rust/kernel/drm/device.rs - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0 OR MIT

 //! DRM device.
 //!
 //! C header: [`include/drm/drm_device.h`](srctree/include/drm/drm_device.h)

 use crate::{
     alloc::allocator::Kmalloc,
     bindings,
     device,
     drm::{
         self,
         driver::AllocImpl,
         private::Sealed, //
     },
     error::from_err_ptr,
     prelude::*,
     sync::aref::{
         ARef,
         AlwaysRefCounted, //
     },
     types::{
         NotThreadSafe,
         Opaque, //
     },
     workqueue::{
         HasDelayedWork,
         HasWork,
         Work,
         WorkItem, //
     }, //
 };
 use core::{
     alloc::Layout,
     marker::PhantomData,
     mem,
     ops::Deref,
     ptr::{
         self,
         NonNull, //
     },
 };

 #[cfg(CONFIG_DRM_LEGACY)]
 macro_rules! drm_legacy_fields {
     ( $($field:ident: $val:expr),* $(,)? ) => {
         bindings::drm_driver {
             $( $field: $val ),*,
             firstopen: None,
             preclose: None,
             dma_ioctl: None,
             dma_quiescent: None,
             context_dtor: None,
             irq_handler: None,
             irq_preinstall: None,
             irq_postinstall: None,
             irq_uninstall: None,
             get_vblank_counter: None,
             enable_vblank: None,
             disable_vblank: None,
             dev_priv_size: 0,
         }
     }
 }

 #[cfg(not(CONFIG_DRM_LEGACY))]
 macro_rules! drm_legacy_fields {
     ( $($field:ident: $val:expr),* $(,)? ) => {
         bindings::drm_driver {
             $( $field: $val ),*
         }
     }
 }

 /// 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`].
 ///
 /// Each stage of this process is described below:
 ///
 /// ```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.
 pub trait DeviceContext: Sealed + Send + Sync {}

 /// The [`DeviceContext`] of a [`Device`] that was registered with userspace at some point.
 ///
 /// 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.
 ///
 /// 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.
 ///
 /// # Invariants
 ///
 /// A [`Device`] in this [`DeviceContext`] is guaranteed to have been registered with userspace
 /// at some point in time.
 pub struct Registered;

 impl Sealed for Registered {}
 impl DeviceContext for Registered {}

 /// The [`DeviceContext`] of a [`Device`] that may be unregistered and partly uninitialized.
 ///
 /// 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`].
 ///
 /// A [`Device`] in this context can be used to create a
 /// [`Registration`](drm::driver::Registration).
 pub struct Uninit;

 impl Sealed for Uninit {}
 impl DeviceContext for Uninit {}

 /// A [`Device`] which is known at compile-time to be unregistered with userspace.
 ///
 /// This type allows performing operations which are only safe to do before userspace registration,
 /// and can be used to create a [`Registration`](drm::driver::Registration) once the driver is ready
 /// to register the device with userspace.
 ///
 /// Since DRM device initialization must be single-threaded, this object is not thread-safe.
 ///
 /// # Invariants
 ///
 /// 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);

 impl<T: drm::Driver> Deref for UnregisteredDevice<T> {
     type Target = Device<T, Uninit>;

     fn deref(&self) -> &Self::Target {
         &self.0
     }
 }

 impl<T: drm::Driver> UnregisteredDevice<T> {
     const fn compute_features() -> u32 {
         let mut features = drm::driver::FEAT_GEM;

         if T::FEAT_RENDER {
             features |= drm::driver::FEAT_RENDER;
         }

         features
     }

     const VTABLE: bindings::drm_driver = drm_legacy_fields! {
         load: None,
         open: Some(drm::File::<T::File>::open_callback),
         postclose: Some(drm::File::<T::File>::postclose_callback),
         unload: None,
         release: Some(Device::<T>::release),
         master_set: None,
         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,

         show_fdinfo: None,
         fbdev_probe: None,

         major: T::INFO.major,
         minor: T::INFO.minor,
         patchlevel: T::INFO.patchlevel,
         name: crate::str::as_char_ptr_in_const_context(T::INFO.name).cast_mut(),
         desc: crate::str::as_char_ptr_in_const_context(T::INFO.desc).cast_mut(),

         driver_features: Self::compute_features(),
         ioctls: T::IOCTLS.as_ptr(),
         num_ioctls: T::IOCTLS.len() as i32,
         fops: &Self::GEM_FOPS,
     };

     const GEM_FOPS: bindings::file_operations = drm::gem::create_fops();

