KWIN_PIVOT: campaign closed end-to-end (part 3 update)

Three patches landed on ohm in sequence today: qt6-base-fourier
(GL_ALPHA → GL_R8 on ES 3.x, 3 sites in qtbase), kwin-fourier
(watchDmaBuf no-op test fixture), chromium-fourier patch 4/4
(V4L2 capture pool floor at 16). Each unsticks one layer.

Together they produce smooth 1080p30 H.264 playback under KDE
Plasma 6.6.4 Wayland on RK3566 PineTab2 mainline, where stock
chromium previously stalled in 3 seconds. Combined chrome CPU
~81% steady, KWin ~9%, zero GL_INVALID_VALUE during playback.

Brave's YouTube on the same compositor session also feels snappier
independently — the kwin-fourier watchDmaBuf bypass is a
general-purpose latency reduction for every wp_linux_dmabuf client
on Mali-class hardware, not chrome-specific.

The kernel-side architectural hole is the right upstream-correct
fix: vb2 / hantro / rga don't populate dma_resv exclusive fences
for V4L2 producers, so dma_buf_export_sync_file substitutes a stub
fence representing nothing real. Per-driver fence wiring (3 small
commits: vb2 helper API, hantro opt-in, rga opt-in) plus a parallel
KWin commit using poll(POLLIN) directly on the dmabuf fd is the
planned MR pair. kwin-fourier as it stands is a working diagnostic,
not the upstream-bound shape.

arch/chromium-fourier/KWIN_PIVOT.md

@@ -1,5 +1,25 @@
 # KWin pivot — fix the chrome-on-KWin video stall
 
+> **2026-04-28 update part 3 — campaign closed end-to-end.** Three
+> patches landed on ohm in sequence: qt6-base-fourier (GL_ALPHA →
+> GL_R8), kwin-fourier (watchDmaBuf no-op), chromium-fourier patch
+> 4/4 (V4L2 capture pool floor at 16). Each unsticks one layer.
+> Together they produce smooth 1080p30 H.264 playback under KDE
+> Plasma 6.6.4 Wayland on the box where stock chromium previously
+> stalled in 3 seconds. Combined chrome CPU ~81 % steady, KWin ~9 %,
+> zero GL_INVALID_VALUE in the journal during playback. Brave's
+> YouTube on the same session feels markedly snappier independently
+> — kwin-fourier is a general-purpose latency reduction for every
+> wp_linux_dmabuf client on this hardware, not a chrome-specific
+> fix. **The kernel-side architectural hole — vb2 / hantro / rga not
+> populating `dma_resv` exclusive fences for V4L2 producers — is the
+> right upstream-correct fix and the planned next move.** kwin-fourier
+> in its current shape (blanket bypass) is a working *diagnostic
+> instrument*; the upstream MR will be the kernel-side per-driver
+> patch (3 commits: vb2 helper API, hantro opt-in, rga opt-in) plus
+> a parallel KWin commit using `poll(POLLIN)` directly on the dmabuf
+> fd instead of the `EXPORT_SYNC_FILE`+`QSocketNotifier` roundtrip.
+
 > **2026-04-28 update part 2 — qt6-base-fourier landed, validated, did
 > not fix the chrome stall.** The Qt 6 GL_ALPHA bug (qopengltextureglyphcache.cpp,
 > qrhigles2.cpp, qopengltextureuploader.cpp) is real, the patch is

