Merge tag 'rust-timekeeping-v6.18' of https://github.com/Rust-for-Linux/linux into rust-next

Pull timekeeping updates from Andreas Hindborg:

 - Add methods on 'HrTimer' that can only be called with exclusive
   access to an unarmed timer, or form timer callback context.

 - Add arithmetic operations to 'Instant' and 'Delta'.

 - Add a few convenience and access methods to 'HrTimer' and 'Instant'.

* tag 'rust-timekeeping-v6.18' of https://github.com/Rust-for-Linux/linux:
  rust: time: Implement basic arithmetic operations for Delta
  rust: time: Implement Add<Delta>/Sub<Delta> for Instant
  rust: hrtimer: Add HrTimer::expires()
  rust: time: Add Instant::from_ktime()
  rust: hrtimer: Add forward_now() to HrTimer and HrTimerCallbackContext
  rust: hrtimer: Add HrTimerCallbackContext and ::forward()
  rust: hrtimer: Add HrTimer::raw_forward() and forward()
  rust: hrtimer: Add HrTimerInstant
  rust: hrtimer: Document the return value for HrTimerHandle::cancel()

1 files changed, 162 insertions, 1 deletions

diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
index 64c8dcf548d6..6ea98dfcd027 100644
--- a/rust/kernel/time.rs
+++ b/rust/kernel/time.rs
@@ -25,6 +25,7 @@
 //! C header: [`include/linux/ktime.h`](srctree/include/linux/ktime.h).
 
 use core::marker::PhantomData;
+use core::ops;
 
 pub mod delay;
 pub mod hrtimer;
@@ -200,9 +201,31 @@ impl<C: ClockSource> Instant<C> {
     pub(crate) fn as_nanos(&self) -> i64 {
         self.inner
     }
+
+    /// Create an [`Instant`] from a `ktime_t` without checking if it is non-negative.
+    ///
+    /// # Panics
+    ///
+    /// On debug builds, this function will panic if `ktime` is not in the range from 0 to
+    /// `KTIME_MAX`.
+    ///
+    /// # Safety
+    ///
+    /// The caller promises that `ktime` is in the range from 0 to `KTIME_MAX`.
+    #[inline]
+    pub(crate) unsafe fn from_ktime(ktime: bindings::ktime_t) -> Self {
+        debug_assert!(ktime >= 0);
+
+        // INVARIANT: Our safety contract ensures that `ktime` is in the range from 0 to
+        // `KTIME_MAX`.
+        Self {
+            inner: ktime,
+            _c: PhantomData,
+        }
+    }
 }
 
-impl<C: ClockSource> core::ops::Sub for Instant<C> {
+impl<C: ClockSource> ops::Sub for Instant<C> {
     type Output = Delta;
 
     // By the type invariant, it never overflows.
@@ -214,6 +237,46 @@ impl<C: ClockSource> core::ops::Sub for Instant<C> {
     }
 }
 
+impl<T: ClockSource> ops::Add<Delta> for Instant<T> {
+    type Output = Self;
+
+    #[inline]
+    fn add(self, rhs: Delta) -> Self::Output {
+        // INVARIANT: With arithmetic over/underflow checks enabled, this will panic if we overflow
+        // (e.g. go above `KTIME_MAX`)
+        let res = self.inner + rhs.nanos;
+
+        // INVARIANT: With overflow checks enabled, we verify here that the value is >= 0
+        #[cfg(CONFIG_RUST_OVERFLOW_CHECKS)]
+        assert!(res >= 0);
+
+        Self {
+            inner: res,
+            _c: PhantomData,
+        }
+    }
+}
+
+impl<T: ClockSource> ops::Sub<Delta> for Instant<T> {
+    type Output = Self;
+
+    #[inline]
+    fn sub(self, rhs: Delta) -> Self::Output {
+        // INVARIANT: With arithmetic over/underflow checks enabled, this will panic if we overflow
+        // (e.g. go above `KTIME_MAX`)
+        let res = self.inner - rhs.nanos;
+
+        // INVARIANT: With overflow checks enabled, we verify here that the value is >= 0
+        #[cfg(CONFIG_RUST_OVERFLOW_CHECKS)]
+        assert!(res >= 0);
+
+        Self {
+            inner: res,
+            _c: PhantomData,
+        }
+    }
+}
+
 /// A span of time.
 ///
 /// This struct represents a span of time, with its value stored as nanoseconds.
@@ -224,6 +287,78 @@ pub struct Delta {
     nanos: i64,
 }
 
+impl ops::Add for Delta {
+    type Output = Self;
+
+    #[inline]
+    fn add(self, rhs: Self) -> Self {
+        Self {
+            nanos: self.nanos + rhs.nanos,
+        }
+    }
+}
+
+impl ops::AddAssign for Delta {
+    #[inline]
+    fn add_assign(&mut self, rhs: Self) {
+        self.nanos += rhs.nanos;
+    }
+}
+
+impl ops::Sub for Delta {
+    type Output = Self;
+
+    #[inline]
+    fn sub(self, rhs: Self) -> Self::Output {
+        Self {
+            nanos: self.nanos - rhs.nanos,
+        }
+    }
+}
+
+impl ops::SubAssign for Delta {
+    #[inline]
+    fn sub_assign(&mut self, rhs: Self) {
+        self.nanos -= rhs.nanos;
+    }
+}
+
+impl ops::Mul<i64> for Delta {
+    type Output = Self;
+
+    #[inline]
+    fn mul(self, rhs: i64) -> Self::Output {
+        Self {
+            nanos: self.nanos * rhs,
+        }
+    }
+}
+
+impl ops::MulAssign<i64> for Delta {
+    #[inline]
+    fn mul_assign(&mut self, rhs: i64) {
+        self.nanos *= rhs;
+    }
+}
+
+impl ops::Div for Delta {
+    type Output = i64;
+
+    #[inline]
+    fn div(self, rhs: Self) -> Self::Output {
+        #[cfg(CONFIG_64BIT)]
+        {
+            self.nanos / rhs.nanos
+        }
+
+        #[cfg(not(CONFIG_64BIT))]
+        {
+            // SAFETY: This function is always safe to call regardless of the input values
+            unsafe { bindings::div64_s64(self.nanos, rhs.nanos) }
+        }
+    }
+}
+
 impl Delta {
     /// A span of time equal to zero.
     pub const ZERO: Self = Self { nanos: 0 };
@@ -312,4 +447,30 @@ impl Delta {
             bindings::ktime_to_ms(self.as_nanos())
         }
     }
+
+    /// Return `self % dividend` where `dividend` is in nanoseconds.
+    ///
+    /// The kernel doesn't have any emulation for `s64 % s64` on 32 bit platforms, so this is
+    /// limited to 32 bit dividends.
+    #[inline]
+    pub fn rem_nanos(self, dividend: i32) -> Self {
+        #[cfg(CONFIG_64BIT)]
+        {
+            Self {
+                nanos: self.as_nanos() % i64::from(dividend),
+            }
+        }
+
+        #[cfg(not(CONFIG_64BIT))]
+        {
+            let mut rem = 0;
+
+            // SAFETY: `rem` is in the stack, so we can always provide a valid pointer to it.
+            unsafe { bindings::div_s64_rem(self.as_nanos(), dividend, &mut rem) };
+
+            Self {
+                nanos: i64::from(rem),
+            }
+        }
+    }
 }