rust/kernel/miscdevice.rs - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0

 // Copyright (C) 2024 Google LLC.

 //! Miscdevice support.
 //!
 //! C headers: [`include/linux/miscdevice.h`](srctree/include/linux/miscdevice.h).
 //!
 //! Reference: <https://www.kernel.org/doc/html/latest/driver-api/misc_devices.html>

 use crate::{
     bindings,
     device::Device,
     error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR},
     ffi::{c_int, c_long, c_uint, c_ulong},
     fs::File,
     mm::virt::VmaNew,
     prelude::*,
     seq_file::SeqFile,
     types::{ForeignOwnable, Opaque},
 };
 use core::{marker::PhantomData, mem::MaybeUninit, pin::Pin};

 /// Options for creating a misc device.
 #[derive(Copy, Clone)]
 pub struct MiscDeviceOptions {
     /// The name of the miscdevice.
     pub name: &'static CStr,
 }

 impl MiscDeviceOptions {
     /// Create a raw `struct miscdev` ready for registration.
     pub const fn into_raw<T: MiscDevice>(self) -> bindings::miscdevice {
         // SAFETY: All zeros is valid for this C type.
         let mut result: bindings::miscdevice = unsafe { MaybeUninit::zeroed().assume_init() };
         result.minor = bindings::MISC_DYNAMIC_MINOR as ffi::c_int;
         result.name = self.name.as_char_ptr();
         result.fops = MiscdeviceVTable::<T>::build();
         result
     }
 }

 /// A registration of a miscdevice.
 ///
 /// # Invariants
 ///
 /// - `inner` contains a `struct miscdevice` that is registered using
 ///   `misc_register()`.
 /// - This registration remains valid for the entire lifetime of the
 ///   [`MiscDeviceRegistration`] instance.
 /// - Deregistration occurs exactly once in [`Drop`] via `misc_deregister()`.
 /// - `inner` wraps a valid, pinned `miscdevice` created using
 ///   [`MiscDeviceOptions::into_raw`].
 #[repr(transparent)]
 #[pin_data(PinnedDrop)]
 pub struct MiscDeviceRegistration<T> {
     #[pin]
     inner: Opaque<bindings::miscdevice>,
     _t: PhantomData<T>,
 }

 // SAFETY: It is allowed to call `misc_deregister` on a different thread from where you called
 // `misc_register`.
 unsafe impl<T> Send for MiscDeviceRegistration<T> {}
 // SAFETY: All `&self` methods on this type are written to ensure that it is safe to call them in
 // parallel.
 unsafe impl<T> Sync for MiscDeviceRegistration<T> {}

 impl<T: MiscDevice> MiscDeviceRegistration<T> {
     /// Register a misc device.
     pub fn register(opts: MiscDeviceOptions) -> impl PinInit<Self, Error> {
         try_pin_init!(Self {
             inner <- Opaque::try_ffi_init(move |slot: *mut bindings::miscdevice| {
                 // SAFETY: The initializer can write to the provided `slot`.
                 unsafe { slot.write(opts.into_raw::<T>()) };

                 // SAFETY: We just wrote the misc device options to the slot. The miscdevice will
                 // get unregistered before `slot` is deallocated because the memory is pinned and
                 // the destructor of this type deallocates the memory.
                 // INVARIANT: If this returns `Ok(())`, then the `slot` will contain a registered
                 // misc device.
                 to_result(unsafe { bindings::misc_register(slot) })
             }),
             _t: PhantomData,
         })
     }

     /// Returns a raw pointer to the misc device.
     pub fn as_raw(&self) -> *mut bindings::miscdevice {
         self.inner.get()
     }

     /// Access the `this_device` field.
     pub fn device(&self) -> &Device {
         // SAFETY: This can only be called after a successful register(), which always
         // initialises `this_device` with a valid device. Furthermore, the signature of this
         // function tells the borrow-checker that the `&Device` reference must not outlive the
         // `&MiscDeviceRegistration<T>` used to obtain it, so the last use of the reference must be
         // before the underlying `struct miscdevice` is destroyed.
         unsafe { Device::from_raw((*self.as_raw()).this_device) }
     }
 }

