Merge patch series "rust: drm: Higher-Ranked Lifetime private data"

Danilo Krummrich <dakr@kernel.org> says:

DRM ioctls run in process context without any guarantee that the parent
bus device is still bound. This series solves the problem by introducing
RegistrationGuard -- a guard representing a drm_dev_enter/exit SRCU
critical section that proves the parent bus device is bound for the
lifetime of the guard.

As initial plumbing for this, the DRM DeviceContext typestates are
reworked: Uninit is renamed to Normal, defaults are adjusted,
AlwaysRefCounted is restricted to Normal, and a Deref chain from
Device<T, Registered> to Device<T, Normal> is established. This gives
Device<T, Registered> the semantic that the device is currently
registered and the parent bus device is bound, which makes the
RegistrationGuard and ioctl dispatch much cleaner. An Ioctl context
restricts registration_guard() to ioctl dispatch, where the DRM core
guarantees prior registration.

On top of that, add RegistrationData as a GAT (Generic Associated Type)
on drm::Driver, allowing drivers to store data whose lifetime is tied to
the parent bus device binding scope. The data is allocated in
Registration::new(), lifetime-erased to 'static for storage, and made
accessible through Device<T, Registered>::registration_data_with(). The
closure's HRTB ties the lifetime to the closure scope; internally the
'static pointer is cast back to the closure-scoped lifetime. The
reference is valid for the duration of the drm_dev_enter/exit critical
section held by RegistrationGuard.

Also update the ioctl dispatch macro to wrap every handler in a
RegistrationGuard, returning ENODEV if the device has been unplugged,
and pass the registration data to handlers.

Link: https://patch.msgid.link/20260628145406.2107056-1-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

15 files changed, 656 insertions, 387 deletions

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 675675480da4..e890052061f3 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -473,6 +473,22 @@ void drm_dev_exit(int idx)
 }
 EXPORT_SYMBOL(drm_dev_exit);
 
+/*
+ * Mark the device as unplugged and wait for any in-flight drm_dev_enter()
+ * critical sections to complete.
+ */
+static void drm_dev_synchronize_unplug(struct drm_device *dev)
+{
+	/*
+	 * After synchronizing any critical read section is guaranteed to see
+	 * the new value of ->unplugged, and any critical section which might
+	 * still have seen the old value of ->unplugged is guaranteed to have
+	 * finished.
+	 */
+	dev->unplugged = true;
+	synchronize_srcu(&drm_unplug_srcu);
+}
+
 /**
  * drm_dev_unplug - unplug a DRM device
  * @dev: DRM device
@@ -485,15 +501,7 @@ EXPORT_SYMBOL(drm_dev_exit);
  */
 void drm_dev_unplug(struct drm_device *dev)
 {
-	/*
-	 * After synchronizing any critical read section is guaranteed to see
-	 * the new value of ->unplugged, and any critical section which might
-	 * still have seen the old value of ->unplugged is guaranteed to have
-	 * finished.
-	 */
-	dev->unplugged = true;
-	synchronize_srcu(&drm_unplug_srcu);
-
+	drm_dev_synchronize_unplug(dev);
 	drm_dev_unregister(dev);
 
 	/* Clear all CPU mappings pointing to this device */
@@ -1091,6 +1099,7 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
 		goto err_minors;
 
 	dev->registered = true;
+	dev->unplugged = false;
 
 	if (driver->load) {
 		ret = driver->load(dev, flags);
@@ -1118,6 +1127,13 @@ err_unload:
 	if (dev->driver->unload)
 		dev->driver->unload(dev);
 err_minors:
+	/*
+	 * If a minor was registered before the failure, userspace could have
+	 * opened it and entered a drm_dev_enter() critical section. Ensure all
+	 * such sections complete before we clean up.
+	 */
+	drm_dev_synchronize_unplug(dev);
+
 	remove_compat_control_link(dev);
 	drm_minor_unregister(dev, DRM_MINOR_ACCEL);
 	drm_minor_unregister(dev, DRM_MINOR_PRIMARY);
diff --git a/drivers/gpu/drm/nova/driver.rs b/drivers/gpu/drm/nova/driver.rs
index 48933d86ddda..739690bc2db5 100644
--- a/drivers/gpu/drm/nova/driver.rs
+++ b/drivers/gpu/drm/nova/driver.rs
@@ -2,7 +2,10 @@
 
 use kernel::{
     auxiliary,
-    device::Core,
+    device::{
+        Core,
+        DeviceContext, //
+    },
     drm::{
         self,
         gem,
@@ -17,18 +20,14 @@ use crate::gem::NovaObject;
 
 pub(crate) struct NovaDriver;
 
-pub(crate) struct Nova {
+pub(crate) struct Nova<'bound> {
     #[expect(unused)]
     drm: ARef<drm::Device<NovaDriver>>,
+    _reg: drm::Registration<'bound, NovaDriver>,
 }
 
 /// Convienence type alias for the DRM device type for this driver
-pub(crate) type NovaDevice<Ctx = drm::Registered> = drm::Device<NovaDriver, Ctx>;
-
-#[pin_data]
-pub(crate) struct NovaData {
-    pub(crate) adev: ARef<auxiliary::Device>,
-}
+pub(crate) type NovaDevice<Ctx = drm::Normal> = drm::Device<NovaDriver, Ctx>;
 
 const INFO: drm::DriverInfo = drm::DriverInfo {
     major: 0,
@@ -53,27 +52,32 @@ kernel::auxiliary_device_table!(
 
 impl auxiliary::Driver for NovaDriver {
     type IdInfo = ();
-    type Data<'bound> = Nova;
+    type Data<'bound> = Nova<'bound>;
     const ID_TABLE: auxiliary::IdTable<Self::IdInfo> = &AUX_TABLE;
 
     fn probe<'bound>(
         adev: &'bound auxiliary::Device<Core<'_>>,
         _info: &'bound Self::IdInfo,
     ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound {
-        let data = try_pin_init!(NovaData { adev: adev.into() });
-
-        let drm = drm::UnregisteredDevice::<Self>::new(adev.as_ref(), data)?;
-        let drm = drm::Registration::new_foreign_owned(drm, adev.as_ref(), 0)?;
-
-        Ok(Nova { drm: drm.into() })
+        let drm = drm::UnregisteredDevice::<Self>::new(adev, Ok(()))?;
+        // SAFETY: `reg` is stored in `Nova` and dropped when the driver is unbound; it is
+        // never forgotten.
+        let reg = unsafe { drm::Registration::new(adev.as_ref(), drm, (), 0)? };
+
+        Ok(Nova {
+            drm: reg.device().into(),
+            _reg: reg,
+        })
     }
 }
 
 #[vtable]
 impl drm::Driver for NovaDriver {
-    type Data = NovaData;
+    type Data = ();
+    type RegistrationData<'a> = ();
     type File = File;
-    type Object<Ctx: drm::DeviceContext> = gem::Object<NovaObject, Ctx>;
+    type Object = gem::Object<NovaObject>;
+    type ParentDevice<Ctx: DeviceContext> = auxiliary::Device<Ctx>;
 
     const INFO: drm::DriverInfo = INFO;
 
diff --git a/drivers/gpu/drm/nova/file.rs b/drivers/gpu/drm/nova/file.rs
index a3b7bd36792c..298c02bacb4b 100644
--- a/drivers/gpu/drm/nova/file.rs
+++ b/drivers/gpu/drm/nova/file.rs
@@ -4,7 +4,13 @@ use crate::driver::{NovaDevice, NovaDriver};
 use crate::gem::NovaObject;
 use kernel::{
     alloc::flags::*,
-    drm::{self, gem::BaseObject},
+    auxiliary,
+    device::Bound,
+    drm::{
+        self,
+        gem::BaseObject,
+        Registered, //
+    },
     pci,
     prelude::*,
     uapi,
@@ -23,13 +29,13 @@ impl drm::file::DriverFile for File {
 impl File {
     /// IOCTL: get_param: Query GPU / driver metadata.
     pub(crate) fn get_param(
-        dev: &NovaDevice,
+        dev: &NovaDevice<Registered>,
+        _reg_data: &(),
         getparam: &mut uapi::drm_nova_getparam,
         _file: &drm::File<File>,
     ) -> Result<u32> {
-        let adev = &dev.adev;
-        let parent = adev.parent();
-        let pdev: &pci::Device = parent.try_into()?;
+        let adev: &auxiliary::Device<Bound> = dev.as_ref();
+        let pdev: &pci::Device<Bound> = adev.parent().try_into()?;
 
         let value = match getparam.param as u32 {
             uapi::NOVA_GETPARAM_VRAM_BAR_SIZE => pdev.resource_len(1)?,
@@ -43,7 +49,8 @@ impl File {
 
     /// IOCTL: gem_create: Create a new DRM GEM object.
     pub(crate) fn gem_create(
-        dev: &NovaDevice,
+        dev: &NovaDevice<Registered>,
+        _reg_data: &(),
         req: &mut uapi::drm_nova_gem_create,
         file: &drm::File<File>,
     ) -> Result<u32> {
@@ -56,7 +63,8 @@ impl File {
 
     /// IOCTL: gem_info: Query GEM metadata.
     pub(crate) fn gem_info(
-        _dev: &NovaDevice,
+        _dev: &NovaDevice<Registered>,
+        _reg_data: &(),
         req: &mut uapi::drm_nova_gem_info,
         file: &drm::File<File>,
     ) -> Result<u32> {
diff --git a/drivers/gpu/drm/nova/gem.rs b/drivers/gpu/drm/nova/gem.rs
index 9d8ff7de2c0f..2b6fe9dc0bfa 100644
--- a/drivers/gpu/drm/nova/gem.rs
+++ b/drivers/gpu/drm/nova/gem.rs
@@ -2,7 +2,10 @@
 
 use kernel::{
     drm,
-    drm::{gem, gem::BaseObject, DeviceContext},
+    drm::{
+        gem,
+        gem::BaseObject, //
+    },
     page,
     prelude::*,
     sync::aref::ARef,
@@ -21,27 +24,20 @@ impl gem::DriverObject for NovaObject {
     type Driver = NovaDriver;
     type Args = ();
 
-    fn new<Ctx: DeviceContext>(
-        _dev: &NovaDevice<Ctx>,
-        _size: usize,
-        _args: Self::Args,
-    ) -> impl PinInit<Self, Error> {
+    fn new(_dev: &NovaDevice, _size: usize, _args: Self::Args) -> impl PinInit<Self, Error> {
         try_pin_init!(NovaObject {})
     }
 }
 
 impl NovaObject {
     /// Create a new DRM GEM object.
-    pub(crate) fn new<Ctx: DeviceContext>(
-        dev: &NovaDevice<Ctx>,
-        size: usize,
-    ) -> Result<ARef<gem::Object<Self, Ctx>>> {
+    pub(crate) fn new(dev: &NovaDevice, size: usize) -> Result<ARef<gem::Object<Self>>> {
         if size == 0 {
             return Err(EINVAL);
         }
         let aligned_size = page::page_align(size).ok_or(EINVAL)?;
 
