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>

1 files changed, 57 insertions, 54 deletions

diff --git a/rust/pin-init/src/macros.rs b/rust/pin-init/src/macros.rs
index c45ad6af5ca03..d41c4f198c423 100644
--- a/rust/pin-init/src/macros.rs
+++ b/rust/pin-init/src/macros.rs
@@ -19,7 +19,7 @@
 //! We will look at the following example:
 //!
 //! ```rust,ignore
-//! # use kernel::init::*;
+//! # use pin_init::*;
 //! # use core::pin::Pin;
 //! #[pin_data]
 //! #[repr(C)]
@@ -75,7 +75,7 @@
 //! Here is the definition of `Bar` from our example:
 //!
 //! ```rust,ignore
-//! # use kernel::init::*;
+//! # use pin_init::*;
 //! #[pin_data]
 //! #[repr(C)]
 //! struct Bar<T> {
@@ -121,22 +121,22 @@
 //!             self,
 //!             slot: *mut T,
 //!             // Since `t` is `#[pin]`, this is `PinInit`.
-//!             init: impl ::kernel::init::PinInit<T, E>,
+//!             init: impl ::pin_init::PinInit<T, E>,
 //!         ) -> ::core::result::Result<(), E> {
-//!             unsafe { ::kernel::init::PinInit::__pinned_init(init, slot) }
+//!             unsafe { ::pin_init::PinInit::__pinned_init(init, slot) }
 //!         }
 //!         pub unsafe fn x<E>(
 //!             self,
 //!             slot: *mut usize,
 //!             // Since `x` is not `#[pin]`, this is `Init`.
-//!             init: impl ::kernel::init::Init<usize, E>,
+//!             init: impl ::pin_init::Init<usize, E>,
 //!         ) -> ::core::result::Result<(), E> {
-//!             unsafe { ::kernel::init::Init::__init(init, slot) }
+//!             unsafe { ::pin_init::Init::__init(init, slot) }
 //!         }
 //!     }
 //!     // Implement the internal `HasPinData` trait that associates `Bar` with the pin-data struct
 //!     // that we constructed above.
-//!     unsafe impl<T> ::kernel::init::__internal::HasPinData for Bar<T> {
+//!     unsafe impl<T> ::pin_init::__internal::HasPinData for Bar<T> {
 //!         type PinData = __ThePinData<T>;
 //!         unsafe fn __pin_data() -> Self::PinData {
 //!             __ThePinData {
@@ -147,7 +147,7 @@
 //!     // Implement the internal `PinData` trait that marks the pin-data struct as a pin-data
 //!     // struct. This is important to ensure that no user can implement a rogue `__pin_data`
 //!     // function without using `unsafe`.
-//!     unsafe impl<T> ::kernel::init::__internal::PinData for __ThePinData<T> {
+//!     unsafe impl<T> ::pin_init::__internal::PinData for __ThePinData<T> {
 //!         type Datee = Bar<T>;
 //!     }
 //!     // Now we only want to implement `Unpin` for `Bar` when every structurally pinned field is
@@ -191,7 +191,7 @@
 //!     #[expect(non_camel_case_types)]
 //!     trait UselessPinnedDropImpl_you_need_to_specify_PinnedDrop {}
 //!     impl<
-//!         T: ::kernel::init::PinnedDrop,
+//!         T: ::pin_init::PinnedDrop,
 //!     > UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for T {}
 //!     impl<T> UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for Bar<T> {}
 //! };
@@ -227,11 +227,11 @@
 //!             // - we `use` the `HasPinData` trait in the block, it is only available in that
 //!             //   scope.
 //!             let data = unsafe {
-//!                 use ::kernel::init::__internal::HasPinData;
+//!                 use ::pin_init::__internal::HasPinData;
 //!                 Self::__pin_data()
 //!             };
 //!             // Ensure that `data` really is of type `PinData` and help with type inference:
-//!             let init = ::kernel::init::__internal::PinData::make_closure::<
+//!             let init = ::pin_init::__internal::PinData::make_closure::<
 //!                 _,
 //!                 __InitOk,
 //!                 ::core::convert::Infallible,
@@ -262,7 +262,7 @@
 //!                     }
 //!                     // We again create a `DropGuard`.
 //!                     let __x_guard = unsafe {
-//!                         ::kernel::init::__internal::DropGuard::new(::core::addr_of_mut!((*slot).x))
+//!                         ::pin_init::__internal::DropGuard::new(::core::addr_of_mut!((*slot).x))
 //!                     };
 //!                     // Since initialization has successfully completed, we can now forget
 //!                     // the guards. This is not `mem::forget`, since we only have
@@ -303,7 +303,7 @@
 //!             };
 //!             // Construct the initializer.
 //!             let init = unsafe {
