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mirror of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-09-04 20:19:47 +08:00

device: rust: expand documentation for DeviceContext

Expand the documentation around DeviceContext states and types, in order
to provide detailed information about their purpose and relationship
with each other.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/r/20250722150110.23565-2-dakr@kernel.org
[ Fix two minor typos. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This commit is contained in:
Danilo Krummrich 2025-07-22 16:59:59 +02:00
parent eb5ca9094a
commit 82b3644d3d

View File

@ -311,28 +311,75 @@ unsafe impl Send for Device {}
// synchronization in `struct device`.
unsafe impl Sync for Device {}
/// Marker trait for the context of a bus specific device.
/// Marker trait for the context or scope 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()`.
/// [`DeviceContext`] is a marker trait for types representing the context of a bus specific
/// [`Device`].
///
/// This is the marker trait for structures representing the context of a bus specific device.
/// The specific device context types are: [`CoreInternal`], [`Core`], [`Bound`] and [`Normal`].
///
/// [`DeviceContext`] types are hierarchical, which means that there is a strict hierarchy that
/// defines which [`DeviceContext`] type can be derived from another. For instance, any
/// [`Device<Core>`] can dereference to a [`Device<Bound>`].
///
/// The following enumeration illustrates the dereference hierarchy of [`DeviceContext`] types.
///
/// - [`CoreInternal`] => [`Core`] => [`Bound`] => [`Normal`]
///
/// Bus devices can automatically implement the dereference hierarchy by using
/// [`impl_device_context_deref`].
///
/// Note that the guarantee for a [`Device`] reference to have a certain [`DeviceContext`] comes
/// from the specific scope the [`Device`] reference is valid in.
///
/// [`impl_device_context_deref`]: kernel::impl_device_context_deref
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.
/// The [`Normal`] context is the default [`DeviceContext`] of any [`Device`].
///
/// The normal context does not indicate any specific context. Any `Device<Ctx>` is also a valid
/// [`Device<Normal>`]. It is the only [`DeviceContext`] for which it is valid to implement
/// [`AlwaysRefCounted`] for.
///
/// [`AlwaysRefCounted`]: kernel::types::AlwaysRefCounted
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()`.
/// The [`Core`] context is the context of a bus specific device when it appears as argument of
/// any bus specific callback, such as `probe()`.
///
/// The core context indicates that the [`Device<Core>`] reference's scope is limited to the bus
/// callback it appears in. It is intended to be used for synchronization purposes. Bus device
/// implementations can implement methods for [`Device<Core>`], such that they can only be called
/// from bus callbacks.
pub struct Core;
/// Semantically the same as [`Core`] but reserved for internal usage of the corresponding bus
/// Semantically the same as [`Core`], but reserved for internal usage of the corresponding bus
/// abstraction.
///
/// The internal core context is intended to be used in exactly the same way as the [`Core`]
/// context, with the difference that this [`DeviceContext`] is internal to the corresponding bus
/// abstraction.
///
/// This context mainly exists to share generic [`Device`] infrastructure that should only be called
/// from bus callbacks with bus abstractions, but without making them accessible for drivers.
pub struct CoreInternal;
/// 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.
/// The [`Bound`] context is the [`DeviceContext`] of a bus specific device when it is guaranteed to
/// be bound to a driver.
///
/// The bound context indicates that for the entire duration of the lifetime of a [`Device<Bound>`]
/// reference, the [`Device`] is guaranteed to be bound to a driver.
///
/// Some APIs, such as [`dma::CoherentAllocation`] or [`Devres`] rely on the [`Device`] to be bound,
/// which can be proven with the [`Bound`] device context.
///
/// Any abstraction that can guarantee a scope where the corresponding bus device is bound, should
/// provide a [`Device<Bound>`] reference to its users for this scope. This allows users to benefit
/// from optimizations for accessing device resources, see also [`Devres::access`].
///
/// [`Devres`]: kernel::devres::Devres
/// [`Devres::access`]: kernel::devres::Devres::access
/// [`dma::CoherentAllocation`]: kernel::dma::CoherentAllocation
pub struct Bound;
mod private {