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).
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.