[PATCH v2 0/5] rust: time: Convert hrtimer to use Instant and Delta

[PATCH v2 0/5] rust: time: Convert hrtimer to use Instant and Delta

[FUJITA Tomonori]

Convert hrtimer to use `Instant` and `Delta`; remove the use of
`Ktime` from the hrtimer code, which was originally introduced as a
temporary workaround.

hrtimer uses either an `Instant` or a `Delta` as its expiration value,
depending on the mode specified at creation time. This patchset
replaces `HrTimerMode` enum with a trait-based abstraction and
associates each mode with either an `Instant` or a `Delta`. By
leveraging Rust's type system, this change enables `HrTimer` to be
statically associated with a specific `HrTimerMode`, the corresponding
`Instant` or `Delta`, and a `ClockSource`.

The `impl_has_hr_timer` macro is extended to allow specifying the
`HrTimerMode`. In the following example, it guarantees that the
`start()` method for `Foo` only accepts `Instant<Monotonic>`. Using a
`Delta` or an `Instant` with a different clock source will result in a
compile-time error:

struct Foo {
    #[pin]
    timer: HrTimer<Self>,
}

impl_has_hr_timer! {
    impl HasHrTimer<Self> for Foo {
        mode : AbsoluteMode<Monotonic>,
        field : self.timer
    }
}

This design eliminates runtime mismatches between expires types and
clock sources, and enables stronger type-level guarantees throughout
hrtimer.

This patchset can be applied on top of the typed clock sources patchset (v3):

https://lore.kernel.org/lkml/20250609010415.3302835-1-fujita.tomonori@gmail.com/

v2
- rebased on 6.16-rc1
- change impl_has_hr_timer! macro format
- remove define_hrtimer_mode! macro
- drop patch to change Delta's methods to take &self instead of self
- add patch to rename Delta's methods from as_* to into_*
v1: https://lore.kernel.org/lkml/20250504045959.238068-1-fujita.tomonori@gmail.com/

FUJITA Tomonori (5):
  rust: time: Rename Delta's methods from as_* to into_*
  rust: time: Replace HrTimerMode enum with trait-based mode types
  rust: time: Add HrTimerExpires trait
  rust: time: Make HasHrTimer generic over HrTimerMode
  rust: time: Remove Ktime in hrtimer

 rust/kernel/time.rs                 |  19 +-
 rust/kernel/time/hrtimer.rs         | 281 ++++++++++++++++++----------
 rust/kernel/time/hrtimer/arc.rs     |   8 +-
 rust/kernel/time/hrtimer/pin.rs     |   8 +-
 rust/kernel/time/hrtimer/pin_mut.rs |   8 +-
 rust/kernel/time/hrtimer/tbox.rs    |   8 +-
 6 files changed, 218 insertions(+), 114 deletions(-)


base-commit: 93b83742d2f6c56030346b3dfe36974688233d31
-- 
2.43.0

[PATCH v2 1/5] rust: time: Rename Delta's methods from as_* to into_*

[FUJITA Tomonori]

Rename Delta's methods that take self from as_* to into_* to align
with Rust naming conventions.

Using `self` is more common Rust practice for small values that can be
freely copied [1].

Clippy warns against using as_* names for trait methods that take self
as follows:

warning: methods called as_* usually take self by reference or self by mutable reference
--> ~/linux/rust/kernel/time/hrtimer.rs:421:17
|
421 |     fn as_nanos(self) -> i64;

Rename the `Delta` struct's methods from as_nanos(), as_micros_ceil(),
and as_millis() to into_nanos(), into_micros_ceil(), and
into_millis(), respectively to maintain consistency with the other
function names.

Link: https://lore.kernel.org/lkml/aD1fgizC4FPT07vt@google.com/ [1]
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 rust/kernel/time.rs | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
index 9fd487276457..2a231c321afa 100644
--- a/rust/kernel/time.rs
+++ b/rust/kernel/time.rs
@@ -261,31 +261,31 @@ pub const fn from_secs(secs: i64) -> Self {
     /// Return `true` if the [`Delta`] spans no time.
     #[inline]
     pub fn is_zero(self) -> bool {
-        self.as_nanos() == 0
+        self.into_nanos() == 0
     }
 
     /// Return `true` if the [`Delta`] spans a negative amount of time.
     #[inline]
     pub fn is_negative(self) -> bool {
-        self.as_nanos() < 0
+        self.into_nanos() < 0
     }
 
     /// Return the number of nanoseconds in the [`Delta`].
     #[inline]
-    pub const fn as_nanos(self) -> i64 {
+    pub const fn into_nanos(self) -> i64 {
         self.nanos
     }
 
     /// Return the smallest number of microseconds greater than or equal
     /// to the value in the [`Delta`].
     #[inline]
-    pub const fn as_micros_ceil(self) -> i64 {
-        self.as_nanos().saturating_add(NSEC_PER_USEC - 1) / NSEC_PER_USEC
+    pub const fn into_micros_ceil(self) -> i64 {
+        self.into_nanos().saturating_add(NSEC_PER_USEC - 1) / NSEC_PER_USEC
     }
 
     /// Return the number of milliseconds in the [`Delta`].
     #[inline]
-    pub const fn as_millis(self) -> i64 {
-        self.as_nanos() / NSEC_PER_MSEC
+    pub const fn into_millis(self) -> i64 {
+        self.into_nanos() / NSEC_PER_MSEC
     }
 }
-- 
2.43.0

[PATCH v2 2/5] rust: time: Replace HrTimerMode enum with trait-based mode types

[FUJITA Tomonori]

Replace the `HrTimerMode` enum with a trait-based approach that uses
zero-sized types to represent each mode of operation. Each mode now
implements the `HrTimerMode` trait.

