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chromium-fourier: - patch 3/3 nv12-external-oes-on-modifier-external-only.patch — adds NativePixmapEGLBinding::ModifierRequiresExternalOES helper, extends OzoneImageGLTexturesHolder::GetBinding to honor EGL external_only flag for NV12 dmabufs on panfrost / panthor. Validated on ohm (RK3566 hantro mainline 6.19.10): bbb_1080p30_h264.mp4 plays at 34.7 % combined CPU vs ~131 % pre-patch baseline (~3.8x). - PKGBUILD pkgrel 1->2, source array + sha256sums + prepare() hook for patch 4, patch numbering 1/2,2/2 -> 1/3,2/3,3/3. - NEXT.md appended with 2026-04-28 section: patch 4 design, validation log, KWin GL_ALPHA bug pinpoint (preexisting since 2026-03-06, affects every wayland video client; unrelated to chromium-fourier), device-renumbering note (/dev/video1 = encoder post-reboot). - KWIN_PIVOT.md: 4-phase plan to identify and patch KWin's glTexImage2D(internalFormat=GL_ALPHA) site, ohm-only test plan, scope discipline. - patches/ now tracked (compiler-rt-adjust-paths, enable-v4l2, wayland-allow-direct-egl-gles2, nv12-external-oes); the dead-end chromeos-pipeline-bypass.patch removed. firefox-fourier: - 4 patches (gfxinfo v4l2 stateless fourccs, libwrapper hwdevice ctx, ffmpegvideo v4l2-request route, prefs v4l2-request default). - PKGBUILD bumped to firefox 150.0.1, Arch toolchain glue patches layered in, mozconfig with --without-wasm-sandboxed-libraries for ALARM, package() launcher fix (rm -f symlink before cat > to avoid ENOENT through the dangling /usr/local symlink mach install drops). - 150.0.1-1-aarch64.pkg.tar.zst built on boltzmann (95 MB), pending fresnel power-on for V4L2 stateless validation on RK3399.
211 lines
10 KiB
Markdown
211 lines
10 KiB
Markdown
# firefox-fourier — V4L2 Stateless Decoder Patch Plan
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Plan to extend Firefox 149's V4L2 hardware decode path to cover Rockchip
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mainline kernel boards (RK3399 rkvdec, RK3566/RK3588 hantro, RK3588
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rkvdec2) by routing stateless `S264`/`S265`/`VP9F` fourccs through
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libavcodec's `v4l2_request` hwaccel, which mainline FFmpeg surfaces via
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`AV_HWDEVICE_TYPE_DRM` (no dedicated `_V4L2REQUEST` enum exists upstream
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— confirmed against `libavutil/hwcontext.h`).
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## 1. Files touched (in order)
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| # | Path | Change | Lines |
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|---|------|--------|-------|
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| 1 | `widget/gtk/GfxInfo.cpp` | `V4L2ProbeDevice` (~L1030–1110): add `S264`/`S265`/`VP9F` matches alongside existing `H264`/`HEVC`/`VP90`. Set `mIsV4L2Supported = Some(true)` and OR the same `CODEC_HW_DEC_*` bits. Tag a new bool `mV4L2IsStateless` so downstream can branch. | +35 / -2 |
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| 2 | `dom/media/platforms/ffmpeg/FFmpegLibWrapper.h` | Add wrappers for `av_hwdevice_ctx_create` (currently only `_alloc`/`_init` per L173–174) and `av_hwdevice_find_type_by_name`. Needed because stateless wants the *device-path-aware* `_create` form to bind `/dev/dri/renderD128`. | +4 / 0 |
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| 3 | `dom/media/platforms/ffmpeg/FFmpegLibWrapper.cpp` | `dlsym` the two new pointers; gate behind `LIBAVUTIL_VERSION_MAJOR >= 56`. | +6 / 0 |
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| 4 | `dom/media/platforms/ffmpeg/FFmpegVideoDecoder.h` | Add `AVBufferRef* mDRMDeviceContext = nullptr;` and `bool mUsingV4L2Request = false;` next to existing `mUsingV4L2`. | +3 / 0 |
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| 5 | `dom/media/platforms/ffmpeg/FFmpegVideoDecoder.cpp` | New `CreateV4L2RequestDeviceContext()` modelled on `CreateVAAPIDeviceContext` (current uses `av_hwdevice_ctx_alloc(AV_HWDEVICE_TYPE_VAAPI)`). Wire it in alongside the existing V4L2 init branch (the one feeding `ChooseV4L2PixelFormat` at L~258). `FindVideoHardwareAVCodec` call at L708 stays unchanged for stateless — we want the *generic* `h264`/`hevc`/`vp9` decoder + a DRM hw_device_ctx, not a `_v4l2m2m` codec. | +90 / -5 |
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| 6 | `modules/libpref/init/StaticPrefList.yaml` | New pref `media.ffmpeg.v4l2-request.enabled` mirroring `media.ffmpeg.vaapi.enabled` (default `@IS_LINUX@`). | +6 / 0 |
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| 7 | `dom/media/ipc/RDDProcessHost.cpp` + sandbox policy file | Whitelist `/dev/media*`, `/dev/dri/renderD*`, `/dev/video*` for the RDD process (already partly done for VAAPI — verify `policy/linux/SandboxBrokerPolicyFactory.cpp`). | +6 / 0 |