 #[pinned_drop]
 impl<T> PinnedDrop for MiscDeviceRegistration<T> {
     fn drop(self: Pin<&mut Self>) {
         // SAFETY: We know that the device is registered by the type invariants.
         unsafe { bindings::misc_deregister(self.inner.get()) };
     }
 }

 /// Trait implemented by the private data of an open misc device.
 #[vtable]
 pub trait MiscDevice: Sized {
     /// What kind of pointer should `Self` be wrapped in.
     type Ptr: ForeignOwnable + Send + Sync;

     /// Called when the misc device is opened.
     ///
     /// The returned pointer will be stored as the private data for the file.
     fn open(_file: &File, _misc: &MiscDeviceRegistration<Self>) -> Result<Self::Ptr>;

     /// Called when the misc device is released.
     fn release(device: Self::Ptr, _file: &File) {
         drop(device);
     }

     /// Handle for mmap.
     ///
     /// This function is invoked when a user space process invokes the `mmap` system call on
     /// `file`. The function is a callback that is part of the VMA initializer. The kernel will do
     /// initial setup of the VMA before calling this function. The function can then interact with
     /// the VMA initialization by calling methods of `vma`. If the function does not return an
     /// error, the kernel will complete initialization of the VMA according to the properties of
     /// `vma`.
     fn mmap(
         _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
         _file: &File,
         _vma: &VmaNew,
     ) -> Result {
         build_error!(VTABLE_DEFAULT_ERROR)
     }

     /// Handler for ioctls.
     ///
     /// The `cmd` argument is usually manipulated using the utilities in [`kernel::ioctl`].
     ///
     /// [`kernel::ioctl`]: mod@crate::ioctl
     fn ioctl(
         _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
         _file: &File,
         _cmd: u32,
         _arg: usize,
     ) -> Result<isize> {
         build_error!(VTABLE_DEFAULT_ERROR)
     }

     /// Handler for ioctls.
     ///
     /// Used for 32-bit userspace on 64-bit platforms.
     ///
     /// This method is optional and only needs to be provided if the ioctl relies on structures
     /// that have different layout on 32-bit and 64-bit userspace. If no implementation is
     /// provided, then `compat_ptr_ioctl` will be used instead.
     #[cfg(CONFIG_COMPAT)]
     fn compat_ioctl(
         _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
         _file: &File,
         _cmd: u32,
         _arg: usize,
     ) -> Result<isize> {
         build_error!(VTABLE_DEFAULT_ERROR)
     }

     /// Show info for this fd.
     fn show_fdinfo(
         _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
         _m: &SeqFile,
         _file: &File,
     ) {
         build_error!(VTABLE_DEFAULT_ERROR)
     }
 }

 /// A vtable for the file operations of a Rust miscdevice.
 struct MiscdeviceVTable<T: MiscDevice>(PhantomData<T>);

 impl<T: MiscDevice> MiscdeviceVTable<T> {
     /// # Safety
     ///
     /// `file` and `inode` must be the file and inode for a file that is undergoing initialization.
     /// The file must be associated with a `MiscDeviceRegistration<T>`.
     unsafe extern "C" fn open(inode: *mut bindings::inode, raw_file: *mut bindings::file) -> c_int {
         // SAFETY: The pointers are valid and for a file being opened.
         let ret = unsafe { bindings::generic_file_open(inode, raw_file) };
         if ret != 0 {
             return ret;
         }

         // SAFETY: The open call of a file can access the private data.
         let misc_ptr = unsafe { (*raw_file).private_data };

         // SAFETY: This is a miscdevice, so `misc_open()` set the private data to a pointer to the
         // associated `struct miscdevice` before calling into this method. Furthermore,
         // `misc_open()` ensures that the miscdevice can't be unregistered and freed during this
         // call to `fops_open`.
         let misc = unsafe { &*misc_ptr.cast::<MiscDeviceRegistration<T>>() };

