rust: Create 'sys' module

The `zephyr-sys` crate contains all of the generated bindings to the C
API in Zephyr.

The `zephyr::sys` module wraps these abstractions in as thin of a way as
possible, but still allowing them to be used without 'unsafe'.  Although
the interfaces are "safe", because they are just wrappers around C
calls, most aren't directly useful without unsafe, and this crate
provides higher-level abstractions around these underlying primitives.

This commit adds a definition for `K_FOREVER`, and `K_NO_WAIT`, which
are too complicated for bindgen to autogenerate bindings for.  We will
rely on a test to ensure that the values match those in the C headers.

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

Author: d3zd3z

lib/rust/zephyr/src/lib.rs

@@ -9,6 +9,7 @@
 #![no_std]
 #![allow(unexpected_cfgs)]
 
+pub mod sys;
 pub mod time;
 
 // Bring in the generated kconfig module

lib/rust/zephyr/src/sys.rs

@@ -0,0 +1,18 @@
+// Copyright (c) 2024 Linaro LTD
+// SPDX-License-Identifier: Apache-2.0
+
+//! Zephyr 'sys' module.
+//!
+//! The `zephyr-sys` crate contains the direct C bindings to the Zephyr API.  All of these are
+//! unsafe.
+//!
+//! This module `zephyr::sys` contains thin wrappers to these C bindings, that can be used without
+//! unsafe, but as unchanged as possible.
+
+use zephyr_sys::k_timeout_t;
+
+// These two constants are not able to be captured by bindgen.  It is unlikely that these values
+// would change in the Zephyr headers, but there will be an explicit test to make sure they are
+// correct.
+pub const K_FOREVER: k_timeout_t = k_timeout_t { ticks: -1 };
+pub const K_NO_WAIT: k_timeout_t = k_timeout_t { ticks: 0 };