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Diffstat (limited to 'rust/kernel/driver.rs')
| -rw-r--r-- | rust/kernel/driver.rs | 442 |
1 files changed, 442 insertions, 0 deletions
diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs new file mode 100644 index 000000000000..0ae9f4d3dbc5 --- /dev/null +++ b/rust/kernel/driver.rs @@ -0,0 +1,442 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Generic support for drivers of different buses (e.g., PCI, Platform, Amba, etc.). +//! +//! Each bus/subsystem is expected to implement [`DriverOps`], which allows drivers to register +//! using the [`Registration`] class. + +use crate::{error::code::*, str::CStr, sync::Ref, Result, ThisModule}; +use alloc::boxed::Box; +use core::{cell::UnsafeCell, marker::PhantomData, ops::Deref, pin::Pin}; + +/// A subsystem (e.g., PCI, Platform, Amba, etc.) that allows drivers to be written for it. +pub trait DriverOps { + /// The type that holds information about the registration. This is typically a struct defined + /// by the C portion of the kernel. + type RegType: Default; + + /// Registers a driver. + /// + /// # Safety + /// + /// `reg` must point to valid, initialised, and writable memory. It may be modified by this + /// function to hold registration state. + /// + /// On success, `reg` must remain pinned and valid until the matching call to + /// [`DriverOps::unregister`]. + unsafe fn register( + reg: *mut Self::RegType, + name: &'static CStr, + module: &'static ThisModule, + ) -> Result; + + /// Unregisters a driver previously registered with [`DriverOps::register`]. + /// + /// # Safety + /// + /// `reg` must point to valid writable memory, initialised by a previous successful call to + /// [`DriverOps::register`]. + unsafe fn unregister(reg: *mut Self::RegType); +} + +/// The registration of a driver. +pub struct Registration<T: DriverOps> { + is_registered: bool, + concrete_reg: UnsafeCell<T::RegType>, +} + +// SAFETY: `Registration` has no fields or methods accessible via `&Registration`, so it is safe to +// share references to it with multiple threads as nothing can be done. +unsafe impl<T: DriverOps> Sync for Registration<T> {} + +impl<T: DriverOps> Registration<T> { + /// Creates a new instance of the registration object. + pub fn new() -> Self { + Self { + is_registered: false, + concrete_reg: UnsafeCell::new(T::RegType::default()), + } + } + + /// Allocates a pinned registration object and registers it. + /// + /// Returns a pinned heap-allocated representation of the registration. + pub fn new_pinned(name: &'static CStr, module: &'static ThisModule) -> Result<Pin<Box<Self>>> { + let mut reg = Pin::from(Box::try_new(Self::new())?); + reg.as_mut().register(name, module)?; + Ok(reg) + } + + /// Registers a driver with its subsystem. + /// + /// It must be pinned because the memory block that represents the registration is potentially + /// self-referential. + pub fn register( + self: Pin<&mut Self>, + name: &'static CStr, + module: &'static ThisModule, + ) -> Result { + // SAFETY: We never move out of `this`. + let this = unsafe { self.get_unchecked_mut() }; + if this.is_registered { + // Already registered. + return Err(EINVAL); + } + + // SAFETY: `concrete_reg` was initialised via its default constructor. It is only freed + // after `Self::drop` is called, which first calls `T::unregister`. + unsafe { T::register(this.concrete_reg.get(), name, module) }?; + + this.is_registered = true; + Ok(()) + } +} + +impl<T: DriverOps> Default for Registration<T> { + fn default() -> Self { + Self::new() + } +} + +impl<T: DriverOps> Drop for Registration<T> { + fn drop(&mut self) { + if self.is_registered { + // SAFETY: This path only runs if a previous call to `T::register` completed + // successfully. + unsafe { T::unregister(self.concrete_reg.get()) }; + } + } +} + +/// Conversion from a device id to