-//!                 ::kernel::init::pin_init_from_closure::<
+//!                 ::pin_init::pin_init_from_closure::<
 //!                     _,
 //!                     ::core::convert::Infallible,
 //!                 >(init)
@@ -350,19 +350,19 @@
 //!         unsafe fn b<E>(
 //!             self,
 //!             slot: *mut Bar<u32>,
-//!             init: impl ::kernel::init::PinInit<Bar<u32>, E>,
+//!             init: impl ::pin_init::PinInit<Bar<u32>, E>,
 //!         ) -> ::core::result::Result<(), E> {
-//!             unsafe { ::kernel::init::PinInit::__pinned_init(init, slot) }
+//!             unsafe { ::pin_init::PinInit::__pinned_init(init, slot) }
 //!         }
 //!         unsafe fn a<E>(
 //!             self,
 //!             slot: *mut usize,
-//!             init: impl ::kernel::init::Init<usize, E>,
+//!             init: impl ::pin_init::Init<usize, E>,
 //!         ) -> ::core::result::Result<(), E> {
-//!             unsafe { ::kernel::init::Init::__init(init, slot) }
+//!             unsafe { ::pin_init::Init::__init(init, slot) }
 //!         }
 //!     }
-//!     unsafe impl ::kernel::init::__internal::HasPinData for Foo {
+//!     unsafe impl ::pin_init::__internal::HasPinData for Foo {
 //!         type PinData = __ThePinData;
 //!         unsafe fn __pin_data() -> Self::PinData {
 //!             __ThePinData {
@@ -370,7 +370,7 @@
 //!             }
 //!         }
 //!     }
-//!     unsafe impl ::kernel::init::__internal::PinData for __ThePinData {
+//!     unsafe impl ::pin_init::__internal::PinData for __ThePinData {
 //!         type Datee = Foo;
 //!     }
 //!     #[allow(dead_code)]
@@ -394,8 +394,8 @@
 //!             let pinned = unsafe { ::core::pin::Pin::new_unchecked(self) };
 //!             // Create the unsafe token that proves that we are inside of a destructor, this
 //!             // type is only allowed to be created in a destructor.
-//!             let token = unsafe { ::kernel::init::__internal::OnlyCallFromDrop::new() };
-//!             ::kernel::init::PinnedDrop::drop(pinned, token);
+//!             let token = unsafe { ::pin_init::__internal::OnlyCallFromDrop::new() };
+//!             ::pin_init::PinnedDrop::drop(pinned, token);
 //!         }
 //!     }
 //! };
@@ -421,8 +421,8 @@
 //!
 //! ```rust,ignore
 //! // `unsafe`, full path and the token parameter are added, everything else stays the same.
-//! unsafe impl ::kernel::init::PinnedDrop for Foo {
-//!     fn drop(self: Pin<&mut Self>, _: ::kernel::init::__internal::OnlyCallFromDrop) {
+//! unsafe impl ::pin_init::PinnedDrop for Foo {
+//!     fn drop(self: Pin<&mut Self>, _: ::pin_init::__internal::OnlyCallFromDrop) {
 //!         pr_info!("{self:p} is getting dropped.");
 //!     }
 //! }
@@ -448,10 +448,10 @@
 //! let initializer = {
 //!     struct __InitOk;
 //!     let data = unsafe {
-//!         use ::kernel::init::__internal::HasPinData;
+//!         use ::pin_init::__internal::HasPinData;
 //!         Foo::__pin_data()
 //!     };
-//!     let init = ::kernel::init::__internal::PinData::make_closure::<
+//!     let init = ::pin_init::__internal::PinData::make_closure::<
 //!         _,
 //!         __InitOk,
 //!         ::core::convert::Infallible,
@@ -462,12 +462,12 @@
 //!                 unsafe { ::core::ptr::write(::core::addr_of_mut!((*slot).a), a) };
 //!             }
 //!             let __a_guard = unsafe {
-//!                 ::kernel::init::__internal::DropGuard::new(::core::addr_of_mut!((*slot).a))
+//!                 ::pin_init::__internal::DropGuard::new(::core::addr_of_mut!((*slot).a))
 //!             };
 //!             let init = Bar::new(36);
 //!             unsafe { data.b(::core::addr_of_mut!((*slot).b), b)? };
 //!             let __b_guard = unsafe {
-//!                 ::kernel::init::__internal::DropGuard::new(::core::addr_of_mut!((*slot).b))
+//!                 ::pin_init::__internal::DropGuard::new(::core::addr_of_mut!((*slot).b))
 //!             };
 //!             ::core::mem::forget(__b_guard);
 //!             ::core::mem::forget(__a_guard);
@@ -492,13 +492,16 @@
 //!         init(slot).map(|__InitOk| ())
 //!     };
 //!     let init = unsafe {
-//!         ::kernel::init::pin_init_from_closure::<_, ::core::convert::Infallible>(init)
+//!         ::pin_init::pin_init_from_closure::<_, ::core::convert::Infallible>(init)
 //!     };
 //!     init
 //! };
 //! ```
 