         // SAFETY:
         // * This underlying file is valid for (much longer than) the duration of `T::open`.
         // * There is no active fdget_pos region on the file on this thread.
         let file = unsafe { File::from_raw_file(raw_file) };

         let ptr = match T::open(file, misc) {
             Ok(ptr) => ptr,
             Err(err) => return err.to_errno(),
         };

         // This overwrites the private data with the value specified by the user, changing the type
         // of this file's private data. All future accesses to the private data is performed by
         // other fops_* methods in this file, which all correctly cast the private data to the new
         // type.
         //
         // SAFETY: The open call of a file can access the private data.
         unsafe { (*raw_file).private_data = ptr.into_foreign() };

         0
     }

     /// # Safety
     ///
     /// `file` and `inode` must be the file and inode for a file that is being released. The file
     /// must be associated with a `MiscDeviceRegistration<T>`.
     unsafe extern "C" fn release(_inode: *mut bindings::inode, file: *mut bindings::file) -> c_int {
         // SAFETY: The release call of a file owns the private data.
         let private = unsafe { (*file).private_data };
         // SAFETY: The release call of a file owns the private data.
         let ptr = unsafe { <T::Ptr as ForeignOwnable>::from_foreign(private) };

         // SAFETY:
         // * The file is valid for the duration of this call.
         // * There is no active fdget_pos region on the file on this thread.
         T::release(ptr, unsafe { File::from_raw_file(file) });

         0
     }

     /// # Safety
     ///
     /// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
     /// `vma` must be a vma that is currently being mmap'ed with this file.
     unsafe extern "C" fn mmap(
         file: *mut bindings::file,
         vma: *mut bindings::vm_area_struct,
     ) -> c_int {
         // SAFETY: The mmap call of a file can access the private data.
         let private = unsafe { (*file).private_data };
         // SAFETY: This is a Rust Miscdevice, so we call `into_foreign` in `open` and
         // `from_foreign` in `release`, and `fops_mmap` is guaranteed to be called between those
         // two operations.
         let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private.cast()) };
         // SAFETY: The caller provides a vma that is undergoing initial VMA setup.
         let area = unsafe { VmaNew::from_raw(vma) };
         // SAFETY:
         // * The file is valid for the duration of this call.
         // * There is no active fdget_pos region on the file on this thread.
         let file = unsafe { File::from_raw_file(file) };

         match T::mmap(device, file, area) {
             Ok(()) => 0,
             Err(err) => err.to_errno(),
         }
     }

     /// # Safety
     ///
     /// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
     unsafe extern "C" fn ioctl(file: *mut bindings::file, cmd: c_uint, arg: c_ulong) -> c_long {
         // SAFETY: The ioctl call of a file can access the private data.
         let private = unsafe { (*file).private_data };
         // SAFETY: Ioctl calls can borrow the private data of the file.
         let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };

         // SAFETY:
         // * The file is valid for the duration of this call.
         // * There is no active fdget_pos region on the file on this thread.
         let file = unsafe { File::from_raw_file(file) };

         match T::ioctl(device, file, cmd, arg) {
             Ok(ret) => ret as c_long,
             Err(err) => err.to_errno() as c_long,
         }
     }

     /// # Safety
     ///
     /// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
     #[cfg(CONFIG_COMPAT)]
     unsafe extern "C" fn compat_ioctl(
         file: *mut bindings::file,
         cmd: c_uint,
         arg: c_ulong,
     ) -> c_long {
         // SAFETY: The compat ioctl call of a file can access the private data.
         let private = unsafe { (*file).private_data };
         // SAFETY: Ioctl calls can borrow the private data of the file.
         let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };

         // SAFETY:
         // * The file is valid for the duration of this call.
         // * There is no active fdget_pos region on the file on this thread.
         let file = unsafe { File::from_raw_file(file) };

         match T::compat_ioctl(device, file, cmd, arg) {
             Ok(ret) => ret as c_long,
             Err(err) => err.to_errno() as c_long,
         }
     }