     /// 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> {
         // `__drm_dev_alloc` uses `kmalloc()` to allocate memory, hence ensure a `kmalloc()`
         // compatible `Layout`.
         let layout = Kmalloc::aligned_layout(Layout::new::<Device<T, Uninit>>());

         // Use a temporary vtable without a `release` callback until `data` is initialized, so
         // init failure can release the DRM device without dropping uninitialized fields.
         let alloc_vtable = bindings::drm_driver {
             release: None,
             ..Self::VTABLE
         };

         // 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 {
             bindings::__drm_dev_alloc(
                 dev.as_raw(),
                 &alloc_vtable,
                 layout.size(),
                 mem::offset_of!(Device<T, Uninit>, dev),
             )
         }
         .cast();
         let raw_drm = NonNull::new(from_err_ptr(raw_drm)?).ok_or(ENOMEM)?;

         // SAFETY: `raw_drm` is a valid pointer to `Self`, given that `__drm_dev_alloc` was
         // successful.
         let drm_dev = unsafe { Device::into_drm_device(raw_drm) };

         // SAFETY: `raw_drm` is a valid pointer to `Self`.
         let raw_data = unsafe { ptr::addr_of_mut!((*raw_drm.as_ptr()).data) };

         // SAFETY:
         // - `raw_data` is a valid pointer to uninitialized memory.
         // - `raw_data` will not move until it is dropped.
         unsafe { data.__pinned_init(raw_data) }.inspect_err(|_| {
             // SAFETY: `__drm_dev_alloc()` was successful, hence `drm_dev` must be valid and the
             // refcount must be non-zero.
             unsafe { bindings::drm_dev_put(drm_dev) };
         })?;

         // SAFETY: `drm_dev` is still private to this function.
         unsafe { (*drm_dev).driver = const { &Self::VTABLE } };

         // 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`.
         // `Self` cannot be copied or sent to another thread - ensuring that `drm_dev_register`
         // won't be called during its lifetime and that the device is unregistered.
         Ok(Self(unsafe { ARef::from_raw(raw_drm) }, NotThreadSafe))
     }
 }

 /// 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.
 ///
 /// # Invariants
 ///
 /// * `self.dev` is a valid instance of a `struct device`.
 /// * 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> {
     dev: Opaque<bindings::drm_device>,
     data: T::Data,
     _ctx: PhantomData<C>,
 }

 impl<T: drm::Driver, C: DeviceContext> Device<T, C> {
     pub(crate) fn as_raw(&self) -> *mut bindings::drm_device {
         self.dev.get()
     }

     /// # Safety
     ///
     /// `ptr` must be a valid pointer to a `struct device` embedded in `Self`.
     unsafe fn from_drm_device(ptr: *const bindings::drm_device) -> *mut Self {
         // SAFETY: By the safety requirements of this function `ptr` is a valid pointer to a
         // `struct drm_device` embedded in `Self`.
         unsafe { crate::container_of!(Opaque::cast_from(ptr), Self, dev) }.cast_mut()
     }

     /// # Safety
     ///
     /// `ptr` must be a valid pointer to `Self`.
     unsafe fn into_drm_device(ptr: NonNull<Self>) -> *mut bindings::drm_device {
         // SAFETY: By the safety requirements of this function, `ptr` is a valid pointer to `Self`.
         unsafe { &raw mut (*ptr.as_ptr()).dev }.cast()
     }

     /// Not intended to be called externally, except via declare_drm_ioctls!()
     ///
     /// # Safety
     ///
     /// * Callers must ensure that `ptr` is valid, non-null, and has a non-zero reference count,
     ///   i.e. it must be ensured that the reference count of the C `struct drm_device` `ptr` points
     ///   to can't drop to zero, for the duration of this function call and the entire duration when
     ///   the returned reference exists.
     /// * Additionally, callers must ensure that the `struct device`, `ptr` is pointing to, is
     ///   embedded in `Self`.
     /// * Callers promise that any type invariants of `C` will be upheld.
     #[doc(hidden)]
     pub unsafe fn from_raw<'a>(ptr: *const bindings::drm_device) -> &'a Self {
         // SAFETY: By the safety requirements of this function `ptr` is a valid pointer to a
         // `struct drm_device` embedded in `Self`.
         let ptr = unsafe { Self::from_drm_device(ptr) };