+#[cfg(kernel)]
 pub use ::macros::paste;
+#[cfg(not(kernel))]
+pub use ::paste::paste;
 
 /// Creates a `unsafe impl<...> PinnedDrop for $type` block.
 ///
@@ -519,7 +522,7 @@ macro_rules! __pinned_drop {
         unsafe $($impl_sig)* {
             // Inherit all attributes and the type/ident tokens for the signature.
             $(#[$($attr)*])*
-            fn drop($($sig)*, _: $crate::init::__internal::OnlyCallFromDrop) {
+            fn drop($($sig)*, _: $crate::__internal::OnlyCallFromDrop) {
                 $($inner)*
             }
         }
@@ -865,7 +868,7 @@ macro_rules! __pin_data {
             // SAFETY: We have added the correct projection functions above to `__ThePinData` and
             // we also use the least restrictive generics possible.
             unsafe impl<$($impl_generics)*>
-                $crate::init::__internal::HasPinData for $name<$($ty_generics)*>
+                $crate::__internal::HasPinData for $name<$($ty_generics)*>
             where $($whr)*
             {
                 type PinData = __ThePinData<$($ty_generics)*>;
@@ -877,7 +880,7 @@ macro_rules! __pin_data {
 
             // SAFETY: TODO.
             unsafe impl<$($impl_generics)*>
-                $crate::init::__internal::PinData for __ThePinData<$($ty_generics)*>
+                $crate::__internal::PinData for __ThePinData<$($ty_generics)*>
             where $($whr)*
             {
                 type Datee = $name<$($ty_generics)*>;
@@ -936,7 +939,7 @@ macro_rules! __pin_data {
         // `PinnedDrop` as the parameter to `#[pin_data]`.
         #[expect(non_camel_case_types)]
         trait UselessPinnedDropImpl_you_need_to_specify_PinnedDrop {}
-        impl<T: $crate::init::PinnedDrop>
+        impl<T: $crate::PinnedDrop>
             UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for T {}
         impl<$($impl_generics)*>
             UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for $name<$($ty_generics)*>
@@ -959,8 +962,8 @@ macro_rules! __pin_data {
                 let pinned = unsafe { ::core::pin::Pin::new_unchecked(self) };
                 // SAFETY: Since this is a drop function, we can create this token to call the
                 // pinned destructor of this type.
-                let token = unsafe { $crate::init::__internal::OnlyCallFromDrop::new() };
-                $crate::init::PinnedDrop::drop(pinned, token);
+                let token = unsafe { $crate::__internal::OnlyCallFromDrop::new() };
+                $crate::PinnedDrop::drop(pinned, token);
             }
         }
     };
@@ -1000,10 +1003,10 @@ macro_rules! __pin_data {
                 $pvis unsafe fn $p_field<E>(
                     self,
                     slot: *mut $p_type,
-                    init: impl $crate::init::PinInit<$p_type, E>,
+                    init: impl $crate::PinInit<$p_type, E>,
                 ) -> ::core::result::Result<(), E> {
                     // SAFETY: TODO.
-                    unsafe { $crate::init::PinInit::__pinned_init(init, slot) }
+                    unsafe { $crate::PinInit::__pinned_init(init, slot) }
                 }
             )*
             $(
@@ -1011,10 +1014,10 @@ macro_rules! __pin_data {
                 $fvis unsafe fn $field<E>(
                     self,
                     slot: *mut $type,
-                    init: impl $crate::init::Init<$type, E>,
+                    init: impl $crate::Init<$type, E>,
                 ) -> ::core::result::Result<(), E> {
                     // SAFETY: TODO.
-                    unsafe { $crate::init::Init::__init(init, slot) }
+                    unsafe { $crate::Init::__init(init, slot) }
                 }
             )*
         }
@@ -1131,15 +1134,15 @@ macro_rules! __init_internal {
         //
         // SAFETY: TODO.
         let data = unsafe {
-            use $crate::init::__internal::$has_data;
+            use $crate::__internal::$has_data;
             // Here we abuse `paste!` to retokenize `$t`. Declarative macros have some internal
             // information that is associated to already parsed fragments, so a path fragment
             // cannot be used in this position. Doing the retokenization results in valid rust
             // code.
-            $crate::init::macros::paste!($t::$get_data())
+            $crate::macros::paste!($t::$get_data())
         };
         // Ensure that `data` really is of type `$data` and help with type inference:
-        let init = $crate::init::__internal::$data::make_closure::<_, __InitOk, $err>(
+        let init = $crate::__internal::$data::make_closure::<_, __InitOk, $err>(
             data,
             move |slot| {
                 {
@@ -1149,7 +1152,7 @@ macro_rules! __init_internal {
                     // error when fields are missing (since they will be zeroed). We also have to
                     // check that the type actually implements `Zeroable`.
                     $({
-                        fn assert_zeroable<T: $crate::init::Zeroable>(_: *mut T) {}
+                        fn assert_zeroable<T: $crate::Zeroable>(_: *mut T) {}
                         // Ensure that the struct is indeed `Zeroable`.
                         assert_zeroable(slot);
                         // SAFETY: The type implements `Zeroable` by the check above.
@@ -1186,7 +1189,7 @@ macro_rules! __init_internal {
             init(slot).map(|__InitOk| ())
         };
         // SAFETY: TODO.
-        let init = unsafe { $crate::init::$construct_closure::<_, $err>(init) };
+        let init = unsafe { $crate::$construct_closure::<_, $err>(init) };
         init
     }};
     (init_slot($($use_data:ident)?):
@@ -1217,10 +1220,10 @@ macro_rules! __init_internal {
         //
         // We rely on macro hygiene to make it impossible for users to access this local variable.
         // We use `paste!` to create new hygiene for `$field`.
-        $crate::init::macros::paste! {
+        $crate::macros::paste! {
             // SAFETY: We forget the guard later when initialization has succeeded.
             let [< __ $field _guard >] = unsafe {
-                $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field))
+                $crate::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field))
             };
 