This refactoring is a preparation for replacing raw `Ktime` in HrTimer
with the `Instant` and `Delta` types, and for making `HrTimer` generic
over a `ClockSource`.

Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 rust/kernel/time/hrtimer.rs | 164 ++++++++++++++++++++----------------
 1 file changed, 90 insertions(+), 74 deletions(-)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index 280128d7e982..23f9f1ba8607 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -98,7 +98,7 @@ pub fn to_ns(self) -> i64 {
 pub struct HrTimer<T> {
     #[pin]
     timer: Opaque<bindings::hrtimer>,
-    mode: HrTimerMode,
+    mode: bindings::hrtimer_mode,
     _t: PhantomData<T>,
 }
 
@@ -112,7 +112,7 @@ unsafe impl<T> Sync for HrTimer<T> {}
 
 impl<T> HrTimer<T> {
     /// Return an initializer for a new timer instance.
-    pub fn new<U: ClockSource>(mode: HrTimerMode) -> impl PinInit<Self>
+    pub fn new<U: ClockSource, M: HrTimerMode>() -> impl PinInit<Self>
     where
         T: HrTimerCallback,
     {
@@ -127,11 +127,11 @@ pub fn new<U: ClockSource>(mode: HrTimerMode) -> impl PinInit<Self>
                         place,
                         Some(T::Pointer::run),
                         U::ID,
-                        mode.into_c(),
+                        M::C_MODE,
                     );
                 }
             }),
-            mode: mode,
+            mode: M::C_MODE,
             _t: PhantomData,
         })
     }
@@ -389,7 +389,7 @@ unsafe fn start(this: *const Self, expires: Ktime) {
                 Self::c_timer_ptr(this).cast_mut(),
                 expires.to_ns(),
                 0,
-                (*Self::raw_get_timer(this)).mode.into_c(),
+                (*Self::raw_get_timer(this)).mode,
             );
         }
     }
@@ -412,77 +412,93 @@ fn into_c(self) -> bindings::hrtimer_restart {
 }
 
 /// Operational mode of [`HrTimer`].
-// NOTE: Some of these have the same encoding on the C side, so we keep
-// `repr(Rust)` and convert elsewhere.
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub enum HrTimerMode {
-    /// Timer expires at the given expiration time.
-    Absolute,
-    /// Timer expires after the given expiration time interpreted as a duration from now.
-    Relative,
-    /// Timer does not move between CPU cores.
-    Pinned,
-    /// Timer handler is executed in soft irq context.
-    Soft,
-    /// Timer handler is executed in hard irq context.
-    Hard,
-    /// Timer expires at the given expiration time.
-    /// Timer does not move between CPU cores.
-    AbsolutePinned,
-    /// Timer expires after the given expiration time interpreted as a duration from now.
-    /// Timer does not move between CPU cores.
-    RelativePinned,
-    /// Timer expires at the given expiration time.
-    /// Timer handler is executed in soft irq context.
-    AbsoluteSoft,
-    /// Timer expires after the given expiration time interpreted as a duration from now.
-    /// Timer handler is executed in soft irq context.
-    RelativeSoft,
-    /// Timer expires at the given expiration time.
-    /// Timer does not move between CPU cores.
-    /// Timer handler is executed in soft irq context.
-    AbsolutePinnedSoft,
-    /// Timer expires after the given expiration time interpreted as a duration from now.
-    /// Timer does not move between CPU cores.
-    /// Timer handler is executed in soft irq context.
-    RelativePinnedSoft,
-    /// Timer expires at the given expiration time.
-    /// Timer handler is executed in hard irq context.
-    AbsoluteHard,
-    /// Timer expires after the given expiration time interpreted as a duration from now.
-    /// Timer handler is executed in hard irq context.
-    RelativeHard,
-    /// Timer expires at the given expiration time.
-    /// Timer does not move between CPU cores.
-    /// Timer handler is executed in hard irq context.
-    AbsolutePinnedHard,
-    /// Timer expires after the given expiration time interpreted as a duration from now.
-    /// Timer does not move between CPU cores.
-    /// Timer handler is executed in hard irq context.
-    RelativePinnedHard,
+pub trait HrTimerMode {
+    /// The C representation of hrtimer mode.
+    const C_MODE: bindings::hrtimer_mode;
 }
 