arch/qt6-base-fourier/PKGBUILD

@@ -110,11 +110,11 @@ optdepends=('freetds: MS SQL driver'
 groups=(qt6)
 _pkgfn=${pkgbase/6-/}
 source=(git+https://code.qt.io/qt/$_pkgfn#tag=v$_pkgver
-        patches/qt6-base-cflags.patch
+        qt6-base-cflags.patch
-        patches/qt6-base-nostrip.patch
+        qt6-base-nostrip.patch
-        patches/0001-qopengltextureglyphcache-pick-GL_R8-on-ES3.patch
+        0001-qopengltextureglyphcache-pick-GL_R8-on-ES3.patch
-        patches/0002-qrhigles2-RED_OR_ALPHA8-pick-GL_R8-on-ES3.patch
+        0002-qrhigles2-RED_OR_ALPHA8-pick-GL_R8-on-ES3.patch
-        patches/0003-qopengltextureuploader-pick-GL_R8-on-ES3.patch)
+        0003-qopengltextureuploader-pick-GL_R8-on-ES3.patch)
 sha256sums=('2223c075e95d86f8dbf6395b025a74d996c418f094453c903290e3c2663fbed2'
             '5411edbe215c24b30448fac69bd0ba7c882f545e8cf05027b2b6e2227abc5e78'
             '4b93f6a79039e676a56f9d6990a324a64a36f143916065973ded89adc621e094'
@@ -123,20 +123,20 @@ sha256sums=('2223c075e95d86f8dbf6395b025a74d996c418f094453c903290e3c2663fbed2'
             'SKIP')
 
 prepare() {
-  patch -d $_pkgfn -p1 < patches/qt6-base-cflags.patch # Use system CFLAGS
+  patch -d $_pkgfn -p1 < qt6-base-cflags.patch # Use system CFLAGS
-  patch -d $_pkgfn -p1 < patches/qt6-base-nostrip.patch # Don't strip binaries with qmake
+  patch -d $_pkgfn -p1 < qt6-base-nostrip.patch # Don't strip binaries with qmake
 
   # cherry-pick needs git author identity; git-cli refuses without it.
   git -C $_pkgfn -c user.email=fourier@build -c user.name='qt6-base-fourier build' \
       cherry-pick -n 8b54513cdcf62047376a5d27d784ad68a8f235bf # Fix qdbus crashes
 
   # qt6-base-fourier — three small runtime-checks that pick GL_R8 over
-  # GL_ALPHA when the live GL context is ES 3 or newer. See patches/
+  # GL_ALPHA when the live GL context is ES 3 or newer. See the
-  # for the per-site diagnosis. The chromium-fourier KWIN_PIVOT.md
+  # individual patch headers for per-site diagnosis. The
-  # writeup carries the discovery thread.
+  # chromium-fourier KWIN_PIVOT.md writeup carries the discovery thread.
-  patch -d $_pkgfn -p1 < patches/0001-qopengltextureglyphcache-pick-GL_R8-on-ES3.patch
+  patch -d $_pkgfn -p1 < 0001-qopengltextureglyphcache-pick-GL_R8-on-ES3.patch
-  patch -d $_pkgfn -p1 < patches/0002-qrhigles2-RED_OR_ALPHA8-pick-GL_R8-on-ES3.patch
+  patch -d $_pkgfn -p1 < 0002-qrhigles2-RED_OR_ALPHA8-pick-GL_R8-on-ES3.patch
-  patch -d $_pkgfn -p1 < patches/0003-qopengltextureuploader-pick-GL_R8-on-ES3.patch
+  patch -d $_pkgfn -p1 < 0003-qopengltextureuploader-pick-GL_R8-on-ES3.patch
 }
 
 build() {
@@ -165,6 +165,7 @@ build() {
     -DFEATURE_system_sqlite=ON \
     -DFEATURE_system_xcb_xinput=ON \
     -DFEATURE_no_direct_extern_access=$_no_direct_extern_access \
+    -DFEATURE_sql_ibase=OFF \
     -DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON \
     -DCMAKE_MESSAGE_LOG_LEVEL=STATUS
   cmake --build build