-        gem::Object::<Self, Ctx>::new(dev, aligned_size, ())
+        gem::Object::<Self>::new(dev, aligned_size, ())
     }
 
     /// Look up a GEM object handle for a `File` and return an `ObjectRef` for it.
diff --git a/drivers/gpu/drm/tyr/driver.rs b/drivers/gpu/drm/tyr/driver.rs
index d063bc664cc1..8348c6cd3929 100644
--- a/drivers/gpu/drm/tyr/driver.rs
+++ b/drivers/gpu/drm/tyr/driver.rs
@@ -7,7 +7,8 @@ use kernel::{
     },
     device::{
         Core,
-        Device, //
+        Device,
+        DeviceContext, //
     },
     dma::{
         Device as DmaDevice,
@@ -46,13 +47,14 @@ pub(crate) type IoMem<'a> = kernel::io::mem::IoMem<'a, SZ_2M>;
 pub(crate) struct TyrDrmDriver;
 
 /// Convenience type alias for the DRM device type for this driver.
-pub(crate) type TyrDrmDevice<Ctx = drm::Registered> = drm::Device<TyrDrmDriver, Ctx>;
+pub(crate) type TyrDrmDevice<Ctx = drm::Normal> = drm::Device<TyrDrmDriver, Ctx>;
 
 pub(crate) struct TyrPlatformDriver;
 
 #[pin_data(PinnedDrop)]
-pub(crate) struct TyrPlatformDriverData {
+pub(crate) struct TyrPlatformDriverData<'bound> {
     _device: ARef<TyrDrmDevice>,
+    _reg: drm::Registration<'bound, TyrDrmDriver>,
 }
 
 #[pin_data]
@@ -97,7 +99,7 @@ kernel::of_device_table!(
 
 impl platform::Driver for TyrPlatformDriver {
     type IdInfo = ();
-    type Data<'bound> = TyrPlatformDriverData;
+    type Data<'bound> = TyrPlatformDriverData<'bound>;
     const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
 
     fn probe<'bound>(
@@ -148,11 +150,14 @@ impl platform::Driver for TyrPlatformDriver {
                 gpu_info,
         });
 
-        let tdev = drm::UnregisteredDevice::<TyrDrmDriver>::new(pdev.as_ref(), data)?;
-        let tdev = drm::driver::Registration::new_foreign_owned(tdev, pdev.as_ref(), 0)?;
+        let tdev = drm::UnregisteredDevice::<TyrDrmDriver>::new(pdev, data)?;
+        // SAFETY: `reg` is stored in `TyrPlatformDriverData` and dropped when the driver is
+        // unbound; it is never forgotten.
+        let reg = unsafe { drm::Registration::new(pdev.as_ref(), tdev, (), 0)? };
 
         let driver = TyrPlatformDriverData {
-            _device: tdev.into(),
+            _device: reg.device().into(),
+            _reg: reg,
         };
 
         // We need this to be dev_info!() because dev_dbg!() does not work at
@@ -163,7 +168,7 @@ impl platform::Driver for TyrPlatformDriver {
 }
 
 #[pinned_drop]
-impl PinnedDrop for TyrPlatformDriverData {
+impl PinnedDrop for TyrPlatformDriverData<'_> {
     fn drop(self: Pin<&mut Self>) {}
 }
 
@@ -180,8 +185,10 @@ const INFO: drm::DriverInfo = drm::DriverInfo {
 #[vtable]
 impl drm::Driver for TyrDrmDriver {
     type Data = TyrDrmDeviceData;
+    type RegistrationData<'a> = ();
     type File = TyrDrmFileData;
-    type Object<R: drm::DeviceContext> = drm::gem::shmem::Object<BoData, R>;
+    type Object = drm::gem::shmem::Object<BoData>;
+    type ParentDevice<Ctx: DeviceContext> = platform::Device<Ctx>;
 
     const INFO: drm::DriverInfo = INFO;
     const FEAT_RENDER: bool = true;
diff --git a/drivers/gpu/drm/tyr/file.rs b/drivers/gpu/drm/tyr/file.rs
index 31411da203c5..b686041d5d6b 100644
--- a/drivers/gpu/drm/tyr/file.rs
+++ b/drivers/gpu/drm/tyr/file.rs
@@ -1,7 +1,10 @@
 // SPDX-License-Identifier: GPL-2.0 or MIT
 
 use kernel::{
-    drm,
+    drm::{
+        self,
+        Registered, //
+    },
     prelude::*,
     uaccess::UserSlice,
     uapi, //
@@ -28,7 +31,8 @@ impl drm::file::DriverFile for TyrDrmFileData {
 
 impl TyrDrmFileData {
     pub(crate) fn dev_query(
-        ddev: &TyrDrmDevice,
+        ddev: &TyrDrmDevice<Registered>,
+        _reg_data: &(),
         devquery: &mut uapi::drm_panthor_dev_query,
         _file: &TyrDrmFile,
     ) -> Result<u32> {
diff --git a/drivers/gpu/drm/tyr/gem.rs b/drivers/gpu/drm/tyr/gem.rs
index c6d4d6f9bae3..1640a161754b 100644
--- a/drivers/gpu/drm/tyr/gem.rs
+++ b/drivers/gpu/drm/tyr/gem.rs
@@ -5,10 +5,7 @@
 //! DRM's GEM subsystem with shmem backing.
 
 use kernel::{
-    drm::{
-        gem,
-        DeviceContext, //
-    },
+    drm::gem,
     prelude::*, //
 };
 
@@ -33,11 +30,7 @@ impl gem::DriverObject for BoData {
     type Driver = TyrDrmDriver;
     type Args = BoCreateArgs;
 
-    fn new<Ctx: DeviceContext>(
-        _dev: &TyrDrmDevice<Ctx>,
-        _size: usize,
-        args: BoCreateArgs,
-    ) -> impl PinInit<Self, Error> {
+    fn new(_dev: &TyrDrmDevice, _size: usize, args: BoCreateArgs) -> impl PinInit<Self, Error> {
         try_pin_init!(Self { flags: args.flags })
     }
 }
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index 7ad124327a83..f43c6887ad23 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -32,6 +32,7 @@ use crate::{
 };
 use core::{
     alloc::Layout,
+    cell::UnsafeCell,
     marker::PhantomData,
     mem,
     ops::Deref,
@@ -74,66 +75,59 @@ macro_rules! drm_legacy_fields {
 
 /// A trait implemented by all possible contexts a [`Device`] can be used in.
 ///
-/// Setting up a new [`Device`] is a multi-stage process. Each step of the process that a user
-/// interacts with in Rust has a respective [`DeviceContext`] typestate. For example,
-/// `Device<T, Registered>` would be a [`Device`] that reached the [`Registered`] [`DeviceContext`].
+/// A [`Device`] can be in one of the following contexts:
 ///
-/// Each stage of this process is described below:
+/// - [`Normal`]: The general-purpose, reference-counted context. A [`Device`] in this context may
+///   or may not be registered with userspace.
+/// - [`Ioctl`]: The device has been registered with userspace at some point; used in ioctl
+///   dispatch context.
+/// - [`Registered`]: The device is currently registered with userspace and the parent bus device
+///   is bound.
 ///
-/// ```text
-///        1                     2                         3
-/// +--------------+   +------------------+   +-----------------------+
-/// |Device created| → |Device initialized| → |Registered w/ userspace|
-/// +--------------+   +------------------+   +-----------------------+
-///    (Uninit)                                      (Registered)
-/// ```
-///
-/// 1. The [`Device`] is in the [`Uninit`] context and is not guaranteed to be initialized or
-///    registered with userspace. Only a limited subset of DRM core functionality is available.
-/// 2. The [`Device`] is guaranteed to be fully initialized, but is not guaranteed to be registered
-///    with userspace. All DRM core functionality which doesn't interact with userspace is
-///    available. We currently don't have a context for representing this.
-/// 3. The [`Device`] is guaranteed to be fully initialized, and is guaranteed to have been
-///    registered with userspace at some point - thus putting it in the [`Registered`] context.
-///
-/// An important caveat of [`DeviceContext`] which must be kept in mind: when used as a typestate
-/// for a reference type, it can only guarantee that a [`Device`] reached a particular stage in the
-/// initialization process _at the time the reference was taken_. No guarantee is made in regards to
-/// what stage of the process the [`Device`] is currently in. This means for instance that a
-/// `&Device<T, Uninit>` may actually be registered with userspace, it just wasn't known to be
-/// registered at the time the reference was taken.
+/// Both `Device<T, Ioctl>` and `Device<T, Registered>` dereference to `Device<T>` ([`Normal`]),
+/// so any method available on a [`Normal`] device is also available in the other contexts.
 pub trait DeviceContext: Sealed + Send + Sync + 'static {}
 
-/// The [`DeviceContext`] of a [`Device`] that was registered with userspace at some point.
+/// The general-purpose, reference-counted [`DeviceContext`].
 ///
-/// This represents a [`Device`] which is guaranteed to have been registered with userspace at
-/// some point in time. Such a DRM device is guaranteed to have been fully-initialized.
+/// A [`Device`] in this context may or may not be registered with userspace. This context is used
+/// for reference-counted device handles and during device setup via [`UnregisteredDevice`].
+///
+/// [`AlwaysRefCounted`] is only implemented for `Device<T, Normal>`, making this the required
+/// context for [`ARef`]-based device handles.
+pub struct Normal;
+
+impl Sealed for Normal {}
+impl DeviceContext for Normal {}
+
+/// The [`DeviceContext`] of a [`Device`] that is currently registered with userspace.
 ///
-/// Note: A device in this context is not guaranteed to remain registered with userspace for its
-/// entire lifetime, as this is impossible to guarantee at compile-time.
+/// A [`Device`] in this context is guaranteed to be registered and its parent bus device is
+/// guaranteed to be bound. This is enforced at runtime by [`RegistrationGuard`], which holds a
+/// `drm_dev_enter()` / `drm_dev_exit()` SRCU critical section.
 ///
 /// # Invariants
 ///
-/// A [`Device`] in this [`DeviceContext`] is guaranteed to have been registered with userspace
-/// at some point in time.
+/// The parent bus device is bound for the duration of any reference to a `Device<T, Registered>`.
 pub struct Registered;
 
 impl Sealed for Registered {}
 impl DeviceContext for Registered {}
 
-/// The [`DeviceContext`] of a [`Device`] that may be unregistered and partly uninitialized.
+/// The [`DeviceContext`] of a [`Device`] that has been registered with userspace previously.
+///
+/// A [`Device`] in this context has been registered at some point, but may be concurrently
+/// unregistering or already unregistered. `drm_dev_enter()` can guard against this, ensuring the
+/// device remains registered for the duration of the critical section.
 ///
-/// A [`Device`] in this context is only guaranteed to be partly initialized, and may or may not
-/// be registered with userspace. Thus operations which depend on the [`Device`] being fully
-/// initialized, or which depend on the [`Device`] being registered with userspace are not
-/// available through this [`DeviceContext`].
+/// # Invariants
 ///
-/// A [`Device`] in this context can be used to create a
-/// [`Registration`](drm::driver::Registration).
-pub struct Uninit;
+/// A [`Device`] in this context has been registered with userspace via `drm_dev_register()` at
+/// some point.
+pub struct Ioctl;
 