         // SAFETY: `ptr` is valid by the safety requirements of this function.
         unsafe { &*ptr.cast() }
     }

     extern "C" fn release(ptr: *mut bindings::drm_device) {
         // SAFETY: `ptr` is a valid pointer to a `struct drm_device` and embedded in `Self`.
         let this = unsafe { Self::from_drm_device(ptr) };

         // SAFETY:
         // - When `release` runs it is guaranteed that there is no further access to `this`.
         // - `this` is valid for dropping.
         unsafe { core::ptr::drop_in_place(this) };
     }

     /// Change the [`DeviceContext`] for a [`Device`].
     ///
     /// # Safety
     ///
     /// The caller promises that `self` fulfills all of the guarantees provided by the given
     /// [`DeviceContext`].
     pub(crate) unsafe fn assume_ctx<NewCtx: DeviceContext>(&self) -> &Device<T, NewCtx> {
         // SAFETY: The data layout is identical via our type invariants.
         unsafe { mem::transmute(self) }
     }
 }

 impl<T: drm::Driver, C: DeviceContext> Deref for Device<T, C> {
     type Target = T::Data;

     fn deref(&self) -> &Self::Target {
         &self.data
     }
 }

 // 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> {
     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()) };
     }

     unsafe fn dec_ref(obj: NonNull<Self>) {
         // SAFETY: `obj` is a valid pointer to `Self`.
         let drm_dev = unsafe { Self::into_drm_device(obj) };

         // SAFETY: The safety requirements guarantee that the refcount is non-zero.
         unsafe { bindings::drm_dev_put(drm_dev) };
     }
 }

 impl<T: drm::Driver, C: DeviceContext> AsRef<device::Device> for Device<T, C> {
     fn as_ref(&self) -> &device::Device {
         // 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) }
     }
 }

 // SAFETY: A `drm::Device` can be released from any thread.
 unsafe impl<T: drm::Driver, C: DeviceContext> Send for Device<T, C> {}

 // SAFETY: A `drm::Device` can be shared among threads because all immutable methods are protected
 // 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>
 where
     T: drm::Driver,
     T::Data: WorkItem<ID, Pointer = ARef<Self>>,
     T::Data: HasWork<Self, ID>,
     C: DeviceContext,
 {
     type Pointer = ARef<Self>;

     fn run(ptr: ARef<Self>) {
         T::Data::run(ptr);
     }
 }

 // SAFETY:
 //
 // - `raw_get_work` and `work_container_of` return valid pointers by relying on
 // `T::Data::raw_get_work` and `container_of`. In particular, `T::Data` is
 // stored inline in `drm::Device`, so the `container_of` call is valid.
 //
 // - The two methods are true inverses of each other: given `ptr: *mut
 // Device<T, C>`, `raw_get_work` will return a `*mut Work<Device<T, C>, ID>` through
 // `T::Data::raw_get_work` and given a `ptr: *mut Work<Device<T, C>, ID>`,
 // `work_container_of` will return a `*mut Device<T, C>` through `container_of`.
 unsafe impl<T, C, const ID: u64> HasWork<Self, ID> for Device<T, C>
 where
     T: drm::Driver,
     T::Data: HasWork<Self, ID>,
     C: DeviceContext,
 {
     unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work<Self, ID> {
         // SAFETY: The caller promises that `ptr` points to a valid `Device<T, C>`.
         let data_ptr = unsafe { &raw mut (*ptr).data };

         // SAFETY: `data_ptr` is a valid pointer to `T::Data`.
         unsafe { T::Data::raw_get_work(data_ptr) }
     }

     unsafe fn work_container_of(ptr: *mut Work<Self, ID>) -> *mut Self {
         // SAFETY: The caller promises that `ptr` points at a `Work` field in
         // `T::Data`.
         let data_ptr = unsafe { T::Data::work_container_of(ptr) };

         // SAFETY: `T::Data` is stored as the `data` field in `Device<T, C>`.
         unsafe { crate::container_of!(data_ptr, Self, data) }
     }
 }

 // SAFETY: Our `HasWork<T, ID>` implementation returns a `work_struct` that is
 // stored in the `work` field of a `delayed_work` with the same access rules as
 // the `work_struct` owing to the bound on `T::Data: HasDelayedWork<Device<T, C>,
 // ID>`, which requires that `T::Data::raw_get_work` return a `work_struct` that
 // is inside a `delayed_work`.
 unsafe impl<T, C, const ID: u64> HasDelayedWork<Self, ID> for Device<T, C>
 where
     T: drm::Driver,
     T::Data: HasDelayedWork<Self, ID>,
     C: DeviceContext,
 {
 }
	// SPDX-License-Identifier: GPL-2.0 OR MIT

