marfrit
c7f6fb90cb
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>
105 lines
3.6 KiB
Markdown
105 lines
3.6 KiB
Markdown
# daedalus-v4l2 — roadmap
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## Sub-phases
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### Phase 8.1 — kernel module skeleton
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Out-of-tree kernel module that:
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- Registers `/dev/videoNN` with `VFL_TYPE_VIDEO` + a no-op
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V4L2 stateless dispatch table.
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- Accepts open/close, S_FMT, REQBUFS ioctls without doing
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anything (yet).
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- Builds against `/lib/modules/$(uname -r)/build`.
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Deliverable: `modprobe daedalus_v4l2` works, `v4l2-ctl --list-devices`
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shows the new device.
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### Phase 8.2 — kernel ↔ daemon chardev bridge
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- Kernel module creates `/dev/daedalus-v4l2` chardev.
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- Defines a simple req/resp protocol in `include/daedalus_v4l2_proto.h`.
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- Daemon connects, exchanges echo requests.
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Deliverable: ping-pong test passes.
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### Phase 8.3 — daemon FFmpeg dlopen + parse
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- Daemon links `libdaedalus_core.a` from sibling.
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- Daemon dlopens FFmpeg.
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- Test program: feed a VP9 IVF file to FFmpeg parsers,
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extract block-level metadata, validate against expected.
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Deliverable: daemon can parse a VP9 frame and walk the
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block-level info.
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### Phase 8.4 — daemon ↔ kernel decode round-trip (closed 2026-05-18)
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Shipped as a debugfs-triggered chardev round-trip rather than
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the original V4L2-ioctl plan (which moved to Phase 8.5).
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- REQ_DECODE / RESP_FRAME wire protocol
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- Daemon decodes VP9 via FFmpeg dlopen, returns FNV-1a digest
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- Verified content-dependent + deterministic; structured
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error handling for bad bitstreams
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See `docs/phase_8_4_closure.md`.
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### Phase 8.5 — full V4L2 m2m driver (closed 2026-05-18)
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Real V4L2 m2m driver — userspace clients drive
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`S_FMT`/`REQBUFS`/`QBUF`/`DQBUF` the standard way. Bitstream
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flows kernel→daemon as inline REQ_DECODE payload; decoded NV12
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pixels flow daemon→kernel as inline RESP_FRAME payload. Works
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end-to-end for small frames (≤ ~64 KiB NV12).
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Deliverable hit: kernel m2m driver passes most v4l2-compliance
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checks; `tools/test_m2m_decode` produces a NV12 frame that's
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byte-for-byte identical to `ffmpeg -pix_fmt nv12` reference.
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See `docs/phase_8_5_closure.md`.
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### Phase 8.6 — dmabuf + AV1 + H.264 + stateless controls (closed 2026-05-18)
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- CAPTURE (and OUTPUT) on `vb2_dma_contig_memops`.
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- New `DAEDALUS_IOC_GET_DMABUF` chardev ioctl — daemon
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mmaps the in-flight CAPTURE buffer, decodes pixels in
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place, sends RESP_FRAME metadata-only.
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- 64 KiB frame-size cap removed. 1080p VP9 + 128×96 AV1
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+ 128×96 H.264 all byte-exact against reference FFmpeg
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decode.
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- V4L2 stateless controls registered for VP9 / AV1 /
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H.264 (11 controls visible to userspace).
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- Colorspace round-trip fix (TRY_FMT preserve, S_FMT
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OUTPUT→CAPTURE propagation).
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- Cookie unified across V4L2 + debugfs paths.
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- v4l2-compliance: 47/48 (only DECODER_CMD remains,
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needs media controller — moved to 8.7).
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See `docs/phase_8_6_closure.md`.
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### Phase 8.7 — media controller, perf, HDR, long-form streams
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1. Media controller binding via
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`v4l2_m2m_register_media_controller` (closes the last
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v4l2-compliance fail and unlocks the request API).
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2. Profile the daemon's per-frame cost on hertz; substitute
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`daedalus_dispatch_*` for FFmpeg's per-block paths where
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the kernel implementation matches. Target the
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`30fps-floor-is-fine` memory's daily-YouTube criterion:
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30fps@1080p with CPU left over for vscode.
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3. HDR / 10-bit support — P010M CAPTURE, depth-aware
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`pack_nv12_to_planes`.
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4. Long-form multi-frame streaming tests (B-frame refs,
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GOP boundaries) — current test client is one keyframe
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per run.
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Deliverable: 30fps stable on real content + full
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compliance pass.
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## Effort estimate
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Each phase: ~1 week of focused work (~40 hours).
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Total: 7 weeks for v1.
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Could be split across multiple sessions / contributors.
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