-impl Sealed for Uninit {}
-impl DeviceContext for Uninit {}
+impl Sealed for Ioctl {}
+impl DeviceContext for Ioctl {}
 
 /// A [`Device`] which is known at compile-time to be unregistered with userspace.
 ///
@@ -147,10 +141,10 @@ impl DeviceContext for Uninit {}
 ///
 /// The device in `self.0` is guaranteed to be a newly created [`Device`] that has not yet been
 /// registered with userspace until this type is dropped.
-pub struct UnregisteredDevice<T: drm::Driver>(ARef<Device<T, Uninit>>, NotThreadSafe);
+pub struct UnregisteredDevice<T: drm::Driver>(ARef<Device<T, Normal>>, NotThreadSafe);
 
 impl<T: drm::Driver> Deref for UnregisteredDevice<T> {
-    type Target = Device<T, Uninit>;
+    type Target = Device<T, Normal>;
 
     fn deref(&self) -> &Self::Target {
         &self.0
@@ -178,15 +172,13 @@ impl<T: drm::Driver> UnregisteredDevice<T> {
         master_drop: None,
         debugfs_init: None,
 
-        // Ignore the Uninit DeviceContext below. It is only provided because it is required by the
-        // compiler, and it is not actually used by these functions.
-        gem_create_object: T::Object::<Uninit>::ALLOC_OPS.gem_create_object,
-        prime_handle_to_fd: T::Object::<Uninit>::ALLOC_OPS.prime_handle_to_fd,
-        prime_fd_to_handle: T::Object::<Uninit>::ALLOC_OPS.prime_fd_to_handle,
-        gem_prime_import: T::Object::<Uninit>::ALLOC_OPS.gem_prime_import,
-        gem_prime_import_sg_table: T::Object::<Uninit>::ALLOC_OPS.gem_prime_import_sg_table,
-        dumb_create: T::Object::<Uninit>::ALLOC_OPS.dumb_create,
-        dumb_map_offset: T::Object::<Uninit>::ALLOC_OPS.dumb_map_offset,
+        gem_create_object: T::Object::ALLOC_OPS.gem_create_object,
+        prime_handle_to_fd: T::Object::ALLOC_OPS.prime_handle_to_fd,
+        prime_fd_to_handle: T::Object::ALLOC_OPS.prime_fd_to_handle,
+        gem_prime_import: T::Object::ALLOC_OPS.gem_prime_import,
+        gem_prime_import_sg_table: T::Object::ALLOC_OPS.gem_prime_import_sg_table,
+        dumb_create: T::Object::ALLOC_OPS.dumb_create,
+        dumb_map_offset: T::Object::ALLOC_OPS.dumb_map_offset,
 
         show_fdinfo: None,
         fbdev_probe: None,
@@ -208,10 +200,13 @@ impl<T: drm::Driver> UnregisteredDevice<T> {
     /// Create a new `UnregisteredDevice` for a `drm::Driver`.
     ///
     /// This can be used to create a [`Registration`](kernel::drm::Registration).
-    pub fn new(dev: &device::Device, data: impl PinInit<T::Data, Error>) -> Result<Self> {
+    pub fn new(
+        dev: &T::ParentDevice<device::Bound>,
+        data: impl PinInit<T::Data, Error>,
+    ) -> Result<Self> {
         // `__drm_dev_alloc` uses `kmalloc()` to allocate memory, hence ensure a `kmalloc()`
         // compatible `Layout`.
-        let layout = Kmalloc::aligned_layout(Layout::new::<Device<T, Uninit>>());
+        let layout = Kmalloc::aligned_layout(Layout::new::<Device<T, Normal>>());
 
         // Use a temporary vtable without a `release` callback until `data` is initialized, so
         // init failure can release the DRM device without dropping uninitialized fields.
@@ -223,12 +218,12 @@ impl<T: drm::Driver> UnregisteredDevice<T> {
         // SAFETY:
         // - `alloc_vtable` reference remains valid until no longer used,
         // - `dev` is valid by its type invarants,
-        let raw_drm: *mut Device<T, Uninit> = unsafe {
+        let raw_drm: *mut Device<T, Normal> = unsafe {
             bindings::__drm_dev_alloc(
-                dev.as_raw(),
+                dev.as_ref().as_raw(),
                 &alloc_vtable,
                 layout.size(),
-                mem::offset_of!(Device<T, Uninit>, dev),
+                mem::offset_of!(Device<T, Normal>, dev),
             )
         }
         .cast();
@@ -253,6 +248,9 @@ impl<T: drm::Driver> UnregisteredDevice<T> {
         // SAFETY: `drm_dev` is still private to this function.
         unsafe { (*drm_dev).driver = const { &Self::VTABLE } };
 
+        // SAFETY: `raw_drm` is valid; no concurrent access before registration.
+        unsafe { (*raw_drm.as_ptr()).registration_data = UnsafeCell::new(NonNull::dangling()) };
+
         // SAFETY: The reference count is one, and now we take ownership of that reference as a
         // `drm::Device`.
         // INVARIANT: We just created the device above, but have yet to call `drm_dev_register`.
@@ -264,16 +262,8 @@ impl<T: drm::Driver> UnregisteredDevice<T> {
 
 /// A typed DRM device with a specific [`drm::Driver`] implementation and [`DeviceContext`].
 ///
-/// Since DRM devices can be used before being fully initialized and registered with userspace, `C`
-/// represents the furthest [`DeviceContext`] we can guarantee that this [`Device`] has reached.
-///
-/// Keep in mind: this means that an unregistered device can still have the registration state
-/// [`Registered`] as long as it was registered with userspace once in the past, and that the
-/// behavior of such a device is still well-defined. Additionally, a device with the registration
-/// state [`Uninit`] simply does not have a guaranteed registration state at compile time, and could
-/// be either registered or unregistered. Since there is no way to guarantee a long-lived reference
-/// to an unregistered device would remain unregistered, we do not provide a [`DeviceContext`] for
-/// this.
+/// A device in the [`Registered`] context is currently registered with userspace and its parent
+/// bus device is bound. The [`Normal`] context is the general-purpose, reference-counted context.
 ///
 /// # Invariants
 ///
@@ -281,9 +271,10 @@ impl<T: drm::Driver> UnregisteredDevice<T> {
 /// * The data layout of `Self` remains the same across all implementations of `C`.
 /// * Any invariants for `C` also apply.
 #[repr(C)]
-pub struct Device<T: drm::Driver, C: DeviceContext = Registered> {
+pub struct Device<T: drm::Driver, C: DeviceContext = Normal> {
     dev: Opaque<bindings::drm_device>,
     data: T::Data,
+    pub(super) registration_data: UnsafeCell<NonNull<T::RegistrationData<'static>>>,
     _ctx: PhantomData<C>,
 }
 
@@ -352,7 +343,111 @@ impl<T: drm::Driver, C: DeviceContext> Device<T, C> {
     }
 }
 
-impl<T: drm::Driver, C: DeviceContext> Deref for Device<T, C> {
+impl<T: drm::Driver> Device<T, Ioctl> {
+    /// Guard against the parent bus device being unbound.
+    ///
+    /// Returns a [`RegistrationGuard`] if the device has not been unplugged, [`None`] otherwise.
+    ///
+    /// While [`RegistrationGuard`] is held the parent device is guaranteed to be bound.
+    #[must_use]
+    pub fn registration_guard(&self) -> Option<RegistrationGuard<'_, T>> {
+        let mut idx: i32 = 0;
+        // SAFETY: `self.as_raw()` is a valid pointer to a `struct drm_device`.
+        if unsafe { bindings::drm_dev_enter(self.as_raw(), &mut idx) } {
+            // INVARIANT:
+            // - `idx` is the SRCU index from the successful `drm_dev_enter()` above.
+            // - The parent bus device is bound: `drm_dev_enter()` succeeded, meaning
+            //   `drm_dev_unplug()` has not completed; since it is only called from
+            //   `Registration::drop()` during parent unbind, the parent is still bound.
+            Some(RegistrationGuard {
+                // SAFETY: See INVARIANT above; the `Registered` context invariant holds.
+                dev: unsafe { self.assume_ctx() },
+                idx,
+                _not_send: NotThreadSafe,
+            })
+        } else {
+            None
+        }
+    }
+}
+
+/// A guard proving the DRM device is registered and the parent bus device is bound.
+///
+/// The guard dereferences to [`Device<T, Registered>`], providing access to the DRM device with
+/// the guarantee that the parent bus device is bound for the entire duration of the critical
+/// section.
+///
+/// Internally this is backed by a `drm_dev_enter()` / `drm_dev_exit()` SRCU critical section.
+///
+/// # Invariants
+///
+/// - `idx` is the SRCU read lock index returned by a successful `drm_dev_enter()` call.
+/// - The parent bus device of `dev` is bound for the lifetime of this guard.
+#[must_use]
+pub struct RegistrationGuard<'a, T: drm::Driver> {
+    dev: &'a Device<T, Registered>,
+    idx: i32,
+    _not_send: NotThreadSafe,
+}
+
+impl<T: drm::Driver> Device<T, Registered> {
+    /// Returns a reference to the registration data with lifetime shortened from `'static`.
+    ///
+    /// # Safety
+    ///
+    /// The returned reference must not be exposed to code that can choose a concrete lifetime for
+    /// it, as that would be unsound for types that are invariant over their lifetime parameter
+    /// (e.g. it must be passed through an HRTB-bounded closure).
+    #[inline]
+    unsafe fn registration_data_unchecked(&self) -> &T::RegistrationData<'_> {
+        // SAFETY:
+        // - `Registered` guarantees the parent bus device is bound, hence the pointer is valid.
+        // - The pointer cast from `Of<'static>` to `Of<'_>` is layout-compatible since lifetimes
+        //   are erased at runtime.
+        // - Caller guarantees the reference is only used behind an HRTB, making the lifetime
+        //   shortening sound regardless of variance.
+        unsafe { (*self.registration_data.get()).cast::<_>().as_ref() }
+    }
+
+    /// Access the registration data through a closure, with the lifetime tied to the closure
+    /// scope.
+    ///
+    /// The data is owned by [`Registration`](drm::Registration) and is guaranteed to remain valid
+    /// as long as the device is registered, since [`Registration`](drm::Registration)'s `drop`
+    /// calls `drm_dev_unplug()` which waits for all `drm_dev_enter()` critical sections to
+    /// complete.
+    #[inline]
+    pub fn registration_data_with<R, F>(&self, f: F) -> R
+    where
+        F: for<'a> FnOnce(&'a T::RegistrationData<'a>) -> R,
+    {
+        // SAFETY: `Registered` guarantees the device is registered and the parent bus device is
+        // bound. The closure's HRTB `for<'a>` prevents the caller from smuggling in references
+        // with a concrete short lifetime, satisfying the lifetime requirement of
+        // `registration_data_unchecked`.
+        f(unsafe { self.registration_data_unchecked() })
+    }
+}
+
+impl<T: drm::Driver> Deref for RegistrationGuard<'_, T> {
+    type Target = Device<T, Registered>;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        self.dev
+    }
+}
+
+impl<T: drm::Driver> Drop for RegistrationGuard<'_, T> {
+    #[inline]
+    fn drop(&mut self) {
+        // SAFETY: `self.idx` was returned by a successful `drm_dev_enter()` call, as guaranteed
+        // by the type invariants of `RegistrationGuard`.
+        unsafe { bindings::drm_dev_exit(self.idx) };
+    }
+}
+
+impl<T: drm::Driver> Deref for Device<T> {
     type Target = T::Data;
 
     fn deref(&self) -> &Self::Target {
@@ -360,9 +455,31 @@ impl<T: drm::Driver, C: DeviceContext> Deref for Device<T, C> {
     }
 }
 
