1.. SPDX-License-Identifier: GPL-2.0
2
3General Information
4===================
5
6This document contains useful information to know when working with
7the Rust support in the kernel.
8
9
10Code documentation
11------------------
12
13Rust kernel code is documented using ``rustdoc``, its built-in documentation
14generator.
15
16The generated HTML docs include integrated search, linked items (e.g. types,
17functions, constants), source code, etc. They may be read at (TODO: link when
18in mainline and generated alongside the rest of the documentation):
19
20	http://kernel.org/
21
22The docs can also be easily generated and read locally. This is quite fast
23(same order as compiling the code itself) and no special tools or environment
24are needed. This has the added advantage that they will be tailored to
25the particular kernel configuration used. To generate them, use the ``rustdoc``
26target with the same invocation used for compilation, e.g.::
27
28	make LLVM=1 rustdoc
29
30To read the docs locally in your web browser, run e.g.::
31
32	xdg-open rust/doc/kernel/index.html
33
34To learn about how to write the documentation, please see coding-guidelines.rst.
35
36
37Extra lints
38-----------
39
40While ``rustc`` is a very helpful compiler, some extra lints and analyses are
41available via ``clippy``, a Rust linter. To enable it, pass ``CLIPPY=1`` to
42the same invocation used for compilation, e.g.::
43
44	make LLVM=1 CLIPPY=1
45
46Please note that Clippy may change code generation, thus it should not be
47enabled while building a production kernel.
48
49
50Abstractions vs. bindings
51-------------------------
52
53Abstractions are Rust code wrapping kernel functionality from the C side.
54
55In order to use functions and types from the C side, bindings are created.
56Bindings are the declarations for Rust of those functions and types from
57the C side.
58
59For instance, one may write a ``Mutex`` abstraction in Rust which wraps
60a ``struct mutex`` from the C side and calls its functions through the bindings.
61
62Abstractions are not available for all the kernel internal APIs and concepts,
63but it is intended that coverage is expanded as time goes on. "Leaf" modules
64(e.g. drivers) should not use the C bindings directly. Instead, subsystems
65should provide as-safe-as-possible abstractions as needed.
66
67
68Conditional compilation
69-----------------------
70
71Rust code has access to conditional compilation based on the kernel
72configuration:
73
74.. code-block:: rust
75
76	#[cfg(CONFIG_X)]       // Enabled               (`y` or `m`)
77	#[cfg(CONFIG_X="y")]   // Enabled as a built-in (`y`)
78	#[cfg(CONFIG_X="m")]   // Enabled as a module   (`m`)
79	#[cfg(not(CONFIG_X))]  // Disabled
80