	//! DRM device.
	//!
	//! C header: [`include/drm/drm_device.h`](srctree/include/drm/drm_device.h)

	use crate::{
	alloc::allocator::Kmalloc,
	bindings,
	device,
	drm::{
	self,
	driver::AllocImpl,
	private::Sealed, //
	},
	error::from_err_ptr,
	prelude::*,
	sync::aref::{
	ARef,
	AlwaysRefCounted, //
	},
	types::{
	NotThreadSafe,
	Opaque, //
	},
	workqueue::{
	HasDelayedWork,
	HasWork,
	Work,
	WorkItem, //
	}, //
	};
	use core::{
	alloc::Layout,
	marker::PhantomData,
	mem,
	ops::Deref,
	ptr::{
	self,
	NonNull, //
	},
	};

	#[cfg(CONFIG_DRM_LEGACY)]
	macro_rules! drm_legacy_fields {
	( $($field:ident: $val:expr),* $(,)? ) => {
	bindings::drm_driver {
	$( $field: $val ),*,
	firstopen: None,
	preclose: None,
	dma_ioctl: None,
	dma_quiescent: None,
	context_dtor: None,
	irq_handler: None,
	irq_preinstall: None,
	irq_postinstall: None,
	irq_uninstall: None,
	get_vblank_counter: None,
	enable_vblank: None,
	disable_vblank: None,
	dev_priv_size: 0,
	}
	}
	}

	#[cfg(not(CONFIG_DRM_LEGACY))]
	macro_rules! drm_legacy_fields {
	( $($field:ident: $val:expr),* $(,)? ) => {
	bindings::drm_driver {
	$( $field: $val ),*
	}
	}
	}

	/// 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`].
	///
	/// Each stage of this process is described below:
	///
	/// ```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.
	pub trait DeviceContext: Sealed + Send + Sync {}

	/// The [`DeviceContext`] of a [`Device`] that was registered with userspace at some point.
	///
	/// 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.
	///
	/// 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.
	///
	/// # Invariants
	///
	/// A [`Device`] in this [`DeviceContext`] is guaranteed to have been registered with userspace
	/// at some point in time.
	pub struct Registered;

	impl Sealed for Registered {}
	impl DeviceContext for Registered {}

	/// The [`DeviceContext`] of a [`Device`] that may be unregistered and partly uninitialized.
	///
	/// 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`].
	///
	/// A [`Device`] in this context can be used to create a
	/// [`Registration`](drm::driver::Registration).
	pub struct Uninit;

	impl Sealed for Uninit {}
	impl DeviceContext for Uninit {}

	/// A [`Device`] which is known at compile-time to be unregistered with userspace.
	///
	/// This type allows performing operations which are only safe to do before userspace registration,
	/// and can be used to create a [`Registration`](drm::driver::Registration) once the driver is ready
	/// to register the device with userspace.
	///
	/// Since DRM device initialization must be single-threaded, this object is not thread-safe.
	///
	/// # Invariants
	///
	/// 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);

	impl<T: drm::Driver> Deref for UnregisteredDevice<T> {
	type Target = Device<T, Uninit>;

	fn deref(&self) -> &Self::Target {
	&self.0
	}
	}

	impl<T: drm::Driver> UnregisteredDevice<T> {
	const fn compute_features() -> u32 {
	let mut features = drm::driver::FEAT_GEM;

	if T::FEAT_RENDER {
	features \|= drm::driver::FEAT_RENDER;
	}

	features
	}

	const VTABLE: bindings::drm_driver = drm_legacy_fields! {
	load: None,
	open: Some(drm::File::<T::File>::open_callback),
	postclose: Some(drm::File::<T::File>::postclose_callback),
	unload: None,
	release: Some(Device::<T>::release),
	master_set: None,
	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,

	show_fdinfo: None,
	fbdev_probe: None,

	major: T::INFO.major,
	minor: T::INFO.minor,
	patchlevel: T::INFO.patchlevel,
	name: crate::str::as_char_ptr_in_const_context(T::INFO.name).cast_mut(),
	desc: crate::str::as_char_ptr_in_const_context(T::INFO.desc).cast_mut(),

	driver_features: Self::compute_features(),
	ioctls: T::IOCTLS.as_ptr(),
	num_ioctls: T::IOCTLS.len() as i32,
	fops: &Self::GEM_FOPS,
	};

	const GEM_FOPS: bindings::file_operations = drm::gem::create_fops();