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Total: roughly **+150 / -10** across 7 files.
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## 2. Probe extension — `GfxInfo.cpp::V4L2ProbeDevice`
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Existing pattern (~L1075):
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```cpp
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if (outFormats.Contains("H264")) { mIsV4L2Supported = Some(true);
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mV4L2SupportedCodecs |= CODEC_HW_DEC_H264; ... }
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```
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Add three siblings, each setting an additional `mV4L2IsStateless = true`:
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```cpp
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if (outFormats.Contains("S264")) { /* CODEC_HW_DEC_H264 | stateless */ }
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if (outFormats.Contains("S265")) { /* CODEC_HW_DEC_HEVC | stateless */ }
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if (outFormats.Contains("VP9F")) { /* CODEC_HW_DEC_VP9 | stateless */ }
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```
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Decision: do **not** introduce a separate `mIsV4L2StatelessSupported`.
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Collapse under `mIsV4L2Supported` so the existing feature-gate plumbing
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(`MediaCodecsSupport`, `gfxFeature::HW_DECODE_VIDEO`) flips identically
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— only `mV4L2IsStateless` distinguishes the routing in step 3. Stateful
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+ stateless on the same SoC (rare, but RK3588 has both rkvdec2 + hantro
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VEPU) gracefully degrades to whichever codec wins enumeration order.
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The capture-format gate (`YV12`/`NV12`) needs widening: stateless
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decoders frequently expose only `NV12` or `NV15` (10-bit, RK3588 HEVC).
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Add `NV15` and `NM12` (multiplanar NV12, hantro). Without this the
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prober rejects an otherwise-good device.
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## 3. Decoder routing — `FFmpegVideoDecoder.cpp`
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Codec selection happens at **L651** (`AV_HWDEVICE_TYPE_VAAPI` →
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`h264_vaapi`) and **L708** (the V4L2 fallback path → `h264_v4l2m2m` via
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`FindVideoHardwareAVCodec(mLib, mCodecID)` resolving by suffix). The
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stateless route diverges from both: the *codec* must remain the generic
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`h264`/`hevc`/`vp9` decoder (libavcodec auto-binds `v4l2_request` from
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its `hw_configs` when a DRM hw_device_ctx is attached). Pseudo-patch:
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```cpp
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if (gfxInfo.mUsingV4L2 && gfxInfo.mV4L2IsStateless) {
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AVCodec* codec = mLib->avcodec_find_decoder(mCodecID); // generic
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mCodecContext = mLib->avcodec_alloc_context3(codec);
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if (!CreateV4L2RequestDeviceContext()) return false;
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mCodecContext->get_format = ChooseV4L2PixelFormat; // already returns DRM_PRIME
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mUsingV4L2Request = true;
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}
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```
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`CreateV4L2RequestDeviceContext()` body:
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```cpp
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const char* drm = "/dev/dri/renderD128";
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if (mLib->av_hwdevice_ctx_create(&mDRMDeviceContext,
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AV_HWDEVICE_TYPE_DRM, drm, nullptr, 0) < 0) return false;
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mCodecContext->hw_device_ctx = mLib->av_buffer_ref(mDRMDeviceContext);
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```
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`av_hwdevice_ctx_create` — not currently wrapped — is the entry point.