+impl<T: drm::Driver> Deref for Device<T, Registered> {
+    type Target = Device<T>;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        // SAFETY: The caller holds a `Device<T, Registered>`, which guarantees all invariants
+        // of the weaker `Normal` context.
+        unsafe { self.assume_ctx() }
+    }
+}
+
+impl<T: drm::Driver> Deref for Device<T, Ioctl> {
+    type Target = Device<T>;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        // SAFETY: The caller holds a `Device<T, Ioctl>`, which guarantees all invariants
+        // of the weaker `Normal` context.
+        unsafe { self.assume_ctx() }
+    }
+}
+
 // SAFETY: DRM device objects are always reference counted and the get/put functions
 // satisfy the requirements.
-unsafe impl<T: drm::Driver, C: DeviceContext> AlwaysRefCounted for Device<T, C> {
+unsafe impl<T: drm::Driver> AlwaysRefCounted for Device<T> {
     fn inc_ref(&self) {
         // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
         unsafe { bindings::drm_dev_get(self.as_raw()) };
@@ -377,11 +494,29 @@ unsafe impl<T: drm::Driver, C: DeviceContext> AlwaysRefCounted for Device<T, C>
     }
 }
 
-impl<T: drm::Driver, C: DeviceContext> AsRef<device::Device> for Device<T, C> {
-    fn as_ref(&self) -> &device::Device {
+impl<T: drm::Driver> AsRef<T::ParentDevice<device::Normal>> for Device<T> {
+    fn as_ref(&self) -> &T::ParentDevice<device::Normal> {
         // SAFETY: `bindings::drm_device::dev` is valid as long as the DRM device itself is valid,
         // which is guaranteed by the type invariant.
-        unsafe { device::Device::from_raw((*self.as_raw()).dev) }
+        let dev = unsafe { device::Device::from_raw((*self.as_raw()).dev) };
+
+        // SAFETY: The DRM device was constructed in `UnregisteredDevice::new()` with a parent
+        // device of type `T::ParentDevice`, hence `dev` is contained in a `T::ParentDevice`.
+        unsafe { device::AsBusDevice::from_device(dev) }
+    }
+}
+
+impl<T: drm::Driver> AsRef<T::ParentDevice<device::Bound>> for Device<T, Registered> {
+    #[inline]
+    fn as_ref(&self) -> &T::ParentDevice<device::Bound> {
+        let dev = (**self).as_ref().as_ref();
+
+        // SAFETY: A `Device<T, Registered>` guarantees that the parent device is bound.
+        let dev = unsafe { dev.as_bound() };
+
+        // SAFETY: The DRM device was constructed in `UnregisteredDevice::new()` with a parent
+        // device of type `T::ParentDevice`, hence `dev` is contained in a `T::ParentDevice`.
+        unsafe { device::AsBusDevice::from_device(dev) }
     }
 }
 
@@ -392,12 +527,10 @@ unsafe impl<T: drm::Driver, C: DeviceContext> Send for Device<T, C> {}
 // by the synchronization in `struct drm_device`.
 unsafe impl<T: drm::Driver, C: DeviceContext> Sync for Device<T, C> {}
 
-impl<T, C, const ID: u64> WorkItem<ID> for Device<T, C>
+impl<T: drm::Driver, const ID: u64> WorkItem<ID> for Device<T>
 where
-    T: drm::Driver,
     T::Data: WorkItem<ID, Pointer = ARef<Self>>,
     T::Data: HasWork<Self, ID>,
-    C: DeviceContext,
 {
     type Pointer = ARef<Self>;
 
diff --git a/rust/kernel/drm/driver.rs b/rust/kernel/drm/driver.rs
index 25f7e233884d..08b2a318cf02 100644
--- a/rust/kernel/drm/driver.rs
+++ b/rust/kernel/drm/driver.rs
@@ -7,16 +7,12 @@
 use crate::{
     bindings,
     device,
-    devres,
     drm,
     error::to_result,
     prelude::*,
     sync::aref::ARef, //
 };
-use core::{
-    mem,
-    ptr::NonNull, //
-};
+use core::ptr::NonNull;
 
 /// Driver use the GEM memory manager. This should be set for all modern drivers.
 pub(crate) const FEAT_GEM: u32 = bindings::drm_driver_feature_DRIVER_GEM;
@@ -110,12 +106,23 @@ pub trait Driver {
     /// Context data associated with the DRM driver
     type Data: Sync + Send;
 
+    /// Data owned by the [`Registration`] and accessible within a
+    /// [`RegistrationGuard`](drm::RegistrationGuard) critical section via
+    /// [`Device::registration_data_with()`](drm::Device::registration_data_with).
+    ///
+    /// The lifetime parameter is tied to the [`Registration`] scope, which is enclosed in the
+    /// parent bus device binding scope but may be shorter.
+    type RegistrationData<'a>: Send + Sync + 'a;
+
     /// The type used to manage memory for this driver.
-    type Object<Ctx: drm::DeviceContext>: AllocImpl;
+    type Object: AllocImpl;
 
     /// The type used to represent a DRM File (client)
     type File: drm::file::DriverFile;
 
+    /// The bus device type of the parent device that the DRM device is associated with.
+    type ParentDevice<Ctx: device::DeviceContext>: device::AsBusDevice<Ctx>;
+
     /// Driver metadata
     const INFO: DriverInfo;
 
@@ -136,68 +143,84 @@ pub trait Driver {
 /// The registration type of a `drm::Device`.
 ///
 /// Once the `Registration` structure is dropped, the device is unregistered.
-pub struct Registration<T: Driver>(ARef<drm::Device<T>>);
-
-impl<T: Driver> Registration<T> {
-    fn new(drm: drm::UnregisteredDevice<T>, flags: usize) -> Result<Self> {
-        // SAFETY: `drm.as_raw()` is valid by the invariants of `drm::Device`.
-        to_result(unsafe { bindings::drm_dev_register(drm.as_raw(), flags) })?;
-
-        // SAFETY: We just called `drm_dev_register` above
-        let new = NonNull::from(unsafe { drm.assume_ctx() });
-
-        // Leak the ARef from UnregisteredDevice in preparation for transferring its ownership.
-        mem::forget(drm);
-
-        // SAFETY: `drm`'s `Drop` constructor was never called, ensuring that there remains at least
-        // one reference to the device - which we take ownership over here.
-        let new = unsafe { ARef::from_raw(new) };
-
-        Ok(Self(new))
-    }
+pub struct Registration<'a, T: Driver> {
+    drm: ARef<drm::Device<T>>,
+    _reg_data: Pin<KBox<T::RegistrationData<'a>>>,
+}
 
-    /// Registers a new [`UnregisteredDevice`](drm::UnregisteredDevice) with userspace.
+impl<'a, T: Driver> Registration<'a, T> {
+    /// Register a new [`UnregisteredDevice`](drm::UnregisteredDevice) with userspace.
     ///
-    /// Ownership of the [`Registration`] object is passed to [`devres::register`].
-    pub fn new_foreign_owned<'a>(
-        drm: drm::UnregisteredDevice<T>,
+    /// # Safety
+    ///
+    /// The caller must not `mem::forget()` the returned [`Registration`] or otherwise prevent its
+    /// [`Drop`] implementation from running, since the registration data may contain borrowed
+    /// references that become invalid after `'a` ends.
+    pub unsafe fn new<E>(
         dev: &'a device::Device<device::Bound>,
+        drm: drm::UnregisteredDevice<T>,
+        reg_data: impl PinInit<T::RegistrationData<'a>, E>,
         flags: usize,
-    ) -> Result<&'a drm::Device<T>>
+    ) -> Result<Self>
     where
-        T: 'static,
+        Error: From<E>,
     {
-        if drm.as_ref().as_raw() != dev.as_raw() {
+        let parent = drm.as_ref();
+        if parent.as_ref().as_raw() != dev.as_raw() {
             return Err(EINVAL);
         }
 
-        let reg = Registration::<T>::new(drm, flags)?;
-        let drm = NonNull::from(reg.device());
+        let reg_data: Pin<KBox<T::RegistrationData<'a>>> = KBox::pin_init(reg_data, GFP_KERNEL)?;
+
+        // Store the registration data pointer in the device before registration, so that it is
+        // visible once ioctls can be called.
+        let ptr: NonNull<T::RegistrationData<'static>> =
+            NonNull::from(Pin::get_ref(reg_data.as_ref())).cast();
 
-        devres::register(dev, reg, GFP_KERNEL)?;
+        // SAFETY: No concurrent access; the device is not yet registered.
+        unsafe { *drm.registration_data.get() = ptr };
+
+        // SAFETY: `drm` is a valid, initialized but not yet registered DRM device.
+        let ret = unsafe { bindings::drm_dev_register(drm.as_raw(), flags) };
+        if let Err(e) = to_result(ret) {
+            // SAFETY: `drm_dev_register()` synchronizes SRCU on failure, so no concurrent
+            // access to `registration_data` is possible at this point.
+            unsafe { *drm.registration_data.get() = NonNull::dangling() };
+            return Err(e);
+        }
 
-        // SAFETY: Since `reg` was passed to devres::register(), the device now owns the lifetime
-        // of the DRM registration - ensuring that this references lives for at least as long as 'a.
-        Ok(unsafe { drm.as_ref() })
+        Ok(Self {
+            drm: (&*drm).into(),
+            _reg_data: reg_data,
+        })
     }
 
     /// Returns a reference to the `Device` instance for this registration.
     pub fn device(&self) -> &drm::Device<T> {
-        &self.0
+        &self.drm
     }
 }
 
 // SAFETY: `Registration` doesn't offer any methods or access to fields when shared between
 // threads, hence it's safe to share it.
-unsafe impl<T: Driver> Sync for Registration<T> {}
+unsafe impl<T: Driver> Sync for Registration<'_, T> {}
 
