[PATCH RFC 2/6] rust: WIP: Introduce ThisModule trait and THIS_MODULE impl

[Kari Argillander <kari.argillander@gmail.com>]

---
 rust/kernel/lib.rs    | 61 +++++++++++++++++++++++++++++++++++----------------
 rust/macros/module.rs | 36 ++++++++++++++++++------------
 2 files changed, 64 insertions(+), 33 deletions(-)

diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 69a798fbb563..224410745734 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -205,31 +205,54 @@ pub trait ModuleMetadata {
     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 bindings::module);
+pub mod this_module {
+    //! TODO
+    //!
+    //! # For driver cretors
+    //!
+    //! For each module we define own custom THIS_MODULE in
+    //! [`macros::module::module`]. Mechanism is equivalent to `THIS_MODULE` in
+    //! the [C API](srctree/include/linux/init.h).
+    //!
+    //! TODO
+    //!
+    //! # For abstraction creators
+    //!
+    //! TODO
 
-// SAFETY: `THIS_MODULE` may be used from all threads within a module.
-unsafe impl Sync for ThisModule {}
+    /// See [`this_module`]
+    pub trait ThisModule {
+        /// TODO Doc
+        const OWNER: ModuleWrapper;
+    }
 
-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 bindings::module) -> ThisModule {
-        ThisModule(ptr)
+    /// See [`this_module`]
+    pub struct ModuleWrapper {
+        ptr: *mut bindings::module,
     }
 
-    /// Access the raw pointer for this module.
-    ///
-    /// It is up to the user to use it correctly.
-    pub const fn as_ptr(&self) -> *mut bindings::module {
-        self.0
+    impl ModuleWrapper {
+        /// Get the raw pointer to the underlying `struct module`.
+        ///
+        /// TODO: Should be only available for kernel create.
+        pub const fn as_ptr(&self) -> *mut bindings::module {
+            self.ptr
+        }
+
+        /// Only meant to use in [`macros::module::module`].
+        ///
+        /// # Safety
+        ///
+        /// - Only modules are allowed to create non null `ModuleWrapper`s.
+        /// - The pointer must point to a valid `struct module` provided by the
+        ///   kernel.
+        #[doc(hidden)]
+        pub const unsafe fn from_ptr(ptr: *mut bindings::module) -> Self {
+            ModuleWrapper { ptr }
+        }
     }
 }
+pub use this_module::*;
 
 #[cfg(not(testlib))]
 #[panic_handler]
diff --git a/rust/macros/module.rs b/rust/macros/module.rs
index 80cb9b16f5aa..6b8753d122cc 100644
--- a/rust/macros/module.rs
+++ b/rust/macros/module.rs
@@ -371,20 +371,28 @@ pub(crate) fn module(ts: TokenStream) -> TokenStream {
             /// Used by the printing macros, e.g. [`info!`].
             const __LOG_PREFIX: &[u8] = b\"{name}\\0\";
 
-            // SAFETY: `__this_module` is constructed by the kernel at load time and will not be
-            // freed until the module is unloaded.
-            #[cfg(MODULE)]
-            static THIS_MODULE: ::kernel::ThisModule = unsafe {{
-                extern \"C\" {{
-                    static __this_module: ::kernel::types::Opaque<::kernel::bindings::module>;
-                }}
+            /// THIS_MODULE for \"{name}\". See more at [`kernel::this_module`].
+            #[allow(non_camel_case_types)]
+            pub struct THIS_MODULE;
+
+            impl ::kernel::prelude::ThisModule for THIS_MODULE {{
+                #[cfg(not(MODULE))] 
+                const OWNER: ::kernel::this_module::ModuleWrapper = unsafe {{
+                    ::kernel::this_module::ModuleWrapper::from_ptr(::core::ptr::null_mut())
+                }};
 
-                ::kernel::ThisModule::from_ptr(__this_module.get())
-            }};
-            #[cfg(not(MODULE))]
-            static THIS_MODULE: ::kernel::ThisModule = unsafe {{
-                ::kernel::ThisModule::from_ptr(::core::ptr::null_mut())
-            }};
+                #[cfg(MODULE)]
+                // SAFETY:
+                // - `__this_module` is constructed by the kernel at module load time.
+                // - We use check that we are module so we can create non-null ModuleWrapper.
+                const OWNER: ::kernel::this_module::ModuleWrapper = unsafe {{
+                    extern \"C\" {{
+                        static __this_module: ::kernel::types::Opaque<::kernel::bindings::module>;
+                    }}
+                    
+                    ::kernel::this_module::ModuleWrapper::from_ptr(__this_module.get())
+                }};
+            }}
 
             /// The `LocalModule` type is the type of the module created by `module!`,
             /// `module_pci_driver!`, `module_platform_driver!`, etc.
@@ -502,7 +510,7 @@ mod __module_init {{
                     /// This function must only be called once.
                     unsafe fn __init() -> ::kernel::ffi::c_int {{
                         let initer =
-                            <{type_} as ::kernel::InPlaceModule>::init(&super::super::THIS_MODULE);
+                            <{type_} as ::kernel::InPlaceModule>::init::<super::super::THIS_MODULE>();
                         // SAFETY: No data race, since `__MOD` can only be accessed by this module
                         // and there only `__init` and `__exit` access it. These functions are only
                         // called once and `__exit` cannot be called before or during `__init`.

-- 
2.43.0