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Diffstat (limited to 'rust/kernel/device.rs')
| -rw-r--r-- | rust/kernel/device.rs | 559 |
1 files changed, 559 insertions, 0 deletions
diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs new file mode 100644 index 000000000000..dea06b79ecb5 --- /dev/null +++ b/rust/kernel/device.rs @@ -0,0 +1,559 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Generic devices that are part of the kernel's driver model. +//! +//! C header: [`include/linux/device.h`](srctree/include/linux/device.h) + +use crate::{ + bindings, + str::CStr, + types::{ARef, Opaque}, +}; +use core::{fmt, marker::PhantomData, ptr}; + +#[cfg(CONFIG_PRINTK)] +use crate::c_str; + +/// A reference-counted device. +/// +/// This structure represents the Rust abstraction for a C `struct device`. This implementation +/// abstracts the usage of an already existing C `struct device` within Rust code that we get +/// passed from the C side. +/// +/// An instance of this abstraction can be obtained temporarily or permanent. +/// +/// A temporary one is bound to the lifetime of the C `struct device` pointer used for creation. +/// A permanent instance is always reference-counted and hence not restricted by any lifetime +/// boundaries. +/// +/// For subsystems it is recommended to create a permanent instance to wrap into a subsystem +/// specific device structure (e.g. `pci::Device`). This is useful for passing it to drivers in +/// `T::probe()`, such that a driver can store the `ARef<Device>` (equivalent to storing a +/// `struct device` pointer in a C driver) for arbitrary purposes, e.g. allocating DMA coherent +/// memory. +/// +/// # Invariants +/// +/// A `Device` instance represents a valid `struct device` created by the C portion of the kernel. +/// +/// Instances of this type are always reference-counted, that is, a call to `get_device` ensures +/// that the allocation remains valid at least until the matching call to `put_device`. +/// +/// `bindings::device::release` is valid to be called from any thread, hence `ARef<Device>` can be +/// dropped from any thread. +#[repr(transparent)] +pub struct Device<Ctx: DeviceContext = Normal>(Opaque<bindings::device>, PhantomData<Ctx>); + +impl Device { + /// Creates a new reference-counted abstraction instance of an existing `struct device` pointer. + /// + /// # Safety + /// + /// Callers must ensure that `ptr` is valid, non-null, and has a non-zero reference count, + /// i.e. it must be ensured that the reference count of the C `struct device` `ptr` points to + /// can't drop to zero, for the duration of this function call. + /// + /// It must also be ensured that `bindings::device::release` can be called from any thread. + /// While not officially documented, this should be the case for any `struct device`. + pub unsafe fn get_device(ptr: *mut bindings::device) -> ARef<Self> { + // SAFETY: By the safety requirements ptr is valid + unsafe { Self::as_ref(ptr) }.into() + } +} + +impl<Ctx: DeviceContext> Device<Ctx> { + /// Obtain the raw `struct device *`. + pub(crate) fn as_raw(&self) -> *mut bindings::device { + self.0.get() + } + + /// 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> { + // SAFETY: + // - By the type invariant `self.as_raw()` is always valid. + // - The parent device is only ever set at device creation. + let parent = unsafe { (*self.as_raw()).parent }; + + if parent.is_null() { + None + } else { + // SAFETY: + // - 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::as_ref(parent) }) + } + } + + /// Convert a raw C `struct device` pointer to a `&'a Device`. + /// + /// # Safety + /// + /// Callers must ensure that `ptr` is valid, non-null, and has a non-zero reference count, + /// i.e. it must be ensured that the reference count of the C `struct device` `ptr` points to + /// can't drop to zero, for the duration of this function call and the entire duration when the + /// returned reference exists. + pub unsafe fn as_ref<'a>(ptr: *mut bindings::device) -> &'a Self { + // SAFETY: Guaranteed by the safety requirements of the function. + unsafe { &*ptr.cast() } + } + + /// Prints an emergency-level message (level 0) prefixed with device information. + /// + /// More details are available from [`dev_emerg`]. + /// + /// [`dev_emerg`]: crate::dev_emerg + pub fn pr_emerg(&self, args: fmt::Arguments<'_>) { + // SAFETY: `klevel` is null-terminated, uses one of the kernel constants. + unsafe { self.printk(bindings::KERN_EMERG, args) }; + } + + /// Prints an alert-level message (level 1) prefixed with