 // SAFETY: Registration with and unregistration from the DRM subsystem can happen from any thread.
-unsafe impl<T: Driver> Send for Registration<T> {}
+unsafe impl<T: Driver> Send for Registration<'_, T> {}
 
-impl<T: Driver> Drop for Registration<T> {
+impl<T: Driver> Drop for Registration<'_, T> {
     fn drop(&mut self) {
+        // Use `drm_dev_unplug` rather than `drm_dev_unregister` to ensure that existing
+        // `drm_dev_enter()` critical sections complete before unregistration proceeds. This
+        // is required for the safety of `RegistrationGuard`, which relies on the SRCU barrier in
+        // `drm_dev_unplug()` to guarantee that the parent device is still bound within the
+        // critical section.
+        //
         // SAFETY: Safe by the invariant of `ARef<drm::Device<T>>`. The existence of this
-        // `Registration` also guarantees the this `drm::Device` is actually registered.
-        unsafe { bindings::drm_dev_unregister(self.0.as_raw()) };
+        // `Registration` also guarantees that this `drm::Device` is actually registered.
+        unsafe { bindings::drm_dev_unplug(self.drm.as_raw()) };
+        // After drm_dev_unplug(), the SRCU barrier guarantees that all RegistrationGuard critical
+        // sections have completed, so no one holds a reference to reg_data anymore.
+        // reg_data is dropped here automatically.
     }
 }
diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index 48fa6e96dfe7..b03b5f9ccd7e 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -10,7 +10,7 @@ use crate::{
         self,
         device::{
             DeviceContext,
-            Registered, //
+            Normal, //
         },
         driver::{
             AllocImpl,
@@ -81,8 +81,7 @@ pub type DriverFile<T> = drm::File<<<T as DriverObject>::Driver as drm::Driver>:
 /// A type alias for retrieving the current [`AllocImpl`] for a given [`DriverObject`].
 ///
 /// [`Driver`]: drm::Driver
-pub type DriverAllocImpl<T, Ctx = Registered> =
-    <<T as DriverObject>::Driver as drm::Driver>::Object<Ctx>;
+pub type DriverAllocImpl<T> = <<T as DriverObject>::Driver as drm::Driver>::Object;
 
 /// GEM object functions, which must be implemented by drivers.
 pub trait DriverObject: Sync + Send + Sized + 'static {
@@ -93,8 +92,8 @@ pub trait DriverObject: Sync + Send + Sized + 'static {
     type Args;
 
     /// Create a new driver data object for a GEM object of a given size.
-    fn new<Ctx: DeviceContext>(
-        dev: &drm::Device<Self::Driver, Ctx>,
+    fn new(
+        dev: &drm::Device<Self::Driver>,
         size: usize,
         args: Self::Args,
     ) -> impl PinInit<Self, Error>;
@@ -109,7 +108,7 @@ pub trait DriverObject: Sync + Send + Sized + 'static {
 }
 
 /// Trait that represents a GEM object subtype
-pub trait IntoGEMObject: Sized + super::private::Sealed + AlwaysRefCounted {
+pub trait IntoGEMObject: Sized + super::private::Sealed {
     /// Returns a reference to the raw `drm_gem_object` structure, which must be valid as long as
     /// this owning object is valid.
     fn as_raw(&self) -> *mut bindings::drm_gem_object;
@@ -183,7 +182,7 @@ pub trait BaseObject: IntoGEMObject {
     fn create_handle<D, F>(&self, file: &drm::File<F>) -> Result<u32>
     where
         Self: AllocImpl<Driver = D>,
-        D: drm::Driver<Object<Registered> = Self, File = F>,
+        D: drm::Driver<Object = Self, File = F>,
         F: drm::file::DriverFile<Driver = D>,
     {
         let mut handle: u32 = 0;
@@ -197,8 +196,8 @@ pub trait BaseObject: IntoGEMObject {
     /// Looks up an object by its handle for a given `File`.
     fn lookup_handle<D, F>(file: &drm::File<F>, handle: u32) -> Result<ARef<Self>>
     where
-        Self: AllocImpl<Driver = D>,
-        D: drm::Driver<Object<Registered> = Self, File = F>,
+        Self: AllocImpl<Driver = D> + AlwaysRefCounted,
+        D: drm::Driver<Object = Self, File = F>,
         F: drm::file::DriverFile<Driver = D>,
     {
         // SAFETY: The arguments are all valid per the type invariants.
@@ -254,7 +253,7 @@ impl<T: IntoGEMObject> BaseObjectPrivate for T {}
 /// * Any type invariants of `Ctx` apply to the parent DRM device for this GEM object.
 #[repr(C)]
 #[pin_data]
-pub struct Object<T: DriverObject + Send + Sync, Ctx: DeviceContext = Registered> {
+pub struct Object<T: DriverObject + Send + Sync, Ctx: DeviceContext = Normal> {
     obj: Opaque<bindings::drm_gem_object>,
     #[pin]
     data: T,
@@ -280,12 +279,43 @@ impl<T: DriverObject, Ctx: DeviceContext> Object<T, Ctx> {
         rss: None,
     };
 
+    /// Returns the `Device` that owns this GEM object.
+    pub fn dev(&self) -> &drm::Device<T::Driver, Ctx> {
+        // SAFETY:
+        // - `struct drm_gem_object.dev` is initialized and valid for as long as the GEM
+        //   object lives.
+        // - The device we used for creating the gem object is passed as &drm::Device<T::Driver> to
+        //   Object::<T>::new(), so we know that `T::Driver` is the right generic parameter to use
+        //   here.
+        // - Any type invariants of `Ctx` are upheld by using the same `Ctx` for the `Device` we
+        //   return.
+        unsafe { drm::Device::from_raw((*self.as_raw()).dev) }
+    }
+
+    fn as_raw(&self) -> *mut bindings::drm_gem_object {
+        self.obj.get()
+    }
+
+    extern "C" fn free_callback(obj: *mut bindings::drm_gem_object) {
+        let ptr: *mut Opaque<bindings::drm_gem_object> = obj.cast();
+
+        // SAFETY: All of our objects are of type `Object<T>`.
+        let this = unsafe { crate::container_of!(ptr, Self, obj) };
+
+        // SAFETY: The C code only ever calls this callback with a valid pointer to a `struct
+        // drm_gem_object`.
+        unsafe { bindings::drm_gem_object_release(obj) };
+
+        // SAFETY: All of our objects are allocated via `KBox`, and we're in the
+        // free callback which guarantees this object has zero remaining references,
+        // so we can drop it.
+        let _ = unsafe { KBox::from_raw(this) };
+    }
+}
+
+impl<T: DriverObject> Object<T> {
     /// Create a new GEM object.
-    pub fn new(
-        dev: &drm::Device<T::Driver, Ctx>,
-        size: usize,
-        args: T::Args,
-    ) -> Result<ARef<Self>> {
+    pub fn new(dev: &drm::Device<T::Driver>, size: usize, args: T::Args) -> Result<ARef<Self>> {
         let obj: Pin<KBox<Self>> = KBox::pin_init(
             try_pin_init!(Self {
                 obj: Opaque::new(bindings::drm_gem_object::default()),
@@ -321,46 +351,12 @@ impl<T: DriverObject, Ctx: DeviceContext> Object<T, Ctx> {
         // SAFETY: We take over the initial reference count from `drm_gem_object_init()`.
         Ok(unsafe { ARef::from_raw(ptr) })
     }
-
-    /// Returns the `Device` that owns this GEM object.
-    pub fn dev(&self) -> &drm::Device<T::Driver, Ctx> {
-        // SAFETY:
-        // - `struct drm_gem_object.dev` is initialized and valid for as long as the GEM
-        //   object lives.
-        // - The device we used for creating the gem object is passed as &drm::Device<T::Driver> to
-        //   Object::<T>::new(), so we know that `T::Driver` is the right generic parameter to use
-        //   here.
-        // - Any type invariants of `Ctx` are upheld by using the same `Ctx` for the `Device` we
-        //   return.
-        unsafe { drm::Device::from_raw((*self.as_raw()).dev) }
-    }
-
-    fn as_raw(&self) -> *mut bindings::drm_gem_object {
-        self.obj.get()
-    }
-
-    extern "C" fn free_callback(obj: *mut bindings::drm_gem_object) {
-        let ptr: *mut Opaque<bindings::drm_gem_object> = obj.cast();
-
-        // SAFETY: All of our objects are of type `Object<T>`.
-        let this = unsafe { crate::container_of!(ptr, Self, obj) };
-
-        // SAFETY: The C code only ever calls this callback with a valid pointer to a `struct
-        // drm_gem_object`.
-        unsafe { bindings::drm_gem_object_release(obj) };
-
-        // SAFETY: All of our objects are allocated via `KBox`, and we're in the
-        // free callback which guarantees this object has zero remaining references,
-        // so we can drop it.
-        let _ = unsafe { KBox::from_raw(this) };
-    }
 }
 
 impl_aref_for_gem_obj! {
-    impl<T, C> for Object<T, C>
+    impl<T> for Object<T>
     where
-        T: DriverObject,
-        C: DeviceContext
+        T: DriverObject
 }
 
 impl<T: DriverObject, Ctx: DeviceContext> super::private::Sealed for Object<T, Ctx> {}
diff --git a/rust/kernel/drm/gem/shmem.rs b/rust/kernel/drm/gem/shmem.rs
index 3ee19ef6264e..60dca8871b87 100644
--- a/rust/kernel/drm/gem/shmem.rs
+++ b/rust/kernel/drm/gem/shmem.rs
@@ -20,9 +20,7 @@ use crate::{
         driver,
         gem,
         private::Sealed,
-        Device,
-        DeviceContext,
-        Registered, //
+        Device, //
     },
     error::{
         from_err_ptr,
@@ -48,7 +46,6 @@ use crate::{
 };
 use core::{
     ffi::c_void,
-    marker::PhantomData,
     mem::{
         ManuallyDrop,
         MaybeUninit, //
@@ -73,17 +70,17 @@ use gem::{
 ///
 /// This is used with [`Object::new()`] to control various properties that can only be set when
 /// initially creating a shmem-backed GEM object.
-pub struct ObjectConfig<'a, T: DriverObject, C: DeviceContext = Registered> {
+pub struct ObjectConfig<'a, T: DriverObject> {
     /// Whether to set the write-combine map flag.
     pub map_wc: bool,
 
     /// Reuse the DMA reservation from another GEM object.
     ///
     /// The newly created [`Object`] will hold an owned refcount to `parent_resv_obj` if specified.
-    pub parent_resv_obj: Option<&'a Object<T, C>>,
+    pub parent_resv_obj: Option<&'a Object<T>>,
 }
 
