linux-kernel - [PATCH v3 12/13] rust: hrtimer: add clocksource selection through `ClockSource`

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Message-Id: <20241017-hrtimer-v3-v6-12-rc2-v3-12-59a75cbb44da@kernel.org>
Date: Thu, 17 Oct 2024 15:04:39 +0200
From: Andreas Hindborg <a.hindborg@...nel.org>
To: Miguel Ojeda <ojeda@...nel.org>, 
 Anna-Maria Behnsen <anna-maria@...utronix.de>, 
 Frederic Weisbecker <frederic@...nel.org>, 
 Thomas Gleixner <tglx@...utronix.de>
Cc: Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
 Gary Guo <gary@...yguo.net>, 
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
 Benno Lossin <benno.lossin@...ton.me>, Alice Ryhl <aliceryhl@...gle.com>, 
 Trevor Gross <tmgross@...ch.edu>, Lyude Paul <lyude@...hat.com>, 
 rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Andreas Hindborg <a.hindborg@...nel.org>
Subject: [PATCH v3 12/13] rust: hrtimer: add clocksource selection through
 `ClockSource`

Allow selecting a clock source for timers by passing a `ClockSource`
variant to `Timer::new`.

Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
---
 rust/kernel/hrtimer.rs | 52 ++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 50 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/hrtimer.rs b/rust/kernel/hrtimer.rs
index 1674d1dcba39cc7ab82e1f189002afa365ee9341..f3d57c6cb1a95075c28192b5cd2f97431989a0b1 100644
--- a/rust/kernel/hrtimer.rs
+++ b/rust/kernel/hrtimer.rs
@@ -57,7 +57,7 @@ unsafe impl<U> Sync for Timer<U> {}
 
 impl<T> Timer<T> {
     /// Return an initializer for a new timer instance.
-    pub fn new(mode: TimerMode) -> impl PinInit<Self>
+    pub fn new(mode: TimerMode, clock: ClockSource) -> impl PinInit<Self>
     where
         T: TimerCallback,
     {
@@ -70,7 +70,7 @@ pub fn new(mode: TimerMode) -> impl PinInit<Self>
                 unsafe {
                     bindings::hrtimer_init(
                         place,
-                        bindings::CLOCK_MONOTONIC as i32,
+                        clock.into(),
                         mode.into(),
                     );
                 }
@@ -442,6 +442,54 @@ fn from(value: TimerMode) -> Self {
     }
 }
 
+/// The clock source to use for a [`Timer`].
+pub enum ClockSource {
+    /// A settable system-wide clock that measures real (i.e., wall-clock) time.
+    /// Setting this clock requires appropriate privileges. This clock is
+    /// affected by discontinuous jumps in the system time (e.g., if the system
+    /// administrator manually changes the clock), and by frequency adjustments
+    /// performed by NTP and similar applications via adjtime(3), adjtimex(2),
+    /// clock_adjtime(2), and ntp_adjtime(3). This clock normally counts the
+    /// number of seconds since 1970-01-01 00:00:00 Coordinated Universal Time
+    /// (UTC) except that it ignores leap seconds; near a leap second it is
+    /// typically adjusted by NTP to stay roughly in sync with UTC.
+    RealTime,
+    /// A nonsettable system-wide clock that represents monotonic time since—as
+    /// described by POSIX—"some unspecified point in the past". On Linux, that
+    /// point corresponds to the number of seconds that the system has been
+    /// running since it was booted.
+    ///
+    /// The CLOCK_MONOTONIC clock is not affected by discontinuous jumps in the
+    /// system time (e.g., if the system administrator manually changes the
+    /// clock), but is affected by frequency adjustments. This clock does not
+    /// count time that the system is suspended.
+    Monotonic,
+    /// A nonsettable system-wide clock that is identical to CLOCK_MONOTONIC,
+    /// except that it also includes any time that the system is suspended. This
+    /// allows applications to get a suspend-aware monotonic clock without
+    /// having to deal with the complications of CLOCK_REALTIME, which may have
+    /// discontinuities if the time is changed using settimeofday(2) or similar.
+    BootTime,
+    /// A nonsettable system-wide clock derived from wall-clock time but
+    /// counting leap seconds. This clock does not experience discontinuities or
+    /// frequency adjustments caused by inserting leap seconds as CLOCK_REALTIME
+    /// does.
+    ///
+    /// The acronym TAI refers to International Atomic Time.
+    TAI,
+}
+
+impl From<ClockSource> for bindings::clockid_t {
+    fn from(value: ClockSource) -> Self {
+        match value {
+            ClockSource::RealTime => bindings::CLOCK_REALTIME as i32,
+            ClockSource::Monotonic => bindings::CLOCK_MONOTONIC as i32,
+            ClockSource::BootTime => bindings::CLOCK_BOOTTIME as i32,
+            ClockSource::TAI => bindings::CLOCK_TAI as i32,
+        }
+    }
+}
+
 /// Use to implement the [`HasTimer<T>`] trait.
 ///
 /// See [`module`] documentation for an example.

-- 
2.46.0