     /// # Safety
     ///
     /// - `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
     /// - `seq_file` must be a valid `struct seq_file` that we can write to.
     unsafe extern "C" fn show_fdinfo(seq_file: *mut bindings::seq_file, file: *mut bindings::file) {
         // SAFETY: The release call of a file owns the private data.
         let private = unsafe { (*file).private_data };
         // SAFETY: Ioctl calls can borrow the private data of the file.
         let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };
         // SAFETY:
         // * The file is valid for the duration of this call.
         // * There is no active fdget_pos region on the file on this thread.
         let file = unsafe { File::from_raw_file(file) };
         // SAFETY: The caller ensures that the pointer is valid and exclusive for the duration in
         // which this method is called.
         let m = unsafe { SeqFile::from_raw(seq_file) };

         T::show_fdinfo(device, m, file);
     }

     const VTABLE: bindings::file_operations = bindings::file_operations {
         open: Some(Self::open),
         release: Some(Self::release),
         mmap: if T::HAS_MMAP { Some(Self::mmap) } else { None },
         unlocked_ioctl: if T::HAS_IOCTL {
             Some(Self::ioctl)
         } else {
             None
         },
         #[cfg(CONFIG_COMPAT)]
         compat_ioctl: if T::HAS_COMPAT_IOCTL {
             Some(Self::compat_ioctl)
         } else if T::HAS_IOCTL {
             Some(bindings::compat_ptr_ioctl)
         } else {
             None
         },
         show_fdinfo: if T::HAS_SHOW_FDINFO {
             Some(Self::show_fdinfo)
         } else {
             None
         },
         // SAFETY: All zeros is a valid value for `bindings::file_operations`.
         ..unsafe { MaybeUninit::zeroed().assume_init() }
     };

     const fn build() -> &'static bindings::file_operations {
         &Self::VTABLE
     }
 }
	// SPDX-License-Identifier: GPL-2.0

	// Copyright (C) 2024 Google LLC.

	//! Miscdevice support.
	//!
	//! C headers: [`include/linux/miscdevice.h`](srctree/include/linux/miscdevice.h).
	//!
	//! Reference: <https://www.kernel.org/doc/html/latest/driver-api/misc_devices.html>

	use crate::{
	bindings,
	device::Device,
	error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR},
	ffi::{c_int, c_long, c_uint, c_ulong},
	fs::File,
	mm::virt::VmaNew,
	prelude::*,
	seq_file::SeqFile,
	types::{ForeignOwnable, Opaque},
	};
	use core::{marker::PhantomData, mem::MaybeUninit, pin::Pin};

	/// Options for creating a misc device.
	#[derive(Copy, Clone)]
	pub struct MiscDeviceOptions {
	/// The name of the miscdevice.
	pub name: &'static CStr,
	}

	impl MiscDeviceOptions {
	/// Create a raw `struct miscdev` ready for registration.
	pub const fn into_raw<T: MiscDevice>(self) -> bindings::miscdevice {
	// SAFETY: All zeros is valid for this C type.
	let mut result: bindings::miscdevice = unsafe { MaybeUninit::zeroed().assume_init() };
	result.minor = bindings::MISC_DYNAMIC_MINOR as ffi::c_int;
	result.name = self.name.as_char_ptr();
	result.fops = MiscdeviceVTable::<T>::build();
	result
	}
	}

	/// A registration of a miscdevice.
	///
	/// # Invariants
	///
	/// - `inner` contains a `struct miscdevice` that is registered using
	/// `misc_register()`.
	/// - This registration remains valid for the entire lifetime of the
	/// [`MiscDeviceRegistration`] instance.
	/// - Deregistration occurs exactly once in [`Drop`] via `misc_deregister()`.
	/// - `inner` wraps a valid, pinned `miscdevice` created using
	/// [`MiscDeviceOptions::into_raw`].
	#[repr(transparent)]
	#[pin_data(PinnedDrop)]
	pub struct MiscDeviceRegistration<T> {
	#[pin]
	inner: Opaque<bindings::miscdevice>,
	_t: PhantomData<T>,
	}