device information. + /// + /// More details are available from [`dev_alert`]. + /// + /// [`dev_alert`]: crate::dev_alert + pub fn pr_alert(&self, args: fmt::Arguments<'_>) { + // SAFETY: `klevel` is null-terminated, uses one of the kernel constants. + unsafe { self.printk(bindings::KERN_ALERT, args) }; + } + + /// Prints a critical-level message (level 2) prefixed with device information. + /// + /// More details are available from [`dev_crit`]. + /// + /// [`dev_crit`]: crate::dev_crit + pub fn pr_crit(&self, args: fmt::Arguments<'_>) { + // SAFETY: `klevel` is null-terminated, uses one of the kernel constants. + unsafe { self.printk(bindings::KERN_CRIT, args) }; + } + + /// Prints an error-level message (level 3) prefixed with device information. + /// + /// More details are available from [`dev_err`]. + /// + /// [`dev_err`]: crate::dev_err + pub fn pr_err(&self, args: fmt::Arguments<'_>) { + // SAFETY: `klevel` is null-terminated, uses one of the kernel constants. + unsafe { self.printk(bindings::KERN_ERR, args) }; + } + + /// Prints a warning-level message (level 4) prefixed with device information. + /// + /// More details are available from [`dev_warn`]. + /// + /// [`dev_warn`]: crate::dev_warn + pub fn pr_warn(&self, args: fmt::Arguments<'_>) { + // SAFETY: `klevel` is null-terminated, uses one of the kernel constants. + unsafe { self.printk(bindings::KERN_WARNING, args) }; + } + + /// Prints a notice-level message (level 5) prefixed with device information. + /// + /// More details are available from [`dev_notice`]. + /// + /// [`dev_notice`]: crate::dev_notice + pub fn pr_notice(&self, args: fmt::Arguments<'_>) { + // SAFETY: `klevel` is null-terminated, uses one of the kernel constants. + unsafe { self.printk(bindings::KERN_NOTICE, args) }; + } + + /// Prints an info-level message (level 6) prefixed with device information. + /// + /// More details are available from [`dev_info`]. + /// + /// [`dev_info`]: crate::dev_info + pub fn pr_info(&self, args: fmt::Arguments<'_>) { + // SAFETY: `klevel` is null-terminated, uses one of the kernel constants. + unsafe { self.printk(bindings::KERN_INFO, args) }; + } + + /// Prints a debug-level message (level 7) prefixed with device information. + /// + /// More details are available from [`dev_dbg`]. + /// + /// [`dev_dbg`]: crate::dev_dbg + pub fn pr_dbg(&self, args: fmt::Arguments<'_>) { + if cfg!(debug_assertions) { + // SAFETY: `klevel` is null-terminated, uses one of the kernel constants. + unsafe { self.printk(bindings::KERN_DEBUG, args) }; + } + } + + /// Prints the provided message to the console. + /// + /// # Safety + /// + /// Callers must ensure that `klevel` is null-terminated; in particular, one of the + /// `KERN_*`constants, for example, `KERN_CRIT`, `KERN_ALERT`, etc. + #[cfg_attr(not(CONFIG_PRINTK), allow(unused_variables))] + unsafe fn printk(&self, klevel: &[u8], msg: fmt::Arguments<'_>) { + // SAFETY: `klevel` is null-terminated and one of the kernel constants. `self.as_raw` + // is valid because `self` is valid. The "%pA" format string expects a pointer to + // `fmt::Arguments`, which is what we're passing as the last argument. + #[cfg(CONFIG_PRINTK)] + unsafe { + bindings::_dev_printk( + klevel as *const _ as *const crate::ffi::c_char, + self.as_raw(), + c_str!("%pA").as_char_ptr(), + &msg as *const _ as *const crate::ffi::c_void, + ) + }; + } + + /// Checks if property is present or not. + pub fn property_present(&self, name: &CStr) -> bool { + // SAFETY: By the invariant of `CStr`, `name` is null-terminated. + unsafe { bindings::device_property_present(self.as_raw().cast_const(), name.as_char_ptr()) } + } +} + +// 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::types::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_raw()) }; + } + + unsafe fn dec_ref(obj: ptr::NonNull<Self>) { + // SAFETY: The safety requirements guarantee that the refcount is non-zero. + unsafe { bindings::put_device(obj.cast().as_ptr()) } + } +} + +// SAFETY: As by the type invariant `Device` can be sent to any thread. +unsafe impl Send for Device {} + +// SAFETY: `Device` can be shared among threads because all immutable methods are protected by the +// synchronization in `struct device`. +unsafe impl Sync for Device {} + +/// Marker trait for the context of a bus specific device. +/// +/// Some functions of a bus specific device should only be called from a certain context, i.e. bus +/// callbacks, such as `probe()`. +/// +/// This is the marker trait for structures representing the context of a bus specific device. +pub trait