diff options
Diffstat (limited to 'rust/kernel/device.rs')
| -rw-r--r-- | rust/kernel/device.rs | 135 |
1 files changed, 126 insertions, 9 deletions
diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs index 1321e6f0b53c..c79be2e2bfe3 100644 --- a/rust/kernel/device.rs +++ b/rust/kernel/device.rs @@ -6,16 +6,21 @@ use crate::{ bindings, fmt, + prelude::*, sync::aref::ARef, types::{ForeignOwnable, Opaque}, }; -use core::{marker::PhantomData, ptr}; +use core::{any::TypeId, marker::PhantomData, ptr}; #[cfg(CONFIG_PRINTK)] use crate::c_str; +use crate::str::CStrExt as _; pub mod property; +// Assert that we can `read()` / `write()` a `TypeId` instance from / into `struct driver_type`. +static_assert!(core::mem::size_of::<bindings::driver_type>() >= core::mem::size_of::<TypeId>()); + /// The core representation of a device in the kernel's driver model. /// /// This structure represents the Rust abstraction for a C `struct device`. A [`Device`] can either @@ -197,10 +202,31 @@ impl Device { } impl Device<CoreInternal> { + fn set_type_id<T: 'static>(&self) { + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. + let private = unsafe { (*self.as_raw()).p }; + + // SAFETY: For a bound device (implied by the `CoreInternal` device context), `private` is + // guaranteed to be a valid pointer to a `struct device_private`. + let driver_type = unsafe { &raw mut (*private).driver_type }; + + // SAFETY: `driver_type` is valid for (unaligned) writes of a `TypeId`. + unsafe { + driver_type + .cast::<TypeId>() + .write_unaligned(TypeId::of::<T>()) + }; + } + /// Store a pointer to the bound driver's private data. - pub fn set_drvdata(&self, data: impl ForeignOwnable) { + pub fn set_drvdata<T: 'static>(&self, data: impl PinInit<T, Error>) -> Result { + let data = KBox::pin_init(data, GFP_KERNEL)?; + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. - unsafe { bindings::dev_set_drvdata(self.as_raw(), data.into_foreign().cast()) } + unsafe { bindings::dev_set_drvdata(self.as_raw(), data.into_foreign().cast()) }; + self.set_type_id::<T>(); + + Ok(()) } /// Take ownership of the private data stored in this [`Device`]. @@ -210,16 +236,19 @@ impl Device<CoreInternal> { /// - Must only be called once after a preceding call to [`Device::set_drvdata`]. /// - The type `T` must match the type of the `ForeignOwnable` previously stored by /// [`Device::set_drvdata`]. - pub unsafe fn drvdata_obtain<T: ForeignOwnable>(&self) -> T { + pub unsafe fn drvdata_obtain<T: 'static>(&self) -> Pin<KBox<T>> { // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. let ptr = unsafe { bindings::dev_get_drvdata(self.as_raw()) }; + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. + unsafe { bindings::dev_set_drvdata(self.as_raw(), core::ptr::null_mut()) }; + // SAFETY: // - By the safety requirements of this function, `ptr` comes from a previous call to // `into_foreign()`. // - `dev_get_drvdata()` guarantees to return the same pointer given to `dev_set_drvdata()` // in `into_foreign()`. - unsafe { T::from_foreign(ptr.cast()) } + unsafe { Pin::<KBox<T>>::from_foreign(ptr.cast()) } } /// Borrow the driver's private data bound to this [`Device`]. @@ -230,7 +259,23 @@ impl Device<CoreInternal> { /// [`Device::drvdata_obtain`]. /// - The type `T` must match the type of the `ForeignOwnable` previously stored by /// [`Device::set_drvdata`]. - pub unsafe fn drvdata_borrow<T: ForeignOwnable>(&self) -> T::Borrowed<'_> { + pub unsafe fn drvdata_borrow<T: 'static>(&self) -> Pin<&T> { + // SAFETY: `drvdata_unchecked()` has the exact same safety requirements as the ones + // required by this method. + unsafe { self.drvdata_unchecked() } + } +} + +impl Device<Bound> { + /// Borrow the driver's private data bound to this [`Device`]. + /// + /// # Safety + /// + /// - Must only be called after a preceding call to [`Device::set_drvdata`] and before + /// [`Device::drvdata_obtain`]. + /// - The type `T` must match