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weston: backport gl-shaders fix to avoid shader compiler crashes

Message ID 20260407094759.3116923-1-mangadi@qti.qualcomm.com
State New
Headers show
Series weston: backport gl-shaders fix to avoid shader compiler crashes | expand

Commit Message

Mahesh Angadi April 7, 2026, 9:47 a.m. UTC 
Some GPU shader compilers do not optimize away unused YUV shader
uniforms, even when the associated code paths are unreachable. This can cause
Weston to hit assertion failures at runtime on non-Mesa platforms, despite
working correctly on Mesa-based drivers.

Backport the upstream gl-shaders fix to restore stable behavior across
GPU drivers.

Signed-off-by: Mahesh Angadi <mangadi@qti.qualcomm.com>
---
 ...e-asserts-relying-on-shader-compiler.patch | 47 +++++++++++++++++++
 .../recipes-graphics/wayland/weston_15.0.0.bb |  1 +
 2 files changed, 48 insertions(+)
 create mode 100644 meta/recipes-graphics/wayland/weston/0001-gl-shaders-Remove-asserts-relying-on-shader-compiler.patch
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Patch

diff --git a/meta/recipes-graphics/wayland/weston/0001-gl-shaders-Remove-asserts-relying-on-shader-compiler.patch b/meta/recipes-graphics/wayland/weston/0001-gl-shaders-Remove-asserts-relying-on-shader-compiler.patch
new file mode 100644
index 0000000000..4c9b740bd2
--- /dev/null
+++ b/meta/recipes-graphics/wayland/weston/0001-gl-shaders-Remove-asserts-relying-on-shader-compiler.patch
@@ -0,0 +1,47 @@ 
+From 5c49563ef49a502a6b8fae44f8778e109d32c2d9 Mon Sep 17 00:00:00 2001
+From: Robert Mader <robert.mader@collabora.com>
+Date: Mon, 2 Mar 2026 13:11:05 +0100
+Subject: [PATCH] gl-shaders: Remove asserts relying on shader compiler
+ behavior
+
+yuv_coefficients and yuv_offsets should get optimized away by shader
+compilers as the related code paths can never be reached. This seems to
+work well on Mesa but not necessarily with other drivers.
+
+While on it, assert that the uniforms *are* present, unless the
+yuv-to-rgb conversion is handled by the driver.
+
+Upstream-Status: Backport [https://gitlab.freedesktop.org/wayland/weston/-/commit/5c49563ef49a502a6b8fae44f8778e109d32c2d9]
+Signed-off-by: Robert Mader <robert.mader@collabora.com>
+---
+ libweston/renderer-gl/gl-shaders.c | 14 ++++++++++++--
+ 1 file changed, 12 insertions(+), 2 deletions(-)
+
+diff --git a/libweston/renderer-gl/gl-shaders.c b/libweston/renderer-gl/gl-shaders.c
+index 98041882..18eeedf6 100644
+--- a/libweston/renderer-gl/gl-shaders.c
++++ b/libweston/renderer-gl/gl-shaders.c
+@@ -762,8 +762,18 @@ gl_shader_load_config_representation(struct weston_compositor *compositor,
+ 
+ 	if (sconf->yuv_coefficients == WESTON_COLOR_MATRIX_COEF_UNSET ||
+ 	    sconf->yuv_coefficients == WESTON_COLOR_MATRIX_COEF_IDENTITY) {
+-		assert(shader->yuv_coefficients_uniform == -1);
+-		assert(shader->yuv_offsets_uniform == -1);
++		/*
++		 * In this case the yuv_coefficients and yuv_offsets uniforms
++		 * should never be used and thus get optimized away by the
++		 * shader compiler. Unfortunately on some drivers this is not
++		 * the case, so we can't assert on it.
++		 */
++		return;
++	}
++
++	if (shader->yuv_coefficients_uniform == -1 ||
++	    shader->yuv_offsets_uniform == -1) {
++		assert(shader->key.variant == SHADER_VARIANT_EXTERNAL);
+ 		return;
+ 	}
+ 
+-- 
+2.34.1
+
diff --git a/meta/recipes-graphics/wayland/weston_15.0.0.bb b/meta/recipes-graphics/wayland/weston_15.0.0.bb
index b67f5f52dd..da347659f1 100644
--- a/meta/recipes-graphics/wayland/weston_15.0.0.bb
+++ b/meta/recipes-graphics/wayland/weston_15.0.0.bb
@@ -8,6 +8,7 @@  LIC_FILES_CHKSUM = "file://COPYING;md5=d79ee9e66bb0f95d3386a7acae780b70 \
 
 SRC_URI = "https://gitlab.freedesktop.org/wayland/weston/-/releases/${PV}/downloads/${BPN}-${PV}.tar.xz \
            file://0001-vulkan-renderer-guard-surface-output-creation-with-b.patch \
+           file://0001-gl-shaders-Remove-asserts-relying-on-shader-compiler.patch \
            file://weston.png \
            file://weston.desktop \
            file://xwayland.weston-start \