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The codec's internal hwaccel selector then walks
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`avcodec_get_hw_config()` and picks the entry whose `device_type ==
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AV_HWDEVICE_TYPE_DRM` and `pix_fmt == AV_PIX_FMT_DRM_PRIME`, which is
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the v4l2_request hwaccel registered in `libavcodec/v4l2_request_*.c`.
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No `av_hwdevice_find_type_by_name("v4l2_request")` needed — stays an
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internal libavcodec name.
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## 4. Dmabuf / DRM_PRIME reuse
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`ChooseV4L2PixelFormat` at L~258–270 already returns
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`AV_PIX_FMT_DRM_PRIME` and is the *only* format the v4l2_request
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hwaccel produces. The downstream consumer (DMABufSurfaceYUV import in
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`FFmpegVideoFramePool.cpp`) is already DRM_PRIME-aware for the
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stateful path — same code reads `AVDRMFrameDescriptor` from
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`frame->data[0]`. **No new output handling required for NV12/YV12.**
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10-bit caveat: RK3588 HEVC outputs `DRM_FORMAT_NV15` / `NV20`
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(Mali-tile). Existing `WaylandDMABufSurface::CreateYUVSurface`
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modifier list does not include `DRM_FORMAT_MOD_ARM_AFBC` or NV15
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fourcc. Either reject 10-bit at probe (capture format gate above) or
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extend `gfx/layers/DMABUFSurfaceImage.cpp` — out of scope for v1; gate
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to NV12 only.
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SAND format pollution Turner mentioned in bug 1969297 c#3 is
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**Pi5-specific**; rkvdec/hantro do not produce SAND. Safe to ignore for
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the Rockchip target.
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## 5. Configuration
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New pref:
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```yaml
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- name: media.ffmpeg.v4l2-request.enabled
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type: RelaxedAtomicBool
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value: @IS_LINUX@
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mirror: always
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```
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No new env var. No `MOZ_X11_EGL`-style kludge. The existing
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`MOZ_LOG=PlatformDecoderModule:5` covers diagnostics. Default-on
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matches `media.ffmpeg.vaapi.enabled` shape; users get fallback to
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software via existing failure paths if `av_hwdevice_ctx_create` fails
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(e.g., missing `/dev/media0`).
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## 6. Test plan (fresnel — RK3399, KDE Wayland)
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1. `ls /dev/video* /dev/media*` — confirm `/dev/video0` (rkvdec
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output) and `/dev/media0` exist.
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2. `v4l2-ctl -d /dev/video0 --list-formats-out` — expect
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`S264`/`S265`/`VP9F`.
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3. Start: `MOZ_LOG="PlatformDecoderModule:5,FFmpegVideo:5"
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firefox-fourier 2>&1 | tee fx.log`.
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4. Open `https://test-videos.co.uk/bigbuckbunny/mp4-h264` 1080p clip.
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5. Success markers in `fx.log`:
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- `V4L2ProbeDevice: /dev/video0 supports S264 (stateless)`
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- `Choosing FFmpeg pixel format for V4L2 video decoding.`
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- `Requesting pixel format DRM PRIME`
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- `av_hwdevice_ctx_create(DRM, /dev/dri/renderD128) ok`
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- **No** `Using preferred software codec h264`.
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6. `cat /sys/kernel/debug/clk/clk_summary | grep vdec` — clock should
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be active during playback.
