[PATCH] docs: rust: quick-start: add Ubuntu

[Miguel Ojeda <ojeda@kernel.org>]

Ubuntu has changed their maintenance model for Rust toolchains and is
now providing recent Rust releases in their releases, including both
LTS and non-LTS (interim) releases.

Therefore, add instructions to the Quick Start guide for Ubuntu, like
it is done for the other distributions.

Link: https://packages.ubuntu.com/search?keywords=rustc-1
Link: https://packages.ubuntu.com/search?keywords=bindgen-0
Cc: Zixing Liu <zixing.liu@canonical.com>
Cc: William Grant <wgrant@ubuntu.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
RFC: https://lore.kernel.org/rust-for-linux/20240816181545.45789-1-ojeda@kernel.org/

Compared to the RFC, Ubuntu now provides the versioned `rustc-*`
packages in older LTSs (the ones with standard support), which is great!

I can confirm I can build the latest kernel in 20.04 LTS (using a
newer LLVM), 22.04 LTS, 24.04 LTS and 24.10.

The `bindgen-*` versioned packages are not backported (yet?) to the
older LTSs, so I added a note about that compared to the RFC patch.

 Documentation/rust/quick-start.rst | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/rust/quick-start.rst b/Documentation/rust/quick-start.rst
index ed5af2b5339a..393b3e2f2a05 100644
--- a/Documentation/rust/quick-start.rst
+++ b/Documentation/rust/quick-start.rst
@@ -87,6 +87,23 @@ they should generally work out of the box, e.g.::
 	zypper install rust rust1.79-src rust-bindgen clang


+Ubuntu
+******
+
+Ubuntu LTS and non-LTS (interim) releases provide recent Rust releases and thus
+they should generally work out of the box, e.g.::
+
+	apt install rustc-1.80 rust-1.80-src bindgen-0.65 rustfmt-1.80 rust-1.80-clippy
+
+``RUST_LIB_SRC`` needs to be set when using the versioned packages, e.g.::
+
+	RUST_LIB_SRC=/usr/src/rustc-$(rustc-1.80 --version | cut -d' ' -f2)/library
+
+In addition, ``bindgen-0.65`` is available in newer releases (24.04 LTS and
+24.10), but it may not be available in older ones (20.04 LTS and 22.04 LTS),
+thus ``bindgen`` may need to be built manually (please see below).
+
+
 Requirements: Building
 ----------------------


base-commit: a2f11547052001bd448ccec81dd1e68409078fbb
--
2.46.2