1// SPDX-License-Identifier: GPL-2.0
 2
 3//! Time related primitives.
 4//!
 5//! This module contains the kernel APIs related to time and timers that
 6//! have been ported or wrapped for usage by Rust code in the kernel.
 7//!
 8//! C header: [`include/linux/jiffies.h`](srctree/include/linux/jiffies.h).
 9//! C header: [`include/linux/ktime.h`](srctree/include/linux/ktime.h).
10
11/// The number of nanoseconds per millisecond.
12pub const NSEC_PER_MSEC: i64 = bindings::NSEC_PER_MSEC as i64;
13
14/// The time unit of Linux kernel. One jiffy equals (1/HZ) second.
15pub type Jiffies = crate::ffi::c_ulong;
16
17/// The millisecond time unit.
18pub type Msecs = crate::ffi::c_uint;
19
20/// Converts milliseconds to jiffies.
21#[inline]
22pub fn msecs_to_jiffies(msecs: Msecs) -> Jiffies {
23    // SAFETY: The `__msecs_to_jiffies` function is always safe to call no
24    // matter what the argument is.
25    unsafe { bindings::__msecs_to_jiffies(msecs) }
26}
27
28/// A Rust wrapper around a `ktime_t`.
29#[repr(transparent)]
30#[derive(Copy, Clone)]
31pub struct Ktime {
32    inner: bindings::ktime_t,
33}
34
35impl Ktime {
36    /// Create a `Ktime` from a raw `ktime_t`.
37    #[inline]
38    pub fn from_raw(inner: bindings::ktime_t) -> Self {
39        Self { inner }
40    }
41
42    /// Get the current time using `CLOCK_MONOTONIC`.
43    #[inline]
44    pub fn ktime_get() -> Self {
45        // SAFETY: It is always safe to call `ktime_get` outside of NMI context.
46        Self::from_raw(unsafe { bindings::ktime_get() })
47    }
48
49    /// Divide the number of nanoseconds by a compile-time constant.
50    #[inline]
51    fn divns_constant<const DIV: i64>(self) -> i64 {
52        self.to_ns() / DIV
53    }
54
55    /// Returns the number of nanoseconds.
56    #[inline]
57    pub fn to_ns(self) -> i64 {
58        self.inner
59    }
60
61    /// Returns the number of milliseconds.
62    #[inline]
63    pub fn to_ms(self) -> i64 {
64        self.divns_constant::<NSEC_PER_MSEC>()
65    }
66}
67
68/// Returns the number of milliseconds between two ktimes.
69#[inline]
70pub fn ktime_ms_delta(later: Ktime, earlier: Ktime) -> i64 {
71    (later - earlier).to_ms()
72}
73
74impl core::ops::Sub for Ktime {
75    type Output = Ktime;
76
77    #[inline]
78    fn sub(self, other: Ktime) -> Ktime {
79        Self {
80            inner: self.inner - other.inner,
81        }
82    }
83}