	// SAFETY: It is allowed to call `misc_deregister` on a different thread from where you called
	// `misc_register`.
	unsafe impl<T> Send for MiscDeviceRegistration<T> {}
	// SAFETY: All `&self` methods on this type are written to ensure that it is safe to call them in
	// parallel.
	unsafe impl<T> Sync for MiscDeviceRegistration<T> {}

	impl<T: MiscDevice> MiscDeviceRegistration<T> {
	/// Register a misc device.
	pub fn register(opts: MiscDeviceOptions) -> impl PinInit<Self, Error> {
	try_pin_init!(Self {
	inner <- Opaque::try_ffi_init(move \|slot: *mut bindings::miscdevice\| {
	// SAFETY: The initializer can write to the provided `slot`.
	unsafe { slot.write(opts.into_raw::<T>()) };

	// SAFETY: We just wrote the misc device options to the slot. The miscdevice will
	// get unregistered before `slot` is deallocated because the memory is pinned and
	// the destructor of this type deallocates the memory.
	// INVARIANT: If this returns `Ok(())`, then the `slot` will contain a registered
	// misc device.
	to_result(unsafe { bindings::misc_register(slot) })
	}),
	_t: PhantomData,
	})
	}

	/// Returns a raw pointer to the misc device.
	pub fn as_raw(&self) -> *mut bindings::miscdevice {
	self.inner.get()
	}

	/// Access the `this_device` field.
	pub fn device(&self) -> &Device {
	// SAFETY: This can only be called after a successful register(), which always
	// initialises `this_device` with a valid device. Furthermore, the signature of this
	// function tells the borrow-checker that the `&Device` reference must not outlive the
	// `&MiscDeviceRegistration<T>` used to obtain it, so the last use of the reference must be
	// before the underlying `struct miscdevice` is destroyed.
	unsafe { Device::from_raw((*self.as_raw()).this_device) }
	}
	}

	#[pinned_drop]
	impl<T> PinnedDrop for MiscDeviceRegistration<T> {
	fn drop(self: Pin<&mut Self>) {
	// SAFETY: We know that the device is registered by the type invariants.
	unsafe { bindings::misc_deregister(self.inner.get()) };
	}
	}

	/// Trait implemented by the private data of an open misc device.
	#[vtable]
	pub trait MiscDevice: Sized {
	/// What kind of pointer should `Self` be wrapped in.
	type Ptr: ForeignOwnable + Send + Sync;

	/// Called when the misc device is opened.
	///
	/// The returned pointer will be stored as the private data for the file.
	fn open(_file: &File, _misc: &MiscDeviceRegistration<Self>) -> Result<Self::Ptr>;

	/// Called when the misc device is released.
	fn release(device: Self::Ptr, _file: &File) {
	drop(device);
	}

	/// Handle for mmap.
	///
	/// This function is invoked when a user space process invokes the `mmap` system call on
	/// `file`. The function is a callback that is part of the VMA initializer. The kernel will do
	/// initial setup of the VMA before calling this function. The function can then interact with
	/// the VMA initialization by calling methods of `vma`. If the function does not return an
	/// error, the kernel will complete initialization of the VMA according to the properties of
	/// `vma`.
	fn mmap(
	_device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
	_file: &File,
	_vma: &VmaNew,
	) -> Result {
	build_error!(VTABLE_DEFAULT_ERROR)
	}

	/// Handler for ioctls.
	///
	/// The `cmd` argument is usually manipulated using the utilities in [`kernel::ioctl`].
	///
	/// [`kernel::ioctl`]: mod@crate::ioctl
	fn ioctl(
	_device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
	_file: &File,
	_cmd: u32,
	_arg: usize,
	) -> Result<isize> {
	build_error!(VTABLE_DEFAULT_ERROR)
	}

