// SPDX-License-Identifier: GPL-2.0 //! Devres abstraction//!//! [`Devres`] represents an abstraction for the kernel devres (device resource management)//! implementation. use crate::{    alloc::Flags,    bindings,    device::{        Bound,        Device, //    },    error::to_result,    prelude::*,    revocable::{        Revocable,        RevocableGuard, //    },    sync::{        aref::ARef,        rcu,        Arc, //    },    types::{        ForeignOwnable,        Opaque, //    },}; /// Inner type that embeds a `struct devres_node` and the `Revocable<T>`.#[repr(C)]#[pin_data]struct Inner<T> {    #[pin]    node: Opaque<bindings::devres_node>,    #[pin]    data: Revocable<T>,} /// This abstraction is meant to be used by subsystems to containerize [`Device`] bound resources to/// manage their lifetime.////// [`Device`] bound resources should be freed when either the resource goes out of scope or the/// [`Device`] is unbound respectively, depending on what happens first. In any case, it is always/// guaranteed that revoking the device resource is completed before the corresponding [`Device`]/// is unbound.////// To achieve that [`Devres`] registers a devres callback on creation, which is called once the/// [`Device`] is unbound, revoking access to the encapsulated resource (see also [`Revocable`]).////// After the [`Devres`] has been unbound it is not possible to access the encapsulated resource/// anymore.////// [`Devres`] users should make sure to simply free the corresponding backing resource in `T`'s/// [`Drop`] implementation.////// # Examples////// ```no_run/// use kernel::{///     bindings,///     device::{///         Bound,///         Device,///     },///     devres::Devres,///     io::{///         Io,///         IoKnownSize,///         Mmio,///         MmioRaw,///         PhysAddr, /////     },///     prelude::*,/// };/// use core::ops::Deref;////// // See also [`pci::Bar`] for a real example./// struct IoMem<const SIZE: usize>(MmioRaw<SIZE>);////// impl<const SIZE: usize> IoMem<SIZE> {///     /// # Safety///     //////     /// [`paddr`, `paddr` + `SIZE`) must be a valid MMIO region that is mappable into the CPUs///     /// virtual address space.///     unsafe fn new(paddr: usize) -> Result<Self>{///         // SAFETY: By the safety requirements of this function [`paddr`, `paddr` + `SIZE`) is///         // valid for `ioremap`.///         let addr = unsafe { bindings::ioremap(paddr as PhysAddr, SIZE) };///         if addr.is_null() {///             return Err(ENOMEM);///         }//////         Ok(IoMem(MmioRaw::new(addr as usize, SIZE)?))///     }/// }////// impl<const SIZE: usize> Drop for IoMem<SIZE> {///     fn drop(&mut self) {///         // SAFETY: `self.0.addr()` is guaranteed to be properly mapped by `Self::new`.///         unsafe { bindings::iounmap(self.0.addr() as *mut c_void); };///     }/// }////// impl<const SIZE: usize> Deref for IoMem<SIZE> {///    type Target = Mmio<SIZE>;//////    fn deref(&self) -> &Self::Target {///         // SAFETY: The memory range stored in `self` has been properly mapped in `Self::new`.///         unsafe { Mmio::from_raw(&self.0) }///    }/// }/// # fn no_run(dev: &Device<Bound>) -> Result<(), Error> {/// // SAFETY: Invalid usage for example purposes./// let iomem = unsafe { IoMem::<{ core::mem::size_of::<u32>() }>::new(0xBAAAAAAD)? };/// let devres = Devres::new(dev, iomem)?;////// let res = devres.try_access().ok_or(ENXIO)?;/// res.write8(0x42, 0x0);/// # Ok(())/// # }/// ```pub struct Devres<T: Send> {    dev: ARef<Device>,    inner: Arc<Inner<T>>,} // Calling the FFI functions from the `base` module directly from the `Devres<T>` impl may result in// them being called directly from driver modules. This happens since the Rust compiler will use// monomorphisation, so it might happen that functions are instantiated within the calling driver// module. For now, work around this with `#[inline(never)]` helpers.//// TODO: Remove once a more generic solution has been implemented. For instance, we may be able to// leverage `bindgen` to take care of this depending on whether a symbol is (already) exported.mod base {    use kernel::{        bindings,        prelude::*, //    };     #[inline(never)]    #[allow(clippy::missing_safety_doc)]    pub(super) unsafe fn devres_node_init(        node: *mut bindings::devres_node,        release: bindings::dr_node_release_t,        free: bindings::dr_node_free_t,    ) {        // SAFETY: Safety requirements are the same as `bindings::devres_node_init`.        