a raw device id. +/// +/// 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: +/// - [`RawDeviceId::ZERO`] is actually a zeroed-out version of the raw device id. +/// - [`RawDeviceId::to_rawid`] stores `offset` in the context/data field of the raw device id so +/// that buses can recover the pointer to the data. +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; + + /// A zeroed-out representation of the raw device id. + /// + /// Id tables created from [`Self`] use [`Self::ZERO`] as the sentinel to indicate the end of + /// the table. + const ZERO: Self::RawType; + + /// Converts an id into a raw id. + /// + /// `offset` is the offset from the memory location where the raw device id is stored to the + /// location where its associated context information is stored. Implementations must store + /// this in the appropriate context/data field of the raw type. + fn to_rawid(&self, offset: isize) -> Self::RawType; +} + +/// A zero-terminated device id array, followed by context data. +#[repr(C)] +pub struct IdArray<T: RawDeviceId, U, const N: usize> { + ids: [T::RawType; N], + sentinel: T::RawType, + id_infos: [Option<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. + pub const fn new(ids: [T; N], infos: [Option<U>; N]) -> Self + where + T: ~const RawDeviceId + Copy, + { + let mut array = Self { + ids: [T::ZERO; N], + sentinel: T::ZERO, + id_infos: infos, + }; + let mut i = 0usize; + while i < N { + // SAFETY: Both pointers are within `array` (or one byte beyond), consequently they are + // derived from the same allocated object. We are using a `u8` pointer, whose size 1, + // so the pointers are necessarily 1-byte aligned. + let offset = unsafe { + (&array.id_infos[i] as *const _ as *const u8) + .offset_from(&array.ids[i] as *const _ as _) + }; + array.ids[i] = ids[i].to_rawid(offset); + i += 1; + } + array + } + + /// Returns an `IdTable` backed by `self`. + /// + /// This is used to essentially erase the array size. + pub const fn as_table(&self) -> IdTable<'_, T, U> { + IdTable { + first: &self.ids[0], + _p: PhantomData, + } + } +} + +/// A device id table. +/// +/// The table is guaranteed to be zero-terminated and to be followed by an array of context data of +/// type `Option<U>`. +pub struct IdTable<'a, T: RawDeviceId, U> { + first: &'a T::RawType, + _p: PhantomData<&'a U>, +} + +impl<T: RawDeviceId, U> const AsRef<T::RawType> for IdTable<'_, T, U> { + fn as_ref(&self) -> &T::RawType { + self.first + } +} + +/// Counts the number of parenthesis-delimited, comma-separated items. +/// +/// # Examples +/// +/// ``` +/// # use kernel::count_paren_items; +/// +/// assert_eq!(0, count_paren_items!()); +/// assert_eq!(1, count_paren_items!((A))); +/// assert_eq!(1, count_paren_items!((A),)); +/// assert_eq!(2, count_paren_items!((A), (B))); +/// assert_eq!(2, count_paren_items!((A), (B),)); +/// assert_eq!(3, count_paren_items!((A), (B), (C))); +/// assert_eq!(3, count_paren_items!((A), (B), (C),)); +/// ``` +#[macro_export] +macro_rules! count_paren_items { + (($($item:tt)*), $($remaining:tt)*) => { 1 + $crate::count_paren_items!($($remaining)*) }; + (($($item:tt)*)) => { 1 }; + () => { 0 }; +} + +/// Converts a comma-separated list of pairs into an array with the first element. That is, it +/// discards the second element of the pair. +/// +/// Additionally, it automatically introduces a type if the first element is warpped in curly +/// braces, for example, if it's `{v: 10}`, it becomes `X { v: 10 }`; this is to avoid repeating +/// the type. +/// +/// # Examples +/// +/// ``` +/// # use kernel::first_item; +/// +/// #[derive(PartialEq, Debug)] +/// struct X { +/// v: u32, +/// } +/// +/// assert_eq!([] as [X; 0], first_item!(X, )); +/// assert_eq!([X { v: 10 }], first_item!(X, ({ v: 10 }, Y))); +/// assert_eq!([X { v: 10 }], first_item!(X, ({ v: 10 }, Y),)); +/// assert_eq!