rust: hrtimer: add clocksource selection through ClockSource

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

Acked-by: Frederic Weisbecker <[email protected]>
Signed-off-by: Andreas Hindborg <[email protected]>
Reviewed-by: Lyude Paul <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Andreas Hindborg

rust/kernel/time/hrtimer.rs

@@ -93,7 +93,7 @@ unsafe impl<T> Sync for HrTimer<T> {}
 
 impl<T> HrTimer<T> {
     /// Return an initializer for a new timer instance.
-    pub fn new(mode: HrTimerMode) -> impl PinInit<Self>
+    pub fn new(mode: HrTimerMode, clock: ClockSource) -> impl PinInit<Self>
     where
         T: HrTimerCallback,
     {
@@ -107,7 +107,7 @@ impl<T> HrTimer<T> {
                     bindings::hrtimer_setup(
                         place,
                         Some(T::Pointer::run),
-                        bindings::CLOCK_MONOTONIC as i32,
+                        clock.into_c(),
                         mode.into_c(),
                     );
                 }
@@ -468,6 +468,61 @@ impl HrTimerMode {
     }
 }
 
+/// The clock source to use for a [`HrTimer`].
+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 monotonically increasing clock.
+    ///
+    /// 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 monotonic that ticks while system is suspended.
+    ///
+    /// 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,
+    /// International Atomic Time.
+    ///
+    /// 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 ClockSource {
+    fn into_c(self) -> bindings::clockid_t {
+        match self {
+            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 [`HasHrTimer<T>`] trait.
 ///
 /// See [`module`] documentation for an example.