linux-kernel - [PATCH v3 0/5] rust: time: Convert hrtimer to use Instant and Delta

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Message-ID: <20250610132823.3457263-1-fujita.tomonori@gmail.com>
Date: Tue, 10 Jun 2025 22:28:18 +0900
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: a.hindborg@...nel.org,
	alex.gaynor@...il.com,
	ojeda@...nel.org
Cc: aliceryhl@...gle.com,
	anna-maria@...utronix.de,
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	linux-kernel@...r.kernel.org,
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	rust-for-linux@...r.kernel.org,
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	tglx@...utronix.de,
	tmgross@...ch.edu
Subject: [PATCH v3 0/5] rust: time: Convert hrtimer to use Instant and Delta

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 (v4):

https://lore.kernel.org/lkml/20250610093258.3435874-1-fujita.tomonori@gmail.com/

v3
- allow optional trailing comma for the field entry in impl_has_hr_timer! macro
v2: https://lore.kernel.org/lkml/20250609102418.3345792-1-fujita.tomonori@gmail.com/
- 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: 8bffa361fb76742eb953ca024a9363c6e9357d65
-- 
2.43.0