// SPDX-License-Identifier: GPL-2.0 //! Abstractions for the auxiliary bus.//!//! C header: [`include/linux/auxiliary_bus.h`](srctree/include/linux/auxiliary_bus.h) use crate::{    bindings,    container_of,    device,    device_id::{        RawDeviceId,        RawDeviceIdIndex, //    },     driver,    error::{        from_result,        to_result, //    },    prelude::*,    types::{        CovariantForLt,        ForLt,        ForeignOwnable,        Opaque, //    },    ThisModule, //};use core::{    any::TypeId,    marker::PhantomData,    mem::offset_of,    pin::Pin,    ptr::{        addr_of_mut,        NonNull, //    },}; /// An adapter for the registration of auxiliary drivers.pub struct Adapter<T: Driver>(T); // SAFETY:// - `bindings::auxiliary_driver` is a C type declared as `repr(C)`.// - `T::Data` is the type of the driver's device private data.// - `struct auxiliary_driver` embeds a `struct device_driver`.// - `DEVICE_DRIVER_OFFSET` is the correct byte offset to the embedded `struct device_driver`.unsafe impl<T: Driver> driver::DriverLayout for Adapter<T> {    type DriverType = bindings::auxiliary_driver;    type DriverData<'bound> = T::Data<'bound>;    const DEVICE_DRIVER_OFFSET: usize = core::mem::offset_of!(Self::DriverType, driver);} // SAFETY: A call to `unregister` for a given instance of `DriverType` is guaranteed to be valid if// a preceding call to `register` has been successful.unsafe impl<T: Driver> driver::RegistrationOps for Adapter<T> {    unsafe fn register(        adrv: &Opaque<Self::DriverType>,        name: &'static CStr,        module: &'static ThisModule,    ) -> Result {        // SAFETY: It's safe to set the fields of `struct auxiliary_driver` on initialization.        unsafe {            (*adrv.get()).name = name.as_char_ptr();            (*adrv.get()).probe = Some(Self::probe_callback);            (*adrv.get()).remove = Some(Self::remove_callback);            (*adrv.get()).id_table = T::ID_TABLE.as_ptr();        }         // SAFETY: `adrv` is guaranteed to be a valid `DriverType`.        to_result(unsafe {            bindings::__auxiliary_driver_register(adrv.get(), module.as_ptr(), name.as_char_ptr())        })    }     unsafe fn unregister(adrv: &Opaque<Self::DriverType>) {        // SAFETY: `adrv` is guaranteed to be a valid `DriverType`.        unsafe { bindings::auxiliary_driver_unregister(adrv.get()) }    }} impl<T: Driver> Adapter<T> {    extern "C" fn probe_callback(        adev: *mut bindings::auxiliary_device,        id: *const bindings::auxiliary_device_id,    ) -> c_int {        // SAFETY: The auxiliary bus only ever calls the probe callback with a valid pointer to a        // `struct auxiliary_device`.        //        // INVARIANT: `adev` is valid for the duration of `probe_callback()`.        let adev = unsafe { &*adev.cast::<Device<device::CoreInternal<'_>>>() };         // SAFETY: `DeviceId` is a `#[repr(transparent)`] wrapper of `struct auxiliary_device_id`        // and does not add additional invariants, so it's safe to transmute.        let id = unsafe { &*id.cast::<DeviceId>() };         // SAFETY: `id` comes from `T::ID_TABLE` which is of type `IdArray<_, T::IdInfo>`.        let info = unsafe { id.info_unchecked::<T::IdInfo>() };         from_result(|| {            let data = T::probe(adev, info);             adev.as_ref().set_drvdata(data)?;            Ok(0)        })    }     extern "C" fn remove_callback(adev: *mut bindings::auxiliary_device) {        // SAFETY: The auxiliary bus only ever calls the probe callback with a valid pointer to a        // `struct auxiliary_device`.        //        // INVARIANT: `adev` is valid for the duration of `remove_callback()`.        let adev = unsafe { &*adev.cast::<Device<device::CoreInternal<'_>>>() };         // SAFETY: `remove_callback` is only ever called after a successful call to        // `probe_callback`, hence it's guaranteed that `Device::set_drvdata()` has been called        // and stored a `Pin<KBox<T::Data<'_>>>`.        let data = unsafe { adev.as_ref().drvdata_borrow::<T::Data<'_>>() };         T::unbind(adev, data);    }} /// Declares a kernel module that exposes a single auxiliary driver.#[macro_export]macro_rules! module_auxiliary_driver {    ($($f:tt)*) => {        $crate::module_driver!(<T>, $crate::auxiliary::Adapter<T>, { $($f)* });    };} /// Abstraction for `bindings::auxiliary_device_id`.