-impl<'a, T: DriverObject, C: DeviceContext> Default for ObjectConfig<'a, T, C> {
+impl<'a, T: DriverObject> Default for ObjectConfig<'a, T> {
     #[inline(always)]
     fn default() -> Self {
         Self {
@@ -99,38 +96,35 @@ impl<'a, T: DriverObject, C: DeviceContext> Default for ObjectConfig<'a, T, C> {
 ///
 /// - `obj` contains a valid initialized `struct drm_gem_shmem_object` for the lifetime of this
 ///   object.
-/// - Any type invariants of `C` apply to the parent DRM device for this GEM object.
 #[repr(C)]
 #[pin_data]
-pub struct Object<T: DriverObject, C: DeviceContext = Registered> {
+pub struct Object<T: DriverObject> {
     #[pin]
     obj: Opaque<bindings::drm_gem_shmem_object>,
     /// Parent object that owns this object's DMA reservation object.
-    parent_resv_obj: Option<ARef<Object<T, C>>>,
+    parent_resv_obj: Option<ARef<Object<T>>>,
     /// Devres object for unmapping any SGTable on driver-unbind.
-    sgt_res: ManuallyDrop<SetOnce<Devres<SGTableMap<T, C>>>>,
+    sgt_res: ManuallyDrop<SetOnce<Devres<SGTableMap<T>>>>,
     #[pin]
     /// Lock for protecting initialization of `sgt_res`.
     sgt_lock: Mutex<()>,
     #[pin]
     inner: T,
-    _ctx: PhantomData<C>,
 }
 
 super::impl_aref_for_gem_obj! {
-    impl<T, C> for Object<T, C>
+    impl<T> for Object<T>
     where
-        T: DriverObject,
-        C: DeviceContext
+        T: DriverObject
 }
 
 // SAFETY: All GEM objects are thread-safe.
-unsafe impl<T: DriverObject, C: DeviceContext> Send for Object<T, C> {}
+unsafe impl<T: DriverObject> Send for Object<T> {}
 
 // SAFETY: All GEM objects are thread-safe.
-unsafe impl<T: DriverObject, C: DeviceContext> Sync for Object<T, C> {}
+unsafe impl<T: DriverObject> Sync for Object<T> {}
 
-impl<T: DriverObject, C: DeviceContext> Object<T, C> {
+impl<T: DriverObject> Object<T> {
     /// `drm_gem_object_funcs` vtable suitable for GEM shmem objects.
     const VTABLE: bindings::drm_gem_object_funcs = bindings::drm_gem_object_funcs {
         free: Some(Self::free_callback),
@@ -157,56 +151,8 @@ impl<T: DriverObject, C: DeviceContext> Object<T, C> {
         self.obj.get()
     }
 
-    /// Create a new shmem-backed DRM object of the given size.
-    ///
-    /// Additional config options can be specified using `config`.
-    pub fn new(
-        dev: &Device<T::Driver, C>,
-        size: usize,
-        config: ObjectConfig<'_, T, C>,
-        args: T::Args,
-    ) -> Result<ARef<Self>> {
-        let new: Pin<KBox<Self>> = KBox::try_pin_init(
-            try_pin_init!(Self {
-                obj <- Opaque::init_zeroed(),
-                parent_resv_obj: config.parent_resv_obj.map(|p| p.into()),
-                sgt_res: ManuallyDrop::new(SetOnce::new()),
-                sgt_lock <- new_mutex!(()),
-                inner <- T::new(dev, size, args),
-                _ctx: PhantomData::<C>,
-            }),
-            GFP_KERNEL,
-        )?;
-
-        // SAFETY: `obj.as_raw()` is guaranteed to be valid by the initialization above.
-        unsafe { (*new.as_raw()).funcs = &Self::VTABLE };
-
-        // SAFETY: The arguments are all valid via the type invariants.
-        to_result(unsafe { bindings::drm_gem_shmem_init(dev.as_raw(), new.as_raw_shmem(), size) })?;
-
-        // SAFETY: We never move out of `self`.
-        let new = KBox::into_raw(unsafe { Pin::into_inner_unchecked(new) });
-
-        // SAFETY: We're taking over the owned refcount from `drm_gem_shmem_init`.
-        let obj = unsafe { ARef::from_raw(NonNull::new_unchecked(new)) };
-
-        // Start filling out values from `config`
-        if let Some(parent_resv) = config.parent_resv_obj {
-            // SAFETY: We have yet to expose the new gem object outside of this function, so it is
-            // safe to modify this field.
-            unsafe { (*obj.obj.get()).base.resv = parent_resv.raw_dma_resv() };
-        }
-
-        // SAFETY: We have yet to expose this object outside of this function, so we're guaranteed
-        // to have exclusive access - thus making this safe to hold a mutable reference to.
-        let shmem = unsafe { &mut *obj.as_raw_shmem() };
-        shmem.set_map_wc(config.map_wc);
-
-        Ok(obj)
-    }
-
     /// Returns the `Device` that owns this GEM object.
-    pub fn dev(&self) -> &Device<T::Driver, C> {
+    pub fn dev(&self) -> &Device<T::Driver> {
         // SAFETY: `dev` will have been initialized in `Self::new()` by `drm_gem_shmem_init()`.
         unsafe { Device::from_raw((*self.as_raw()).dev) }
     }
@@ -220,8 +166,8 @@ impl<T: DriverObject, C: DeviceContext> Object<T, C> {
 
         // SAFETY:
         // - We verified above that `obj` is valid, which makes `this` valid
-        // - This function is set in AllocOps, so we know that `this` is contained within a
-        //   `Object<T, C>`
+        // - This function is set in AllocOps, so we know that `this` is contained within an
+        //   `Object<T>`
         let this = unsafe { container_of!(Opaque::cast_from(base), Self, obj) }.cast_mut();
 
         // We need to drop `sgt_res` first, since doing so requires that the GEM object is still
@@ -242,7 +188,7 @@ impl<T: DriverObject, C: DeviceContext> Object<T, C> {
     }
 
     /// Attempt to create a vmap from the gem object, and confirm the size of said vmap.
-    fn make_vmap<'a, R, const SIZE: usize>(&'a self) -> Result<VMap<T, R, C, SIZE>>
+    fn make_vmap<'a, R, const SIZE: usize>(&'a self) -> Result<VMap<T, R, SIZE>>
     where
         R: Deref<Target = Self> + From<&'a Self>,
     {
@@ -304,13 +250,7 @@ impl<T: DriverObject, C: DeviceContext> Object<T, C> {
 
     /// Creates and returns a virtual kernel memory mapping for this object.
     #[inline]
-    pub fn vmap<const SIZE: usize>(&self) -> Result<VMapRef<'_, T, C, SIZE>> {
-        self.make_vmap()
-    }
-
-    /// Creates and returns an owned reference to a virtual kernel memory mapping for this object.
-    #[inline]
-    pub fn owned_vmap<const SIZE: usize>(&self) -> Result<VMapOwned<T, C, SIZE>> {
+    pub fn vmap<const SIZE: usize>(&self) -> Result<VMapRef<'_, T, SIZE>> {
         self.make_vmap()
     }
 
@@ -324,7 +264,8 @@ impl<T: DriverObject, C: DeviceContext> Object<T, C> {
         &'a self,
         dev: &'a device::Device<Bound>,
     ) -> Result<&'a scatterlist::SGTable> {
-        if dev.as_raw() != self.dev().as_ref().as_raw() {
+        let parent = self.dev().as_ref();
+        if dev.as_raw() != parent.as_ref().as_raw() {
             return Err(EINVAL);
         }
 
@@ -353,9 +294,62 @@ impl<T: DriverObject, C: DeviceContext> Object<T, C> {
 
         Ok(sgt_res.access(dev)?)
     }
+
+    /// Create a new shmem-backed DRM object of the given size.
+    ///
+    /// Additional config options can be specified using `config`.
+    pub fn new(
+        dev: &Device<T::Driver>,
+        size: usize,
+        config: ObjectConfig<'_, T>,
+        args: T::Args,
+    ) -> Result<ARef<Self>> {
+        let new: Pin<KBox<Self>> = KBox::try_pin_init(
+            try_pin_init!(Self {
+                obj <- Opaque::init_zeroed(),
+                parent_resv_obj: config.parent_resv_obj.map(|p| p.into()),
+                sgt_res: ManuallyDrop::new(SetOnce::new()),
+                sgt_lock <- new_mutex!(()),
+                inner <- T::new(dev, size, args),
+            }),
+            GFP_KERNEL,
+        )?;
+
+        // SAFETY: `obj.as_raw()` is guaranteed to be valid by the initialization above.
+        unsafe { (*new.as_raw()).funcs = &Self::VTABLE };
+
+        // SAFETY: The arguments are all valid via the type invariants.
+        to_result(unsafe { bindings::drm_gem_shmem_init(dev.as_raw(), new.as_raw_shmem(), size) })?;
+
+        // SAFETY: We never move out of `self`.
+        let new = KBox::into_raw(unsafe { Pin::into_inner_unchecked(new) });
+
+        // SAFETY: We're taking over the owned refcount from `drm_gem_shmem_init`.
+        let obj = unsafe { ARef::from_raw(NonNull::new_unchecked(new)) };
+
+        // Start filling out values from `config`
+        if let Some(parent_resv) = config.parent_resv_obj {
+            // SAFETY: We have yet to expose the new gem object outside of this function, so it is
+            // safe to modify this field.
+            unsafe { (*obj.obj.get()).base.resv = parent_resv.raw_dma_resv() };
+        }
+
+        // SAFETY: We have yet to expose this object outside of this function, so we're guaranteed
+        // to have exclusive access - thus making this safe to hold a mutable reference to.
+        let shmem = unsafe { &mut *obj.as_raw_shmem() };
+        shmem.set_map_wc(config.map_wc);
+
+        Ok(obj)
+    }
+
+    /// Creates and returns an owned reference to a virtual kernel memory mapping for this object.
+    #[inline]
+    pub fn owned_vmap<const SIZE: usize>(&self) -> Result<VMapOwned<T, SIZE>> {
+        self.make_vmap()
+    }
 }
 
-impl<T: DriverObject, C: DeviceContext> Deref for Object<T, C> {
+impl<T: DriverObject> Deref for Object<T> {
     type Target = T;
 
     fn deref(&self) -> &Self::Target {
@@ -363,15 +357,15 @@ impl<T: DriverObject, C: DeviceContext> Deref for Object<T, C> {
     }
 }
 
-impl<T: DriverObject, C: DeviceContext> DerefMut for Object<T, C> {
+impl<T: DriverObject> DerefMut for Object<T> {
     fn deref_mut(&mut self) -> &mut Self::Target {
         &mut self.inner
     }
 }
 
-impl<T: DriverObject, C: DeviceContext> Sealed for Object<T, C> {}
+impl<T: DriverObject> Sealed for Object<T> {}
 
-impl<T: DriverObject, C: DeviceContext> gem::IntoGEMObject for Object<T, C> {
+impl<T: DriverObject> gem::IntoGEMObject for Object<T> {
     fn as_raw(&self) -> *mut bindings::drm_gem_object {
         // SAFETY:
         // - Our immutable reference is proof that this is safe to dereference.
@@ -390,7 +384,7 @@ impl<T: DriverObject, C: DeviceContext> gem::IntoGEMObject for Object<T, C> {
     }
 }
 
