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Message-ID: <20241025033118.44452-3-fujita.tomonori@gmail.com>
Date: Fri, 25 Oct 2024 12:31:13 +0900
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: anna-maria@...utronix.de,
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Subject: [PATCH v4 2/7] rust: time: Introduce Delta type
Introduce a type representing a span of time. Define our own type
because `core::time::Duration` is large and could panic during
creation.
time::Ktime could be also used for time duration but timestamp and
timedelta are different so better to use a new type.
i64 is used instead of u64 to represent a span of time; some C drivers
uses negative Deltas and i64 is more compatible with Ktime using i64
too (e.g., ktime_[us|ms]_delta() APIs return i64 so we create Delta
object without type conversion.
i64 is used instead of bindings::ktime_t because when the ktime_t
type is used as timestamp, it represents values from 0 to
KTIME_MAX, which different from Delta.
Delta::from_[millis|secs] APIs take i64. When a span of time
overflows, i64::MAX is used.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>
---
rust/kernel/time.rs | 49 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 49 insertions(+)
diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
index 4a7c6037c256..574e72d3956b 100644
--- a/rust/kernel/time.rs
+++ b/rust/kernel/time.rs
@@ -8,9 +8,15 @@
//! C header: [`include/linux/jiffies.h`](srctree/include/linux/jiffies.h).
//! C header: [`include/linux/ktime.h`](srctree/include/linux/ktime.h).
+/// The number of nanoseconds per microsecond.
+pub const NSEC_PER_USEC: i64 = bindings::NSEC_PER_USEC as i64;
+
/// The number of nanoseconds per millisecond.
pub const NSEC_PER_MSEC: i64 = bindings::NSEC_PER_MSEC as i64;
+/// The number of nanoseconds per second.
+pub const NSEC_PER_SEC: i64 = bindings::NSEC_PER_SEC as i64;
+
/// The time unit of Linux kernel. One jiffy equals (1/HZ) second.
pub type Jiffies = core::ffi::c_ulong;
@@ -81,3 +87,46 @@ fn sub(self, other: Ktime) -> Ktime {
}
}
}
+
+/// A span of time.
+#[derive(Copy, Clone, PartialEq, PartialOrd, Eq, Ord, Debug)]
+pub struct Delta {
+ nanos: i64,
+}
+
+impl Delta {
+ /// Create a new `Delta` from a number of milliseconds.
+ #[inline]
+ pub const fn from_millis(millis: i64) -> Self {
+ Self {
+ nanos: millis.saturating_mul(NSEC_PER_MSEC),
+ }
+ }
+
+ /// Create a new `Delta` from a number of seconds.
+ #[inline]
+ pub const fn from_secs(secs: i64) -> Self {
+ Self {
+ nanos: secs.saturating_mul(NSEC_PER_SEC),
+ }
+ }
+
+ /// Return `true` if the `Detla` spans no time.
+ #[inline]
+ pub fn is_zero(self) -> bool {
+ self.as_nanos() == 0
+ }
+
+ /// Return the number of nanoseconds in the `Delta`.
+ #[inline]
+ pub fn as_nanos(self) -> i64 {
+ self.nanos
+ }
+
+ /// Return the smallest number of microseconds greater than or equal
+ /// to the value in the `Delta`.
+ #[inline]
+ pub fn as_micros_ceil(self) -> i64 {
+ self.as_nanos().saturating_add(NSEC_PER_USEC - 1) / NSEC_PER_USEC
+ }
+}
--
2.43.0
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