* [PATCH v3 1/2] rust: add basic Pin<Vec<T, A>> abstractions
2025-10-10 22:53 [PATCH v3 0/2] rust: leds: add led classdev abstractions Markus Probst
@ 2025-10-10 22:53 ` Markus Probst
2025-10-10 22:53 ` [PATCH v3 2/2] rust: leds: add basic led classdev abstractions Markus Probst
1 sibling, 0 replies; 4+ messages in thread
From: Markus Probst @ 2025-10-10 22:53 UTC (permalink / raw)
To: Danilo Krummrich, Miguel Ojeda, Alex Gaynor, Lee Jones,
Pavel Machek
Cc: Lorenzo Stoakes, Vlastimil Babka, Liam R. Howlett,
Uladzislau Rezki, Boqun Feng, Gary Guo, bjorn3_gh, Benno Lossin,
Andreas Hindborg, Alice Ryhl, Trevor Gross, Markus Probst,
rust-for-linux, linux-kernel, linux-leds
Implement core Pin<Vec<T, A>> abstractions, including
* `Vec::pin` and `Vec::into_pin` for constructing a `Pin<Vec<T, A>>`.
If T does not implement `Unpin`, its values will never be moved.
* an extension for `Pin<Vec<T, A>>` allowing PinInit to be initialied on a
Pin<Vec>, as well as truncating and popping values from the Vec
Signed-off-by: Markus Probst <markus.probst@posteo.de>
---
rust/kernel/alloc.rs | 1 +
rust/kernel/alloc/kvec.rs | 86 +++++++++++++++++++++++++++++++++++++++
rust/kernel/prelude.rs | 2 +-
3 files changed, 88 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
index a2c49e5494d3..d1a1200fc1bd 100644
--- a/rust/kernel/alloc.rs
+++ b/rust/kernel/alloc.rs
@@ -22,6 +22,7 @@
pub use self::kvec::IntoIter;
pub use self::kvec::KVVec;
pub use self::kvec::KVec;
+pub use self::kvec::PinnedVecExt;
pub use self::kvec::VVec;
pub use self::kvec::Vec;
diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
index 3c72e0bdddb8..d5582a7f17e9 100644
--- a/rust/kernel/alloc/kvec.rs
+++ b/rust/kernel/alloc/kvec.rs
@@ -16,11 +16,13 @@
ops::DerefMut,
ops::Index,
ops::IndexMut,
+ pin::Pin,
ptr,
ptr::NonNull,
slice,
slice::SliceIndex,
};
+use pin_init::PinInit;
mod errors;
pub use self::errors::{InsertError, PushError, RemoveError};
@@ -109,6 +111,21 @@ pub struct Vec<T, A: Allocator> {
_p: PhantomData<A>,
}
+/// Extension for Pin<Vec<T, A>>
+pub trait PinnedVecExt<T> {
+ /// Pin-initializes P and appends it to the back of the [`Vec`] instance without reallocating.
+ fn push_pin_init<E: From<PushError<P>>, P: PinInit<T, E>>(&mut self, init: P) -> Result<(), E>;
+
+ /// Shortens the vector, setting the length to `len` and drops the removed values.
+ /// If `len` is greater than or equal to the current length, this does nothing.
+ ///
+ /// This has no effect on the capacity and will not allocate.
+ fn truncate(&mut self, len: usize);
+
+ /// Removes the last element from a vector and drops it returning true, or false if it is empty.
+ fn pop(&mut self) -> bool;
+}
+
/// Type alias for [`Vec`] with a [`Kmalloc`] allocator.
///
/// # Examples
@@ -719,6 +736,18 @@ pub fn retain(&mut self, mut f: impl FnMut(&mut T) -> bool) {
}
self.truncate(num_kept);
}
+
+ /// Constructs a new `Pin<Vec<T, A>>`.
+ #[inline]
+ pub fn pin(capacity: usize, flags: Flags) -> Result<Pin<Self>, AllocError> {
+ Self::with_capacity(capacity, flags).map(Pin::<Self>::from)
+ }
+
+ /// Convert a [`Vec<T,A>`] to a [`Pin<Vec<T,A>>`]. If `T` does not implement
+ /// [`Unpin`], then its values will be pinned in memory and can't be moved.
