From: Danilo Krummrich Date: Tue, 22 Jul 2025 14:59:59 +0000 (+0200) Subject: device: rust: expand documentation for DeviceContext X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=82b3644d3deab496cc09f29f3449ede6824b3e8e;p=users%2Fjedix%2Flinux-maple.git 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 Reviewed-by: Alexandre Courbot Reviewed-by: Alice Ryhl Reviewed-by: Daniel Almeida Link: https://lore.kernel.org/r/20250722150110.23565-2-dakr@kernel.org [ Fix two minor typos. - Danilo ] Signed-off-by: Danilo Krummrich --- diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs index b8613289de8e7..fe095a8eccb1c 100644 --- a/rust/kernel/device.rs +++ b/rust/kernel/device.rs @@ -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`] can dereference to a [`Device`]. +/// +/// 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` is also a valid +/// [`Device`]. 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`] 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`], 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`] +/// 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`] 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 {