mesa-panvk-bifrost: new package — Vulkan-compositor Brave for Bifrost SBCs

iter9 of the panvk-bifrost campaign — operator-confirmed Vulkan output
on PineTab2 (Mali-G52 r1 MC1) 2026-05-20.

Patches Mesa 26.0.6's PanVk Vulkan driver:
  - VK_KHR/EXT_robustness2 + nullDescriptor exposed for PAN_ARCH 6/7
  - has_vk1_1 / has_vk1_2 = true on Bifrost
Patches applied via sed in PKGBUILD prepare() (cleaner than maintaining
a Mesa fork for two two-line tweaks; upstream context drifts between
Mesa releases would make a literal .patch brittle).

Co-installs at /usr/lib/panvk-bifrost/ — stock mesa untouched. Stock
libvulkan_panfrost.so and its ICD JSON keep working for everyone not
opting into the patched driver.

Ships /usr/bin/brave-vulkan that wires up:
  VK_ICD_FILENAMES=/usr/lib/panvk-bifrost/icd.json
  PAN_I_WANT_A_BROKEN_VULKAN_DRIVER=1
  MESA_VK_VERSION_OVERRIDE=1.2     # ANGLE needs apiVersion>=1.1; the
                                   # has_vk1_x flags don't move it, so
                                   # the env-var override carries that
  brave --use-gl=disabled --enable-features=Vulkan --use-vulkan=native
        --ozone-platform=x11 --no-sandbox --disable-gpu-sandbox
        --ignore-gpu-blocklist "$@"

Side-steps the stock "GLES3 is unsupported / GPU process exits" failure
documented in panvk-bifrost/README's "Consumer-side benefit" section.

Known limitation: WebGL/WebGL2 in-page won't work — ANGLE needs GLES3
which needs VK_EXT_transform_feedback, which PanVk-Bifrost doesn't
currently support. Browser chrome + standard page rendering work fine.

Gitea Actions job mesa-panvk-bifrost-aarch64 added to build.yml,
patterned on libva-v4l2-request-fourier-aarch64. Mesa build is slow
(~30-60min on actrunner-aarch64). Standalone (no needs:),
continue-on-error so it doesn't block other jobs.

Campaign artifacts: ~/src/panvk-bifrost/{README.md, phase8_iteration9_close.md,
phase0_evidence/iter9_brave_vulkan_breakthrough.txt}.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

arch/mesa-panvk-bifrost/0001-panvk-expose-robustness2-nullDescriptor-bifrost.patch

@@ -0,0 +1,57 @@
+From: claude-noether (on behalf of mfritsche)
+Date: 2026-05-19
+Subject: panvk: expose VK_KHR/EXT_robustness2 + nullDescriptor on Bifrost (PAN_ARCH 6/7)
+
+Without this, Mesa's Zink driver refuses to use PanVk-Bifrost as its Vulkan
+backend, falling back silently to llvmpipe (software rasterizer) for all
+GL-via-Zink on Bifrost SBCs. That defeats the entire purpose of having a
+Vulkan driver on Bifrost — GL acceleration via Zink is the most natural
+near-term consumer.
+
+panvk_vX_nir_lower_descriptors.c:1309 and panvk_vX_shader.c:1355 already
+plumb dev->vk.enabled_features.nullDescriptor arch-agnostically — the gate
+at panvk_vX_physical_device.c was set conservatively when Bifrost was
+unmaintained, not because of hardware incapability.
+
+iter1–7 of the panvk-bifrost campaign proved fundamental driver functions
+on Mali-G52 r1 MC1 (PAN_ARCH=7). This patch is the iter8 follow-up.
+
+robustBufferAccess2 and robustImageAccess2 are NOT flipped — they're
+independent rb2 features Zink doesn't require, gated differently
+(robustBufferAccess2 = PAN_ARCH >= 11, robustImageAccess2 = false), and
+out of scope for iter8.
+
+---
+ src/panfrost/vulkan/panvk_vX_physical_device.c | 6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+diff --git a/src/panfrost/vulkan/panvk_vX_physical_device.c b/src/panfrost/vulkan/panvk_vX_physical_device.c
+--- a/src/panfrost/vulkan/panvk_vX_physical_device.c
++++ b/src/panfrost/vulkan/panvk_vX_physical_device.c
+@@ -91,7 +91,7 @@ get_device_extensions(const struct panvk_physical_device *device,
+       .KHR_pipeline_binary = true,
+       .KHR_pipeline_executable_properties = true,
+       .KHR_pipeline_library = true,
+-      .KHR_robustness2 = PAN_ARCH >= 10,
++      .KHR_robustness2 = true,
+       .KHR_sampler_mirror_clamp_to_edge = true,
+       .KHR_sampler_ycbcr_conversion = true,
+       .KHR_separate_depth_stencil_layouts = true,
+@@ -168,7 +168,7 @@ get_device_extensions(const struct panvk_physical_device *device,
+       .EXT_queue_family_foreign = true,
+       .EXT_robustness = pan_arch(device->kmod.dev->props.gpu_id) >= 9,
+       .EXT_image_robustness = true,
+-      .EXT_robustness2 = PAN_ARCH >= 10,
++      .EXT_robustness2 = true,
+       .EXT_sampler_filter_minmax = PAN_ARCH >= 10,
+       .EXT_scalar_block_layout = true,
+       .EXT_separate_stencil_usage = true,
+@@ -493,7 +493,7 @@ get_device_features(const struct panvk_physical_device *device,
+       /* VK_KHR_robustness2 */
+       .robustBufferAccess2 = PAN_ARCH >= 11,
+       .robustImageAccess2 = false,
+-      .nullDescriptor = PAN_ARCH >= 10,
++      .nullDescriptor = true,
+
+       /* VK_KHR_shader_clock */
+       .shaderSubgroupClock = device->kmod.dev->props.gpu_can_query_timestamp,