[PATCH v2 01/20] kbuild: rust: allow `clippy::comparison_chain` globally

[Gary Guo <gary@garyguo.net>]

The lint would suggest comparison chains to be converted to match on
`Ordering` instead. The suggestions do not always produce more readable
code, and also it can produce false-positive when not all ordering has a
branch.

The issue is known upstream and thus it has been downgraded from style
lints to pedantic lints, which makes it allow-by-default since Rust 1.87.0.
The current kernel MSRV is 1.85.0, and thus the lint still triggers; allow
it globally to match the updated upstream behaviour.

Acked-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Gary Guo <gary@garyguo.net>
---
 Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Makefile b/Makefile
index 0f1b80100b47..2839c6c5045b 100644
--- a/Makefile
+++ b/Makefile
@@ -476,6 +476,7 @@ KBUILD_USERLDFLAGS := $(USERLDFLAGS)
 # These flags apply to all Rust code in the tree, including the kernel and
 # host programs.
 #
+# `-Aclippy::comparison_chain`: the lint has been demoted since 1.87.
 # `-Aclippy::unwrap_or_default`: the lint is buggy [1] and ignores our
 # MSRV. It can trigger depending on the optimization level.
 # [1] https://github.com/rust-lang/rust-clippy/issues/17379
@@ -494,6 +495,7 @@ export rust_common_flags := --edition=2021 \
 			    -Wclippy::cast_lossless \
 			    -Aclippy::collapsible_if \
 			    -Aclippy::collapsible_match \
+			    -Aclippy::comparison_chain \
 			    -Wclippy::ignored_unit_patterns \
 			    -Aclippy::incompatible_msrv \
 			    -Wclippy::mut_mut \

-- 
2.54.0