From 4503a722da60beb30f928955d4b86db8675e33e4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bastian=20K=C3=B6cher?= <bkchr@users.noreply.github.com>
Date: Mon, 9 Aug 2021 13:39:50 +0200
Subject: [PATCH] Clarify how `ApiId` is being generated (#9519)

* Clarify how `ApiId` is being generated

* Clarify more
---
 substrate/primitives/version/src/lib.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/substrate/primitives/version/src/lib.rs b/substrate/primitives/version/src/lib.rs
index b3ddb7d7fe..da2cb342d2 100644
--- a/substrate/primitives/version/src/lib.rs
+++ b/substrate/primitives/version/src/lib.rs
@@ -98,6 +98,11 @@ pub mod embed;
 pub use sp_version_proc_macro::runtime_version;
 
 /// The identity of a particular API interface that the runtime might provide.
+///
+/// The id is generated by hashing the name of the runtime api with BLAKE2 using a hash size
+/// of 8 bytes.
+///
+/// The name of the runtime api is the name of the trait when using `decl_runtime_apis!` macro.
 pub type ApiId = [u8; 8];
 
 /// A vector of pairs of `ApiId` and a `u32` for version.