rust: use custom FFI integer types

Currently FFI integer types are defined in libcore. This commit creates
the `ffi` crate and asks bindgen to use that crate for FFI integer types
instead of `core::ffi`.

This commit is preparatory and no type changes are made in this commit
yet.

Signed-off-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/r/20240913213041.395655-4-gary@garyguo.net
[ Added `rustdoc`, `rusttest` and KUnit tests support. Rebased on top of
  `rust-next` (e.g. migrated more `core::ffi` cases). Reworded crate
  docs slightly and formatted. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

3 files changed, 11 insertions, 11 deletions

diff --git a/rust/kernel/block/mq/operations.rs b/rust/kernel/block/mq/operations.rs
index 9ba7fdfeb4b2..c8646d0d9866 100644
--- a/rust/kernel/block/mq/operations.rs
+++ b/rust/kernel/block/mq/operations.rs
@@ -131,7 +131,7 @@ impl<T: Operations> OperationsVTable<T> {
     unsafe extern "C" fn poll_callback(
         _hctx: *mut bindings::blk_mq_hw_ctx,
         _iob: *mut bindings::io_comp_batch,
-    ) -> core::ffi::c_int {
+    ) -> crate::ffi::c_int {
         T::poll().into()
     }
 
@@ -145,9 +145,9 @@ impl<T: Operations> OperationsVTable<T> {
     /// for the same context.
     unsafe extern "C" fn init_hctx_callback(
         _hctx: *mut bindings::blk_mq_hw_ctx,
-        _tagset_data: *mut core::ffi::c_void,
-        _hctx_idx: core::ffi::c_uint,
-    ) -> core::ffi::c_int {
+        _tagset_data: *mut crate::ffi::c_void,
+        _hctx_idx: crate::ffi::c_uint,
+    ) -> crate::ffi::c_int {
         from_result(|| Ok(0))
     }
 
@@ -159,7 +159,7 @@ impl<T: Operations> OperationsVTable<T> {
     /// This function may only be called by blk-mq C infrastructure.
     unsafe extern "C" fn exit_hctx_callback(
         _hctx: *mut bindings::blk_mq_hw_ctx,
-        _hctx_idx: core::ffi::c_uint,
+        _hctx_idx: crate::ffi::c_uint,
     ) {
     }
 
@@ -176,9 +176,9 @@ impl<T: Operations> OperationsVTable<T> {
     unsafe extern "C" fn init_request_callback(
         _set: *mut bindings::blk_mq_tag_set,
         rq: *mut bindings::request,
-        _hctx_idx: core::ffi::c_uint,
-        _numa_node: core::ffi::c_uint,
-    ) -> core::ffi::c_int {
+        _hctx_idx: crate::ffi::c_uint,
+        _numa_node: crate::ffi::c_uint,
+    ) -> crate::ffi::c_int {
         from_result(|| {
             // SAFETY: By the safety requirements of this function, `rq` points
             // to a valid allocation.
@@ -203,7 +203,7 @@ impl<T: Operations> OperationsVTable<T> {
     unsafe extern "C" fn exit_request_callback(
         _set: *mut bindings::blk_mq_tag_set,
         rq: *mut bindings::request,
-        _hctx_idx: core::ffi::c_uint,
+        _hctx_idx: crate::ffi::c_uint,
     ) {
         // SAFETY: The tagset invariants guarantee that all requests are allocated with extra memory
         // for the request data.
diff --git a/rust/kernel/block/mq/raw_writer.rs b/rust/kernel/block/mq/raw_writer.rs
index 9222465d670b..7e2159e4f6a6 100644
--- a/rust/kernel/block/mq/raw_writer.rs
+++ b/rust/kernel/block/mq/raw_writer.rs
@@ -25,7 +25,7 @@ impl<'a> RawWriter<'a> {
     }
 
     pub(crate) fn from_array<const N: usize>(
-        a: &'a mut [core::ffi::c_char; N],
+        a: &'a mut [crate::ffi::c_char; N],
     ) -> Result<RawWriter<'a>> {
         Self::new(
             // SAFETY: the buffer of `a` is valid for read and write as `u8` for
diff --git a/rust/kernel/block/mq/tag_set.rs b/rust/kernel/block/mq/tag_set.rs
index f9a1ca655a35..d7f175a05d99 100644
--- a/rust/kernel/block/mq/tag_set.rs
+++ b/rust/kernel/block/mq/tag_set.rs
@@ -53,7 +53,7 @@ impl<T: Operations> TagSet<T> {
                     queue_depth: num_tags,
                     cmd_size,
                     flags: bindings::BLK_MQ_F_SHOULD_MERGE,
-                    driver_data: core::ptr::null_mut::<core::ffi::c_void>(),
+                    driver_data: core::ptr::null_mut::<crate::ffi::c_void>(),
                     nr_maps: num_maps,
                     ..tag_set
                 }