Add documentation for `chromium_internal_dual_source_blending`.
Bug: None
Change-Id: Ieebba27f01a8e0e39c76215081a366296e778fd9
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/177541
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
diff --git a/docs/tint/extensions/chromium_experimental_framebuffer_fetch.md b/docs/tint/extensions/chromium_experimental_framebuffer_fetch.md
index 0715cb6..45b4909 100644
--- a/docs/tint/extensions/chromium_experimental_framebuffer_fetch.md
+++ b/docs/tint/extensions/chromium_experimental_framebuffer_fetch.md
@@ -26,4 +26,5 @@
## To-dos
-Are f16 types allowed for the `@color` inputs?
+ - Are f16 types allowed for the `@color` inputs?
+ - Are any changes needed for Vulkan support?
diff --git a/docs/tint/extensions/chromium_internal_dual_source_blending.md b/docs/tint/extensions/chromium_internal_dual_source_blending.md
new file mode 100644
index 0000000..9d1aa89
--- /dev/null
+++ b/docs/tint/extensions/chromium_internal_dual_source_blending.md
@@ -0,0 +1,38 @@
+# Chromium Internal Dual Source Blending
+
+The `chromium_internal_dual_source_blending` extension adds support for specifying dual-source blending outputs in fragment shaders.
+This is useful in combination with `wgpu::BlendFactor` enum values to do hardware blending for Porter-Duff gradients between others.
+
+## Status
+
+Dual source blending support in Tint is for internal use in Chromium and subprojects.
+It follows the agreed-upon design decided by the WebGPU W3C group but cannot be a stable extension until the `dual-source-blending` is added to the main WebGPU spec.
+
+## Pseudo-specification
+
+A new attribute `@blend_src(N)` (N = 0 or 1) is added that can be specified on fragment shader outputs.
+It can only be used on outputs for `@location(0)` and if one of the outputs for `@location(0)` has an `@blend_src` then they must all have one.
+
+## Example usages
+
+```
+enable chromium_internal_dual_source_blending;
+
+struct FragInput {
+ @location(0) a : vec4<f32>,
+ @location(1) b : vec4<f32>,
+};
+
+struct FragOutput {
+ @location(0) @blend_src(0) color : vec4<f32>,
+ @location(0) @blend_src(1) blend : vec4<f32>,
+};
+
+@fragment
+fn frag_main(in : FragInput) -> FragOutput {
+ var output : FragOutput;
+ output.color = in.a;
+ output.blend = in.b;
+ return output;
+}
+```
