marfrit
6f4b580f7c
Replaces the Phase 8.4 debugfs-triggered chardev path with a
real V4L2 m2m driver. Userspace clients now drive decoding the
standard way — S_FMT / REQBUFS / QBUF on the OUTPUT (bitstream)
queue, DQBUF on the CAPTURE (NV12M) queue. Kernel device_run
packs the bitstream into REQ_DECODE; daemon decodes via FFmpeg;
RESP_FRAME's inline NV12 pixel payload lands in the CAPTURE
buffer. Phase 8.6 swaps the inline payload for dmabuf so big
frames stop being capped at 64 KiB.
Kernel (daedalus_v4l2_main.c, rewritten + main.h added):
- Per-open struct daedalus_ctx: v4l2_fh, m2m_ctx, ctrl_handler,
per-queue v4l2_pix_format_mplane.
- Two vb2_queues (vb2_vmalloc_memops for both — no DMA needed
yet; 8.6 switches CAPTURE to dma_contig for dmabuf-export):
OUTPUT = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE, VP9_FRAME
CAPTURE = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE, NV12M
- Full v4l2_ioctl_ops table: querycap, enum_fmt, g/s/try_fmt
for both queues, reqbufs/querybuf/qbuf/dqbuf/create_bufs/
prepare_buf/expbuf/streamon/streamoff via v4l2_m2m_ioctl_*
helpers.
- v4l2_m2m_ops.device_run: peeks next OUTPUT buf, builds
REQ_DECODE inline with the bitstream bytes, enqueues with an
auto-incrementing cookie, stores {ctx, src_buf, dst_buf} in
a per-device inflight list. Job stays open until RESP_FRAME.
- daedalus_complete_resp_frame(): pops the inflight entry,
memcpys inline NV12 pixels into the CAPTURE buffer (Y plane
+ interleaved CbCr), finishes via
v4l2_m2m_buf_done_and_job_finish — NOT plain buf_done +
job_finish, which leaves the src buf on the m2m queue and
causes device_run to immediately re-run on the same input
(caught on first run; second REQ_DECODE for same bitstream +
eventual oops in stop_streaming on teardown).
Kernel (daedalus_v4l2_chardev.c):
- RESP_FRAME handler now hands inline pixel payload to
daedalus_complete_resp_frame so it lands in the CAPTURE
vb2 buffer. Existing PONG and debugfs test_decode paths still
work; the latter produces a harmless ratelimited "unknown
cookie" since it bypasses V4L2 m2m.
Daemon (decoder.c, decoder.h):
- daedalus_decoder_run_request signature extended with
(nv12_out, nv12_cap, nv12_used). After the FNV-1a digest the
decoder packs YUV420P into NV12 in the caller's buffer: Y
plane line-by-line stripped of stride padding; Cb/Cr
interleaved into a single chroma plane. Truncation silent —
kernel only memcpys what fits in the CAPTURE plane.
Daemon (chardev_client.c):
- handle_req_decode allocates a response buffer sized for the
full chardev payload, lets decoder fill the pixel area
after the resp_frame struct, sends the full payload via the
existing send_response.
Test client (tools/test_m2m_decode.c, new):
- Minimal V4L2 m2m client: S_FMT both queues, REQBUFS 1 each,
mmap+fill OUTPUT, QBUF both, STREAMON, poll, DQBUF, dump
CAPTURE planes to a raw NV12 file. ~250 LOC; verifies the
whole flow without needing v4l2-ctl framing.
Roadmap update (docs/roadmap.md):
- Phase 8.4 retitled "daemon ↔ kernel decode round-trip"
to reflect what actually shipped (vs. the original V4L2-
ioctl-driven plan which moved here).
- Phase 8.5 retitled "full V4L2 m2m driver" with closure
status.
- Phase 8.6 reshaped to two tracks: dmabuf + AV1/H.264/
stateless controls + media controller. Adds the punch list
of v4l2-compliance failures (DECODER_CMD, S_FMT colorspace)
that 8.6 will fix.
Verification on hertz (Pi 5, 6.12.75+rpt-rpi-2712):
Kernel + daemon build clean (-Wall -Wextra clean both sides).
Test harness drives one VP9 keyframe end-to-end:
OUTPUT REQBUFS -> 2
CAPTURE REQBUFS -> 2
QBUF OUTPUT[0] bytesused=1566
QBUF CAPTURE[0]; STREAMON both
poll revents=0x5
DQBUF OUTPUT[0] flags=0x4001 (DONE)
DQBUF CAPTURE[0] flags=0x4000 payloads=[12288, 6144]
wrote 12288 Y + 6144 UV bytes to /tmp/out_m2m.nv12
Pixel correctness vs reference:
ffmpeg -i vp9_small.ivf -pix_fmt nv12 -f rawvideo -y ref.nv12
cmp /tmp/out_m2m.nv12 /tmp/ref.nv12 → match ✓
Byte-for-byte identical to FFmpeg's stock CPU decode.
v4l2-compliance: detected as Stateless Decoder; most ioctls
pass; two expected fails documented in closure doc
(DECODER_CMD/media controller, S_FMT colorspace).
