marfrit
a7d585eee8
ffmpeg -hwaccel vaapi → libva-v4l2-request-fourier → /dev/video0 → daedalus_v4l2 kernel → REQ_DECODE on the chardev → daemon FFmpeg decode → byte-exact NV12 (FNV-1a 0x1eb34bfe, same hash the standalone test_m2m_stream produces for the same 128x96 VP9 keyframe). The pixel-correct decode through the libva path is the milestone. What's NOT yet working: libva times out on the media_request fd because buf_request_complete never fires (vb->req_obj.req is NULL when buf_done runs — the S_EXT_CTRLS EINVAL leaves the buffer un-bound to the request even though the buffer queues anyway). Phase 8.13 fixes the EINVAL so the request bind takes and the completion signal propagates. Kernel V4L2 request API integration: - media_device_ops.req_validate / req_queue = vb2_request_ validate / v4l2_m2m_request_queue (Phase 8.11) — MEDIA_IOC_REQUEST_ALLOC succeeds. - vb2_queue.supports_requests = true on OUTPUT queue — without this v4l2-core rejects S_EXT_CTRLS(REQUEST_VAL). - vb2_ops.buf_request_complete = daedalus_buf_request_complete → v4l2_ctrl_request_complete(req, &ctx->hdl). Without this v4l2-core WARNs at videobuf2-v4l2.c:440. - vb2_ops.buf_out_validate: sets field=V4L2_FIELD_NONE on OUTPUT buf. Required for the same WARN check. - requires_requests intentionally NOT set: lets the existing test_m2m_stream (direct QBUF, no request) keep working alongside the libva path. Stateless control re-registration: - Switched from v4l2_ctrl_new_std_compound(NULL p_def) to v4l2_ctrl_new_custom(&cfg, NULL) — pattern rkvdec / cedrus / hantro use. v4l2-core auto-fills elem_size + type from std table (verified: VP9_FRAME elem_size=168, matches sizeof(struct v4l2_ctrl_vp9_frame)). - No-op s_ctrl callback so SET requests don't crash — daemon ignores values, FFmpeg re-parses the bitstream. Verification on hertz (Pi 5, 6.12.75+rpt-rpi-2712): ffmpeg -hwaccel vaapi -i vp9_small.ivf … daemon: REQ_DECODE cookie=1 codec=1 bitstream=1566 bytes capture=128x96 1 planes daemon: decoder: opened vp9 context daemon: decoder: OK 128x96 fmt=0 (yuv420p) fnv1a=0x1eb34bfe … Same FNV-1a hash as the standalone test_m2m_stream produces for the same VP9 keyframe. End-to-end through libva. Remaining (Phase 8.13): - S_EXT_CTRLS EINVAL on V4L2_CID_STATELESS_VP9_FRAME despite matching elem_size — needs deeper validate-path debugging. - Once the request bind takes, buf_request_complete fires on buf_done, request fd signals completion, libva DQBUFs the decoded NV12. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
kernel/ — daedalus-v4l2 Linux kernel module
Out-of-tree kernel module providing a V4L2 stateless decoder device that forwards work to a userspace daemon.
Status
Scaffold only. Phase 8.1 not yet started.
Build (when implemented)
make -C /lib/modules/$(uname -r)/build M=$(pwd)
sudo insmod daedalus_v4l2.ko
v4l2-ctl --list-devices # confirm /dev/videoNN appears
Layout (planned)
Makefile— kbuild stubdaedalus_v4l2_main.c— module init + V4L2 device registrationdaedalus_v4l2_chardev.c—/dev/daedalus-v4l2chardev for daemon communicationdaedalus_v4l2_v4l2.c— V4L2 ioctl dispatch (stateless controls)
License
GPLv2. Required for kernel module symbol compatibility.
Phase 8.1 starting point
Minimal example: register a /dev/videoNN that returns -ENOSYS on every ioctl. Validates that the kernel build works and v4l2-ctl can see the device.