-impl HrTimerMode {
-    fn into_c(self) -> bindings::hrtimer_mode {
-        use bindings::*;
-        match self {
-            HrTimerMode::Absolute => hrtimer_mode_HRTIMER_MODE_ABS,
-            HrTimerMode::Relative => hrtimer_mode_HRTIMER_MODE_REL,
-            HrTimerMode::Pinned => hrtimer_mode_HRTIMER_MODE_PINNED,
-            HrTimerMode::Soft => hrtimer_mode_HRTIMER_MODE_SOFT,
-            HrTimerMode::Hard => hrtimer_mode_HRTIMER_MODE_HARD,
-            HrTimerMode::AbsolutePinned => hrtimer_mode_HRTIMER_MODE_ABS_PINNED,
-            HrTimerMode::RelativePinned => hrtimer_mode_HRTIMER_MODE_REL_PINNED,
-            HrTimerMode::AbsoluteSoft => hrtimer_mode_HRTIMER_MODE_ABS_SOFT,
-            HrTimerMode::RelativeSoft => hrtimer_mode_HRTIMER_MODE_REL_SOFT,
-            HrTimerMode::AbsolutePinnedSoft => hrtimer_mode_HRTIMER_MODE_ABS_PINNED_SOFT,
-            HrTimerMode::RelativePinnedSoft => hrtimer_mode_HRTIMER_MODE_REL_PINNED_SOFT,
-            HrTimerMode::AbsoluteHard => hrtimer_mode_HRTIMER_MODE_ABS_HARD,
-            HrTimerMode::RelativeHard => hrtimer_mode_HRTIMER_MODE_REL_HARD,
-            HrTimerMode::AbsolutePinnedHard => hrtimer_mode_HRTIMER_MODE_ABS_PINNED_HARD,
-            HrTimerMode::RelativePinnedHard => hrtimer_mode_HRTIMER_MODE_REL_PINNED_HARD,
-        }
-    }
+/// Timer that expires at a fixed point in time.
+pub struct AbsoluteMode;
+
+impl HrTimerMode for AbsoluteMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS;
+}
+
+/// Timer that expires after a delay from now.
+pub struct RelativeMode;
+
+impl HrTimerMode for RelativeMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL;
+}
+
+/// Timer with absolute expiration time, pinned to its current CPU.
+pub struct AbsolutePinnedMode;
+
+impl HrTimerMode for AbsolutePinnedMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS_PINNED;
+}
+
+/// Timer with relative expiration time, pinned to its current CPU.
+pub struct RelativePinnedMode;
+
+impl HrTimerMode for RelativePinnedMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL_PINNED;
+}
+
+/// Timer with absolute expiration, handled in soft irq context.
+pub struct AbsoluteSoftMode;
+
+impl HrTimerMode for AbsoluteSoftMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS_SOFT;
+}
+
+/// Timer with relative expiration, handled in soft irq context.
+pub struct RelativeSoftMode;
+
+impl HrTimerMode for RelativeSoftMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL_SOFT;
+}
+
+/// Timer with absolute expiration, pinned to CPU and handled in soft irq context.
+pub struct AbsolutePinnedSoftMode;
+
+impl HrTimerMode for AbsolutePinnedSoftMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS_PINNED_SOFT;
+}
+
+/// Timer with relative expiration, pinned to CPU and handled in soft irq context.
+pub struct RelativePinnedSoftMode;
+
+impl HrTimerMode for RelativePinnedSoftMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL_PINNED_SOFT;
+}
+
+/// Timer with absolute expiration, handled in hard irq context.
+pub struct AbsoluteHardMode;
+
+impl HrTimerMode for AbsoluteHardMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS_HARD;
+}
+
+/// Timer with relative expiration, handled in hard irq context.
+pub struct RelativeHardMode;
+
+impl HrTimerMode for RelativeHardMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL_HARD;
+}
+
+/// Timer with absolute expiration, pinned to CPU and handled in hard irq context.
+pub struct AbsolutePinnedHardMode;
+
+impl HrTimerMode for AbsolutePinnedHardMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS_PINNED_HARD;
+}
+
+/// Timer with relative expiration, pinned to CPU and handled in hard irq context.
+pub struct RelativePinnedHardMode;
+
+impl HrTimerMode for RelativePinnedHardMode {
+    const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL_PINNED_HARD;
 }
 
 /// Use to implement the [`HasHrTimer<T>`] trait.
-- 
2.43.0

[PATCH v2 3/5] rust: time: Add HrTimerExpires trait

[FUJITA Tomonori]

Introduce the `HrTimerExpires` trait to represent types that can be
used as expiration values for high-resolution timers. Define a
required method, `into_nanos()`, which returns the expiration time as a
raw nanosecond value suitable for use with C's hrtimer APIs.

Also extend the `HrTimerMode` to use the `HrTimerExpires` trait.

This refactoring is a preparation for enabling hrtimer code to work
uniformly with both absolute and relative expiration modes.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 rust/kernel/time.rs         |   5 ++
 rust/kernel/time/hrtimer.rs | 126 +++++++++++++++++++++++++-----------
 2 files changed, 95 insertions(+), 36 deletions(-)

diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
index 2a231c321afa..70bd3be0facc 100644
--- a/rust/kernel/time.rs
+++ b/rust/kernel/time.rs
@@ -194,6 +194,11 @@ pub fn now() -> Self {
     pub fn elapsed(&self) -> Delta {
         Self::now() - *self
     }
+
+    #[inline]
+    pub(crate) fn into_nanos(self) -> i64 {
+        self.inner
+    }
 }
 
 impl<C: ClockSource> core::ops::Sub for Instant<C> {
diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index 23f9f1ba8607..0ba87f1233cd 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -67,7 +67,7 @@
 //! A `restart` operation on a timer in the **stopped** state is equivalent to a
 //! `start` operation.
 