unsafe { bindings::devres_node_init(node, release, free) }    }     #[inline(never)]    #[allow(clippy::missing_safety_doc)]    pub(super) unsafe fn devres_set_node_dbginfo(        node: *mut bindings::devres_node,        name: *const c_char,        size: usize,    ) {        // SAFETY: Safety requirements are the same as `bindings::devres_set_node_dbginfo`.        unsafe { bindings::devres_set_node_dbginfo(node, name, size) }    }     #[inline(never)]    #[allow(clippy::missing_safety_doc)]    pub(super) unsafe fn devres_node_add(        dev: *mut bindings::device,        node: *mut bindings::devres_node,    ) {        // SAFETY: Safety requirements are the same as `bindings::devres_node_add`.        unsafe { bindings::devres_node_add(dev, node) }    }     #[must_use]    #[inline(never)]    #[allow(clippy::missing_safety_doc)]    pub(super) unsafe fn devres_node_remove(        dev: *mut bindings::device,        node: *mut bindings::devres_node,    ) -> bool {        // SAFETY: Safety requirements are the same as `bindings::devres_node_remove`.        unsafe { bindings::devres_node_remove(dev, node) }    }} impl<T: Send> Devres<T> {    /// Creates a new [`Devres`] instance of the given `data`.    ///    /// The `data` encapsulated within the returned `Devres` instance' `data` will be    /// (revoked)[`Revocable`] once the device is detached.    pub fn new<E>(dev: &Device<Bound>, data: impl PinInit<T, E>) -> Result<Self>    where        Error: From<E>,    {        let inner = Arc::pin_init::<Error>(            try_pin_init!(Inner {                node <- Opaque::ffi_init(|node: *mut bindings::devres_node| {                    // SAFETY: `node` is a valid pointer to an uninitialized `struct devres_node`.                    unsafe {                        base::devres_node_init(                            node,                            Some(Self::devres_node_release),                            Some(Self::devres_node_free_node),                        )                    };                     // SAFETY: `node` is a valid pointer to an uninitialized `struct devres_node`.                    unsafe {                        base::devres_set_node_dbginfo(                            node,                            // TODO: Use `core::any::type_name::<T>()` once it is a `const fn`,                            // such that we can convert the `&str` to a `&CStr` at compile-time.                            c"Devres<T>".as_char_ptr(),                            core::mem::size_of::<Revocable<T>>(),                        )                    };                }),                data <- Revocable::new(data),            }),            GFP_KERNEL,        )?;         // SAFETY:        // - `dev` is a valid pointer to a bound `struct device`.        // - `node` is a valid pointer to a `struct devres_node`.        // - `devres_node_add()` is guaranteed not to call `devres_node_release()` for the entire        //    lifetime of `dev`.        unsafe { base::devres_node_add(dev.as_raw(), inner.node.get()) };         // Take additional reference count for `devres_node_add()`.        core::mem::forget(inner.clone());         Ok(Self {            dev: dev.into(),            inner,        })    }     fn data(&self) -> &Revocable<T> {        &self.inner.data    }     #[allow(clippy::missing_safety_doc)]    unsafe extern "C" fn devres_node_release(        _dev: *mut bindings::device,        node: *mut bindings::devres_node,    ) {        let node = Opaque::cast_from(node);         // SAFETY: `node` is in the same allocation as its container.        let inner = unsafe { kernel::container_of!(node, Inner<T>, node) };         // SAFETY: `inner` is a valid `Inner<T>` pointer.        let inner = unsafe { &*inner };         inner.data.revoke();    }     #[allow(clippy::missing_safety_doc)]    unsafe extern "C" fn devres_node_free_node(node: *mut bindings::devres_node) {        let node = Opaque::cast_from(node);         // SAFETY: `node` is in the same allocation as its container.        let inner = unsafe { kernel::container_of!(node, Inner<T>, node) };         // SAFETY: `inner` points to the entire `Inner<T>` allocation.        drop(unsafe { Arc::from_raw(inner) });    }     fn remove_node(&self) -> bool {        // SAFETY:        // - `self.device().as_raw()` is a valid pointer to a bound `struct device`.        // - `self.inner.node.get()` is a valid pointer to a `struct devres_node`.        unsafe { base::devres_node_remove(self.device().as_raw(), self.inner.node.get()) }    }     /// Return a reference of the [`Device`] this [`Devres`] instance has been created with.    pub fn device(&self) -> &Device {        &self.dev    }     /// Obtain `&'a T`, bypassing the [`Revocable`].    ///    /// This method allows to directly obtain a `&'a T`, bypassing the [`Revocable`], by presenting    /// a `&'a Device<Bound>` of the same [`Device`] this [`Devres`] instance has been created with.    ///    /// # Errors    ///    /// An error is returned if `dev` does not match the same [`Device`] this [`Devres`] instance    /// has been created with.    ///    /// # Examples    ///    /// ```no_run    /// #![cfg(CONFIG_PCI)]    /// use kernel::{    ///     device::Core,    ///     devres::Devres,    ///     io::{    ///         Io,    ///         IoKnownSize, //    ///     },    ///     pci, //    /// };    ///    /// fn from_core(dev: &pci::Device<Core>, devres: Devres<pci::Bar<0x4>>) -> Result {    ///     let bar = devres.access(dev.as_ref())?;    ///    ///     let _ = bar.read32(0x0);    ///    ///     // might_sleep()    ///    ///     bar.write32(0x42, 0x0);    ///    ///     Ok(())    /// }    /// ```    pub fn access<'a>(&'a self, dev: &'a Device<Bound>) -> Result<&'a T> {        if self.dev.as_raw() != dev.as_raw() {            return Err(EINVAL);        }         // SAFETY: `dev` being the same device as the device this `Devres` has been created for        // proves that `self.data` hasn't been revoked and is guaranteed to not be revoked as long        // as `dev` lives; `dev` lives at least as long as `self`.        Ok(unsafe { self.data().access() })    }     /// [`Devres`] accessor for [`Revocable::try_access`].    pub fn try_access(&self) -> Option<RevocableGuard<'_, T>> {        self.data().try_access()    }     /// [`Devres`] accessor for [`Revocable::try_access_with`].    pub fn try_access_with<R, F: FnOnce(&T) -> R>(&self, f: F) -> Option<R> {        self.data().try_access_with(f)    }     /// [`Devres`] accessor for [`Revocable::try_access_with_guard`].    pub fn try_access_with_guard<'a>(&'a self, guard: &'a rcu::Guard) -> Option<&'a T> {        self.data().try_access_with_guard(guard)    }} // SAFETY: `Devres` can be send to any task, if `T: Send`.unsafe impl<T: Send> Send for Devres<T> {} // SAFETY: `Devres` can be shared with any task, if `T: Sync`.unsafe impl<T: Send + Sync> Sync for Devres<T> {} impl<T: Send> Drop for Devres<T> {    fn drop(&mut self) {        // SAFETY: When `drop` runs, it is guaranteed that nobody is accessing the revocable data        // anymore, hence it is safe not to wait for the grace period to finish.        if unsafe { self.data().revoke_nosync() } {            // We revoked `self.data` before devres did, hence try to remove it.            if self.remove_node() {                // SAFETY: In `Self::new` we have taken an additional reference count of `self.data`                // for `devres_node_add()`. Since `remove_node()` was successful, we have to drop                // this additional reference count.                drop(unsafe { Arc::from_raw(Arc::as_ptr(&self.inner)) });            }        }    }} /// Consume `data` and [`Drop::drop`] `data` once `dev` is unbound.fn register_foreign<P>(dev: &Device<Bound>, data: P) -> Resultwhere    P: ForeignOwnable + Send + 'static,{    let ptr = data.into_foreign();     #[allow(clippy::missing_safety_doc)]    unsafe extern "C" fn callback<P: ForeignOwnable>(ptr: *mut kernel::ffi::c_void) {        // SAFETY: `ptr` is the pointer to the `ForeignOwnable` leaked above and hence valid.        drop(unsafe { P::from_foreign(ptr.cast()) });    }     // SAFETY:    // - `dev.as_raw()` is a pointer to a valid and bound device.    // - `ptr` is a valid pointer the `ForeignOwnable` devres takes ownership of.    to_result(unsafe {        // `devm_add_action_or_reset()` also calls `callback` on failure, such that the        // `ForeignOwnable` is released eventually.        bindings::devm_add_action_or_reset(dev.as_raw(), Some(callback::<P>), ptr.cast())    })} /// Encapsulate `data` in a [`KBox`] and [`Drop::drop`] `data` once `dev` is unbound.////// # Examples////// ```no_run/// use kernel::{///     device::{///         Bound,///         Device, /////     },///     devres, ///// };////// /// Registration of e.g. a class device, IRQ, etc./// struct Registration;////// impl Registration {///     fn new() -> Self {///         // register//////         Self///     }/// }////// impl Drop for Registration {///     fn drop(&mut self) {///        // unregister///     }/// }////// fn from_bound_context(dev: &Device<Bound>) -> Result {///     devres::register(dev, Registration::new(), GFP_KERNEL)/// }/// ```pub fn register<T, E>(dev: &Device<Bound>, data: impl PinInit<T, E>, flags: Flags) -> Resultwhere    T: Send + 'static,    Error: From<E>,{    let data = KBox::pin_init(data, flags)?;     register_foreign(dev, data)}