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7. `top` — CPU < 40% on a single A72 core for 1080p H.264 (stock =
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100% on all 6 cores).
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## 7. Build + ship — `firefox-fourier` PKGBUILD
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Mirror `chromium-fourier` shape exactly (sibling).
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```bash
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pkgname=firefox-fourier
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pkgver=149.0
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arch=('aarch64' 'x86_64')
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makedepends=(rust clang lld nodejs python cbindgen nasm yasm wasi-libc-bin
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gtk3 mesa libva ffmpeg) # ffmpeg only for headers via system libs
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source=(
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"https://archive.mozilla.org/pub/firefox/releases/${pkgver}/source/firefox-${pkgver}.source.tar.xz"
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patches/0001-gfxinfo-v4l2-stateless-fourccs.patch
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patches/0002-libwrapper-hwdevice-ctx-create.patch
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patches/0003-ffmpegvideo-v4l2-request-route.patch
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patches/0004-prefs-v4l2-request.patch
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mozconfig
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)
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```
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`prepare()`: `cd firefox-${pkgver}` → apply patches with `patch -Np1`.
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`build()`: `MOZ_NOSPAM=1 ./mach build`. `package()`: `./mach install
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DESTDIR=${pkgdir}`. `mozconfig` enables
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`--enable-default-toolkit=cairo-gtk3-wayland`, `--with-system-ffmpeg`,
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`ac_add_options --disable-tests`. **No** `--enable-media-gpu-process`
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— let it default. Tarball is the official Mozilla source release (not
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gecko-dev).
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Extra makedepends vs. stock firefox PKGBUILD: none — this only
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modifies existing C++.
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## 8. Risk register (ranked)
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1. **libavcodec ABI mismatch.** ALARM ships ffmpeg 7.x; Firefox dlopens
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whatever's at `libavcodec.so.61`. If the v4l2_request hwaccel was
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compiled out (Arch's ffmpeg has it; ALARM rebuild may not),
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`av_hwdevice_ctx_create(DRM, ...)` succeeds but no codec binds —
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silent fallback. Mitigation: `ffmpeg -hwaccels` should list `drm`.
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2. **Renderer-process sandbox** blocks `/dev/dri/renderD128` open.
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VAAPI already brokered this for RDD process; verify
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`SandboxBrokerPolicyFactory.cpp` covers `/dev/media*` too — likely
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doesn't.
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3. **glxtest probe runs in stripped env.** `v4l2test` (the
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FireTestProcess child) needs `cap_sys_admin` for
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`VIDIOC_S_EXT_CTRLS` request API ioctls? No — request API just
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needs `O_RDWR` on `/dev/media*`. Should be fine.
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4. **Regression of stateful path.** Adding new fourccs is additive;
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the routing branch is gated on `mV4L2IsStateless`. Stateful boards
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(Pi4) untouched.
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5. **NV15/10-bit on RK3588** — explicitly out-of-scope v1;
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gate-rejected.
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6. **rkvdec2 driver maturity.** Linux 6.12 mainline rkvdec2 H.264
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works; HEVC/VP9 still upstream-pending on some boards. Probe will
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skip what kernel doesn't expose.
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7. **DMA-BUF modifier negotiation** with panfrost/panthor on Wayland
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— already shaken out by chromium-fourier on RK3566; same code
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path.
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## 9. Upstream path (bug 1969297)
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Split into 4 reviewable commits matching files 1, 2+3, 5, 6 from the
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table. Add a gtest exercising `V4L2ProbeDevice` against a synthetic
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v4l2test stdout containing `S264` (no kernel needed). Reach out to
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skyevg (D252119 author) for review continuity. r? jya for the
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FFmpegVideoDecoder change. The `av_hwdevice_ctx_create` wrapper
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addition is a self-contained 6-liner that should land independently.
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The 10-bit/SAND concerns Turner raised remain valid for Pi5 —
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explicitly scope this series to **stateless DRM_PRIME NV12 only**,
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leaving SAND for a follow-up bug.
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