doc: Create a separate docgen app

Although this is started identically to the hello_world app, this will
be an app where we can enable as many features as possible to try and
build up the docs as fully as possible.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

docgen/CMakeLists.txt

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+
+project(hello_rust_world)
+rust_cargo_application()

docgen/Cargo.toml

@@ -0,0 +1,16 @@
+# Copyright (c) 2024 Linaro LTD
+# SPDX-License-Identifier: Apache-2.0
+
+[package]
+# This must be rustapp for now.
+name = "rustapp"
+version = "0.1.0"
+edition = "2021"
+description = "A sample hello world application in Rust"
+license = "Apache-2.0 or MIT"
+
+[lib]
+crate-type = ["staticlib"]
+
+[dependencies]
+zephyr = "0.1.0"

docgen/prj.conf

@@ -0,0 +1,4 @@
+# Copyright (c) 2024 Linaro LTD
+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_RUST=y

docgen/src/lib.rs

@@ -0,0 +1,16 @@
+// Copyright (c) 2024 Linaro LTD
+// SPDX-License-Identifier: Apache-2.0
+
+#![no_std]
+
+use zephyr::printkln;
+
+// Reference the Zephyr crate so that the panic handler gets used.  This is only needed if no
+// symbols from the crate are directly used.
+extern crate zephyr;
+
+#[no_mangle]
+extern "C" fn rust_main() {
+    printkln!("Hello world from Rust on {}",
+              zephyr::kconfig::CONFIG_BOARD);
+}