-use super::ClockSource;
+use super::{ClockSource, Delta, Instant};
 use crate::{prelude::*, types::Opaque};
 use core::marker::PhantomData;
 use pin_init::PinInit;
@@ -411,94 +411,148 @@ fn into_c(self) -> bindings::hrtimer_restart {
     }
 }
 
+/// Time representations that can be used as expiration values in [`HrTimer`].
+pub trait HrTimerExpires {
+    /// Converts the expiration time into a nanosecond representation.
+    ///
+    /// This value corresponds to a raw ktime_t value, suitable for passing to kernel
+    /// timer functions. The interpretation (absolute vs relative) depends on the
+    /// associated [HrTimerMode] in use.
+    fn into_nanos(self) -> i64;
+}
+
+impl<C: ClockSource> HrTimerExpires for Instant<C> {
+    fn into_nanos(self) -> i64 {
+        Instant::<C>::into_nanos(self)
+    }
+}
+
+impl HrTimerExpires for Delta {
+    fn into_nanos(self) -> i64 {
+        Delta::into_nanos(self)
+    }
+}
+
 /// Operational mode of [`HrTimer`].
 pub trait HrTimerMode {
     /// The C representation of hrtimer mode.
     const C_MODE: bindings::hrtimer_mode;
+
+    /// Type representing the clock source.
+    type Clock: ClockSource;
+
+    /// Type representing the expiration specification (absolute or relative time).
+    type Expires: HrTimerExpires;
 }
 
 /// Timer that expires at a fixed point in time.
-pub struct AbsoluteMode;
+pub struct AbsoluteMode<C: ClockSource>(PhantomData<C>);
 
-impl HrTimerMode for AbsoluteMode {
+impl<C: ClockSource> HrTimerMode for AbsoluteMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS;
+
+    type Clock = C;
+    type Expires = Instant<C>;
 }
 
 /// Timer that expires after a delay from now.
-pub struct RelativeMode;
+pub struct RelativeMode<C: ClockSource>(PhantomData<C>);
 
-impl HrTimerMode for RelativeMode {
+impl<C: ClockSource> HrTimerMode for RelativeMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL;
+
+    type Clock = C;
+    type Expires = Delta;
 }
 
 /// Timer with absolute expiration time, pinned to its current CPU.
-pub struct AbsolutePinnedMode;
-
-impl HrTimerMode for AbsolutePinnedMode {
+pub struct AbsolutePinnedMode<C: ClockSource>(PhantomData<C>);
+impl<C: ClockSource> HrTimerMode for AbsolutePinnedMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS_PINNED;
+
+    type Clock = C;
+    type Expires = Instant<C>;
 }
 
 /// Timer with relative expiration time, pinned to its current CPU.
-pub struct RelativePinnedMode;
-
-impl HrTimerMode for RelativePinnedMode {
+pub struct RelativePinnedMode<C: ClockSource>(PhantomData<C>);
+impl<C: ClockSource> HrTimerMode for RelativePinnedMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL_PINNED;
+
+    type Clock = C;
+    type Expires = Delta;
 }
 
 /// Timer with absolute expiration, handled in soft irq context.
-pub struct AbsoluteSoftMode;
-
-impl HrTimerMode for AbsoluteSoftMode {
+pub struct AbsoluteSoftMode<C: ClockSource>(PhantomData<C>);
+impl<C: ClockSource> HrTimerMode for AbsoluteSoftMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS_SOFT;
+
+    type Clock = C;
+    type Expires = Instant<C>;
 }
 
 /// Timer with relative expiration, handled in soft irq context.
-pub struct RelativeSoftMode;
-
-impl HrTimerMode for RelativeSoftMode {
+pub struct RelativeSoftMode<C: ClockSource>(PhantomData<C>);
+impl<C: ClockSource> HrTimerMode for RelativeSoftMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL_SOFT;
+
+    type Clock = C;
+    type Expires = Delta;
 }
 
 /// Timer with absolute expiration, pinned to CPU and handled in soft irq context.
-pub struct AbsolutePinnedSoftMode;
-
-impl HrTimerMode for AbsolutePinnedSoftMode {
+pub struct AbsolutePinnedSoftMode<C: ClockSource>(PhantomData<C>);
+impl<C: ClockSource> HrTimerMode for AbsolutePinnedSoftMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS_PINNED_SOFT;
-}
 
-/// Timer with relative expiration, pinned to CPU and handled in soft irq context.
-pub struct RelativePinnedSoftMode;
+    type Clock = C;
+    type Expires = Instant<C>;
+}
 
-impl HrTimerMode for RelativePinnedSoftMode {
+/// Timer with absolute expiration, pinned to CPU and handled in soft irq context.
+pub struct RelativePinnedSoftMode<C: ClockSource>(PhantomData<C>);
+impl<C: ClockSource> HrTimerMode for RelativePinnedSoftMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL_PINNED_SOFT;
+
+    type Clock = C;
+    type Expires = Delta;
 }
 