	/// 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> {
	// `__drm_dev_alloc` uses `kmalloc()` to allocate memory, hence ensure a `kmalloc()`
	// compatible `Layout`.
	let layout = Kmalloc::aligned_layout(Layout::new::<Device<T, Uninit>>());

	// Use a temporary vtable without a `release` callback until `data` is initialized, so
	// init failure can release the DRM device without dropping uninitialized fields.
	let alloc_vtable = bindings::drm_driver {
	release: None,
	..Self::VTABLE
	};

	// 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 {
	bindings::__drm_dev_alloc(
	dev.as_raw(),
	&alloc_vtable,
	layout.size(),
	mem::offset_of!(Device<T, Uninit>, dev),
	)
	}
	.cast();
	let raw_drm = NonNull::new(from_err_ptr(raw_drm)?).ok_or(ENOMEM)?;

	// SAFETY: `raw_drm` is a valid pointer to `Self`, given that `__drm_dev_alloc` was
	// successful.
	let drm_dev = unsafe { Device::into_drm_device(raw_drm) };

	// SAFETY: `raw_drm` is a valid pointer to `Self`.
	let raw_data = unsafe { ptr::addr_of_mut!((*raw_drm.as_ptr()).data) };

	// SAFETY:
	// - `raw_data` is a valid pointer to uninitialized memory.
	// - `raw_data` will not move until it is dropped.
	unsafe { data.__pinned_init(raw_data) }.inspect_err(\|_\| {
	// SAFETY: `__drm_dev_alloc()` was successful, hence `drm_dev` must be valid and the
	// refcount must be non-zero.
	unsafe { bindings::drm_dev_put(drm_dev) };
	})?;

	// SAFETY: `drm_dev` is still private to this function.
	unsafe { (*drm_dev).driver = const { &Self::VTABLE } };

	// 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`.
	// `Self` cannot be copied or sent to another thread - ensuring that `drm_dev_register`
	// won't be called during its lifetime and that the device is unregistered.
	Ok(Self(unsafe { ARef::from_raw(raw_drm) }, NotThreadSafe))
	}
	}

	/// 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.
	///
	/// # Invariants
	///
	/// * `self.dev` is a valid instance of a `struct device`.
	/// * 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> {
	dev: Opaque<bindings::drm_device>,
	data: T::Data,
	_ctx: PhantomData<C>,
	}

	impl<T: drm::Driver, C: DeviceContext> Device<T, C> {
	pub(crate) fn as_raw(&self) -> *mut bindings::drm_device {
	self.dev.get()
	}

	/// # Safety
	///
	/// `ptr` must be a valid pointer to a `struct device` embedded in `Self`.
	unsafe fn from_drm_device(ptr: const bindings::drm_device) -> mut Self {
	// SAFETY: By the safety requirements of this function `ptr` is a valid pointer to a
	// `struct drm_device` embedded in `Self`.
	unsafe { crate::container_of!(Opaque::cast_from(ptr), Self, dev) }.cast_mut()
	}

	/// # Safety
	///
	/// `ptr` must be a valid pointer to `Self`.
	unsafe fn into_drm_device(ptr: NonNull<Self>) -> *mut bindings::drm_device {
	// SAFETY: By the safety requirements of this function, `ptr` is a valid pointer to `Self`.
	unsafe { &raw mut (*ptr.as_ptr()).dev }.cast()
	}

	/// Not intended to be called externally, except via declare_drm_ioctls!()
	///
	/// # Safety
	///
	/// * Callers must ensure that `ptr` is valid, non-null, and has a non-zero reference count,
	/// i.e. it must be ensured that the reference count of the C `struct drm_device` `ptr` points
	/// to can't drop to zero, for the duration of this function call and the entire duration when
	/// the returned reference exists.
	/// * Additionally, callers must ensure that the `struct device`, `ptr` is pointing to, is
	/// embedded in `Self`.
	/// * Callers promise that any type invariants of `C` will be upheld.
	#[doc(hidden)]
	pub unsafe fn from_raw<'a>(ptr: *const bindings::drm_device) -> &'a Self {
	// SAFETY: By the safety requirements of this function `ptr` is a valid pointer to a
	// `struct drm_device` embedded in `Self`.
	let ptr = unsafe { Self::from_drm_device(ptr) };

	// SAFETY: `ptr` is valid by the safety requirements of this function.
	unsafe { &*ptr.cast() }
	}

	extern "C" fn release(ptr: *mut bindings::drm_device) {
	// SAFETY: `ptr` is a valid pointer to a `struct drm_device` and embedded in `Self`.
	let this = unsafe { Self::from_drm_device(ptr) };