the type of the `ForeignOwnable` previously stored by + /// [`Device::set_drvdata`]. + unsafe fn drvdata_unchecked<T: 'static>(&self) -> Pin<&T> { // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. let ptr = unsafe { bindings::dev_get_drvdata(self.as_raw()) }; @@ -239,7 +284,46 @@ impl Device<CoreInternal> { // `into_foreign()`. // - `dev_get_drvdata()` guarantees to return the same pointer given to `dev_set_drvdata()` // in `into_foreign()`. - unsafe { T::borrow(ptr.cast()) } + unsafe { Pin::<KBox<T>>::borrow(ptr.cast()) } + } + + fn match_type_id<T: 'static>(&self) -> Result { + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. + let private = unsafe { (*self.as_raw()).p }; + + // SAFETY: For a bound device, `private` is guaranteed to be a valid pointer to a + // `struct device_private`. + let driver_type = unsafe { &raw mut (*private).driver_type }; + + // SAFETY: + // - `driver_type` is valid for (unaligned) reads of a `TypeId`. + // - A bound device guarantees that `driver_type` contains a valid `TypeId` value. + let type_id = unsafe { driver_type.cast::<TypeId>().read_unaligned() }; + + if type_id != TypeId::of::<T>() { + return Err(EINVAL); + } + + Ok(()) + } + + /// Access a driver's private data. + /// + /// Returns a pinned reference to the driver's private data or [`EINVAL`] if it doesn't match + /// the asserted type `T`. + pub fn drvdata<T: 'static>(&self) -> Result<Pin<&T>> { + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. + if unsafe { bindings::dev_get_drvdata(self.as_raw()) }.is_null() { + return Err(ENOENT); + } + + self.match_type_id::<T>()?; + + // SAFETY: + // - The above check of `dev_get_drvdata()` guarantees that we are called after + // `set_drvdata()` and before `drvdata_obtain()`. + // - We've just checked that the type of the driver's private data is in fact `T`. + Ok(unsafe { self.drvdata_unchecked() }) } } @@ -251,7 +335,7 @@ impl<Ctx: DeviceContext> Device<Ctx> { /// Returns a reference to the parent device, if any. #[cfg_attr(not(CONFIG_AUXILIARY_BUS), expect(dead_code))] - pub(crate) fn parent(&self) -> Option<&Self> { + pub(crate) fn parent(&self) -> Option<&Device> { // SAFETY: // - By the type invariant `self.as_raw()` is always valid. // - The parent device is only ever set at device creation. @@ -264,7 +348,7 @@ impl<Ctx: DeviceContext> Device<Ctx> { // - Since `parent` is not NULL, it must be a valid pointer to a `struct device`. // - `parent` is valid for the lifetime of `self`, since a `struct device` holds a // reference count of its parent. - Some(unsafe { Self::from_raw(parent) }) + Some(unsafe { Device::from_raw(parent) }) } } @@ -511,6 +595,39 @@ impl DeviceContext for Core {} impl DeviceContext for CoreInternal {} impl DeviceContext for Normal {} +/// Convert device references to bus device references. +/// +/// Bus devices can implement this trait to allow abstractions to provide the bus device in +/// class device callbacks. +/// +/// This must not be used by drivers and is intended for bus and class device abstractions only. +/// +/// # Safety +/// +/// `AsBusDevice::OFFSET` must be the offset of the embedded base `struct device` field within a +/// bus device structure. +pub unsafe trait AsBusDevice<Ctx: DeviceContext>: AsRef<Device<Ctx>> { + /// The relative offset to the device field. + /// + /// Use `offset_of!(bindings, field)` macro to avoid breakage. + const OFFSET: usize; + + /// Convert a reference to [`Device`] into `Self`. + /// + /// # Safety + /// + /// `dev` must be contained in `Self`. + unsafe fn from_device(dev: &Device<Ctx>) -> &Self + where + Self: Sized, + { + let raw = dev.as_raw(); + // SAFETY: `raw - Self::OFFSET` is guaranteed by the safety requirements + // to be a valid pointer to `Self`. + unsafe { &*raw.byte_sub(Self::OFFSET).cast::<Self>() } + } +} + /// # Safety /// /// The type given as `$device` must be a transparent wrapper of a type that doesn't depend on the |