rust: module: move module types into `module.rs`

Move `Module`, `InPlaceModule`, `ModuleMetadata` and `ThisModule` from
`lib.rs` into a new `rust/kernel/module.rs`. Re-export them from `lib.rs`
to avoid tree-wide changes.

Switch six bus driver registrations from `module.0` to the public
`ThisModule::as_ptr()` accessor, since the field is no longer visible
outside the new `module` submodule.

No functional change.

Assisted-by: opencode:glm-5.2
Suggested-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/all/DJFIQPLOVO4T.1K8T0VZM30LDA@garyguo.net/
Reviewed-by: Gary Guo <gary@garyguo.net>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Alvin Sun <alvin.sun@linux.dev>
Link: https://patch.msgid.link/20260811-fix-fops-owner-v10-1-7e71776f9dbe@linux.dev
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 71 insertions, 0 deletions

diff --git a/rust/kernel/module.rs b/rust/kernel/module.rs
new file mode 100644
index 000000000000..be242a82e86d
--- /dev/null
+++ b/rust/kernel/module.rs
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Module-related types and helpers.
+
+/// The entrypoint to implementing a kernel module.
+///
+/// For any teardown or cleanup operations, your type may implement [`Drop`].
+pub trait Module: Sized + Sync + Send {
+    /// Called at module initialization time.
+    ///
+    /// Use this method to perform whatever setup or registration your module
+    /// should do.
+    ///
+    /// Equivalent to the `module_init` macro in the C API.
+    fn init(module: &'static ThisModule) -> crate::error::Result<Self>;
+}
+
+/// A module that is pinned and initialised in-place.
+pub trait InPlaceModule: Sync + Send {
+    /// Creates an initialiser for the module.
+    ///
+    /// It is called when the module is loaded.
+    fn init(module: &'static ThisModule) -> impl pin_init::PinInit<Self, crate::error::Error>;
+}
+
+impl<T: Module> InPlaceModule for T {
+    fn init(module: &'static ThisModule) -> impl pin_init::PinInit<Self, crate::error::Error> {
+        let initer = move |slot: *mut Self| {
+            let m = <Self as Module>::init(module)?;
+
+            // SAFETY: `slot` is valid for write per the contract with `pin_init_from_closure`.
+            unsafe { slot.write(m) };
+            Ok(())
+        };
+
+        // SAFETY: On success, `initer` always fully initialises an instance of `Self`.
+        unsafe { pin_init::pin_init_from_closure(initer) }
+    }
+}
+
+/// Metadata attached to a [`Module`] or [`InPlaceModule`].
+pub trait ModuleMetadata {
+    /// The name of the module as specified in the `module!` macro.
+    const NAME: &'static crate::str::CStr;
+}
+
+/// Equivalent to `THIS_MODULE` in the C API.
+///
+/// C header: [`include/linux/init.h`](srctree/include/linux/init.h)
+pub struct ThisModule(*mut crate::bindings::module);
+
+// SAFETY: `THIS_MODULE` may be used from all threads within a module.
+unsafe impl Sync for ThisModule {}
+
+impl ThisModule {
+    /// Creates a [`ThisModule`] given the `THIS_MODULE` pointer.
+    ///
+    /// # Safety
+    ///
+    /// The pointer must be equal to the right `THIS_MODULE`.
+    pub const unsafe fn from_ptr(ptr: *mut crate::bindings::module) -> ThisModule {
+        ThisModule(ptr)
+    }
+
+    /// Access the raw pointer for this module.
+    ///
+    /// It is up to the user to use it correctly.
+    pub const fn as_ptr(&self) -> *mut crate::bindings::module {
+        self.0
+    }
+}