marfrit
0de0288dce
Brings daedalus_v4l2 from "standalone test client" to "VAAPI-
discoverable decoder" by adding the surface formats and
media-controller plumbing that libva-v4l2-request-fourier
(sibling repo) requires.
libva-v4l2-request-fourier patches (pushed separately):
- b5b3acf: daedalus_v4l2 added to known_decoder_drivers
- 2146341: meson option gate
This commit (daedalus-v4l2 side, 3 production changes):
1. V4L2_PIX_FMT_NV12 (single-plane) on CAPTURE
- Added to daedalus_capture_formats[] alongside NV12M + P010
- daedalus_fill_capture_fmt handles num_planes=1 case
(sizeimage = W*H*3/2, bytesperline = W)
- daemon pack_nv12_single_to_plane: Y at base+0,
interleaved CbCr at base+(stride*H); same byte content
as NV12M two-plane, different layout
- Required because libva-v4l2-request-fourier's video.c
only knows non-multi-plane NV12 (it advertises
v4l2_mplane=true but uses the single-plane fourcc).
- Verified byte-exact via test_m2m_stream against
ffmpeg -pix_fmt nv12 reference (VP9 1080p 10 frames,
31 MB).
2. V4L2 Request API media ops
- daedalus_media_ops = { vb2_request_validate,
v4l2_m2m_request_queue } assigned to mdev.ops before
media_device_init.
- Without this, MEDIA_IOC_REQUEST_ALLOC returned
-ENOTTY and no VAAPI consumer could allocate a
media_request.
3. Stateless control registration via v4l2_ctrl_new_custom
- Switched from v4l2_ctrl_new_std_compound(NULL p_def)
to v4l2_ctrl_new_custom — pattern rkvdec/cedrus/
hantro use. Adds a no-op s_ctrl callback.
Verification (hertz, Pi 5, 6.12.75+rpt-rpi-2712):
LibVA trace through `ffmpeg -hwaccel vaapi`:
vaInitialize / Profiles / Entrypoints / CreateConfig /
QuerySurfaceAttributes / CreateSurfaces / CreateContext
(cap_pool: 24 slots, 1 plane each) / CreateBuffer
(slice + picture params) / MEDIA_IOC_REQUEST_ALLOC
— all succeed.
Standalone NV12 decode path:
test_m2m_stream vp9_1080_stream.ivf out.nv12 1920 1080 vp9 nv12
→ 10/10 frames, byte-exact vs ffmpeg -pix_fmt nv12
vainfo (via libva-v4l2-request-fourier with our driver):
7 VAProfile entries with VAEntrypointVLD
(H264 Main/High/CBaseline/MultiviewHigh/StereoHigh,
VP9Profile0, AV1Profile0)
What's NOT here (Phase 8.12):
The libva trace stops at VIDIOC_S_EXT_CTRLS returning
EINVAL when populating V4L2_CID_STATELESS_VP9_FRAME on
the request. The compound-control payload validation
against the kernel's expected struct shape rejects.
This isn't a "missing line" fix — it needs proper
stateless control plumbing (the SPS/PPS/SliceParams
get_dims, validate, default-value paths that in-tree
rkvdec/cedrus/hantro implement to satisfy v4l2-core's
std_validate). Documented as Phase 8.12 scope.
The shipped integration is itself a meaningful deliverable:
all the framework scaffolding is in place; the remaining
gap is well-characterised and bounded.
See docs/phase_8_10_11_closure.md for the full trace
analysis + next-phase plan.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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).