Add a Rust abstraction for `struct device_node`, the device tree node type.
`Node` wraps `device_node` type pointer and implements `AlwaysRefCounted`, allowing owned references to device tree nodes to be held. To do so, add C helpers to make them always accesible from Rust bindings, independently from the configuration. This abstraction is needed for subsequent patches, in particular for creating drm_panel instances from a `const struct device_node` pointer argument. Signed-off-by: Albert Esteve <[email protected]> --- rust/helpers/of.c | 10 ++++++++++ rust/kernel/of.rs | 43 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 53 insertions(+) diff --git a/rust/helpers/of.c b/rust/helpers/of.c index 8f62ca69e8ba5..dca306852975e 100644 --- a/rust/helpers/of.c +++ b/rust/helpers/of.c @@ -6,3 +6,13 @@ __rust_helper bool rust_helper_is_of_node(const struct fwnode_handle *fwnode) { return is_of_node(fwnode); } + +__rust_helper struct device_node *rust_helper_of_node_get(struct device_node *node) +{ + return of_node_get(node); +} + +__rust_helper void rust_helper_of_node_put(struct device_node *node) +{ + of_node_put(node); +} diff --git a/rust/kernel/of.rs b/rust/kernel/of.rs index 58b20c367f993..e75ab81cfe1f7 100644 --- a/rust/kernel/of.rs +++ b/rust/kernel/of.rs @@ -6,7 +6,10 @@ bindings, device_id::{RawDeviceId, RawDeviceIdIndex}, prelude::*, + sync::aref::AlwaysRefCounted, + types::Opaque, }; +use core::ptr::NonNull; /// IdTable type for OF drivers. pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>; @@ -63,3 +66,43 @@ macro_rules! of_device_table { $crate::module_device_table!("of", $module_table_name, $table_name); }; } + +/// A device tree node (`struct device_node`). +/// +/// # Invariants +/// +/// The inner pointer is always a valid, non-null pointer to a `struct device_node` +/// with a positive reference count. +#[repr(transparent)] +pub struct Node(Opaque<bindings::device_node>); + +impl Node { + /// Creates a reference from a raw pointer. + /// + /// # Safety + /// + /// `ptr` must be a valid, non-null `struct device_node` pointer that remains + /// valid for the lifetime `'a`. + pub unsafe fn from_raw<'a>(ptr: *const bindings::device_node) -> &'a Self { + // SAFETY: Caller guarantees `ptr` is valid and lives for `'a`. + unsafe { &*ptr.cast() } + } + + /// Returns the raw pointer to the underlying `struct device_node`. + pub fn as_raw(&self) -> *const bindings::device_node { + self.0.get() as _ + } +} + +// SAFETY: By the type invariants, this type is always refcounted. +unsafe impl AlwaysRefCounted for Node { + fn inc_ref(&self) { + // SAFETY: The type invariant guarantees the pointer is valid. + unsafe { bindings::of_node_get(self.as_raw().cast_mut()) }; + } + + unsafe fn dec_ref(obj: NonNull<Self>) { + // SAFETY: The safety requirements guarantee that the refcount is non-zero. + unsafe { bindings::of_node_put(obj.cast().as_ptr()) }; + } +} -- 2.55.0