+ pub fn into_pin(this: Self) -> Pin<Self> {
+ this.into()
+ }
}
impl<T: Clone, A: Allocator> Vec<T, A> {
@@ -1294,6 +1323,63 @@ fn drop(&mut self) {
}
}
+impl<T, A: Allocator> PinnedVecExt<T> for Pin<Vec<T, A>> {
+ fn truncate(&mut self, len: usize) {
+ // SAFETY: truncate will not reallocate the Vec
+ // CAST: Pin<Ptr> is a transparent wrapper of Ptr
+ unsafe { &mut *core::ptr::from_mut(self).cast::<Vec<T, A>>() }.truncate(len);
+ }
+
+ fn push_pin_init<E: From<PushError<P>>, P: PinInit<T, E>>(&mut self, init: P) -> Result<(), E> {
+ // SAFETY: capacity, spare_capacity_mut and inc_len will not
+ // reallocate the Vec.
+ // CAST: Pin<Ptr> is a transparent wrapper of Ptr
+ let this = unsafe { &mut *core::ptr::from_mut(self).cast::<Vec<T, A>>() };
+
+ if this.len() < this.capacity() {
+ let spare = this.spare_capacity_mut();
+ // SAFETY: the length is less than the capacity, so `spare` is non-empty.
+ unsafe { init.__pinned_init(spare.get_unchecked_mut(0).as_mut_ptr())? };
+ // SAFETY: We just initialised the first spare entry, so it is safe to
+ // increase the length by 1. We also know that the new length is <= capacity.
+ unsafe { this.inc_len(1) };
+ Ok(())
+ } else {
+ Err(E::from(PushError(init)))
+ }
+ }
+
+ fn pop(&mut self) -> bool {
+ if self.is_empty() {
+ return false;
+ }
+
+ // SAFETY:
+ // - We just checked that the length is at least one.
+ // - dec_len will not reallocate the Vec
+ // CAST: Pin<Ptr> is a transparent wrapper of Ptr
+ let ptr: *mut [T] = unsafe { (*core::ptr::from_mut(self).cast::<Vec<T, A>>()).dec_len(1) };
+
+ // SAFETY: the contract of `dec_len` guarantees that the elements in `ptr` are
+ // valid elements whose ownership has been transferred to the caller.
+ unsafe { ptr::drop_in_place(ptr) };
+ true
+ }
+}
+
+impl<T, A: Allocator> From<Vec<T, A>> for Pin<Vec<T, A>> {
+ /// Converts a `Vec<T, A>` into a `Pin<Vec<T, A>>`. If `T` does not implement [`Unpin`], then
+ /// every value in v will be pinned in memory and can't be moved.
+ ///
+ /// This moves `v` into `Pin` without moving any of the values of `v` or allocating and copying
+ /// any memory.
+ fn from(v: Vec<T, A>) -> Self {
+ // SAFETY: The values wrapped inside a `Pin<Vec<T, A>>` cannot be moved or replaced as long
+ // as `T` does not implement `Unpin`.
+ unsafe { Pin::new_unchecked(v) }
+ }
+}
+
#[macros::kunit_tests(rust_kvec_kunit)]
mod tests {
use super::*;
diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
index 25fe97aafd02..7179e2ca2a14 100644
--- a/rust/kernel/prelude.rs
+++ b/rust/kernel/prelude.rs
@@ -19,7 +19,7 @@
c_ushort, c_void,
};
-pub use crate::alloc::{flags::*, Box, KBox, KVBox, KVVec, KVec, VBox, VVec, Vec};
+pub use crate::alloc::{flags::*, Box, KBox, KVBox, KVVec, KVec, PinnedVecExt, VBox, VVec, Vec};
#[doc(no_inline)]
pub use macros::{export, kunit_tests, module, vtable};
--
2.49.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v3 2/2] rust: leds: add basic led classdev abstractions
2025-10-10 22:53 [PATCH v3 0/2] rust: leds: add led classdev abstractions Markus Probst
2025-10-10 22:53 ` [PATCH v3 1/2] rust: add basic Pin<Vec<T, A>> abstractions Markus Probst
@ 2025-10-10 22:53 ` Markus Probst
2025-10-12 10:40 ` kernel test robot
1 sibling, 1 reply; 4+ messages in thread
From: Markus Probst @ 2025-10-10 22:53 UTC (permalink / raw)
To: Danilo Krummrich, Miguel Ojeda, Alex Gaynor, Lee Jones,
Pavel Machek
Cc: Lorenzo Stoakes, Vlastimil Babka, Liam R. Howlett,
Uladzislau Rezki, Boqun Feng, Gary Guo, bjorn3_gh, Benno Lossin,
Andreas Hindborg, Alice Ryhl, Trevor Gross, Markus Probst,
rust-for-linux, linux-kernel, linux-leds
Implement the core abstractions needed for led class devices, including:
* `led::LedOps` - the trait for handling leds, including
`brightness_set`, `brightness_get` and `blink_set`
* `led::InitData` - data set for the led class device
* `led::Device` - a safe wrapper around `led_classdev`
Signed-off-by: Markus Probst <markus.probst@posteo.de>
---
rust/kernel/led.rs | 332 +++++++++++++++++++++++++++++++++++++++++++++
rust/kernel/lib.rs | 1 +
2 files changed, 333 insertions(+)
create mode 100644 rust/kernel/led.rs
diff --git a/rust/kernel/led.rs b/rust/kernel/led.rs
new file mode 100644
index 000000000000..feac509bda3f
--- /dev/null
+++ b/rust/kernel/led.rs
@@ -0,0 +1,332 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Abstractions for the leds driver model.