	/// Handler for ioctls.
	///
	/// Used for 32-bit userspace on 64-bit platforms.
	///
	/// This method is optional and only needs to be provided if the ioctl relies on structures
	/// that have different layout on 32-bit and 64-bit userspace. If no implementation is
	/// provided, then `compat_ptr_ioctl` will be used instead.
	#[cfg(CONFIG_COMPAT)]
	fn compat_ioctl(
	_device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
	_file: &File,
	_cmd: u32,
	_arg: usize,
	) -> Result<isize> {
	build_error!(VTABLE_DEFAULT_ERROR)
	}

	/// Show info for this fd.
	fn show_fdinfo(
	_device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
	_m: &SeqFile,
	_file: &File,
	) {
	build_error!(VTABLE_DEFAULT_ERROR)
	}
	}

	/// A vtable for the file operations of a Rust miscdevice.
	struct MiscdeviceVTable<T: MiscDevice>(PhantomData<T>);

	impl<T: MiscDevice> MiscdeviceVTable<T> {
	/// # Safety
	///
	/// `file` and `inode` must be the file and inode for a file that is undergoing initialization.
	/// The file must be associated with a `MiscDeviceRegistration<T>`.
	unsafe extern "C" fn open(inode: mut bindings::inode, raw_file: mut bindings::file) -> c_int {
	// SAFETY: The pointers are valid and for a file being opened.
	let ret = unsafe { bindings::generic_file_open(inode, raw_file) };
	if ret != 0 {
	return ret;
	}

	// SAFETY: The open call of a file can access the private data.
	let misc_ptr = unsafe { (*raw_file).private_data };

	// SAFETY: This is a miscdevice, so `misc_open()` set the private data to a pointer to the
	// associated `struct miscdevice` before calling into this method. Furthermore,
	// `misc_open()` ensures that the miscdevice can't be unregistered and freed during this
	// call to `fops_open`.
	let misc = unsafe { &*misc_ptr.cast::<MiscDeviceRegistration<T>>() };

	// SAFETY:
	// * This underlying file is valid for (much longer than) the duration of `T::open`.
	// * There is no active fdget_pos region on the file on this thread.
	let file = unsafe { File::from_raw_file(raw_file) };

	let ptr = match T::open(file, misc) {
	Ok(ptr) => ptr,
	Err(err) => return err.to_errno(),
	};

	// This overwrites the private data with the value specified by the user, changing the type
	// of this file's private data. All future accesses to the private data is performed by
	// other fops_* methods in this file, which all correctly cast the private data to the new
	// type.
	//
	// SAFETY: The open call of a file can access the private data.
	unsafe { (*raw_file).private_data = ptr.into_foreign() };

	0
	}

	/// # Safety
	///
	/// `file` and `inode` must be the file and inode for a file that is being released. The file
	/// must be associated with a `MiscDeviceRegistration<T>`.
	unsafe extern "C" fn release(_inode: mut bindings::inode, file: mut bindings::file) -> c_int {
	// SAFETY: The release call of a file owns the private data.
	let private = unsafe { (*file).private_data };
	// SAFETY: The release call of a file owns the private data.
	let ptr = unsafe { <T::Ptr as ForeignOwnable>::from_foreign(private) };

	// SAFETY:
	// * The file is valid for the duration of this call.
	// * There is no active fdget_pos region on the file on this thread.
	T::release(ptr, unsafe { File::from_raw_file(file) });

