iter6 was an off-path investigation. Sonnet round-1 review + my
own corrected memory feedback_rfc_v2_vb2_dma_resv_scope.md make
clear: vb2 fence series targets Wayland compositor green-frames,
not libva cached-mmap readback. iter6 found a real upstream NULL
deref bug (filed for kernel-agent#16 when UART captures the trace)
but it's not on the critical path for iter5.
iter7 returns to iter5's actual hypothesis ladder:
- H1(a) DT dma-coherent on rkvdec node — cheapest, first
- H1(b) backend DMA_BUF_IOCTL_SYNC userspace fix — if H1(a) fails
- H2 wrong-DMA-address — if H1(a)+(b) fail
- H3 false-positive DEC_RDY — last resort
Test on vanilla kernel + iter3+iter4-fixed modules (already
verified working pipeline). Pass criterion: ffmpeg-vaapi output
shows more than {16, 128} unique bytes.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Markus Fritsche