+//!
+//! C header: [`include/linux/leds.h`](srctree/include/linux/leds.h)
+
+use core::{marker::PhantomData, pin::Pin, ptr::NonNull};
+
+use pin_init::{pin_data, pinned_drop, PinInit};
+
+use crate::{
+ build_error, container_of,
+ device::{self, property::FwNode, Bound},
+ devres::Devres,
+ error::{from_result, to_result, Error, Result, VTABLE_DEFAULT_ERROR},
+ macros::vtable,
+ str::CStr,
+ try_pin_init,
+ types::{ARef, Opaque},
+};
+
+/// The led class device representation.
+///
+/// This structure represents the Rust abstraction for a C `struct led_classdev`.
+#[pin_data(PinnedDrop)]
+pub struct Device<T: LedOps> {
+ ops: T,
+ #[pin]
+ classdev: Opaque<bindings::led_classdev>,
+}
+
+/// The led init data representation.
+///
+/// This structure represents the Rust abstraction for a C `struct led_init_data`.
+#[derive(Default)]
+pub struct InitData<'a> {
+ fwnode: Option<&'a FwNode>,
+ default_label: Option<&'a CStr>,
+ devicename: Option<&'a CStr>,
+ devname_mandatory: bool,
+}
+
+impl InitData<'static> {
+ /// Creates a new [`InitData`]
+ pub fn new() -> Self {
+ Self::default()
+ }
+}
+
+impl<'a> InitData<'a> {
+ /// Sets the firmware node
+ pub fn fwnode<'b, 'c>(self, fwnode: &'b FwNode) -> InitData<'c>
+ where
+ 'a: 'c,
+ 'b: 'c,
+ {
+ InitData {
+ fwnode: Some(fwnode),
+ ..self
+ }
+ }
+
+ /// Sets a default label
+ pub fn default_label<'b, 'c>(self, label: &'b CStr) -> InitData<'c>
+ where
+ 'a: 'c,
+ 'b: 'c,
+ {
+ InitData {
+ default_label: Some(label),
+ ..self
+ }
+ }
+
+ /// Sets the device name
+ pub fn devicename<'b, 'c>(self, devicename: &'b CStr) -> InitData<'c>
+ where
+ 'a: 'c,
+ 'b: 'c,
+ {
+ InitData {
+ devicename: Some(devicename),
+ ..self
+ }
+ }
+
+ /// Sets if a device name is mandatory
+ pub fn devicename_mandatory(self, mandatory: bool) -> Self {
+ Self {
+ devname_mandatory: mandatory,
+
+ ..self
+ }
+ }
+}
+
+/// Trait defining the operations for a LED driver.
+///
+/// # Examples
+///
+///```
+/// # use kernel::{c_str, led, alloc::KBox, error::Result, macros::vtable};
+/// # use core::pin::Pin;
+///
+/// struct MyLedOps;
+///
+///
+/// #[vtable]
+/// impl led::LedOps for MyLedOps {
+/// const BLOCKING = false;
+/// const MAX_BRIGHTNESS = 255;
+///
+/// fn brightness_set(&self, _brightness: u32) -> Result<()> {
+/// // Set the brightness for the led here
+/// Ok(())
+/// }
+/// }
+///
+/// fn register_my_led() -> Result<Pin<KBox<led::Device>>> {
+/// KBox::pin_init(led::Device::new(
+/// None,
+/// None,
+/// led::InitData::new()
+/// .default_label(c_str!("my_led")),
+/// MyLedOps,
+/// ))
+/// }
+///```
+/// Led drivers must implement this trait in order to register and handle a [`Device`].
+#[vtable]
+pub trait LedOps: Send + 'static + Sized {
+ /// If set true, [`LedOps::brightness_set`] and [`LedOps::blink_set`] must not sleep
+ /// and perform the operation immediately.