 /// Timer with absolute expiration, handled in hard irq context.
-pub struct AbsoluteHardMode;
-
-impl HrTimerMode for AbsoluteHardMode {
+pub struct AbsoluteHardMode<C: ClockSource>(PhantomData<C>);
+impl<C: ClockSource> HrTimerMode for AbsoluteHardMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS_HARD;
+
+    type Clock = C;
+    type Expires = Instant<C>;
 }
 
 /// Timer with relative expiration, handled in hard irq context.
-pub struct RelativeHardMode;
-
-impl HrTimerMode for RelativeHardMode {
+pub struct RelativeHardMode<C: ClockSource>(PhantomData<C>);
+impl<C: ClockSource> HrTimerMode for RelativeHardMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL_HARD;
+
+    type Clock = C;
+    type Expires = Delta;
 }
 
 /// Timer with absolute expiration, pinned to CPU and handled in hard irq context.
-pub struct AbsolutePinnedHardMode;
-
-impl HrTimerMode for AbsolutePinnedHardMode {
+pub struct AbsolutePinnedHardMode<C: ClockSource>(PhantomData<C>);
+impl<C: ClockSource> HrTimerMode for AbsolutePinnedHardMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_ABS_PINNED_HARD;
+
+    type Clock = C;
+    type Expires = Instant<C>;
 }
 
 /// Timer with relative expiration, pinned to CPU and handled in hard irq context.
-pub struct RelativePinnedHardMode;
-
-impl HrTimerMode for RelativePinnedHardMode {
+pub struct RelativePinnedHardMode<C: ClockSource>(PhantomData<C>);
+impl<C: ClockSource> HrTimerMode for RelativePinnedHardMode<C> {
     const C_MODE: bindings::hrtimer_mode = bindings::hrtimer_mode_HRTIMER_MODE_REL_PINNED_HARD;
+
+    type Clock = C;
+    type Expires = Delta;
 }
 
 /// Use to implement the [`HasHrTimer<T>`] trait.
-- 
2.43.0

[PATCH v2 4/5] rust: time: Make HasHrTimer generic over HrTimerMode

[FUJITA Tomonori]

Add a `TimerMode` associated type to the `HasHrTimer` trait to
represent the operational mode of the timer, such as absolute or
relative expiration. This new type must implement the `HrTimerMode`
trait, which defines how expiration values are interpreted.

Update the `start()` method to accept an `expires` parameter of type
`<Self::TimerMode as HrTimerMode>::Expires` instead of the fixed `Ktime`.
This enables different timer modes to provide strongly typed expiration
values, such as `Instant<C>` or `Delta`.

The `impl_has_hr_timer` macro is also extended to allow specifying the
`HrTimerMode`. In the following example, it guarantees that the
`start()` method for `Foo` only accepts `Instant<Monotonic>`. Using a
`Delta` or an `Instant` with a different clock source will result in a
compile-time error:

struct Foo {
    #[pin]
    timer: HrTimer<Self>,
}

impl_has_hr_timer! {
    impl HasHrTimer<Self> for Foo {
        mode : AbsoluteMode<Monotonic>,
        field : self.timer
    }
}

This design eliminates runtime mismatches between expires types and
clock sources, and enables stronger type-level guarantees throughout
hrtimer.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 rust/kernel/time/hrtimer.rs         | 55 ++++++++++++++++++++++-------
 rust/kernel/time/hrtimer/arc.rs     |  8 +++--
 rust/kernel/time/hrtimer/pin.rs     |  8 +++--
 rust/kernel/time/hrtimer/pin_mut.rs |  8 +++--
 rust/kernel/time/hrtimer/tbox.rs    |  8 +++--
 5 files changed, 66 insertions(+), 21 deletions(-)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index 0ba87f1233cd..fe68d8de4101 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -98,7 +98,6 @@ pub fn to_ns(self) -> i64 {
 pub struct HrTimer<T> {
     #[pin]
     timer: Opaque<bindings::hrtimer>,
-    mode: bindings::hrtimer_mode,
     _t: PhantomData<T>,
 }
 
@@ -112,9 +111,10 @@ unsafe impl<T> Sync for HrTimer<T> {}
 
 impl<T> HrTimer<T> {
     /// Return an initializer for a new timer instance.
-    pub fn new<U: ClockSource, M: HrTimerMode>() -> impl PinInit<Self>
+    pub fn new() -> impl PinInit<Self>
     where
         T: HrTimerCallback,
+        T: HasHrTimer<T>,
     {
         pin_init!(Self {
             // INVARIANT: We initialize `timer` with `hrtimer_setup` below.
@@ -126,12 +126,11 @@ pub fn new<U: ClockSource, M: HrTimerMode>() -> impl PinInit<Self>
                     bindings::hrtimer_setup(
                         place,
                         Some(T::Pointer::run),
-                        U::ID,
-                        M::C_MODE,
+                        <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Clock::ID,
+                        <T as HasHrTimer<T>>::TimerMode::C_MODE,
                     );
                 }
             }),
-            mode: M::C_MODE,
             _t: PhantomData,
         })
     }
@@ -193,6 +192,11 @@ pub(crate) unsafe fn raw_cancel(this: *const Self) -> bool {
 /// exist. A timer can be manipulated through any of the handles, and a handle
 /// may represent a cancelled timer.
 pub trait HrTimerPointer: Sync + Sized {
+    /// The operational mode associated with this timer.
+    ///
+    /// This defines how the expiration value is interpreted.
+    type TimerMode: HrTimerMode;
+
     /// A handle representing a started or restarted timer.
     ///
     /// If the timer is running or if the timer callback is executing when the
@@ -205,7 +209,7 @@ pub trait HrTimerPointer: Sync + Sized {
 