#[repr(transparent)]#[derive(Clone, Copy)]pub struct DeviceId(bindings::auxiliary_device_id); impl DeviceId {    /// Create a new [`DeviceId`] from name.    pub const fn new(modname: &'static CStr, name: &'static CStr) -> Self {        let name = name.to_bytes_with_nul();        let modname = modname.to_bytes_with_nul();         let mut id: bindings::auxiliary_device_id = pin_init::zeroed();        let mut i = 0;        while i < modname.len() {            id.name[i] = modname[i];            i += 1;        }         // Reuse the space of the NULL terminator.        id.name[i - 1] = b'.';         let mut j = 0;        while j < name.len() {            id.name[i] = name[j];            i += 1;            j += 1;        }         Self(id)    }} // SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `auxiliary_device_id` and does not add// additional invariants, so it's safe to transmute to `RawType`.unsafe impl RawDeviceId for DeviceId {    type RawType = bindings::auxiliary_device_id;} // SAFETY: `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.unsafe impl RawDeviceIdIndex for DeviceId {    const DRIVER_DATA_OFFSET: usize =        core::mem::offset_of!(bindings::auxiliary_device_id, driver_data);} /// IdTable type for auxiliary drivers.pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>; /// Create a auxiliary `IdTable` with its alias for modpost.#[macro_export]macro_rules! auxiliary_device_table {    ($($tt:tt)*) => {        $crate::module_device_table!("auxiliary", $crate::auxiliary::DeviceId, $($tt)*);    };} /// The auxiliary driver trait.////// Drivers must implement this trait in order to get an auxiliary driver registered.pub trait Driver {    /// The type holding information about each device id supported by the driver.    ///    /// TODO: Use associated_type_defaults once stabilized:    ///    /// type IdInfo: 'static = ();    type IdInfo: 'static;     /// The type of the driver's bus device private data.    type Data<'bound>: Send + 'bound;     /// The table of device ids supported by the driver.    const ID_TABLE: IdTable<Self::IdInfo>;     /// Auxiliary driver probe.    ///    /// Called when an auxiliary device is matches a corresponding driver.    fn probe<'bound>(        dev: &'bound Device<device::Core<'_>>,        id_info: &'bound Self::IdInfo,    ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound;     /// Auxiliary driver unbind.    ///    /// Called when a [`Device`] is unbound from its bound [`Driver`]. Implementing this callback    /// is optional.    ///    /// This callback serves as a place for drivers to perform teardown operations that require a    /// `&Device<Core>` or `&Device<Bound>` reference. For instance, drivers may try to perform I/O    /// operations to gracefully tear down the device.    ///    /// Otherwise, release operations for driver resources should be performed in `Drop`.    fn unbind<'bound>(dev: &'bound Device<device::Core<'_>>, this: Pin<&Self::Data<'bound>>) {        let _ = (dev, this);    }} /// The auxiliary device representation.////// This structure represents the Rust abstraction for a C `struct auxiliary_device`. The/// implementation abstracts the usage of an already existing C `struct auxiliary_device` within/// Rust code that we get passed from the C side.////// # Invariants////// A [`Device`] instance represents a valid `struct auxiliary_device` created by the C portion of/// the kernel.#[repr(transparent)]pub struct Device<Ctx: device::DeviceContext = device::Normal>(    Opaque<bindings::auxiliary_device>,    PhantomData<Ctx>,); impl<Ctx: device::DeviceContext> Device<Ctx> {    fn as_raw(&self) -> *mut bindings::auxiliary_device {        self.0.get()    }     /// Returns the auxiliary device' id.    pub fn id(&self) -> u32 {        // SAFETY: By the type invariant `self.as_raw()` is a valid pointer to a        // `struct auxiliary_device`.        unsafe { (*self.as_raw()).id }    }} impl Device<device::Bound> {    /// Returns a bound reference to the parent [`device::Device`].    pub fn parent(&self) -> &device::Device<device::Bound> {        let parent = (**self).parent();         // SAFETY: A bound auxiliary device always has a bound parent device.        unsafe { parent.as_bound() }    }     /// Returns the stored registration data as a pinned reference.    ///    /// Performs null and [`TypeId`] checks, then borrows the stored [`KBox`].    ///    /// # Safety    ///    /// Callers must ensure that the lifetime shortening from the original `'static` storage to    /// `'_` is sound, e.g. via an HRTB closure or [`CovariantForLt`] guarantee.    unsafe fn registration_data_pinned<F: ForLt + 'static>(&self) -> Result<Pin<&F::Of<'_>>> {        // SAFETY: By the type invariant, `self.as_raw()` is a valid `struct auxiliary_device`.        