([X { v: 10 }], first_item!(X, (X { v: 10 }, Y))); +/// assert_eq!([X { v: 10 }], first_item!(X, (X { v: 10 }, Y),)); +/// assert_eq!([X { v: 10 }, X { v: 20 }], first_item!(X, ({ v: 10 }, Y), ({ v: 20 }, Y))); +/// assert_eq!([X { v: 10 }, X { v: 20 }], first_item!(X, ({ v: 10 }, Y), ({ v: 20 }, Y),)); +/// assert_eq!([X { v: 10 }, X { v: 20 }], first_item!(X, (X { v: 10 }, Y), (X { v: 20 }, Y))); +/// assert_eq!([X { v: 10 }, X { v: 20 }], first_item!(X, (X { v: 10 }, Y), (X { v: 20 }, Y),)); +/// assert_eq!([X { v: 10 }, X { v: 20 }, X { v: 30 }], +/// first_item!(X, ({ v: 10 }, Y), ({ v: 20 }, Y), ({v: 30}, Y))); +/// assert_eq!([X { v: 10 }, X { v: 20 }, X { v: 30 }], +/// first_item!(X, ({ v: 10 }, Y), ({ v: 20 }, Y), ({v: 30}, Y),)); +/// assert_eq!([X { v: 10 }, X { v: 20 }, X { v: 30 }], +/// first_item!(X, (X { v: 10 }, Y), (X { v: 20 }, Y), (X {v: 30}, Y))); +/// assert_eq!([X { v: 10 }, X { v: 20 }, X { v: 30 }], +/// first_item!(X, (X { v: 10 }, Y), (X { v: 20 }, Y), (X {v: 30}, Y),)); +/// ``` +#[macro_export] +macro_rules! first_item { + ($id_type:ty, $(({$($first:tt)*}, $second:expr)),* $(,)?) => { + { + type IdType = $id_type; + [$(IdType{$($first)*},)*] + } + }; + ($id_type:ty, $(($first:expr, $second:expr)),* $(,)?) => { [$($first,)*] }; +} + +/// Converts a comma-separated list of pairs into an array with the second element. That is, it +/// discards the first element of the pair. +/// +/// # Examples +/// +/// ``` +/// # use kernel::second_item; +/// +/// assert_eq!([] as [u32; 0], second_item!()); +/// assert_eq!([10u32], second_item!((X, 10u32))); +/// assert_eq!([10u32], second_item!((X, 10u32),)); +/// assert_eq!([10u32], second_item!(({X}, 10u32))); +/// assert_eq!([10u32], second_item!(({X}, 10u32),)); +/// assert_eq!([10u32, 20], second_item!((X, 10u32), (X, 20))); +/// assert_eq!([10u32, 20], second_item!((X, 10u32), (X, 20),)); +/// assert_eq!([10u32, 20], second_item!(({X}, 10u32), ({X}, 20))); +/// assert_eq!([10u32, 20], second_item!(({X}, 10u32), ({X}, 20),)); +/// assert_eq!([10u32, 20, 30], second_item!((X, 10u32), (X, 20), (X, 30))); +/// assert_eq!([10u32, 20, 30], second_item!((X, 10u32), (X, 20), (X, 30),)); +/// assert_eq!([10u32, 20, 30], second_item!(({X}, 10u32), ({X}, 20), ({X}, 30))); +/// assert_eq!([10u32, 20, 30], second_item!(({X}, 10u32), ({X}, 20), ({X}, 30),)); +/// ``` +#[macro_export] +macro_rules! second_item { + ($(({$($first:tt)*}, $second:expr)),* $(,)?) => { [$($second,)*] }; + ($(($first:expr, $second:expr)),* $(,)?) => { [$($second,)*] }; +} + +/// Defines a new constant [`IdArray`] with a concise syntax. +/// +/// It is meant to be used by buses and subsystems to create a similar macro with their device id +/// type already specified, i.e., with fewer parameters to the end user. +/// +/// # Examples +/// +// TODO: Exported but not usable by kernel modules (requires `const_trait_impl`). +/// ```ignore +/// #![feature(const_trait_impl)] +/// # use kernel::{define_id_array, driver::RawDeviceId}; +/// +/// #[derive(Copy, Clone)] +/// struct Id(u32); +/// +/// // SAFETY: `ZERO` is all zeroes and `to_rawid` stores `offset` as the second element of the raw +/// // device id pair. +/// unsafe impl const RawDeviceId for Id { +/// type RawType = (u64, isize); +/// const ZERO: Self::RawType = (0, 0); +/// fn to_rawid(&self, offset: isize) -> Self::RawType { +/// (self.0 as u64 + 1, offset) +/// } +/// } +/// +/// define_id_array!(A1, Id, (), []); +/// define_id_array!(A2, Id, &'static [u8], [(Id(10), None)]); +/// define_id_array!(A3, Id, &'static [u8], [(Id(10), Some(b"id1")), ]); +/// define_id_array!(A4, Id, &'static [u8], [(Id(10), Some(b"id1")), (Id(20), Some(b"id2"))]); +/// define_id_array!(A5, Id, &'static [u8], [(Id(10), Some(b"id1")), (Id(20), Some(b"id2")), ]); +/// define_id_array!(A6, Id, &'static [u8], [(Id(10), None), (Id(20), Some(b"id2")), ]); +/// define_id_array!