marfrit
7708744eb2
Backports Mesa main's unconditional flip of VK_EXT_legacy_dithering.
Pure-software composition; no new HW path. vk_render_pass already gates
on enabled_features.legacyDithering and panvk_vX_blend + pan_format
already plumb the dithered BLEND descriptor (BFMT2 table has MALI_BLEND_AU
encodings for RGB565/RGB5A1/RGBA4/RGB10A2 on PAN_ARCH 7). Our r5 base
just hadn't picked up the cherry-pick.
Phase 7 verify on ohm (PineTab2 / RK3566 / Mali-G52 r1 MC1) with a
locally-built r6 lib at /tmp/r6_test_lib/:
Feature advertisement:
r5: VK_EXT_legacy_dithering not in extension list, legacyDithering=false
r6: VK_EXT_legacy_dithering rev 2 advertised, legacyDithering=true
dEQP subsets (delta):
dEQP-VK.api.*.legacy_dithering* r5/r6 both: 2 P / 0 F (identical)
dEQP-VK.renderpass.dithering.* r5/r6 both: 0 P / 0 F / 94 NS (identical)
dEQP-VK.renderpass2.dithering.* r5/r6 both: 0 P / 0 F / 94 NS (identical)
Net: zero regressions, advertisement-only delta as expected.
Second-model review (per bugfix-process step 4) traced the full code
path through vk_render_pass + panvk_vX_cmd_draw + panvk_vX_blend +
pan_format BFMT2. No interaction with our r1 nullDescriptor (disjoint
paths). Mesa upstream marks ext DONE for panvk in docs/features.txt.
ARM's own libmali r51p0 driver (BXODROIDN2PL, 2024-08) lists
VK_EXT_legacy_dithering in its Vulkan extension string table,
confirming the feature is shipped by ARM for Mali-G52-class hardware.
Follow-up out of scope: the 94 renderpass-dithering tests show as
NotSupported on both r5 and r6 — there's a separate panvk-side
prereq the dEQP harness checks (likely a specific format-feature
combination). Worth investigating in a future iteration.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
mesa-panvk-bifrost
Patched Mesa libvulkan_panfrost.so exposing Bifrost-gen Mali GPUs
(Mali-G31/G52/G72/G76, PAN_ARCH 6/7) to Chromium-family browsers'
Vulkan compositor.
Result of the panvk-bifrost campaign (~/src/panvk-bifrost/),
iter9 close 2026-05-20 (technical milestone — operator-confirmed Brave
window) followed by this package as the actual delivery.
What it solves
Stock Chromium / Brave on Bifrost SBCs (PineTab2, etc.) currently dies at GL bindings init:
ERROR: ui/gl/gl_context_egl.cc:120 GLES3 is unsupported and ES version fallback is disabled
ERROR: ui/gl/init/gl_factory.cc:111 Requested GL implementation not found
ERROR: components/viz/service/main/viz_main_impl.cc:189 Exiting GPU process due to errors during initialization
This package makes Brave's Vulkan compositor path work on Bifrost, side-stepping the failing GL stack. Browser chrome and standard page rendering work.
Known limitations (not addressed)
- WebGL / WebGL2 in-page: blocked. ANGLE needs
VK_EXT_transform_feedbackto expose GLES3 contexts; PanVk-Bifrost doesn't currently support that. Sites using WebGL will degrade or refuse. - VAAPI hardware video decode: unrelated to this package — see the
libva-v4l2-request-fourierpackage for that path.
Install
# Ensure [marfrit] is in /etc/pacman.conf, then:
sudo pacman -Sy mesa-panvk-bifrost
Use
brave-vulkan # launches Brave with Vulkan
brave-vulkan https://www.example.com
brave-vulkan --your-flags-here # extra args passed through
The launcher sets:
VK_ICD_FILENAMES=/usr/lib/panvk-bifrost/icd.json(the patched driver)PAN_I_WANT_A_BROKEN_VULKAN_DRIVER=1(Mesa upstream gate)MESA_VK_VERSION_OVERRIDE=1.2(apiVersion bump for ANGLE)- Brave flags:
--use-gl=disabled --enable-features=Vulkan --use-vulkan=native --ozone-platform=x11 --no-sandbox --disable-gpu-sandbox --ignore-gpu-blocklist
What's in the package
/usr/lib/panvk-bifrost/libvulkan_panfrost.so— patched Mesa Vulkan driver (Mesa 26.0.6 + 2 sed-applied patches)/usr/lib/panvk-bifrost/icd.json— Vulkan ICD JSON pointing at the patched .so (NOT auto-loaded; only viaVK_ICD_FILENAMES)/usr/bin/brave-vulkan— launcher script
System Mesa is untouched. The stock /usr/lib/libvulkan_panfrost.so and
/usr/share/vulkan/icd.d/panfrost_icd.json continue to work for any
other Vulkan app.
Co-existence
Both stock Mesa and this package can be installed. Stock Vulkan apps
(vulkaninfo, vkcube, etc.) use the stock driver by default. Only
apps started via brave-vulkan (or with VK_ICD_FILENAMES manually
set to our path) use the patched driver.
Campaign close criterion
Per feedback_package_done_means_installable
three-point check:
- PR merged to
marfrit-packages - CI green AND
packages.reauktion.de/arch/aarch64/mesa-panvk-bifrost-*.pkg.tar.zstexists pacman -Ss mesa-panvk-bifroston a fresh consumer host (e.g. ohm afterpacman -Syufrom clean state) returns the package + brave-vulkan launches
When all three pass, panvk-bifrost iter9 closes.