The Driver trait describes the layout of a specific driver structure,
such as `struct pci_driver` or `struct platform_driver`.

In a first step, this replaces the associated type RegType of the
RegistrationOps with the Driver::DriverType associated type.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
  rust/kernel/auxiliary.rs | 18 +++++++++++-------
  rust/kernel/driver.rs    | 40 +++++++++++++++++++++++++---------------
  rust/kernel/i2c.rs       | 18 +++++++++++-------
  rust/kernel/pci.rs       | 18 +++++++++++-------
  rust/kernel/platform.rs  | 18 +++++++++++-------
  rust/kernel/usb.rs       | 18 +++++++++++-------
  6 files changed, 80 insertions(+), 50 deletions(-)

diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index 6931f8a4267f..4636b6f41195 100644
--- a/rust/kernel/auxiliary.rs
+++ b/rust/kernel/auxiliary.rs

@@ -23,13 +23,17 @@
  /// An adapter for the registration of auxiliary drivers.
  pub struct Adapter<T: Driver>(T);
  
-// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
+// SAFETY:
+// - `bindings::auxiliary_driver` is a C type declared as `repr(C)`.
+unsafe impl<T: Driver + 'static> driver::Driver for Adapter<T> {
+    type DriverType = bindings::auxiliary_driver;
+}
+
+// SAFETY: A call to `unregister` for a given instance of `DriverType` is guaranteed to be valid if
  // a preceding call to `register` has been successful.
  unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
-    type RegType = bindings::auxiliary_driver;
-
      unsafe fn register(
-        adrv: &Opaque<Self::RegType>,
+        adrv: &Opaque<Self::DriverType>,
          name: &'static CStr,
          module: &'static ThisModule,
      ) -> Result {

@@ -41,14 +45,14 @@ unsafe fn register(
              (*adrv.get()).id_table = T::ID_TABLE.as_ptr();
          }
  
-        // SAFETY: `adrv` is guaranteed to be a valid `RegType`.
+        // SAFETY: `adrv` is guaranteed to be a valid `DriverType`.
          to_result(unsafe {
              bindings::__auxiliary_driver_register(adrv.get(), module.0, name.as_char_ptr())
          })
      }
  
-    unsafe fn unregister(adrv: &Opaque<Self::RegType>) {
-        // SAFETY: `adrv` is guaranteed to be a valid `RegType`.
+    unsafe fn unregister(adrv: &Opaque<Self::DriverType>) {
+        // SAFETY: `adrv` is guaranteed to be a valid `DriverType`.
          unsafe { bindings::auxiliary_driver_unregister(adrv.get()) }
      }
  }

diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs
index 649d06468f41..cd1d36c313e1 100644
--- a/rust/kernel/driver.rs
+++ b/rust/kernel/driver.rs

@@ -99,23 +99,33 @@
  use core::pin::Pin;
  use pin_init::{pin_data, pinned_drop, PinInit};
  
+/// Trait describing the layout of a specific device driver.
+///
+/// This trait describes the layout of a specific driver structure, such as `struct pci_driver` or
+/// `struct platform_driver`.
+///
+/// # Safety
+///
+/// Implementors must guarantee that:
+/// - `DriverType` is `repr(C)`.
+pub unsafe trait Driver {
+    /// The specific driver type embedding a `struct device_driver`.
+    type DriverType: Default;
+}
+
  /// The [`RegistrationOps`] trait serves as generic interface for subsystems (e.g., PCI, Platform,
  /// Amba, etc.) to provide the corresponding subsystem specific implementation to register /
-/// unregister a driver of the particular type (`RegType`).
+/// unregister a driver of the particular type (`DriverType`).
  ///
-/// For instance, the PCI subsystem would set `RegType` to `bindings::pci_driver` and call
+/// For instance, the PCI subsystem would set `DriverType` to `bindings::pci_driver` and call
  /// `bindings::__pci_register_driver` from `RegistrationOps::register` and
  /// `bindings::pci_unregister_driver` from `RegistrationOps::unregister`.
  ///
  /// # Safety
  ///
-/// A call to [`RegistrationOps::unregister`] for a given instance of `RegType` is only valid if a
-/// preceding call to [`RegistrationOps::register`] has been successful.
-pub unsafe trait RegistrationOps {
-    /// The type that holds information about the registration. This is typically a struct defined
-    /// by the C portion of the kernel.
-    type RegType: Default;
-
+/// A call to [`RegistrationOps::unregister`] for a given instance of `DriverType` is only valid if
+/// a preceding call to [`RegistrationOps::register`] has been successful.
+pub unsafe trait RegistrationOps: Driver {
      /// Registers a driver.
      ///
      /// # Safety