DeviceContext: private::Sealed {} + +/// The [`Normal`] context is the context of a bus specific device when it is not an argument of +/// any bus callback. +pub struct Normal; + +/// The [`Core`] context is the context of a bus specific device when it is supplied as argument of +/// any of the bus callbacks, such as `probe()`. +pub struct Core; + +/// The [`Bound`] context is the context of a bus specific device reference when it is guaranteed to +/// be bound for the duration of its lifetime. +pub struct Bound; + +mod private { + pub trait Sealed {} + + impl Sealed for super::Bound {} + impl Sealed for super::Core {} + impl Sealed for super::Normal {} +} + +impl DeviceContext for Bound {} +impl DeviceContext for Core {} +impl DeviceContext for Normal {} + +/// # Safety +/// +/// The type given as `$device` must be a transparent wrapper of a type that doesn't depend on the +/// generic argument of `$device`. +#[doc(hidden)] +#[macro_export] +macro_rules! __impl_device_context_deref { + (unsafe { $device:ident, $src:ty => $dst:ty }) => { + impl ::core::ops::Deref for $device<$src> { + type Target = $device<$dst>; + + fn deref(&self) -> &Self::Target { + let ptr: *const Self = self; + + // CAST: `$device<$src>` and `$device<$dst>` transparently wrap the same type by the + // safety requirement of the macro. + let ptr = ptr.cast::<Self::Target>(); + + // SAFETY: `ptr` was derived from `&self`. + unsafe { &*ptr } + } + } + }; +} + +/// Implement [`core::ops::Deref`] traits for allowed [`DeviceContext`] conversions of a (bus +/// specific) device. +/// +/// # Safety +/// +/// The type given as `$device` must be a transparent wrapper of a type that doesn't depend on the +/// generic argument of `$device`. +#[macro_export] +macro_rules! impl_device_context_deref { + (unsafe { $device:ident }) => { + // SAFETY: This macro has the exact same safety requirement as + // `__impl_device_context_deref!`. + ::kernel::__impl_device_context_deref!(unsafe { + $device, + $crate::device::Core => $crate::device::Bound + }); + + // SAFETY: This macro has the exact same safety requirement as + // `__impl_device_context_deref!`. + ::kernel::__impl_device_context_deref!(unsafe { + $device, + $crate::device::Bound => $crate::device::Normal + }); + }; +} + +#[doc(hidden)] +#[macro_export] +macro_rules! __impl_device_context_into_aref { + ($src:ty, $device:tt) => { + impl ::core::convert::From<&$device<$src>> for $crate::types::ARef<$device> { + fn from(dev: &$device<$src>) -> Self { + (&**dev).into() + } + } + }; +} + +/// Implement [`core::convert::From`], such that all `&Device<Ctx>` can be converted to an +/// `ARef<Device>`. +#[macro_export] +macro_rules! impl_device_context_into_aref { + ($device:tt) => { + ::kernel::__impl_device_context_into_aref!($crate::device::Core, $device); + ::kernel::__impl_device_context_into_aref!($crate::device::Bound, $device); + }; +} + +#[doc(hidden)] +#[macro_export] +macro_rules! dev_printk { + ($method:ident, $dev:expr, $($f:tt)*) => { + { + ($dev).$method(::core::format_args!($($f)*)); + } + } +} + +/// Prints an emergency-level message (level 0) prefixed with device information. +/// +/// This level should be used if the system is unusable. +/// +/// Equivalent to the kernel's `dev_emerg` macro. +/// +/// Mimics the interface of [`std::print!`]. More information about the syntax is available from +/// [`core::fmt`] and [`std::format!`]. +/// +/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html +/// [`std::format!`]: https://doc.rust-lang.org/std/macro.format.html +/// +/// # Examples +/// +/// ``` +/// # use kernel::device::Device; +/// +/// fn example(dev: &Device) { +/// dev_emerg!(dev, "hello {}\n", "there"); +/// } +/// ``` +#[macro_export] +macro_rules! dev_emerg { + ($($f:tt)*) => { $crate::dev_printk!(pr_emerg, $($f)*); } +} + +/// Prints an alert-level message (level 1) prefixed with device information. +/// +/// This level should be used if action must be taken immediately. +/// +/// Equivalent to the kernel's `dev_alert` macro. +/// +/// Mimics the interface of [`std::print!`]. More information about the syntax is available from +/// [`core::fmt`] and [`std::format!`]. +/// +/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html +/// [`std::format!`]: https://doc.rust-lang.org/std/macro.format.html +/// +/// # Examples +/// +/// ``` +/// # use kernel::device::Device; +/// +/// fn example(dev: &Device) { +/// dev_alert!(dev, "hello {}\n", "there"); +/// } +/// ``` +#[macro_export] +macro_rules! dev_alert { + ($($f:tt)*) => { $crate::dev_printk!