             $crate::__init_internal!(init_slot($use_data):
@@ -1243,15 +1246,15 @@ macro_rules! __init_internal {
         //
         // SAFETY: `slot` is valid, because we are inside of an initializer closure, we
         // return when an error/panic occurs.
-        unsafe { $crate::init::Init::__init(init, ::core::ptr::addr_of_mut!((*$slot).$field))? };
+        unsafe { $crate::Init::__init(init, ::core::ptr::addr_of_mut!((*$slot).$field))? };
         // Create the drop guard:
         //
         // We rely on macro hygiene to make it impossible for users to access this local variable.
         // We use `paste!` to create new hygiene for `$field`.
-        $crate::init::macros::paste! {
+        $crate::macros::paste! {
             // SAFETY: We forget the guard later when initialization has succeeded.
             let [< __ $field _guard >] = unsafe {
-                $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field))
+                $crate::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field))
             };
 
             $crate::__init_internal!(init_slot():
@@ -1280,10 +1283,10 @@ macro_rules! __init_internal {
         //
         // We rely on macro hygiene to make it impossible for users to access this local variable.
         // We use `paste!` to create new hygiene for `$field`.
-        $crate::init::macros::paste! {
+        $crate::macros::paste! {
             // SAFETY: We forget the guard later when initialization has succeeded.
             let [< __ $field _guard >] = unsafe {
-                $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field))
+                $crate::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field))
             };
 
             $crate::__init_internal!(init_slot($($use_data)?):
@@ -1317,7 +1320,7 @@ macro_rules! __init_internal {
             // information that is associated to already parsed fragments, so a path fragment
             // cannot be used in this position. Doing the retokenization results in valid rust
             // code.
-            $crate::init::macros::paste!(
+            $crate::macros::paste!(
                 ::core::ptr::write($slot, $t {
                     $($acc)*
                     ..zeroed
@@ -1341,7 +1344,7 @@ macro_rules! __init_internal {
             // information that is associated to already parsed fragments, so a path fragment
             // cannot be used in this position. Doing the retokenization results in valid rust
             // code.
-            $crate::init::macros::paste!(
+            $crate::macros::paste!(
                 ::core::ptr::write($slot, $t {
                     $($acc)*
                 });
@@ -1396,12 +1399,12 @@ macro_rules! __derive_zeroable {
     ) => {
         // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero.
         #[automatically_derived]
-        unsafe impl<$($impl_generics)*> $crate::init::Zeroable for $name<$($ty_generics)*>
+        unsafe impl<$($impl_generics)*> $crate::Zeroable for $name<$($ty_generics)*>
         where
             $($($whr)*)?
         {}
         const _: () = {
-            fn assert_zeroable<T: ?::core::marker::Sized + $crate::init::Zeroable>() {}
+            fn assert_zeroable<T: ?::core::marker::Sized + $crate::Zeroable>() {}
             fn ensure_zeroable<$($impl_generics)*>()
                 where $($($whr)*)?
             {