Clean teardown: SIGTERM the daemon, rmmod the module, no
oops/WARN in dmesg.
Per correctness-before-speed:
- Real V4L2 ioctl table (not stubs); uses v4l2-core helpers
where they exist instead of reinventing.
- v4l2_m2m_buf_done_and_job_finish (not the manual sequence)
to keep scheduler state consistent.
- Bit-exact reference comparison, not just "looks right."
- Documented every compliance failure with the planned fix.
- All resource paths (kmalloc/kfree, inflight list cleanup,
src/dst buf removal in stop_streaming) handled on every
error branch.
Phase 8.6 next: dmabuf-export for CAPTURE (removes 64 KiB
frame-size cap), add AV1+H.264 codecs, add V4L2 stateless
controls + media controller binding, fix the colorspace +
cookie-namespace compliance issues.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
71 lines
2.5 KiB
C
71 lines
2.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
|
|
/*
|
|
* daedalus-v4l2 — kernel-internal device/state declarations.
|
|
*
|
|
* Shared between daedalus_v4l2_main.c (V4L2 m2m driver) and
|
|
* daedalus_v4l2_chardev.c (kernel↔daemon bridge). The chardev
|
|
* needs to look up in-flight V4L2 requests by cookie to complete
|
|
* the m2m job when RESP_FRAME arrives — that path lives in
|
|
* daedalus_complete_resp_frame().
|
|
*/
|
|
#ifndef DAEDALUS_V4L2_MAIN_H
|
|
#define DAEDALUS_V4L2_MAIN_H
|
|
|
|
#include <linux/list.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/platform_device.h>
|
|
|
|
#include <media/v4l2-device.h>
|
|
#include <media/v4l2-dev.h>
|
|
#include <media/v4l2-mem2mem.h>
|
|
|
|
#include "daedalus_v4l2_proto.h"
|
|
|
|
/**
|
|
* struct daedalus_dev - top-level device state (singleton for now)
|
|
* @pdev: owning platform device (synthesised in module_init)
|
|
* @v4l2_dev: V4L2 device parent for any video_device we register
|
|
* @vdev: video_device exposed as /dev/videoNN
|
|
* @m2m_dev: mem2mem device shared by all per-open contexts
|
|
* @m2m_lock: serialises vb2 queue + v4l2 ioctl ops
|
|
* @inflight: list of struct daedalus_inflight (REQ_DECODE sent,
|
|
* RESP_FRAME not yet returned)
|
|
* @inflight_lock: protects @inflight
|
|
*
|
|
* Singleton per-module instance. Multi-instance support (one
|
|
* decoder per /dev/videoNN) would require breaking g_daedalus_dev
|
|
* out of daedalus_v4l2_main.c; not needed yet.
|
|
*/
|
|
struct daedalus_dev {
|
|
struct platform_device *pdev;
|
|
struct v4l2_device v4l2_dev;
|
|
struct video_device vdev;
|
|
struct v4l2_m2m_dev *m2m_dev;
|
|
struct mutex m2m_lock;
|
|
struct list_head inflight;
|
|
struct mutex inflight_lock;
|
|
};
|
|
|
|
/* Module-wide singleton accessor (chardev needs this for RESP_FRAME). */
|
|
struct daedalus_dev *daedalus_get_dev(void);
|
|
|
|
/**
|
|
* daedalus_complete_resp_frame() - chardev RESP_FRAME completion
|
|
* @cookie: cookie carried by the matching REQ_DECODE
|
|
* @fr: RESP_FRAME header from the daemon
|
|
* @pixels: inline pixel bytes following the header in the
|
|
* chardev payload (may be NULL if @pixels_len == 0)
|
|
* @pixels_len: number of inline pixel bytes
|
|
*
|
|
* Called from the chardev write() path on RESP_FRAME. Looks up
|
|
* the in-flight request, copies inline pixel data into the
|
|
* CAPTURE vb2 buffer if available, then completes both src+dst
|
|
* buffers and finishes the m2m job. Silently drops responses
|
|
* for unknown cookies (pr_warn_ratelimited).
|
|
*/
|
|
void daedalus_complete_resp_frame(u32 cookie,
|
|
const struct daedalus_resp_frame *fr,
|
|
const u8 *pixels, size_t pixels_len);
|
|
|
|
#endif /* DAEDALUS_V4L2_MAIN_H */
|