docs: rust: include other expressions in conditional compilation section

Expand the conditional compilation section to explain how to support other expressions, such as testing whether `RUSTC_VERSION` is at least a given version, which requires a numerical comparison that Rust's `cfg` predicates do not support (yet?). Reviewed-by: Nicolas Schier <[email protected]> Tested-by: Alice Ryhl <[email protected]> Acked-by: Masahiro Yamada <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Miguel Ojeda <[email protected]>
intel-lab-lkp · Sep 5, 2024 · 93dc3be · 93dc3be
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commit 93dc3be
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diff --git a/Documentation/rust/general-information.rst b/Documentation/rust/general-information.rst
@@ -151,3 +151,11 @@ configuration:
 	#[cfg(CONFIG_X="y")]   // Enabled as a built-in (`y`)
 	#[cfg(CONFIG_X="m")]   // Enabled as a module   (`m`)
 	#[cfg(not(CONFIG_X))]  // Disabled
+
+For other predicates that Rust's ``cfg`` does not support, e.g. expressions with
+numerical comparisons, one may define a new Kconfig symbol:
+
+.. code-block:: kconfig
+
+	config RUSTC_VERSION_MIN_107900
+		def_bool y if RUSTC_VERSION >= 107900