	0
	}

	/// # Safety
	///
	/// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
	/// `vma` must be a vma that is currently being mmap'ed with this file.
	unsafe extern "C" fn mmap(
	file: *mut bindings::file,
	vma: *mut bindings::vm_area_struct,
	) -> c_int {
	// SAFETY: The mmap call of a file can access the private data.
	let private = unsafe { (*file).private_data };
	// SAFETY: This is a Rust Miscdevice, so we call `into_foreign` in `open` and
	// `from_foreign` in `release`, and `fops_mmap` is guaranteed to be called between those
	// two operations.
	let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private.cast()) };
	// SAFETY: The caller provides a vma that is undergoing initial VMA setup.
	let area = unsafe { VmaNew::from_raw(vma) };
	// SAFETY:
	// * The file is valid for the duration of this call.
	// * There is no active fdget_pos region on the file on this thread.
	let file = unsafe { File::from_raw_file(file) };

	match T::mmap(device, file, area) {
	Ok(()) => 0,
	Err(err) => err.to_errno(),
	}
	}

	/// # Safety
	///
	/// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
	unsafe extern "C" fn ioctl(file: *mut bindings::file, cmd: c_uint, arg: c_ulong) -> c_long {
	// SAFETY: The ioctl call of a file can access the private data.
	let private = unsafe { (*file).private_data };
	// SAFETY: Ioctl calls can borrow the private data of the file.
	let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };

	// SAFETY:
	// * The file is valid for the duration of this call.
	// * There is no active fdget_pos region on the file on this thread.
	let file = unsafe { File::from_raw_file(file) };

	match T::ioctl(device, file, cmd, arg) {
	Ok(ret) => ret as c_long,
	Err(err) => err.to_errno() as c_long,
	}
	}

	/// # Safety
	///
	/// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
	#[cfg(CONFIG_COMPAT)]
	unsafe extern "C" fn compat_ioctl(
	file: *mut bindings::file,
	cmd: c_uint,
	arg: c_ulong,
	) -> c_long {
	// SAFETY: The compat ioctl call of a file can access the private data.
	let private = unsafe { (*file).private_data };
	// SAFETY: Ioctl calls can borrow the private data of the file.
	let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };

	// SAFETY:
	// * The file is valid for the duration of this call.
	// * There is no active fdget_pos region on the file on this thread.
	let file = unsafe { File::from_raw_file(file) };

	match T::compat_ioctl(device, file, cmd, arg) {
	Ok(ret) => ret as c_long,
	Err(err) => err.to_errno() as c_long,
	}
	}

	/// # Safety
	///
	/// - `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
	/// - `seq_file` must be a valid `struct seq_file` that we can write to.
	unsafe extern "C" fn show_fdinfo(seq_file: mut bindings::seq_file, file: mut bindings::file) {
	// SAFETY: The release call of a file owns the private data.
	let private = unsafe { (*file).private_data };
	// SAFETY: Ioctl calls can borrow the private data of the file.
	let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };
	// SAFETY:
	// * The file is valid for the duration of this call.
	// * There is no active fdget_pos region on the file on this thread.
	let file = unsafe { File::from_raw_file(file) };
	// SAFETY: The caller ensures that the pointer is valid and exclusive for the duration in
	// which this method is called.
	let m = unsafe { SeqFile::from_raw(seq_file) };

	T::show_fdinfo(device, m, file);
	}

	const VTABLE: bindings::file_operations = bindings::file_operations {
	open: Some(Self::open),
	release: Some(Self::release),
	mmap: if T::HAS_MMAP { Some(Self::mmap) } else { None },
	unlocked_ioctl: if T::HAS_IOCTL {
	Some(Self::ioctl)
	} else {
	None
	},
	#[cfg(CONFIG_COMPAT)]
	compat_ioctl: if T::HAS_COMPAT_IOCTL {
	Some(Self::compat_ioctl)
	} else if T::HAS_IOCTL {
	Some(bindings::compat_ptr_ioctl)
	} else {
	None
	},
	show_fdinfo: if T::HAS_SHOW_FDINFO {
	Some(Self::show_fdinfo)
	} else {
	None
	},
	// SAFETY: All zeros is a valid value for `bindings::file_operations`.
	..unsafe { MaybeUninit::zeroed().assume_init() }
	};

	const fn build() -> &'static bindings::file_operations {
	&Self::VTABLE
	}
	}