rust: make pin-init its own crate

Rename relative paths inside of the crate to still refer to the same
items, also rename paths inside of the kernel crate and adjust the build
system to build the crate.

[ Remove the `expect` (and thus the `lint_reasons` feature) since
  the tree now uses `quote!` from `rust/macros/export.rs`. Remove the
  `TokenStream` import removal, since it is now used as well.

  In addition, temporarily (i.e. just for this commit) use an `--extern
  force:alloc` to prevent an unknown `new_uninit` error in the `rustdoc`
  target. For context, please see a similar case in:

      https://lore.kernel.org/lkml/20240422090644.525520-1-ojeda@kernel.org/

  And adjusted the message above. - Miguel ]

Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Fiona Behrens <me@kloenk.dev>
Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/20250308110339.2997091-16-benno.lossin@proton.me
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

6 files changed, 26 insertions, 11 deletions

diff --git a/rust/pin-init/internal/src/_lib.rs b/rust/pin-init/internal/src/_lib.rs
deleted file mode 100644
index 0874cf04e4cb..000000000000
--- a/rust/pin-init/internal/src/_lib.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-// SPDX-License-Identifier: Apache-2.0 OR MIT
-
-//! Will be removed in a future commit, only exists to prevent compilation errors.
diff --git a/rust/pin-init/internal/src/helpers.rs b/rust/pin-init/internal/src/helpers.rs
index 2f4fc75c014e..78521ba19d0b 100644
--- a/rust/pin-init/internal/src/helpers.rs
+++ b/rust/pin-init/internal/src/helpers.rs
@@ -1,5 +1,7 @@
 // SPDX-License-Identifier: Apache-2.0 OR MIT
 
+use proc_macro::{TokenStream, TokenTree};
+
 /// Parsed generics.
 ///
 /// See the field documentation for an explanation what each of the fields represents.
diff --git a/rust/pin-init/internal/src/lib.rs b/rust/pin-init/internal/src/lib.rs
index 3146da5cc47c..c201b8a53915 100644
--- a/rust/pin-init/internal/src/lib.rs
+++ b/rust/pin-init/internal/src/lib.rs
@@ -4,6 +4,22 @@
 // and thus add a dependency on `include/config/RUSTC_VERSION_TEXT`, which is
 // touched by Kconfig when the version string from the compiler changes.
 
+//! `pin-init` proc macros.
+
+#![cfg_attr(not(RUSTC_LINT_REASONS_IS_STABLE), feature(lint_reasons))]
+
+use proc_macro::TokenStream;
+
+#[cfg(kernel)]
+#[path = "../../../macros/quote.rs"]
+#[macro_use]
+mod quote;
+
+mod helpers;
+mod pin_data;
+mod pinned_drop;
+mod zeroable;
+
 #[allow(missing_docs)]
 #[proc_macro_attribute]
 pub fn pin_data(inner: TokenStream, item: TokenStream) -> TokenStream {
diff --git a/rust/pin-init/internal/src/pin_data.rs b/rust/pin-init/internal/src/pin_data.rs
index 1d4a3547c684..9b974498f4a8 100644
--- a/rust/pin-init/internal/src/pin_data.rs
+++ b/rust/pin-init/internal/src/pin_data.rs
@@ -5,7 +5,7 @@ use proc_macro::{Group, Punct, Spacing, TokenStream, TokenTree};
 
 pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
     // This proc-macro only does some pre-parsing and then delegates the actual parsing to
-    // `kernel::__pin_data!`.
+    // `pin_init::__pin_data!`.
 
     let (
         Generics {
@@ -71,7 +71,7 @@ pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
         .collect::<Vec<_>>();
     // This should be the body of the struct `{...}`.
     let last = rest.pop();
-    let mut quoted = quote!(::kernel::__pin_data! {
+    let mut quoted = quote!(::pin_init::__pin_data! {
         parse_input:
         @args(#args),
         @sig(#(#rest)*),
diff --git a/rust/pin-init/internal/src/pinned_drop.rs b/rust/pin-init/internal/src/pinned_drop.rs
index 88fb72b20660..386f52f73c06 100644
--- a/rust/pin-init/internal/src/pinned_drop.rs
+++ b/rust/pin-init/internal/src/pinned_drop.rs
@@ -35,11 +35,11 @@ pub(crate) fn pinned_drop(_args: TokenStream, input: TokenStream) -> TokenStream
     let idx = pinned_drop_idx
         .unwrap_or_else(|| panic!("Expected an `impl` block implementing `PinnedDrop`."));
     // Fully qualify the `PinnedDrop`, as to avoid any tampering.
-    toks.splice(idx..idx, quote!(::kernel::init::));
+    toks.splice(idx..idx, quote!(::pin_init::));
     // Take the `{}` body and call the declarative macro.
     if let Some(TokenTree::Group(last)) = toks.pop() {
         let last = last.stream();
-        quote!(::kernel::__pinned_drop! {
+        quote!(::pin_init::__pinned_drop! {
             @impl_sig(#(#toks)*),
             @impl_body(#last),
         })
diff --git a/rust/pin-init/internal/src/zeroable.rs b/rust/pin-init/internal/src/zeroable.rs
index cfee2cec18d5..0cf6732f27dc 100644
--- a/rust/pin-init/internal/src/zeroable.rs
+++ b/rust/pin-init/internal/src/zeroable.rs
@@ -27,7 +27,7 @@ pub(crate) fn derive(input: TokenStream) -> TokenStream {
             // If we find a `,`, then we have finished a generic/constant/lifetime parameter.
             TokenTree::Punct(p) if nested == 0 && p.as_char() == ',' => {
                 if in_generic && !inserted {
-                    new_impl_generics.extend(quote! { : ::kernel::init::Zeroable });
+                    new_impl_generics.extend(quote! { : ::pin_init::Zeroable });
                 }
                 in_generic = true;
                 inserted = false;
@@ -41,7 +41,7 @@ pub(crate) fn derive(input: TokenStream) -> TokenStream {
             TokenTree::Punct(p) if nested == 0 && p.as_char() == ':' => {
                 new_impl_generics.push(tt);
                 if in_generic {
-                    new_impl_generics.extend(quote! { ::kernel::init::Zeroable + });
+                    new_impl_generics.extend(quote! { ::pin_init::Zeroable + });
                     inserted = true;
                 }
             }
@@ -59,10 +59,10 @@ pub(crate) fn derive(input: TokenStream) -> TokenStream {
     }
     assert_eq!(nested, 0);
     if in_generic && !inserted {
-        new_impl_generics.extend(quote! { : ::kernel::init::Zeroable });
+        new_impl_generics.extend(quote! { : ::pin_init::Zeroable });
     }
     quote! {
-        ::kernel::__derive_zeroable!(
+        ::pin_init::__derive_zeroable!(
             parse_input:
                 @sig(#(#rest)*),
                 @impl_generics(#(#new_impl_generics)*),