arch/vulkan-panfrost/PKGBUILD

@@ -0,0 +1,110 @@
+# Maintainer: Markus Fritsche <mfritsche@reauktion.de>
+#
+# vulkan-panfrost — Mesa's panvk Vulkan driver, packaged as a
+# standalone ICD on Arch Linux ARM. Stock ALARM `mesa` does not build
+# with -Dvulkan-drivers=panfrost, so panvk doesn't ship.
+#
+# Targets both Mali kernel drivers:
+#   - panfrost (Bifrost: Mali-G31 / G52 / G57) on RK3566 / RK3568 etc.
+#   - panthor  (Valhall: Mali-G610+)            on RK3588 / RK3588S etc.
+#
+# panvk on Mali-G52 r1 (Bifrost-gen2) currently returns
+# VK_ERROR_INCOMPATIBLE_DRIVER on probe — that's an upstream mesa
+# issue, not a packaging one. The driver lights up cleanly on
+# Mali-G610 Valhall (RK3588) which is the immediate target. Install on
+# Bifrost boards anyway; future mesa releases may unblock G52 r1
+# without re-packaging.
+
+pkgname=vulkan-panfrost
+pkgver=26.0.5
+pkgrel=1
+epoch=1
+pkgdesc='Mesa Vulkan ICD for Mali Bifrost / Valhall (panvk)'
+arch=('aarch64')
+url='https://gitlab.freedesktop.org/mesa/mesa'
+license=('MIT')
+depends=(
+  vulkan-icd-loader
+  libdrm
+  zlib
+  zstd
+  expat
+  libelf
+  wayland
+)
+makedepends=(
+  meson
+  ninja
+  python-mako
+  glslang
+  libxrandr
+  libxshmfence
+  libxxf86vm
+  vulkan-headers
+  wayland-protocols
+  rust-bindgen
+  rust
+  llvm
+  llvm-libs
+  libclc
+  spirv-tools
+  spirv-llvm-translator
+)
+provides=('vulkan-driver')
+options=('!lto')
+source=("https://archive.mesa3d.org/mesa-${pkgver}.tar.xz")
+sha256sums=('SKIP')
+
+build() {
+  cd "${srcdir}/mesa-${pkgver}"
+
+  # Strip mesa down to just the panvk Vulkan driver — no Gallium
+  # drivers, no GL/GLES, no GLX, no EGL, no VAAPI/VDPAU. The host's
+  # stock `mesa` package keeps providing all of those; this PKGBUILD
+  # only adds the missing Vulkan ICD next to it.
+  #
+  # --auto-features=disabled means features have to be opt-in. Avoids
+  # mesa's default "enable everything we can find headers for" pulling
+  # in xlib-lease / gallium-va / etc. that we don't want here.
+  meson setup . build \
+    --prefix=/usr \
+    --libexecdir=lib \
+    --sbindir=bin \
+    --buildtype=release \
+    --auto-features=disabled \
+    --wrap-mode=nodownload \
+    -Db_lto=false \
+    -Db_pie=true \
+    -Dvulkan-drivers=panfrost \
+    -Dgallium-drivers= \
+    -Dplatforms=wayland \
+    -Dshared-glapi=disabled \
+    -Dgallium-rusticl=false \
+    -Dmicrosoft-clc=disabled \
+    -Dvideo-codecs= \
+    -Dllvm=enabled \
+    -Dshared-llvm=enabled \
+    -Dspirv-tools=enabled \
+    -Dvulkan-icd-dir=/usr/share/vulkan/icd.d
+
+  meson compile -C build
+}
+
+package() {
+  cd "${srcdir}/mesa-${pkgver}"
+
+  # Mesa's install rules drop a lot of files we don't want in this
+  # narrow package — stage to a temp dir, then cherry-pick.
+  DESTDIR="${srcdir}/staging" meson install -C build --no-rebuild
+
+  # The ICD shared object
+  install -Dm755 "${srcdir}/staging/usr/lib/libvulkan_panfrost.so" \
+    "${pkgdir}/usr/lib/libvulkan_panfrost.so"
+
+  # The Vulkan loader manifest. Mesa installs it as
+  # `panfrost_icd.<arch>.json` (the userspace driver name) — that
+  # filename is what the Vulkan loader expects, no need to rename.
+  install -dm755 "${pkgdir}/usr/share/vulkan/icd.d"
+  cp -av "${srcdir}/staging/usr/share/vulkan/icd.d/"panfrost_icd*.json \
+    "${pkgdir}/usr/share/vulkan/icd.d/"
+}