// SPDX-License-Identifier: GPL-2.0 //! Generic implementation of device IDs.//!//! Each bus / subsystem that matches device and driver through a bus / subsystem specific ID is//! expected to implement [`RawDeviceId`]. use core::mem::MaybeUninit; /// Marker trait to indicate a Rust device ID type represents a corresponding C device ID type.////// This is meant to be implemented by buses/subsystems so that they can use [`IdTable`] to/// guarantee (at compile-time) zero-termination of device id tables provided by drivers.////// # Safety////// Implementers must ensure that `Self` is layout-compatible with [`RawDeviceId::RawType`];/// i.e. it's safe to transmute to `RawType`.////// This requirement is needed so `IdArray::new` can convert `Self` to `RawType` when building/// the ID table.////// Ideally, this should be achieved using a const function that does conversion instead of/// transmute; however, const trait functions relies on `const_trait_impl` unstable feature,/// which is broken/gone in Rust 1.73.pub unsafe trait RawDeviceId {    /// The raw type that holds the device id.    ///    /// Id tables created from [`Self`] are going to hold this type in its zero-terminated array.    type RawType: Copy;} /// Extension trait for [`RawDeviceId`] for devices that embed an index or context value.////// This is typically used when the device ID struct includes a field like `driver_data`/// that is used to store a pointer-sized value (e.g., an index or context pointer).////// # Safety////// Implementers must ensure that `DRIVER_DATA_OFFSET` is the correct offset (in bytes) to/// the context/data field (e.g., the `driver_data` field) within the raw device ID structure./// This field must be correctly sized to hold a `usize`.////// Ideally, the data should be added during `Self` to `RawType` conversion,/// but there's currently no way to do it when using traits in const.pub unsafe trait RawDeviceIdIndex: RawDeviceId {    /// The offset (in bytes) to the context/data field in the raw device ID.    const DRIVER_DATA_OFFSET: usize;     /// The index stored at `DRIVER_DATA_OFFSET` of the implementor of the [`RawDeviceIdIndex`]    /// trait.    fn index(&self) -> usize;} /// A zero-terminated device id array.#[repr(C)]pub struct RawIdArray<T: RawDeviceId, const N: usize> {    ids: [T::RawType; N],    sentinel: MaybeUninit<T::RawType>,} impl<T: RawDeviceId, const N: usize> RawIdArray<T, N> {    #[doc(hidden)]    pub const fn size(&self) -> usize {        core::mem::size_of::<Self>()    }} /// A zero-terminated device id array, followed by context data.#[repr(C)]pub struct IdArray<T: RawDeviceId, U, const N: usize> {    raw_ids: RawIdArray<T, N>,    id_infos: [U; N],} impl<T: RawDeviceId, U, const N: usize> IdArray<T, U, N> {    /// Creates a new instance of the array.    ///    /// The contents are derived from the given identifiers and context information.    ///    /// # Safety    ///    /// `data_offset` as `None` is always safe.    /// If `data_offset` is `Some(data_offset)`, then:    /// - `data_offset` must be the correct offset (in bytes) to the context/data field    ///   (e.g., the `driver_data` field) within the raw device ID structure.    /// - The field at `data_offset` must be correctly sized to hold a `usize`.    const unsafe fn build(ids: [(T, U); N], data_offset: Option<usize>) -> Self {        let mut raw_ids = [const { MaybeUninit::<T::RawType>::uninit() }; N];        let mut infos = [const { MaybeUninit::uninit() }; N];         let mut i = 0usize;        while i < N {            // SAFETY: by the safety requirement of `RawDeviceId`, we're guaranteed that `T` is            // layout-wise compatible with `RawType`.            raw_ids[i] = unsafe { core::mem::transmute_copy(&ids[i].0) };            if let Some(data_offset) = data_offset {                // SAFETY: by the safety requirement of this function, this would be effectively                // `raw_ids[i].driver_data = i;`.                unsafe {                    raw_ids[i]                        .as_mut_ptr()                        .byte_add(data_offset)                        .cast::<usize>()                        .write(i);                }            }             // SAFETY: this is effectively a move: `infos[i] = ids[i].1`. We make a copy here but            // later forget `ids`.            infos[i] = MaybeUninit::new(unsafe { core::ptr::read(&ids[i].1) });            i += 1;        }         core::mem::forget(ids);         Self {            raw_ids: RawIdArray {                // SAFETY: this is effectively `array_assume_init`, which is unstable, so we use                // `transmute_copy` instead. We have initialized all elements of `raw_ids` so this                // `array_assume_init` is safe.                ids: unsafe { core::mem::transmute_copy(&raw_ids) },                sentinel: MaybeUninit::zeroed(),            },            // SAFETY: We have initialized all elements of `infos` so this `array_assume_init` is            // safe.            id_infos: unsafe { core::mem::transmute_copy(&infos) },        }    }     /// Creates a new instance of the array without writing index values.    ///    /// The contents are derived from the given identifiers and context information.    /// If the device implements [`RawDeviceIdIndex`], consider using [`IdArray::new`] instead.    pub const fn new_without_index(ids: [(T, U); N]) -> Self {        // SAFETY: Calling `Self::build` with `offset = None` is always safe,        // because no raw memory writes are performed in this case.        unsafe { Self::build(ids, None) }    }     /// Reference to the contained [`RawIdArray`].    pub const fn raw_ids(&self) -> &RawIdArray<T, N> {        &self.raw_ids    }} impl<T: RawDeviceId + RawDeviceIdIndex, U, const N: usize> IdArray<T, U, N> {    /// Creates a new instance of the array.    ///    /// The contents are derived from the given identifiers and context information.    pub const fn new(ids: [(T, U); N]) -> Self {        // SAFETY: by the safety requirement of `RawDeviceIdIndex`,        // `T::DRIVER_DATA_OFFSET` is guaranteed to be the correct offset (in bytes) to        // a field within `T::RawType`.        unsafe { Self::build(ids, Some(T::DRIVER_DATA_OFFSET)) }    }} /// A device id table.////// This trait is only implemented by `IdArray`.////// The purpose of this trait is to allow `&'static dyn IdArray<T, U>` to be in context when `N` in/// `IdArray` doesn't matter.pub trait IdTable<T: RawDeviceId, U> {    /// Obtain the pointer to the ID table.    fn as_ptr(&self) -> *const T::RawType;     /// Obtain the pointer to the bus specific device ID from an index.    fn id(&self, index: usize) -> &T::RawType;     /// Obtain the pointer to the driver-specific information from an index.    fn info(&self, index: usize) -> &U;} impl<T: RawDeviceId, U, const N: usize> IdTable<T, U> for IdArray<T, U, N> {    fn as_ptr(&self) -> *const T::RawType {        // This cannot be `self.ids.as_ptr()`, as the return pointer must have correct provenance        // to access the sentinel.        core::ptr::from_ref(self).cast()    }     fn id(&self, index: usize) -> &T::RawType {        &self.raw_ids.ids[index]    }     fn info(&self, index: usize) -> &U {        &self.id_infos[index]    }} /// Create device table alias for modpost.#[macro_export]macro_rules! module_device_table {    ($table_type: literal, $module_table_name:ident, $table_name:ident) => {        #[rustfmt::skip]        #[export_name =            concat!("__mod_device_table__", line!(),                    "__kmod_", module_path!(),                    "__", $table_type,                    "__", stringify!($table_name))        ]        static $module_table_name: [::core::mem::MaybeUninit<u8>; $table_name.raw_ids().size()] =            unsafe { ::core::mem::transmute_copy($table_name.raw_ids()) };    };}