(pr_alert, $($f)*); } +} + +/// Prints a critical-level message (level 2) prefixed with device information. +/// +/// This level should be used in critical conditions. +/// +/// Equivalent to the kernel's `dev_crit` macro. +/// +/// Mimics the interface of [`std::print!`]. More information about the syntax is available from +/// [`core::fmt`] and [`std::format!`]. +/// +/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html +/// [`std::format!`]: https://doc.rust-lang.org/std/macro.format.html +/// +/// # Examples +/// +/// ``` +/// # use kernel::device::Device; +/// +/// fn example(dev: &Device) { +/// dev_crit!(dev, "hello {}\n", "there"); +/// } +/// ``` +#[macro_export] +macro_rules! dev_crit { + ($($f:tt)*) => { $crate::dev_printk!(pr_crit, $($f)*); } +} + +/// Prints an error-level message (level 3) prefixed with device information. +/// +/// This level should be used in error conditions. +/// +/// Equivalent to the kernel's `dev_err` macro. +/// +/// Mimics the interface of [`std::print!`]. More information about the syntax is available from +/// [`core::fmt`] and [`std::format!`]. +/// +/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html +/// [`std::format!`]: https://doc.rust-lang.org/std/macro.format.html +/// +/// # Examples +/// +/// ``` +/// # use kernel::device::Device; +/// +/// fn example(dev: &Device) { +/// dev_err!(dev, "hello {}\n", "there"); +/// } +/// ``` +#[macro_export] +macro_rules! dev_err { + ($($f:tt)*) => { $crate::dev_printk!(pr_err, $($f)*); } +} + +/// Prints a warning-level message (level 4) prefixed with device information. +/// +/// This level should be used in warning conditions. +/// +/// Equivalent to the kernel's `dev_warn` macro. +/// +/// Mimics the interface of [`std::print!`]. More information about the syntax is available from +/// [`core::fmt`] and [`std::format!`]. +/// +/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html +/// [`std::format!`]: https://doc.rust-lang.org/std/macro.format.html +/// +/// # Examples +/// +/// ``` +/// # use kernel::device::Device; +/// +/// fn example(dev: &Device) { +/// dev_warn!(dev, "hello {}\n", "there"); +/// } +/// ``` +#[macro_export] +macro_rules! dev_warn { + ($($f:tt)*) => { $crate::dev_printk!(pr_warn, $($f)*); } +} + +/// Prints a notice-level message (level 5) prefixed with device information. +/// +/// This level should be used in normal but significant conditions. +/// +/// Equivalent to the kernel's `dev_notice` macro. +/// +/// Mimics the interface of [`std::print!`]. More information about the syntax is available from +/// [`core::fmt`] and [`std::format!`]. +/// +/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html +/// [`std::format!`]: https://doc.rust-lang.org/std/macro.format.html +/// +/// # Examples +/// +/// ``` +/// # use kernel::device::Device; +/// +/// fn example(dev: &Device) { +/// dev_notice!(dev, "hello {}\n", "there"); +/// } +/// ``` +#[macro_export] +macro_rules! dev_notice { + ($($f:tt)*) => { $crate::dev_printk!(pr_notice, $($f)*); } +} + +/// Prints an info-level message (level 6) prefixed with device information. +/// +/// This level should be used for informational messages. +/// +/// Equivalent to the kernel's `dev_info` macro. +/// +/// Mimics the interface of [`std::print!`]. More information about the syntax is available from +/// [`core::fmt`] and [`std::format!`]. +/// +/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html +/// [`std::format!`]: https://doc.rust-lang.org/std/macro.format.html +/// +/// # Examples +/// +/// ``` +/// # use kernel::device::Device; +/// +/// fn example(dev: &Device) { +/// dev_info!(dev, "hello {}\n", "there"); +/// } +/// ``` +#[macro_export] +macro_rules! dev_info { + ($($f:tt)*) => { $crate::dev_printk!(pr_info, $($f)*); } +} + +/// Prints a debug-level message (level 7) prefixed with device information. +/// +/// This level should be used for debug messages. +/// +/// Equivalent to the kernel's `dev_dbg` macro, except that it doesn't support dynamic debug yet. +/// +/// Mimics the interface of [`std::print!`]. More information about the syntax is available from +/// [`core::fmt`] and [`std::format!`]. +/// +/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html +/// [`std::format!`]: https://doc.rust-lang.org/std/macro.format.html +/// +/// # Examples +/// +/// ``` +/// # use kernel::device::Device; +/// +/// fn example(dev: &Device) { +/// dev_dbg!(dev, "hello {}\n", "there"); +/// } +/// ``` +#[macro_export] +macro_rules! dev_dbg { + ($($f:tt)*) => { $crate::dev_printk!(pr_dbg, $($f)*); } +} |