let ptr = unsafe { (*self.as_raw()).registration_data_rust };        if ptr.is_null() {            dev_warn!(                self.as_ref(),                "No registration data set; parent is not a Rust driver.\n"            );            return Err(ENOENT);        }         // SAFETY: `ptr` is non-null and was set via `into_foreign()` in `Registration::new()`;        // `RegistrationData` is `#[repr(C)]` with `type_id` at offset 0, so reading a `TypeId`        // at the start of the allocation is valid regardless of `F`.        let type_id = unsafe { ptr.cast::<TypeId>().read() };        if type_id != TypeId::of::<F>() {            return Err(EINVAL);        }         // SAFETY: The `TypeId` check above confirms that the stored type matches `F`'s        // encoding; lifetimes are erased at runtime, so borrowing as `F::Of<'_>` is        // layout-compatible with the stored `F::Of<'static>`. `ptr` remains valid until        // `Registration::drop()` calls `from_foreign()`.        let wrapper = unsafe { Pin::<KBox<RegistrationData<F::Of<'_>>>>::borrow(ptr) };         // SAFETY: `data` is a structurally pinned field of `RegistrationData`.        Ok(unsafe { wrapper.map_unchecked(|w| &w.data) })    }     /// Access the registration data set by the registering (parent) driver through a closure.    ///    /// `F` is the [`ForLt`](trait@ForLt) encoding of the data type. The closure receives a pinned    /// reference to the registration data.    ///    /// For covariant types that implement [`trait@CovariantForLt`], prefer    /// [`registration_data`](Self::registration_data) which returns a direct reference.    ///    /// Returns [`EINVAL`] if `F` does not match the type used by the parent driver when calling    /// [`Registration::new()`].    ///    /// Returns [`ENOENT`] if no registration data has been set, e.g. when the device was    /// registered by a C driver.    #[inline]    pub fn registration_data_with<F: ForLt + 'static, R>(        &self,        f: impl for<'a> FnOnce(Pin<&'a F::Of<'a>>) -> R,    ) -> Result<R> {        // SAFETY: The HRTB closure prevents the caller from smuggling in references with a        // concrete short lifetime, making the round-trip from `'static` sound regardless of        // variance.        let pinned = unsafe { self.registration_data_pinned::<F>()? };         Ok(f(pinned))    }     /// Returns a pinned reference to the registration data set by the registering (parent) driver.    ///    /// This method is only available when `F` implements [`trait@CovariantForLt`], which guarantees    /// that the lifetime shortening is sound.    ///    /// For non-covariant types, use the closure-based [`Self::registration_data_with`].    ///    /// Returns [`EINVAL`] if `F` does not match the type used by the parent driver when calling    /// [`Registration::new()`].    ///    /// Returns [`ENOENT`] if no registration data has been set, e.g. when the device was    /// registered by a C driver.    #[inline]    pub fn registration_data<F: CovariantForLt + 'static>(&self) -> Result<Pin<&F::Of<'_>>> {        // SAFETY: `CovariantForLt` guarantees covariance, which makes the lifetime shortening        // from `'static` to `'_` performed by `registration_data_pinned` sound.        unsafe { self.registration_data_pinned::<F>() }    }} impl Device {    /// Returns a reference to the parent [`device::Device`].    pub fn parent(&self) -> &device::Device {        // SAFETY: A `struct auxiliary_device` always has a parent.        unsafe { self.as_ref().parent().unwrap_unchecked() }    }     extern "C" fn release(dev: *mut bindings::device) {        // SAFETY: By the type invariant `self.0.as_raw` is a pointer to the `struct device`        // embedded in `struct auxiliary_device`.        let adev = unsafe { container_of!(dev, bindings::auxiliary_device, dev) };         // SAFETY: `adev` points to the memory that has been allocated in `Registration::new`, via        // `KBox::new(Opaque::<bindings::auxiliary_device>::zeroed(), GFP_KERNEL)`.        let _ = unsafe { KBox::<Opaque<bindings::auxiliary_device>>::from_raw(adev.cast()) };    }} // SAFETY: `auxiliary::Device` is a transparent wrapper of `struct auxiliary_device`.// The offset is guaranteed to point to a valid device field inside `auxiliary::Device`.unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for Device<Ctx> {    const OFFSET: usize = offset_of!(bindings::auxiliary_device, dev);} // SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic// argument.kernel::impl_device_context_deref!(unsafe { Device });kernel::impl_device_context_into_aref!