forked from marfrit/libva-v4l2-request-fourier
test0r
4246d5d537
Identified by cross-reference against GStreamer's
gst-plugins-bad/sys/v4l2codecs/gstv4l2codech264dec.c (upstream commit
9e3e775). At lines 1263-1304, GStreamer gates SLICE_PARAMS and
PRED_WEIGHTS submission on is_slice_based(self):
if (is_slice_based (self)) {
control[num_controls].id = V4L2_CID_STATELESS_H264_SLICE_PARAMS;
...
control[num_controls].id = V4L2_CID_STATELESS_H264_PRED_WEIGHTS;
...
}
In V4L2_STATELESS_H264_DECODE_MODE_FRAME_BASED, the kernel parses the
bitstream itself from the OUTPUT-queue payload; per-slice controls in
the request trigger cluster-validation EINVAL at error_idx=count
(observed on RK3568 hantro-vpu, kernel 6.19.10).
This patch:
- Reorders controls[] so FRAME_BASED-required entries come first
(SPS, PPS, SCALING_MATRIX, DECODE_PARAMS at indices 0..3) and the
SLICE_BASED-only entries come last (SLICE_PARAMS, PRED_WEIGHTS at
indices 4..5).
- Defaults num_controls=4 (FRAME_BASED), expanding to 5 for
SLICE_BASED and 6 when V4L2_H264_CTRL_PRED_WEIGHTS_REQUIRED.
- Hardcodes slice_based=false for now since patch 0002 sets the
device to FRAME_BASED unconditionally. A TODO marks the spot for
the planned probe-then-set commit, which will populate
context->decode_mode at CreateContext via VIDIOC_QUERYCTRL/
G_EXT_CTRLS and replace the hardcoded false with a runtime check.
Diagnosis chain:
- patch 0005 reduced one EINVAL per frame on PRED_WEIGHTS
submission, but cluster-level rejection persisted at error_idx=5
(count) — meaning kernel walked all 5 controls cleanly but
rejected the request as a whole.
- dmesg silent → rejection in V4L2 core (v4l2-ctrls-request.c /
v4l2-h264.c), not in hantro driver where it could log.
- GStreamer reference confirmed FRAME_BASED contract: only 4
sequence-and-frame-level controls go in the per-request batch.
After this patch the kernel should accept the per-request controls
and actually decode the bitstream into the CAPTURE buffer.
Signed-off-by: Markus Fritsche <fritsche.markus@gmail.com>