and other 8-bit planar layouts.
  Generalised after first run decoded testsrc as GBRP (71)
  rather than the assumed YUV420P.
- `daemon` command in main.c opens the chardev and runs the loop
  until SIGINT/SIGTERM. Cookie correlation handled end-to-end.
- ffmpeg_loader gained av_pix_fmt_desc_get (23 symbols total).

Build:
- CMakeLists adds chardev_client.c + decoder.c; explicit
  -I../include for the shared protocol header.
- Still -Wall -Wextra -Wpedantic clean.

Verification on hertz (Pi 5, 6.12.75+rpt-rpi-2712):

  $ ffmpeg ... -pix_fmt yuv420p -c:v libvpx-vp9 -frames:v 1 \
           -y /tmp/vp9_test.ivf
  $ python3 ... strip IVF framing → vp9_keyframe.bin (3268 B)

  $ sudo insmod kernel/daedalus_v4l2.ko
  $ daedalus_v4l2_daemon -v daemon &
  $ sudo dd if=vp9_keyframe.bin \
         of=/sys/kernel/debug/daedalus_v4l2/test_decode

  daemon: REQ_DECODE cookie=2 → decoded yuv420p 320x240
          fnv1a=0x6ef10d71 luma=76800 chroma=38400
  kernel: RESP_FRAME cookie=2 status=0 320x240 pixfmt=0
          fnv1a=0x6ef10d71  ← matches daemon ✓

Hash properties verified:
  cookie=2  testsrc 3268 B → 0x6ef10d71  (first decode)
  cookie=3  red     44 B   → 0x7f6e5dc5  (content-dependent ✓)
  cookie=4  testsrc 3268 B → 0x6ef10d71  (deterministic ✓)
  cookie=5  64 B random    → status=101  (ERR_SEND, daemon alive)

Daemon survives bad input (FFmpeg "Invalid sync code" wrapped
into structured ERR_SEND response). Clean SIGTERM shutdown,
clean rmmod.

Phase 8.4 acceptance criteria met:
- ✓ end-to-end kernel→daemon→FFmpeg→kernel round-trip
- ✓ cookie correlation per request/response pair
- ✓ content-dependent + deterministic digest
- ✓ structured error responses (no daemon crash on bad input)
- ✓ clean teardown (SIGTERM + rmmod)
- ✓ builds clean on both kernel kbuild and daemon CMake

Per correctness-before-speed:
- Real chardev I/O (no shortcuts, no select-loop hacks)
- Real FFmpeg AVCodecContext lifecycle (lazily opened, properly
  freed on cleanup)
- Descriptor-driven plane walk (generalises across pix_fmts)
- Structured error path (not just log-and-continue)
- All resource paths cleaned up on every error branch
- Documented why FNV-1a digest, why write() not writev(), why
  pix_desc walk in docs/phase_8_4_closure.md

Phase 8.5 next: V4L2 m2m queue submits REQ_DECODE from
vidioc_qbuf; dmabuf carries actual pixel data so the chardev's
64 KiB cap doesn't gate frame size; begin substituting
daedalus_dispatch_* into the daemon's decode path.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
 2026-05-18 15:22:16 +00:00
marfrit 895f57c63a Phase 8.2: kernel ↔ daemon chardev bridge with round-trip test 
Adds /dev/daedalus-v4l2 misc chardev to the kernel module. The
chardev is the IPC channel for the future userspace decoder
daemon: kernel enqueues REQ_* messages, daemon read()s them,
processes, write()s RESP_* back.

Wire protocol (pre-1.0, header in include/daedalus_v4l2_proto.h):
- struct daedalus_msg_hdr: magic (D04V) + version + type +
  cookie + payload_len + reserved
- Request/response separated by high bit of type field
- Max 64 KiB payload per message
- Cookie correlates request with matching response

Kernel implementation (kernel/daedalus_v4l2_chardev.{c,h}):
- Single-instance chardev (-EBUSY on second open)
- In-kernel FIFO bounded at 64 messages
- Blocking + non-blocking read; poll() with EPOLLIN on queued
- write() parses + validates header, logs response at pr_debug
- Bad magic → -EBADMSG, bad version → -EPROTO, oversize → -EMSGSIZE
- All error paths free resources

Phase 8.2 test trigger via debugfs:
- /sys/kernel/debug/daedalus_v4l2/test_ping — any byte
  enqueues a PING with a fixed 24-byte payload. Removed in
  Phase 8.4 when real REQ_DECODE from V4L2 path takes over.

Userspace verification tool (tools/test_chardev_pingpong.c):
- Real C program, proper error reporting via strerror
- Validates the 6-step round-trip: open → empty-queue EAGAIN →
  trigger ping → read PING → verify all fields → write PONG → close
- Builds with -Wall -Wextra clean

Verification on hertz (Pi 5, 6.12.75+rpt-rpi-2712):
  $ sudo insmod daedalus_v4l2.ko
  $ sudo tools/test_chardev_pingpong
  opening /dev/daedalus-v4l2...
    non-blocking read on empty queue: EAGAIN ✓
    injected PING via debugfs ✓
    read PING: magic ✓ version ✓ type=PING ✓ cookie=0x1234 ✓ payload=24 bytes
      payload: "DAEDALUS-V4L2-PING-PL"
    wrote PONG (cookie=0x1234) ✓
  ALL TESTS PASSED.
  $ sudo rmmod daedalus_v4l2      # clean

Per correctness-before-speed: full kerneldoc on structs, 8-tab
kernel style, SPDX headers, proper error paths, real test
program (not "I ran it once"), failure-mode coverage documented.

Phase 8.3 next: userspace daemon with dlopen'd FFmpeg parse path.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
 2026-05-18 15:05:54 +00:00