(Device); // SAFETY: Instances of `Device` are always reference-counted.unsafe impl crate::sync::aref::AlwaysRefCounted for Device {    fn inc_ref(&self) {        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.        unsafe { bindings::get_device(self.as_ref().as_raw()) };    }     unsafe fn dec_ref(obj: NonNull<Self>) {        // CAST: `Self` a transparent wrapper of `bindings::auxiliary_device`.        let adev: *mut bindings::auxiliary_device = obj.cast().as_ptr();         // SAFETY: By the type invariant of `Self`, `adev` is a pointer to a valid        // `struct auxiliary_device`.        let dev = unsafe { addr_of_mut!((*adev).dev) };         // SAFETY: The safety requirements guarantee that the refcount is non-zero.        unsafe { bindings::put_device(dev) }    }} impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {    fn as_ref(&self) -> &device::Device<Ctx> {        // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid        // `struct auxiliary_device`.        let dev = unsafe { addr_of_mut!((*self.as_raw()).dev) };         // SAFETY: `dev` points to a valid `struct device`.        unsafe { device::Device::from_raw(dev) }    }} // SAFETY: A `Device` is always reference-counted and can be released from any thread.unsafe impl Send for Device {} // SAFETY: `Device` can be shared among threads because all methods of `Device`// (i.e. `Device<Normal>) are thread safe.unsafe impl Sync for Device {} // SAFETY: Same as `Device<Normal>` -- the underlying `struct auxiliary_device` is the same;// `Bound` is a zero-sized type-state marker that does not affect thread safety.unsafe impl Sync for Device<device::Bound> {} /// Wrapper that stores a [`TypeId`] alongside the registration data for runtime type checking.#[repr(C)]#[pin_data]struct RegistrationData<T> {    type_id: TypeId,    #[pin]    data: T,} /// The registration of an auxiliary device.////// This type represents the registration of a [`struct auxiliary_device`]. When its parent device/// is unbound, the corresponding auxiliary device will be unregistered from the system.////// The type parameter `F` is a [`ForLt`](trait@ForLt) encoding of the registration/// data type. For non-lifetime-parameterized types, use [`ForLt!(T)`](macro@ForLt).////// The data can be accessed by the auxiliary driver through [`Device::registration_data()`] and/// [`Device::registration_data_with()`].////// # Invariants////// `self.adev` always holds a valid pointer to an initialized and registered/// [`struct auxiliary_device`] whose `registration_data_rust` field points to a/// valid `Pin<KBox<RegistrationData<F::Of<'static>>>>`.pub struct Registration<'a, F: ForLt + 'static> {    adev: NonNull<bindings::auxiliary_device>,    _phantom: PhantomData<F::Of<'a>>,} impl<'a, F: ForLt> Registration<'a, F>where    for<'b> F::Of<'b>: Send + Sync,{    /// Create and register a new auxiliary device with the given registration data.    ///    /// The `data` is owned by the registration and can be accessed through the auxiliary device    /// via [`Device::registration_data()`].    ///    /// # 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.    ///    /// If the registration data is `'static`, use the safe [`Registration::new()`] instead.    pub unsafe fn new_with_lt<E>(        parent: &'a device::Device<device::Bound>,        name: &CStr,        id: u32,        modname: &CStr,        data: impl PinInit<F::Of<'a>, E>,    ) -> Result<Self>    where        Error: From<E>,    {        let data = KBox::pin_init::<Error>(            try_pin_init!(RegistrationData {                type_id: TypeId::of::<F>(),                data <- data,            }),            GFP_KERNEL,        )?;         // SAFETY: `'a` is invariant (via `Registration`'s `PhantomData`). Lifetimes do not        // affect layout, so RegistrationData<F::Of<'a>> and RegistrationData<F::Of<'static>>        // have identical representation.        let data: Pin<KBox<RegistrationData<F::Of<'static>>>> =            unsafe { core::mem::transmute(data) };         let boxed: KBox<Opaque<bindings::auxiliary_device>> = KBox::zeroed(GFP_KERNEL)?;        let adev = boxed.get();         // SAFETY: It's safe to set the fields of `struct auxiliary_device` on initialization.        unsafe {            (*adev).dev.parent = parent.as_raw();            (*adev).dev.release = Some(Device::release);            (*adev).name = name.as_char_ptr();            (*adev).id = id;            (*adev).registration_data_rust = data.into_foreign();        }

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