-impl<T: DriverObject, C: DeviceContext> driver::AllocImpl for Object<T, C> {
+impl<T: DriverObject> driver::AllocImpl for Object<T> {
     type Driver = T::Driver;
 
     const ALLOC_OPS: driver::AllocOps = driver::AllocOps {
@@ -409,14 +403,11 @@ impl<T: DriverObject, C: DeviceContext> driver::AllocImpl for Object<T, C> {
 /// When this is dropped, the `dma_resv` lock is dropped as well.
 ///
 // TODO: This should be replace with a WwMutex equivalent once we have such bindings in the kernel.
-struct DmaResvGuard<'a, T: DriverObject, C: DeviceContext = Registered>(
-    &'a Object<T, C>,
-    NotThreadSafe,
-);
+struct DmaResvGuard<'a, T: DriverObject>(&'a Object<T>, NotThreadSafe);
 
-impl<'a, T: DriverObject, C: DeviceContext> DmaResvGuard<'a, T, C> {
+impl<'a, T: DriverObject> DmaResvGuard<'a, T> {
     #[inline]
-    fn new(obj: &'a Object<T, C>) -> Self {
+    fn new(obj: &'a Object<T>) -> Self {
         // SAFETY: This lock is initialized throughout the lifetime of `object`.
         unsafe { bindings::dma_resv_lock(obj.raw_dma_resv(), ptr::null_mut()) };
 
@@ -424,7 +415,7 @@ impl<'a, T: DriverObject, C: DeviceContext> DmaResvGuard<'a, T, C> {
     }
 }
 
-impl<'a, T: DriverObject, C: DeviceContext> Drop for DmaResvGuard<'a, T, C> {
+impl<'a, T: DriverObject> Drop for DmaResvGuard<'a, T> {
     #[inline]
     fn drop(&mut self) {
         // SAFETY: We are releasing the lock grabbed during the creation of this object.
@@ -438,40 +429,37 @@ impl<'a, T: DriverObject, C: DeviceContext> Drop for DmaResvGuard<'a, T, C> {
 ///
 /// - The size of `owner` is >= SIZE.
 /// - The memory pointed to by `addr` remains valid at least until this object is dropped.
-pub struct VMap<D, R, C = Registered, const SIZE: usize = 0>
+pub struct VMap<D, R, const SIZE: usize = 0>
 where
     D: DriverObject,
-    C: DeviceContext,
-    R: Deref<Target = Object<D, C>>,
+    R: Deref<Target = Object<D>>,
 {
     addr: *mut c_void,
     owner: R,
 }
 
 /// An alias type for a reference to a shmem-based GEM object's VMap.
-pub type VMapRef<'a, D, C, const SIZE: usize = 0> = VMap<D, &'a Object<D, C>, C, SIZE>;
+pub type VMapRef<'a, D, const SIZE: usize = 0> = VMap<D, &'a Object<D>, SIZE>;
 
 /// An alias type for an owned reference to a shmem-based GEM object's VMap.
-pub type VMapOwned<D, C, const SIZE: usize = 0> = VMap<D, ARef<Object<D, C>>, C, SIZE>;
+pub type VMapOwned<D, const SIZE: usize = 0> = VMap<D, ARef<Object<D>>, SIZE>;
 
-impl<D, R, C, const SIZE: usize> VMap<D, R, C, SIZE>
+impl<D, R, const SIZE: usize> VMap<D, R, SIZE>
 where
     D: DriverObject,
-    C: DeviceContext,
-    R: Deref<Target = Object<D, C>>,
+    R: Deref<Target = Object<D>>,
 {
     /// Borrows a reference to the object that owns this virtual mapping.
     #[inline]
-    pub fn owner(&self) -> &Object<D, C> {
+    pub fn owner(&self) -> &Object<D> {
         &self.owner
     }
 }
 
-impl<D, R, C, const SIZE: usize> Drop for VMap<D, R, C, SIZE>
+impl<D, R, const SIZE: usize> Drop for VMap<D, R, SIZE>
 where
     D: DriverObject,
-    C: DeviceContext,
-    R: Deref<Target = Object<D, C>>,
+    R: Deref<Target = Object<D>>,
 {
     #[inline]
     fn drop(&mut self) {
@@ -490,29 +478,26 @@ where
 
 // SAFETY: `addr` points to a valid memory address for as long as `owner` exists, meaning that so
 // long as `owner` is `Send` so is `VMap`.
-unsafe impl<D, R, C, const SIZE: usize> Send for VMap<D, R, C, SIZE>
+unsafe impl<D, R, const SIZE: usize> Send for VMap<D, R, SIZE>
 where
     D: DriverObject,
-    C: DeviceContext,
-    R: Deref<Target = Object<D, C>> + Send,
+    R: Deref<Target = Object<D>> + Send,
 {
 }
 
 // SAFETY: `addr` points to a valid memory address for as long as `owner` exists, meaning that so
 // long as `owner` is `Sync` so is `VMap`.
-unsafe impl<D, R, C, const SIZE: usize> Sync for VMap<D, R, C, SIZE>
+unsafe impl<D, R, const SIZE: usize> Sync for VMap<D, R, SIZE>
 where
     D: DriverObject,
-    C: DeviceContext,
-    R: Deref<Target = Object<D, C>> + Sync,
+    R: Deref<Target = Object<D>> + Sync,
 {
 }
 
-impl<D, R, C, const SIZE: usize> Io for VMap<D, R, C, SIZE>
+impl<D, R, const SIZE: usize> Io for VMap<D, R, SIZE>
 where
     D: DriverObject,
-    C: DeviceContext,
-    R: Deref<Target = Object<D, C>>,
+    R: Deref<Target = Object<D>>,
 {
     #[inline]
     fn addr(&self) -> usize {
@@ -525,22 +510,20 @@ where
     }
 }
 
-impl<D, R, C, const SIZE: usize> IoKnownSize for VMap<D, R, C, SIZE>
+impl<D, R, const SIZE: usize> IoKnownSize for VMap<D, R, SIZE>
 where
     D: DriverObject,
-    C: DeviceContext,
-    R: Deref<Target = Object<D, C>>,
+    R: Deref<Target = Object<D>>,
 {
     const MIN_SIZE: usize = SIZE;
 }
 
 macro_rules! impl_vmap_io_capable {
     ($ty:ty) => {
-        impl<D, R, C, const SIZE: usize> IoCapable<$ty> for VMap<D, R, C, SIZE>
+        impl<D, R, const SIZE: usize> IoCapable<$ty> for VMap<D, R, SIZE>
         where
             D: DriverObject,
-            C: DeviceContext,
-            R: Deref<Target = Object<D, C>>,
+            R: Deref<Target = Object<D>>,
         {
             #[inline]
             unsafe fn io_read(&self, address: usize) -> $ty {
@@ -583,11 +566,11 @@ impl_vmap_io_capable!(u64);
 ///   [`SGTable`].
 ///
 /// [`SGTable`]: scatterlist::SGTable
-pub struct SGTableMap<T: DriverObject, C: DeviceContext> {
-    obj: NonNull<Object<T, C>>,
+pub struct SGTableMap<T: DriverObject> {
+    obj: NonNull<Object<T>>,
 }
 
-impl<T: DriverObject, C: DeviceContext> Deref for SGTableMap<T, C> {
+impl<T: DriverObject> Deref for SGTableMap<T> {
     type Target = scatterlist::SGTable;
 
     fn deref(&self) -> &Self::Target {
@@ -598,7 +581,7 @@ impl<T: DriverObject, C: DeviceContext> Deref for SGTableMap<T, C> {
     }
 }
 
-impl<T: DriverObject, C: DeviceContext> Drop for SGTableMap<T, C> {
+impl<T: DriverObject> Drop for SGTableMap<T> {
     fn drop(&mut self) {
         // SAFETY: `obj` is always valid via our type invariants
         let obj = unsafe { self.obj.as_ref() };
@@ -609,8 +592,8 @@ impl<T: DriverObject, C: DeviceContext> Drop for SGTableMap<T, C> {
     }
 }
 
-impl<T: DriverObject, C: DeviceContext> SGTableMap<T, C> {
-    fn new(obj: &Object<T, C>) -> impl Init<Self, Error> {
+impl<T: DriverObject> SGTableMap<T> {
+    fn new(obj: &Object<T>) -> impl Init<Self, Error> {
         // INVARIANT:
         // - We call drm_gem_shmem_get_pages_sgt below and check whether or not it succeeds,
         //   fulfilling the invariant of SGTableMap that the object's `sgt` field is initialized.
@@ -624,10 +607,10 @@ impl<T: DriverObject, C: DeviceContext> SGTableMap<T, C> {
 
 // SAFETY: The NonNull in SGTableMap is guaranteed valid by our type invariants, and the GEM object
 // it points to is guaranteed to be thread-safe.
-unsafe impl<T: DriverObject, C: DeviceContext> Send for SGTableMap<T, C> {}
+unsafe impl<T: DriverObject> Send for SGTableMap<T> {}
 // SAFETY: The NonNull in SGTableMap is guaranteed valid by our type invariants, and the GEM object
 // it points to is guaranteed to be thread-safe.
-unsafe impl<T: DriverObject, C: DeviceContext> Sync for SGTableMap<T, C> {}
+unsafe impl<T: DriverObject> Sync for SGTableMap<T> {}
 
 #[kunit_tests(rust_drm_gem_shmem)]
 mod tests {
@@ -670,8 +653,8 @@ mod tests {
         type Driver = KunitDriver;
         type Args = ();
 
-        fn new<C: DeviceContext>(
-            _dev: &drm::Device<KunitDriver, C>,
+        fn new(
+            _dev: &drm::Device<KunitDriver>,
             _size: usize,
             _args: Self::Args,
         ) -> impl PinInit<Self, Error> {
@@ -682,8 +665,10 @@ mod tests {
     #[vtable]
     impl drm::Driver for KunitDriver {
         type Data = KunitData;
+        type RegistrationData<'a> = ();
         type File = KunitFile;
-        type Object<Ctx: DeviceContext> = Object<KunitObject, Ctx>;
+        type Object = Object<KunitObject>;
+        type ParentDevice<Ctx: device::DeviceContext> = faux::Device<Ctx>;
 
         const INFO: drm::DriverInfo = INFO;
         const IOCTLS: &'static [drm::ioctl::DrmIoctlDescriptor] = &[];
@@ -692,17 +677,18 @@ mod tests {
     fn create_drm_dev() -> Result<(faux::Registration, UnregisteredDevice<KunitDriver>)> {
         // Create a faux DRM device so we can test gem object creation.
         let data = try_pin_init!(KunitData {});
-        let dev = faux::Registration::new(c"Kunit", None)?;
-        let drm = UnregisteredDevice::new(dev.as_ref(), data)?;
+        let reg = faux::Registration::new(c"Kunit", None)?;
+        let fdev = reg.as_ref();
+        let drm = UnregisteredDevice::new(fdev, data)?;
 