     /// Start the timer with expiry after `expires` time units. If the timer was
     /// already running, it is restarted with the new expiry time.
-    fn start(self, expires: Ktime) -> Self::TimerHandle;
+    fn start(self, expires: <Self::TimerMode as HrTimerMode>::Expires) -> Self::TimerHandle;
 }
 
 /// Unsafe version of [`HrTimerPointer`] for situations where leaking the
@@ -220,6 +224,11 @@ pub trait HrTimerPointer: Sync + Sized {
 /// [`UnsafeHrTimerPointer`] outlives any associated [`HrTimerPointer::TimerHandle`]
 /// instances.
 pub unsafe trait UnsafeHrTimerPointer: Sync + Sized {
+    /// The operational mode associated with this timer.
+    ///
+    /// This defines how the expiration value is interpreted.
+    type TimerMode: HrTimerMode;
+
     /// A handle representing a running timer.
     ///
     /// # Safety
@@ -236,7 +245,7 @@ pub unsafe trait UnsafeHrTimerPointer: Sync + Sized {
     ///
     /// Caller promises keep the timer structure alive until the timer is dead.
     /// Caller can ensure this by not leaking the returned [`Self::TimerHandle`].
-    unsafe fn start(self, expires: Ktime) -> Self::TimerHandle;
+    unsafe fn start(self, expires: <Self::TimerMode as HrTimerMode>::Expires) -> Self::TimerHandle;
 }
 
 /// A trait for stack allocated timers.
@@ -246,9 +255,14 @@ pub unsafe trait UnsafeHrTimerPointer: Sync + Sized {
 /// Implementers must ensure that `start_scoped` does not return until the
 /// timer is dead and the timer handler is not running.
 pub unsafe trait ScopedHrTimerPointer {
+    /// The operational mode associated with this timer.
+    ///
+    /// This defines how the expiration value is interpreted.
+    type TimerMode: HrTimerMode;
+
     /// Start the timer to run after `expires` time units and immediately
     /// after call `f`. When `f` returns, the timer is cancelled.
-    fn start_scoped<T, F>(self, expires: Ktime, f: F) -> T
+    fn start_scoped<T, F>(self, expires: <Self::TimerMode as HrTimerMode>::Expires, f: F) -> T
     where
         F: FnOnce() -> T;
 }
@@ -260,7 +274,13 @@ unsafe impl<T> ScopedHrTimerPointer for T
 where
     T: UnsafeHrTimerPointer,
 {
-    fn start_scoped<U, F>(self, expires: Ktime, f: F) -> U
+    type TimerMode = T::TimerMode;
+
+    fn start_scoped<U, F>(
+        self,
+        expires: <<T as UnsafeHrTimerPointer>::TimerMode as HrTimerMode>::Expires,
+        f: F,
+    ) -> U
     where
         F: FnOnce() -> U,
     {
@@ -335,6 +355,11 @@ pub unsafe trait HrTimerHandle {
 /// their documentation. All the methods of this trait must operate on the same
 /// field.
 pub unsafe trait HasHrTimer<T> {
+    /// The operational mode associated with this timer.
+    ///
+    /// This defines how the expiration value is interpreted.
+    type TimerMode: HrTimerMode;
+
     /// Return a pointer to the [`HrTimer`] within `Self`.
     ///
     /// This function is useful to get access to the value without creating
@@ -382,14 +407,14 @@ unsafe fn c_timer_ptr(this: *const Self) -> *const bindings::hrtimer {
     /// - `this` must point to a valid `Self`.
     /// - Caller must ensure that the pointee of `this` lives until the timer
     ///   fires or is canceled.
-    unsafe fn start(this: *const Self, expires: Ktime) {
+    unsafe fn start(this: *const Self, expires: <Self::TimerMode as HrTimerMode>::Expires) {
         // SAFETY: By function safety requirement, `this` is a valid `Self`.
         unsafe {
             bindings::hrtimer_start_range_ns(
                 Self::c_timer_ptr(this).cast_mut(),
-                expires.to_ns(),
+                expires.into_nanos(),
                 0,
-                (*Self::raw_get_timer(this)).mode,
+                <Self::TimerMode as HrTimerMode>::Clock::ID as u32,
             );
         }
     }
@@ -566,12 +591,16 @@ macro_rules! impl_has_hr_timer {
         impl$({$($generics:tt)*})?
             HasHrTimer<$timer_type:ty>
             for $self:ty
-        { self.$field:ident }
+        {
+            mode : $mode:ty,
+            field : self.$field:ident
+        }
         $($rest:tt)*
     ) => {
         // SAFETY: This implementation of `raw_get_timer` only compiles if the
         // field has the right type.
         unsafe impl$(<$($generics)*>)? $crate::time::hrtimer::HasHrTimer<$timer_type> for $self {
+            type TimerMode = $mode;
 