	// SAFETY:
	// - When `release` runs it is guaranteed that there is no further access to `this`.
	// - `this` is valid for dropping.
	unsafe { core::ptr::drop_in_place(this) };
	}

	/// Change the [`DeviceContext`] for a [`Device`].
	///
	/// # Safety
	///
	/// The caller promises that `self` fulfills all of the guarantees provided by the given
	/// [`DeviceContext`].
	pub(crate) unsafe fn assume_ctx<NewCtx: DeviceContext>(&self) -> &Device<T, NewCtx> {
	// SAFETY: The data layout is identical via our type invariants.
	unsafe { mem::transmute(self) }
	}
	}

	impl<T: drm::Driver, C: DeviceContext> Deref for Device<T, C> {
	type Target = T::Data;

	fn deref(&self) -> &Self::Target {
	&self.data
	}
	}

	// 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> {
	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()) };
	}

	unsafe fn dec_ref(obj: NonNull<Self>) {
	// SAFETY: `obj` is a valid pointer to `Self`.
	let drm_dev = unsafe { Self::into_drm_device(obj) };

	// SAFETY: The safety requirements guarantee that the refcount is non-zero.
	unsafe { bindings::drm_dev_put(drm_dev) };
	}
	}

	impl<T: drm::Driver, C: DeviceContext> AsRef<device::Device> for Device<T, C> {
	fn as_ref(&self) -> &device::Device {
	// 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) }
	}
	}

	// SAFETY: A `drm::Device` can be released from any thread.
	unsafe impl<T: drm::Driver, C: DeviceContext> Send for Device<T, C> {}

	// SAFETY: A `drm::Device` can be shared among threads because all immutable methods are protected
	// 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>
	where
	T: drm::Driver,
	T::Data: WorkItem<ID, Pointer = ARef<Self>>,
	T::Data: HasWork<Self, ID>,
	C: DeviceContext,
	{
	type Pointer = ARef<Self>;

	fn run(ptr: ARef<Self>) {
	T::Data::run(ptr);
	}
	}

	// SAFETY:
	//
	// - `raw_get_work` and `work_container_of` return valid pointers by relying on
	// `T::Data::raw_get_work` and `container_of`. In particular, `T::Data` is
	// stored inline in `drm::Device`, so the `container_of` call is valid.
	//
	// - The two methods are true inverses of each other: given `ptr: *mut
	// Device<T, C>`, `raw_get_work` will return a `*mut Work<Device<T, C>, ID>` through
	// `T::Data::raw_get_work` and given a `ptr: *mut Work<Device<T, C>, ID>`,
	// `work_container_of` will return a `*mut Device<T, C>` through `container_of`.
	unsafe impl<T, C, const ID: u64> HasWork<Self, ID> for Device<T, C>
	where
	T: drm::Driver,
	T::Data: HasWork<Self, ID>,
	C: DeviceContext,
	{
	unsafe fn raw_get_work(ptr: mut Self) -> mut Work<Self, ID> {
	// SAFETY: The caller promises that `ptr` points to a valid `Device<T, C>`.
	let data_ptr = unsafe { &raw mut (*ptr).data };

	// SAFETY: `data_ptr` is a valid pointer to `T::Data`.
	unsafe { T::Data::raw_get_work(data_ptr) }
	}

	unsafe fn work_container_of(ptr: mut Work<Self, ID>) -> mut Self {
	// SAFETY: The caller promises that `ptr` points at a `Work` field in
	// `T::Data`.
	let data_ptr = unsafe { T::Data::work_container_of(ptr) };

	// SAFETY: `T::Data` is stored as the `data` field in `Device<T, C>`.
	unsafe { crate::container_of!(data_ptr, Self, data) }
	}
	}

	// SAFETY: Our `HasWork<T, ID>` implementation returns a `work_struct` that is
	// stored in the `work` field of a `delayed_work` with the same access rules as
	// the `work_struct` owing to the bound on `T::Data: HasDelayedWork<Device<T, C>,
	// ID>`, which requires that `T::Data::raw_get_work` return a `work_struct` that
	// is inside a `delayed_work`.
	unsafe impl<T, C, const ID: u64> HasDelayedWork<Self, ID> for Device<T, C>
	where
	T: drm::Driver,
	T::Data: HasDelayedWork<Self, ID>,
	C: DeviceContext,
	{
	}