-        Ok((dev, drm))
+        Ok((reg, drm))
     }
 
     #[test]
     fn compile_time_vmap_sizes() -> Result {
         let (_dev, drm) = create_drm_dev()?;
 
-        let obj = Object::<KunitObject, _>::new(&drm, PAGE_SIZE, ObjectConfig::default(), ())?;
+        let obj = Object::<KunitObject>::new(&drm, PAGE_SIZE, ObjectConfig::default(), ())?;
 
         // Try creating a normal vmap
         obj.vmap::<PAGE_SIZE>()?;
@@ -726,7 +712,7 @@ mod tests {
     fn vmap_io() -> Result {
         let (_dev, drm) = create_drm_dev()?;
 
-        let obj = Object::<KunitObject, _>::new(&drm, PAGE_SIZE, ObjectConfig::default(), ())?;
+        let obj = Object::<KunitObject>::new(&drm, PAGE_SIZE, ObjectConfig::default(), ())?;
 
         let vmap = obj.vmap::<PAGE_SIZE>()?;
 
@@ -755,9 +741,10 @@ mod tests {
     #[test]
     fn fail_sg_table_on_wrong_dev() -> Result {
         let (_dev, drm) = create_drm_dev()?;
-        let wrong_dev = faux::Registration::new(c"EvilKunit", None)?;
+        let reg = faux::Registration::new(c"EvilKunit", None)?;
+        let wrong_dev = reg.as_ref();
 
-        let obj = Object::<KunitObject, _>::new(&drm, PAGE_SIZE, ObjectConfig::default(), ())?;
+        let obj = Object::<KunitObject>::new(&drm, PAGE_SIZE, ObjectConfig::default(), ())?;
 
         assert_eq!(obj.sg_table(wrong_dev.as_ref()).err().unwrap(), EINVAL);
 
diff --git a/rust/kernel/drm/ioctl.rs b/rust/kernel/drm/ioctl.rs
index cf328101dde4..64af9eacc306 100644
--- a/rust/kernel/drm/ioctl.rs
+++ b/rust/kernel/drm/ioctl.rs
@@ -70,6 +70,18 @@ pub mod internal {
     pub use bindings::drm_device;
     pub use bindings::drm_file;
     pub use bindings::drm_ioctl_desc;
+
+    /// Cast an [`Ioctl`] DRM device pointer to [`Registered`], preserving the driver type
+    /// parameter `T`.
+    ///
+    /// Used by [`declare_drm_ioctls!`] to anchor type inference.
+    #[doc(hidden)]
+    #[inline]
+    pub const fn __dev_ctx_cast<T: crate::drm::Driver>(
+        ptr: *const crate::drm::Device<T, crate::drm::Ioctl>,
+    ) -> *const crate::drm::Device<T, crate::drm::Registered> {
+        ptr.cast()
+    }
 }
 
 /// Declare the DRM ioctls for a driver.
@@ -82,7 +94,8 @@ pub mod internal {
 /// `user_callback` should have the following prototype:
 ///
 /// ```ignore
-/// fn foo(device: &kernel::drm::Device<Self>,
+/// fn foo(device: &kernel::drm::Device<Self, kernel::drm::Registered>,
+///        reg_data: &Self::RegistrationData<'_>,
 ///        data: &mut uapi::argument_type,
 ///        file: &kernel::drm::File<Self::File>,
 /// ) -> Result<u32>
@@ -131,10 +144,45 @@ macro_rules! declare_drm_ioctls {
                             // - The DRM device must have been registered when we're called through
                             //   an IOCTL.
                             //
+                            // INVARIANT: The `Ioctl` context requires that the device has been
+                            // registered via `drm_dev_register()` at some point; the DRM core
+                            // guarantees this for ioctl dispatch callbacks.
+                            //
                             // FIXME: Currently there is nothing enforcing that the types of the
                             // dev/file match the current driver these ioctls are being declared
                             // for, and it's not clear how to enforce this within the type system.
-                            let dev = $crate::drm::device::Device::from_raw(raw_dev);
+                            let dev: &$crate::drm::device::Device<_, $crate::drm::Ioctl> =
+                                $crate::drm::device::Device::from_raw(raw_dev);
+
+                            // Type-inference anchor: the closure is never called but ties `dev`'s
+                            // type to `$func`'s first parameter, which the compiler cannot infer
+                            // through method resolution and associated-type projections alone.
+                            #[allow(unreachable_code)]
+                            let _ = || {
+                                let __ptr = $crate::drm::ioctl::internal::__dev_ctx_cast(
+                                    ::core::ptr::from_ref(dev),
+                                );
+
+                                $func(
+                                    // SAFETY: This closure is never executed; the dereference
+                                    // exists purely to unify the type parameter with `$func`.
+                                    // The pointer is valid regardless.
+                                    unsafe { &*__ptr },
+                                    unreachable!(),
+                                    unreachable!(),
+                                    unreachable!(),
+                                )
+                            };
+
+                            // Enforce that the handler accepts higher-ranked
+                            // lifetimes, preventing it from requiring 'static
+                            // references that could escape this scope.
+                            let _: for<'a> fn(&'a _, &'a _, &'a mut _, &'a _) -> _ = $func;
+
+                            let Some(guard) = dev.registration_guard() else {
+                                return $crate::error::code::ENODEV.to_errno();
+                            };
+
                             // SAFETY: The ioctl argument has size `_IOC_SIZE(cmd)`, which we
                             // asserted above matches the size of this type, and all bit patterns of
                             // UAPI structs must be valid.
@@ -147,7 +195,9 @@ macro_rules! declare_drm_ioctls {
                             // SAFETY: This is just the DRM file structure
                             let file = unsafe { $crate::drm::File::from_raw(raw_file) };
 
-                            match $func(dev, data, file) {
+                            match guard.registration_data_with(|reg_data| {
+                                $func(&*guard, reg_data, data, file)
+                            }) {
                                 Err(e) => e.to_errno(),
                                 Ok(i) => i.try_into()
                                             .unwrap_or($crate::error::code::ERANGE.to_errno()),
diff --git a/rust/kernel/drm/mod.rs b/rust/kernel/drm/mod.rs
index a66e7166f66b..fd6ed35bc35a 100644
--- a/rust/kernel/drm/mod.rs
+++ b/rust/kernel/drm/mod.rs
@@ -11,8 +11,10 @@ pub mod ioctl;
 
 pub use self::device::Device;
 pub use self::device::DeviceContext;
+pub use self::device::Ioctl;
+pub use self::device::Normal;
 pub use self::device::Registered;
-pub use self::device::Uninit;
+pub use self::device::RegistrationGuard;
 pub use self::device::UnregisteredDevice;
 pub use self::driver::Driver;
 pub use self::driver::DriverInfo;
diff --git a/rust/kernel/faux.rs b/rust/kernel/faux.rs
index 36c92ae2943c..cd4198fbb232 100644
--- a/rust/kernel/faux.rs
+++ b/rust/kernel/faux.rs
@@ -9,15 +9,63 @@
 use crate::{
     bindings,
     device,
-    prelude::*, //
+    prelude::*,
+    types::Opaque, //
 };
-use core::ptr::{
-    addr_of_mut,
-    null,
-    null_mut,
-    NonNull, //
+use core::{
+    marker::PhantomData,
+    ptr::{
+        null,
+        null_mut,
+        NonNull, //
+    },
 };
 
+/// A faux device.
+///
+/// A faux device is a virtual device backed by the faux bus, primarily used for scenarios where a
+/// real hardware device is not available or for testing.
+///
+/// # Invariants
+///
+/// The underlying `struct faux_device` is valid.
+#[repr(transparent)]
+pub struct Device<Ctx: device::DeviceContext = device::Normal>(
+    Opaque<bindings::faux_device>,
+    PhantomData<Ctx>,
+);
+
+impl<Ctx: device::DeviceContext> Device<Ctx> {
+    #[inline]
+    fn as_raw(&self) -> *mut bindings::faux_device {
+        self.0.get()
+    }
+
+    /// # Safety
+    ///
+    /// `ptr` must be a valid pointer to a `struct faux_device`.
+    #[inline]
+    unsafe fn from_raw<'a>(ptr: *mut bindings::faux_device) -> &'a Self {
+        // SAFETY: `Device` is a transparent wrapper of `Opaque<bindings::faux_device>`.
+        unsafe { &*ptr.cast() }
+    }
+}
+
+impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
+    #[inline]
+    fn as_ref(&self) -> &device::Device<Ctx> {
+        // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
+        // `struct faux_device`. `dev` points to a valid `struct device`.
+        unsafe { device::Device::from_raw(&raw mut (*self.as_raw()).dev) }
+    }
+}
+
+// SAFETY: `faux::Device` is a transparent wrapper of `struct faux_device`.
+// The offset is guaranteed to point to a valid device field inside `faux::Device`.
+unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for Device<Ctx> {
+    const OFFSET: usize = core::mem::offset_of!(bindings::faux_device, dev);
+}
+
 /// The registration of a faux device.
 ///
 /// This type represents the registration of a [`struct faux_device`]. When an instance of this type
@@ -60,10 +108,11 @@ impl Registration {
     }
 }
 
-impl AsRef<device::Device<device::Bound>> for Registration {
-    fn as_ref(&self) -> &device::Device<device::Bound> {
+impl AsRef<Device<device::Bound>> for Registration {
+    #[inline]
+    fn as_ref(&self) -> &Device<device::Bound> {
         // SAFETY:
-        // - The underlying `device` in `faux_device` is guaranteed by the C API to be a valid
+        // - The underlying `struct faux_device` is guaranteed by the C API to be a valid
         //   initialized `device`.
         // - `faux_match()` always returns 1, and probe runs synchronously
         //   (PROBE_FORCE_SYNCHRONOUS).
@@ -71,7 +120,7 @@ impl AsRef<device::Device<device::Bound>> for Registration {
         //   sysfs.
         // - `mem::forget(Registration)` is not a problem; if the `Registration` is leaked, the faux
         //   device stays bound forever.
-        unsafe { device::Device::from_raw(addr_of_mut!((*self.as_raw()).dev)) }
+        unsafe { Device::from_raw(self.as_raw()) }
     }
 }
 
diff --git a/samples/rust/rust_driver_faux.rs b/samples/rust/rust_driver_faux.rs
index 99876c8e3743..27b6d3e2bb44 100644
--- a/samples/rust/rust_driver_faux.rs
+++ b/samples/rust/rust_driver_faux.rs
@@ -25,8 +25,9 @@ impl Module for SampleModule {
         pr_info!("Initialising Rust Faux Device Sample\n");
 
         let reg = faux::Registration::new(c"rust-faux-sample-device", None)?;
+        let fdev = reg.as_ref();
 
-        dev_info!(reg, "Hello from faux device!\n");
+        dev_info!(fdev, "Hello from faux device!\n");
 
         Ok(Self { _reg: reg })
     }