+ const BLOCKING: bool;
+ /// The max brightness level
+ const MAX_BRIGHTNESS: u32;
+
+ /// Sets the brightness level.
+ ///
+ /// See also [`LedOps::BLOCKING`]
+ fn brightness_set(&self, brightness: u32) -> Result<()>;
+
+ /// Gets the current brightness level.
+ fn brightness_get(&self) -> u32 {
+ build_error!(VTABLE_DEFAULT_ERROR)
+ }
+
+ /// Activates hardware accelerated blinking.
+ ///
+ /// delays are in milliseconds. If both are zero, a sensible default should be chosen.
+ /// The caller should adjust the timings in that case and if it can't match the values
+ /// specified exactly. Setting the brightness to 0 will disable the hardware accelerated
+ /// blinking.
+ ///
+ /// See also [`LedOps::BLOCKING`]
+ fn blink_set(&self, _delay_on: &mut usize, _delay_off: &mut usize) -> Result<()> {
+ build_error!(VTABLE_DEFAULT_ERROR)
+ }
+}
+
+// SAFETY: A `led::Device` can be unregistered from any thread.
+unsafe impl<T: LedOps + Send> Send for Device<T> {}
+
+// SAFETY: `led::Device` can be shared among threads because all methods of `led::Device`
+// are thread safe.
+unsafe impl<T: LedOps + Sync> Sync for Device<T> {}
+
+impl<T: LedOps> Device<T> {
+ /// Registers a new led classdev.
+ ///
+ /// The [`Device`] will be unregistered on drop.
+ pub fn new<'a>(
+ parent: &'a device::Device<Bound>,
+ init_data: InitData<'a>,
+ ops: T,
+ ) -> impl PinInit<Devres<Self>, Error> + 'a {
+ Devres::new(
+ parent,
+ try_pin_init!(Self {
+ ops,
+ classdev <- Opaque::try_ffi_init(|ptr: *mut bindings::led_classdev| {
+ // SAFETY: `try_ffi_init` guarantees that `ptr` is valid for write.
+ // `led_classdev` gets fully initialized in-place by
+ // `led_classdev_register_ext` including `mutex` and `list_head`.
+ unsafe { ptr.write(bindings::led_classdev {
+ max_brightness: T::MAX_BRIGHTNESS,
+ brightness_set: T::BLOCKING
+ .then_some(Adapter::<T>::brightness_set_callback),
+ brightness_set_blocking: (!T::BLOCKING)
+ .then_some(Adapter::<T>::brightness_set_blocking_callback),
+ brightness_get: T::HAS_BRIGHTNESS_GET
+ .then_some(Adapter::<T>::brightness_get_callback),
+ blink_set: T::HAS_BLINK_SET
+ .then_some(Adapter::<T>::blink_set_callback),
+ .. bindings::led_classdev::default()
+ }) };
+
+ let fwnode = init_data.fwnode.map(ARef::from);
+
+ let mut init_data = bindings::led_init_data {
+ fwnode: fwnode.as_ref()
+ .map_or(core::ptr::null_mut(), |fwnode| fwnode.as_raw()),
+ default_label: init_data.default_label
+ .map_or(core::ptr::null(), CStr::as_char_ptr),
+ devicename: init_data.devicename
+ .map_or(core::ptr::null(), CStr::as_char_ptr),
+ devname_mandatory: init_data.devname_mandatory,
+ };
+
+ // SAFETY:
+ // - `parent.as_raw()` is guaranteed to be a pointer to a valid `device`
+ // or a null pointer.
+ // - `ptr` is guaranteed to be a pointer to an initialized `led_classdev`.
+ to_result(unsafe {
+ bindings::led_classdev_register_ext(parent.as_raw(), ptr, &mut init_data)
+ })?;
+
+ core::mem::forget(fwnode); // keep the reference count incremented
+
+ Ok::<_, Error>(())
+ }),
+ }),
+ )
+ }
+
+ /// # Safety
+ /// `led_cdev` must be a valid pointer to a `led_classdev` embedded within a
+ /// `led::Device`.
+ unsafe fn from_raw<'a>(led_cdev: *mut bindings::led_classdev) -> &'a Self {
+ // SAFETY: The function's contract guarantees that `led_cdev` points to a `led_classdev`
+ // field embedded within a valid `led::Device`. `container_of!` can therefore
+ // safely calculate the address of the containing struct.