(A7, Id, &'static [u8], [(Id(10), Some(b"id1")), (Id(20), None), ]); +/// define_id_array!(A8, Id, &'static [u8], [(Id(10), None), (Id(20), None), ]); +/// ``` +#[macro_export] +macro_rules! define_id_array { + ($table_name:ident, $id_type:ty, $data_type:ty, [ $($t:tt)* ]) => { + const $table_name: + $crate::driver::IdArray<$id_type, $data_type, { $crate::count_paren_items!($($t)*) }> = + $crate::driver::IdArray::new( + $crate::first_item!($id_type, $($t)*), $crate::second_item!($($t)*)); + }; +} + +/// Defines a new constant [`IdTable`] with a concise syntax. +/// +/// It is meant to be used by buses and subsystems to create a similar macro with their device id +/// type already specified, i.e., with fewer parameters to the end user. +/// +/// # Examples +/// +// TODO: Exported but not usable by kernel modules (requires `const_trait_impl`). +/// ```ignore +/// #![feature(const_trait_impl)] +/// # use kernel::{define_id_table, driver::RawDeviceId}; +/// +/// #[derive(Copy, Clone)] +/// struct Id(u32); +/// +/// // SAFETY: `ZERO` is all zeroes and `to_rawid` stores `offset` as the second element of the raw +/// // device id pair. +/// unsafe impl const RawDeviceId for Id { +/// type RawType = (u64, isize); +/// const ZERO: Self::RawType = (0, 0); +/// fn to_rawid(&self, offset: isize) -> Self::RawType { +/// (self.0 as u64 + 1, offset) +/// } +/// } +/// +/// define_id_table!(T1, Id, &'static [u8], [(Id(10), None)]); +/// define_id_table!(T2, Id, &'static [u8], [(Id(10), Some(b"id1")), ]); +/// define_id_table!(T3, Id, &'static [u8], [(Id(10), Some(b"id1")), (Id(20), Some(b"id2"))]); +/// define_id_table!(T4, Id, &'static [u8], [(Id(10), Some(b"id1")), (Id(20), Some(b"id2")), ]); +/// define_id_table!(T5, Id, &'static [u8], [(Id(10), None), (Id(20), Some(b"id2")), ]); +/// define_id_table!(T6, Id, &'static [u8], [(Id(10), Some(b"id1")), (Id(20), None), ]); +/// define_id_table!(T7, Id, &'static [u8], [(Id(10), None), (Id(20), None), ]); +/// ``` +#[macro_export] +macro_rules! define_id_table { + ($table_name:ident, $id_type:ty, $data_type:ty, [ $($t:tt)* ]) => { + const $table_name: Option<$crate::driver::IdTable<'static, $id_type, $data_type>> = { + $crate::define_id_array!(ARRAY, $id_type, $data_type, [ $($t)* ]); + Some(ARRAY.as_table()) + }; + }; +} + +/// Custom code within device removal. +pub trait DeviceRemoval { + /// Cleans resources up when the device is removed. + /// + /// This is called when a device is removed and offers implementers the chance to run some code + /// that cleans state up. + fn device_remove(&self); +} + +impl DeviceRemoval for () { + fn device_remove(&self) {} +} + +impl<T: DeviceRemoval> DeviceRemoval for Ref<T> { + fn device_remove(&self) { + self.deref().device_remove(); + } +} + +impl<T: DeviceRemoval> DeviceRemoval for Box<T> { + fn device_remove(&self) { + self.deref().device_remove(); + } +} + +/// A kernel module that only registers the given driver on init. +/// +/// This is a helper struct to make it easier to define single-functionality modules, in this case, +/// modules that offer a single driver. +pub struct Module<T: DriverOps> { + _driver: Pin<Box<Registration<T>>>, +} + +impl<T: DriverOps> crate::Module for Module<T> { + fn init(name: &'static CStr, module: &'static ThisModule) -> Result<Self> { + Ok(Self { + _driver: Registration::new_pinned(name, module)?, + }) + } +} + +/// Declares a kernel module that exposes a single driver. +/// +/// It is meant to be used as a helper by other subsystems so they can more easily expose their own +/// macros. +#[macro_export] +macro_rules! module_driver { + (<$gen_type:ident>, $driver_ops:ty, { type: $type:ty, $($f:tt)* }) => { + type Ops<$gen_type> = $driver_ops; + type ModuleType = $crate::driver::Module<Ops<$type>>; + $crate::prelude::module! { + type: ModuleType, + $($f)* + } + } +} |