On Fri, 6 Oct 2023 18:55:23 +0200
Andrew Lunn [off-list ref] wrote:

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How about adding CONFIG_RUST_PHYLIB to the first patch. Not
selectable, it's just a flag for Rust PHYLIB support.

We have to be careful with names. To some extent, CONFIG_PHYLIB means
the core of phylib. So it could be that CONFIG_RUST_PHYLIB means the
core of phylib written in rust? I doubt that will ever happen, but we
are setting a naming scheme here which i expect others will blindly
cut/paste. What we actually want is a symbol which represents the Rust
binding onto the phylib core. So i think it should have BINDING, or
WRAPPER or something like that in the name.

Good point. Let's save CONFIG_PHYLIB for someday.

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diff --git a/init/Kconfig b/init/Kconfig
index 4b4e3df1658d..2b6627aeb98c 100644
--- a/init/Kconfig
+++ b/init/Kconfig

@@ -1889,7 +1889,7 @@ config RUST
 	depends on !GCC_PLUGINS
 	depends on !RANDSTRUCT
 	depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE

	depends on PHYLIB=y
+	select RUST_PHYLIB

I know the rust build system is rather limited at the moment, but is
this required? Is it possible to build the rust code without the
phylib binding? Can your `RUST_PHYLIB` add phylib.rs to a Makefile
target only if it is enabled?

A short-term solution could work, I think.

config RUST
	bool "Rust support"
	depends on HAVE_RUST
	depends on RUST_IS_AVAILABLE
	depends on !MODVERSIONS
	depends on !GCC_PLUGINS
	depends on !RANDSTRUCT
	depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
	select CONSTRUCTORS
	help
	  Enables Rust support in the kernel.

	  This allows other Rust-related options, like drivers written in Rust,
	  to be selected.

	  It is also required to be able to load external kernel modules
	  written in Rust.

	  See Documentation/rust/ for more information.

	  If unsure, say N.

config RUST_PHYLIB_BINDING
	bool "PHYLIB bindings support"
	depends on RUST
	depends on PHYLIB=y
	help
          Adds support needed for PHY drivers written in Rust. It provides
          a wrapper around the C phlib core.


Then we can conditionally build build the PHYLIB bindings.

diff --git a/rust/kernel/net.rs b/rust/kernel/net.rs
index fbb6d9683012..33fc1531a6c0 100644
--- a/rust/kernel/net.rs
+++ b/rust/kernel/net.rs

@@ -2,4 +2,5 @@

 //! Networking.

+#[cfg(CONFIG_RUST_BINDINGS_PHYLIB)]
 pub mod phy;