@@ -123,7 +133,7 @@ pub unsafe trait RegistrationOps {
      /// On success, `reg` must remain pinned and valid until the matching call to
      /// [`RegistrationOps::unregister`].
      unsafe fn register(
-        reg: &Opaque<Self::RegType>,
+        reg: &Opaque<Self::DriverType>,
          name: &'static CStr,
          module: &'static ThisModule,
      ) -> Result;

@@ -134,7 +144,7 @@ unsafe fn register(
      ///
      /// Must only be called after a preceding successful call to [`RegistrationOps::register`] for
      /// the same `reg`.
-    unsafe fn unregister(reg: &Opaque<Self::RegType>);
+    unsafe fn unregister(reg: &Opaque<Self::DriverType>);
  }
  
  /// A [`Registration`] is a generic type that represents the registration of some driver type (e.g.

@@ -146,7 +156,7 @@ unsafe fn register(
  #[pin_data(PinnedDrop)]
  pub struct Registration<T: RegistrationOps> {
      #[pin]
-    reg: Opaque<T::RegType>,
+    reg: Opaque<T::DriverType>,
  }
  
  // SAFETY: `Registration` has no fields or methods accessible via `&Registration`, so it is safe to

@@ -161,13 +171,13 @@ impl<T: RegistrationOps> Registration<T> {
      /// Creates a new instance of the registration object.
      pub fn new(name: &'static CStr, module: &'static ThisModule) -> impl PinInit<Self, Error> {
          try_pin_init!(Self {
-            reg <- Opaque::try_ffi_init(|ptr: *mut T::RegType| {
+            reg <- Opaque::try_ffi_init(|ptr: *mut T::DriverType| {
                  // SAFETY: `try_ffi_init` guarantees that `ptr` is valid for write.
-                unsafe { ptr.write(T::RegType::default()) };
+                unsafe { ptr.write(T::DriverType::default()) };
  
                  // SAFETY: `try_ffi_init` guarantees that `ptr` is valid for write, and it has
                  // just been initialised above, so it's also valid for read.
-                let drv = unsafe { &*(ptr as *const Opaque<T::RegType>) };
+                let drv = unsafe { &*(ptr as *const Opaque<T::DriverType>) };
  
                  // SAFETY: `drv` is guaranteed to be pinned until `T::unregister`.
                  unsafe { T::register(drv, name, module) }

diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index 35b678b78d91..de35961c6903 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs

@@ -92,13 +92,17 @@ macro_rules! i2c_device_table {
  /// An adapter for the registration of I2C drivers.
  pub struct Adapter<T: Driver>(T);
  
-// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
+// SAFETY:
+// - `bindings::i2c_driver` is a C type declared as `repr(C)`.
+unsafe impl<T: Driver + 'static> driver::Driver for Adapter<T> {
+    type DriverType = bindings::i2c_driver;
+}
+
+// SAFETY: A call to `unregister` for a given instance of `DriverType` is guaranteed to be valid if
  // a preceding call to `register` has been successful.
  unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
-    type RegType = bindings::i2c_driver;
-
      unsafe fn register(
-        idrv: &Opaque<Self::RegType>,
+        idrv: &Opaque<Self::DriverType>,
          name: &'static CStr,
          module: &'static ThisModule,
      ) -> Result {

@@ -133,12 +137,12 @@ unsafe fn register(
              (*idrv.get()).driver.acpi_match_table = acpi_table;
          }
  
-        // SAFETY: `idrv` is guaranteed to be a valid `RegType`.
+        // SAFETY: `idrv` is guaranteed to be a valid `DriverType`.
          to_result(unsafe { bindings::i2c_register_driver(module.0, idrv.get()) })
      }
  
-    unsafe fn unregister(idrv: &Opaque<Self::RegType>) {
-        // SAFETY: `idrv` is guaranteed to be a valid `RegType`.
+    unsafe fn unregister(idrv: &Opaque<Self::DriverType>) {
+        // SAFETY: `idrv` is guaranteed to be a valid `DriverType`.
          unsafe { bindings::i2c_del_driver(idrv.get()) }
      }
  }

diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 82e128431f08..f58ce35d9c60 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs

@@ -50,13 +50,17 @@
  /// An adapter for the registration of PCI drivers.
  pub struct Adapter<T: Driver>(T);
  
-// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
+// SAFETY:
+// - `bindings::pci_driver` is a C type declared as `repr(C)`.
+unsafe impl<T: Driver + 'static> driver::Driver for Adapter<T> {
+    type DriverType = bindings::pci_driver;
+}
+
+// SAFETY: A call to `unregister` for a given instance of `DriverType` is guaranteed to be valid if
  // a preceding call to `register` has been successful.
  unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
-    type RegType = bindings::pci_driver;
-
      unsafe fn register(
-        pdrv: &Opaque<Self::RegType>,
+        pdrv: &Opaque<Self::DriverType>,
          name: &'static CStr,
          module: &'static ThisModule,
      ) -> Result {

@@ -68,14 +72,14 @@ unsafe fn register(
              (*pdrv.get()).id_table = T::ID_TABLE.as_ptr();
          }
  
-        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
+        // SAFETY: `pdrv` is guaranteed to be a valid `DriverType`.
          to_result(unsafe {
              bindings::__pci_register_driver(pdrv.get(), module.0, name.as_char_ptr())
          })
      }
  
-    unsafe fn unregister(pdrv: &Opaque<Self::RegType>) {
-        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
+    unsafe fn unregister(pdrv: &Opaque<Self::DriverType>) {
+        // SAFETY: `pdrv` is guaranteed to be a valid `DriverType`.
          unsafe { bindings::pci_unregister_driver(pdrv.get()) }
      }
  }

diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index ed889f079cab..e48d055fdc8a 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs

@@ -26,13 +26,17 @@
  /// An adapter for the registration of platform drivers.
  pub struct Adapter<T: Driver>(T);
  
-// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
+// SAFETY:
+// - `bindings::platform_driver` is a C type declared as `repr(C)`.
+unsafe impl<T: Driver + 'static> driver::Driver for Adapter<T> {
+    type DriverType = bindings::platform_driver;
+}
+
+// SAFETY: A call to `unregister` for a given instance of `DriverType` is guaranteed to be valid if
  // a preceding call to `register` has been successful.
  unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
-    type RegType = bindings::platform_driver;
-
      unsafe fn register(
-        pdrv: &Opaque<Self::RegType>,
+        pdrv: &Opaque<Self::DriverType>,
          name: &'static CStr,
          module: &'static ThisModule,
      ) -> Result {

@@ -55,12 +59,12 @@ unsafe fn register(
              (*pdrv.get()).driver.acpi_match_table = acpi_table;
          }
  
-        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
+        // SAFETY: `pdrv` is guaranteed to be a valid `DriverType`.
          to_result(unsafe { bindings::__platform_driver_register(pdrv.get(), module.0) })
      }
  
-    unsafe fn unregister(pdrv: &Opaque<Self::RegType>) {
-        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
+    unsafe fn unregister(pdrv: &Opaque<Self::DriverType>) {
+        // SAFETY: `pdrv` is guaranteed to be a valid `DriverType`.
          unsafe { bindings::platform_driver_unregister(pdrv.get()) };
      }
  }

diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
index d10b65e9fb6a..32f4b2d55dfb 100644
--- a/rust/kernel/usb.rs
+++ b/rust/kernel/usb.rs

@@ -27,13 +27,17 @@
  /// An adapter for the registration of USB drivers.
  pub struct Adapter<T: Driver>(T);
  
-// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
+// SAFETY:
+// - `bindings::usb_driver` is a C type declared as `repr(C)`.
+unsafe impl<T: Driver + 'static> driver::Driver for Adapter<T> {
+    type DriverType = bindings::usb_driver;
+}
+
+// SAFETY: A call to `unregister` for a given instance of `DriverType` is guaranteed to be valid if
  // a preceding call to `register` has been successful.
  unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
-    type RegType = bindings::usb_driver;
-
      unsafe fn register(
-        udrv: &Opaque<Self::RegType>,
+        udrv: &Opaque<Self::DriverType>,
          name: &'static CStr,
          module: &'static ThisModule,
      ) -> Result {

@@ -45,14 +49,14 @@ unsafe fn register(
              (*udrv.get()).id_table = T::ID_TABLE.as_ptr();
          }
  
-        // SAFETY: `udrv` is guaranteed to be a valid `RegType`.
+        // SAFETY: `udrv` is guaranteed to be a valid `DriverType`.
          to_result(unsafe {
              bindings::usb_register_driver(udrv.get(), module.0, name.as_char_ptr())
          })
      }
  
-    unsafe fn unregister(udrv: &Opaque<Self::RegType>) {
-        // SAFETY: `udrv` is guaranteed to be a valid `RegType`.
+    unsafe fn unregister(udrv: &Opaque<Self::DriverType>) {
+        // SAFETY: `udrv` is guaranteed to be a valid `DriverType`.
          unsafe { bindings::usb_deregister(udrv.get()) };
      }
  }