             #[inline]
             unsafe fn raw_get_timer(
diff --git a/rust/kernel/time/hrtimer/arc.rs b/rust/kernel/time/hrtimer/arc.rs
index ccf1e66e5b2d..ed490a7a8950 100644
--- a/rust/kernel/time/hrtimer/arc.rs
+++ b/rust/kernel/time/hrtimer/arc.rs
@@ -4,8 +4,8 @@
 use super::HrTimer;
 use super::HrTimerCallback;
 use super::HrTimerHandle;
+use super::HrTimerMode;
 use super::HrTimerPointer;
-use super::Ktime;
 use super::RawHrTimerCallback;
 use crate::sync::Arc;
 use crate::sync::ArcBorrow;
@@ -54,9 +54,13 @@ impl<T> HrTimerPointer for Arc<T>
     T: HasHrTimer<T>,
     T: for<'a> HrTimerCallback<Pointer<'a> = Self>,
 {
+    type TimerMode = <T as HasHrTimer<T>>::TimerMode;
     type TimerHandle = ArcHrTimerHandle<T>;
 
-    fn start(self, expires: Ktime) -> ArcHrTimerHandle<T> {
+    fn start(
+        self,
+        expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
+    ) -> ArcHrTimerHandle<T> {
         // SAFETY:
         //  - We keep `self` alive by wrapping it in a handle below.
         //  - Since we generate the pointer passed to `start` from a valid
diff --git a/rust/kernel/time/hrtimer/pin.rs b/rust/kernel/time/hrtimer/pin.rs
index 293ca9cf058c..550aad28d987 100644
--- a/rust/kernel/time/hrtimer/pin.rs
+++ b/rust/kernel/time/hrtimer/pin.rs
@@ -4,7 +4,7 @@
 use super::HrTimer;
 use super::HrTimerCallback;
 use super::HrTimerHandle;
-use super::Ktime;
+use super::HrTimerMode;
 use super::RawHrTimerCallback;
 use super::UnsafeHrTimerPointer;
 use core::pin::Pin;
@@ -54,9 +54,13 @@ unsafe impl<'a, T> UnsafeHrTimerPointer for Pin<&'a T>
     T: HasHrTimer<T>,
     T: HrTimerCallback<Pointer<'a> = Self>,
 {
+    type TimerMode = <T as HasHrTimer<T>>::TimerMode;
     type TimerHandle = PinHrTimerHandle<'a, T>;
 
-    unsafe fn start(self, expires: Ktime) -> Self::TimerHandle {
+    unsafe fn start(
+        self,
+        expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
+    ) -> Self::TimerHandle {
         // Cast to pointer
         let self_ptr: *const T = self.get_ref();
 
diff --git a/rust/kernel/time/hrtimer/pin_mut.rs b/rust/kernel/time/hrtimer/pin_mut.rs
index 6033572d35ad..bacd3d5d972a 100644
--- a/rust/kernel/time/hrtimer/pin_mut.rs
+++ b/rust/kernel/time/hrtimer/pin_mut.rs
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
 use super::{
-    HasHrTimer, HrTimer, HrTimerCallback, HrTimerHandle, Ktime, RawHrTimerCallback,
+    HasHrTimer, HrTimer, HrTimerCallback, HrTimerHandle, HrTimerMode, RawHrTimerCallback,
     UnsafeHrTimerPointer,
 };
 use core::{marker::PhantomData, pin::Pin, ptr::NonNull};
@@ -52,9 +52,13 @@ unsafe impl<'a, T> UnsafeHrTimerPointer for Pin<&'a mut T>
     T: HasHrTimer<T>,
     T: HrTimerCallback<Pointer<'a> = Self>,
 {
+    type TimerMode = <T as HasHrTimer<T>>::TimerMode;
     type TimerHandle = PinMutHrTimerHandle<'a, T>;
 
-    unsafe fn start(mut self, expires: Ktime) -> Self::TimerHandle {
+    unsafe fn start(
+        mut self,
+        expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
+    ) -> Self::TimerHandle {
         // SAFETY:
         // - We promise not to move out of `self`. We only pass `self`
         //   back to the caller as a `Pin<&mut self>`.
diff --git a/rust/kernel/time/hrtimer/tbox.rs b/rust/kernel/time/hrtimer/tbox.rs
index 29526a5da203..ec08303315f2 100644
--- a/rust/kernel/time/hrtimer/tbox.rs
+++ b/rust/kernel/time/hrtimer/tbox.rs
@@ -4,8 +4,8 @@
 use super::HrTimer;
 use super::HrTimerCallback;
 use super::HrTimerHandle;
+use super::HrTimerMode;
 use super::HrTimerPointer;
-use super::Ktime;
 use super::RawHrTimerCallback;
 use crate::prelude::*;
 use core::ptr::NonNull;
@@ -64,9 +64,13 @@ impl<T, A> HrTimerPointer for Pin<Box<T, A>>
     T: for<'a> HrTimerCallback<Pointer<'a> = Pin<Box<T, A>>>,
     A: crate::alloc::Allocator,
 {
+    type TimerMode = <T as HasHrTimer<T>>::TimerMode;
     type TimerHandle = BoxHrTimerHandle<T, A>;
 
-    fn start(self, expires: Ktime) -> Self::TimerHandle {
+    fn start(
+        self,
+        expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
+    ) -> Self::TimerHandle {
         // SAFETY:
         //  - We will not move out of this box during timer callback (we pass an
         //    immutable reference to the callback).
-- 
2.43.0

[PATCH v2 5/5] rust: time: Remove Ktime in hrtimer

[FUJITA Tomonori]

Remove the use of `Ktime` from the hrtimer code, which was originally
introduced as a temporary workaround. The hrtimer has now been fully
converted to use the `Instant` and `Delta` types instead.

Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 rust/kernel/time/hrtimer.rs | 16 ----------------
 1 file changed, 16 deletions(-)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index fe68d8de4101..a683da540e67 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -72,22 +72,6 @@
 use core::marker::PhantomData;
 use pin_init::PinInit;
 
-/// A Rust wrapper around a `ktime_t`.
-// NOTE: Ktime is going to be removed when hrtimer is converted to Instant/Delta.
-#[repr(transparent)]
-#[derive(Copy, Clone, PartialEq, PartialOrd, Eq, Ord)]
-pub struct Ktime {
-    inner: bindings::ktime_t,
-}
-
-impl Ktime {
-    /// Returns the number of nanoseconds.
-    #[inline]
-    pub fn to_ns(self) -> i64 {
-        self.inner
-    }
-}
-
 /// A timer backed by a C `struct hrtimer`.
 ///
 /// # Invariants
-- 
2.43.0

Re: [PATCH v2 1/5] rust: time: Rename Delta's methods from as_* to into_*

[Andreas Hindborg]

"FUJITA Tomonori" <fujita.tomonori@gmail.com> writes:

> Rename Delta's methods that take self from as_* to into_* to align
> with Rust naming conventions.
>
> Using `self` is more common Rust practice for small values that can be
> freely copied [1].
>
> Clippy warns against using as_* names for trait methods that take self
> as follows:
>
> warning: methods called as_* usually take self by reference or self by mutable reference
> --> ~/linux/rust/kernel/time/hrtimer.rs:421:17
> |
> 421 |     fn as_nanos(self) -> i64;
>
> Rename the `Delta` struct's methods from as_nanos(), as_micros_ceil(),
> and as_millis() to into_nanos(), into_micros_ceil(), and
> into_millis(), respectively to maintain consistency with the other
> function names.
>
> Link: https://lore.kernel.org/lkml/aD1fgizC4FPT07vt@google.com/ [1]
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>


Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>


Best regards,
Andreas Hindborg

Re: [PATCH v2 3/5] rust: time: Add HrTimerExpires trait

[Andreas Hindborg]

"FUJITA Tomonori" <fujita.tomonori@gmail.com> writes:

> Introduce the `HrTimerExpires` trait to represent types that can be
> used as expiration values for high-resolution timers. Define a
> required method, `into_nanos()`, which returns the expiration time as a
> raw nanosecond value suitable for use with C's hrtimer APIs.
>
> Also extend the `HrTimerMode` to use the `HrTimerExpires` trait.
>
> This refactoring is a preparation for enabling hrtimer code to work
> uniformly with both absolute and relative expiration modes.
>
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>

Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>


Best regards,
Andreas Hindborg

Re: [PATCH v2 4/5] rust: time: Make HasHrTimer generic over HrTimerMode

[Andreas Hindborg]

"FUJITA Tomonori" <fujita.tomonori@gmail.com> writes:

> Add a `TimerMode` associated type to the `HasHrTimer` trait to
> represent the operational mode of the timer, such as absolute or
> relative expiration. This new type must implement the `HrTimerMode`
> trait, which defines how expiration values are interpreted.
>
> Update the `start()` method to accept an `expires` parameter of type
> `<Self::TimerMode as HrTimerMode>::Expires` instead of the fixed `Ktime`.
> This enables different timer modes to provide strongly typed expiration
> values, such as `Instant<C>` or `Delta`.
>
> The `impl_has_hr_timer` macro is also extended to allow specifying the
> `HrTimerMode`. In the following example, it guarantees that the
> `start()` method for `Foo` only accepts `Instant<Monotonic>`. Using a
> `Delta` or an `Instant` with a different clock source will result in a
> compile-time error:
>
> struct Foo {
>     #[pin]
>     timer: HrTimer<Self>,
> }
>
> impl_has_hr_timer! {
>     impl HasHrTimer<Self> for Foo {
>         mode : AbsoluteMode<Monotonic>,
>         field : self.timer
>     }

Can you add an optional comma after the `field` entry? I think it is
`$(,)?` in the macro declaration.


Best regards,
Andreas Hindborg

Re: [PATCH v2 4/5] rust: time: Make HasHrTimer generic over HrTimerMode

[FUJITA Tomonori]

On Tue, 10 Jun 2025 13:25:37 +0200
Andreas Hindborg <a.hindborg@kernel.org> wrote:

>> struct Foo {
>>     #[pin]
>>     timer: HrTimer<Self>,
>> }
>>
>> impl_has_hr_timer! {
>>     impl HasHrTimer<Self> for Foo {
>>         mode : AbsoluteMode<Monotonic>,
>>         field : self.timer
>>     }
> 
> Can you add an optional comma after the `field` entry? I think it is
> `$(,)?` in the macro declaration.

Sounds good. I'll send v3 shortly.