Not all property-related APIs can be exposed directly on a device. For example, iterating over child nodes of a device will yield fwnode_handle. Thus, in order to access properties on these child nodes, the APIs has to be duplicated on a fwnode as they are in C. A related discussion can be found on the R4L Zulip[1]. [1] https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/DS90UB954.20driver.20done.2C.20ready.20to.20upstream.3F/near/505415697 Signed-off-by: Remo Senekowitsch <remo@xxxxxxxxxxx> --- rust/helpers/helpers.c | 1 + rust/helpers/property.c | 13 ++++++++ rust/kernel/device.rs | 7 ---- rust/kernel/lib.rs | 1 + rust/kernel/property.rs | 73 +++++++++++++++++++++++++++++++++++++++++ 5 files changed, 88 insertions(+), 7 deletions(-) create mode 100644 rust/helpers/property.c create mode 100644 rust/kernel/property.rs diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index 0640b7e11..b4eec5bf2 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -23,6 +23,7 @@ #include "platform.c" #include "pci.c" #include "pid_namespace.c" +#include "property.c" #include "rbtree.c" #include "rcu.c" #include "refcount.c" diff --git a/rust/helpers/property.c b/rust/helpers/property.c new file mode 100644 index 000000000..c37c74488 --- /dev/null +++ b/rust/helpers/property.c @@ -0,0 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/property.h> + +struct fwnode_handle *rust_helper_dev_fwnode(struct device *dev) +{ + return dev_fwnode(dev); +} + +void rust_helper_fwnode_handle_put(struct fwnode_handle *fwnode) +{ + fwnode_handle_put(fwnode); +} diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs index db2d9658b..d5e6a19ff 100644 --- a/rust/kernel/device.rs +++ b/rust/kernel/device.rs @@ -6,7 +6,6 @@ use crate::{ bindings, - str::CStr, types::{ARef, Opaque}, }; use core::{fmt, ptr}; @@ -181,12 +180,6 @@ unsafe fn printk(&self, klevel: &[u8], msg: fmt::Arguments<'_>) { ) }; } - - /// 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: Instances of `Device` are always reference-counted. diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 496ed32b0..ca233fd20 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -67,6 +67,7 @@ pub mod platform; pub mod prelude; pub mod print; +pub mod property; pub mod rbtree; pub mod revocable; pub mod security; diff --git a/rust/kernel/property.rs b/rust/kernel/property.rs new file mode 100644 index 000000000..b0a4bb63a --- /dev/null +++ b/rust/kernel/property.rs @@ -0,0 +1,73 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Unified device property interface. +//! +//! C header: [`include/linux/property.h`](srctree/include/linux/property.h) + +use core::ptr; + +use crate::{bindings, device::Device, str::CStr, types::Opaque}; + +impl Device { + /// Obtain the fwnode corresponding to the device. + fn fwnode(&self) -> &FwNode { + // SAFETY: `self` is valid. + let fwnode_handle = unsafe { bindings::dev_fwnode(self.as_raw()) }; + if fwnode_handle.is_null() { + panic!("fwnode_handle cannot be null"); + } + // SAFETY: `fwnode_handle` is valid. Its lifetime is tied to `&self`. We + // return a reference instead of an `ARef<FwNode>` because `dev_fwnode()` + // doesn't increment the refcount. + unsafe { &*fwnode_handle.cast() } + } + + /// Checks if property is present or not. + pub fn property_present(&self, name: &CStr) -> bool { + self.fwnode().property_present(name) + } +} + +/// A reference-counted fwnode_handle. +/// +/// This structure represents the Rust abstraction for a +/// C `struct fwnode_handle`. This implementation abstracts the usage of an +/// already existing C `struct fwnode_handle` within Rust code that we get +/// passed from the C side. +/// +/// # Invariants +/// +/// A `FwNode` instance represents a valid `struct fwnode_handle` created by the +/// C portion of the kernel. +/// +/// Instances of this type are always reference-counted, that is, a call to +/// `fwnode_handle_get` ensures that the allocation remains valid at least until +/// the matching call to `fwnode_handle_put`. +#[repr(transparent)] +pub struct FwNode(Opaque<bindings::fwnode_handle>); + +impl FwNode { + /// Obtain the raw `struct fwnode_handle *`. + pub(crate) fn as_raw(&self) -> *mut bindings::fwnode_handle { + self.0.get() + } + + /// 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::fwnode_property_present(self.as_raw().cast_const(), name.as_char_ptr()) } + } +} + +// SAFETY: Instances of `FwNode` are always reference-counted. +unsafe impl crate::types::AlwaysRefCounted for FwNode { + fn inc_ref(&self) { + // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. + unsafe { bindings::fwnode_handle_get(self.as_raw()) }; + } + + unsafe fn dec_ref(obj: ptr::NonNull<Self>) { + // SAFETY: The safety requirements guarantee that the refcount is non-zero. + unsafe { bindings::fwnode_handle_put(obj.cast().as_ptr()) } + } +} -- 2.49.0