+ unsafe { &*container_of!(Opaque::cast_from(led_cdev), Self, classdev) }
+ }
+}
+
+struct Adapter<T: LedOps> {
+ _p: PhantomData<T>,
+}
+
+impl<T: LedOps> Adapter<T> {
+ /// # Safety
+ /// `led_cdev` must be a valid pointer to a `led_classdev` embedded within a
+ /// `led::Device`.
+ /// This function is called on setting the brightness of a led.
+ unsafe extern "C" fn brightness_set_callback(
+ led_cdev: *mut bindings::led_classdev,
+ brightness: u32,
+ ) {
+ // SAFETY: The function's contract guarantees that `led_cdev` is a valid pointer to a
+ // `led_classdev` embedded within a `led::Device`.
+ let _ = unsafe { Device::<T>::from_raw(led_cdev) }
+ .ops
+ .brightness_set(brightness);
+ }
+
+ /// # Safety
+ /// `led_cdev` must be a valid pointer to a `led_classdev` embedded within a
+ /// `led::Device`.
+ /// This function is called on setting the brightness of a led immediately.
+ unsafe extern "C" fn brightness_set_blocking_callback(
+ led_cdev: *mut bindings::led_classdev,
+ brightness: u32,
+ ) -> i32 {
+ from_result(|| {
+ // SAFETY: The function's contract guarantees that `led_cdev` is a valid pointer to a
+ // `led_classdev` embedded within a `led::Device`.
+ unsafe { Device::<T>::from_raw(led_cdev) }
+ .ops
+ .brightness_set(brightness)?;
+ Ok(0)
+ })
+ }
+
+ /// # Safety
+ /// `led_cdev` must be a valid pointer to a `led_classdev` embedded within a
+ /// `led::Device`.
+ /// This function is called on getting the brightness of a led.
+ unsafe extern "C" fn brightness_get_callback(led_cdev: *mut bindings::led_classdev) -> u32 {
+ // SAFETY: The function's contract guarantees that `led_cdev` is a valid pointer to a
+ // `led_classdev` embedded within a `led::Device`.
+ unsafe { Device::<T>::from_raw(led_cdev) }
+ .ops
+ .brightness_get()
+ }
+
+ /// # Safety
+ /// `led_cdev` must be a valid pointer to a `led_classdev` embedded within a
+ /// `led::Device`.
+ /// `delay_on` and `delay_off` must be valid pointers to `usize` and have
+ /// exclusive access for the period of this function.
+ /// This function is called on enabling hardware accelerated blinking.
+ unsafe extern "C" fn blink_set_callback(
+ led_cdev: *mut bindings::led_classdev,
+ delay_on: *mut usize,
+ delay_off: *mut usize,
+ ) -> i32 {
+ from_result(|| {
+ // SAFETY: The function's contract guarantees that `led_cdev` is a valid pointer to a
+ // `led_classdev` embedded within a `led::Device`.
+ unsafe { Device::<T>::from_raw(led_cdev) }.ops.blink_set(
+ // SAFETY: The function's contract guarantees that `delay_on` points to a `usize`
+ // and is exclusive for the period of this function.
+ unsafe { &mut *delay_on },
+ // SAFETY: The function's contract guarantees that `delay_off` points to a `usize`
+ // and is exclusive for the period of this function.
+ unsafe { &mut *delay_off },
+ )?;
+ Ok(0)
+ })
+ }
+}
+
+#[pinned_drop]
+impl<T: LedOps> PinnedDrop for Device<T> {
+ fn drop(self: Pin<&mut Self>) {
+ let raw = self.classdev.get();
+ // SAFETY: The existence of `self` guarantees that `self.classdev.get()` is a pointer to a
+ // valid `struct led_classdev`.
+ let dev: &device::Device = unsafe { device::Device::from_raw((*raw).dev) };
+
+ let _fwnode = dev
+ .fwnode()
+ // SAFETY: the reference count of `fwnode` has previously been
+ // incremented in `led::Device::new`.
+ .map(|fwnode| unsafe { ARef::from_raw(NonNull::from(fwnode)) });
+
+ // SAFETY: The existence of `self` guarantees that `self.classdev` has previously been
+ // successfully registered with `led_classdev_register_ext`.
+ unsafe { bindings::led_classdev_unregister(self.classdev.get()) };
+ }
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index e5247f584ad2..f42c60da21ae 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -97,6 +97,7 @@
pub mod jump_label;
#[cfg(CONFIG_KUNIT)]
pub mod kunit;
+pub mod led;
pub mod list;
pub mod miscdevice;
pub mod mm;
--
2.49.1
^ permalink raw reply related [flat|nested] 4+ messages in thread