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[180.15.148.177]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-ad51ea79a47sm2877843a12.76.2025.02.07.05.31.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Feb 2025 05:31:48 -0800 (PST) From: FUJITA Tomonori To: linux-kernel@vger.kernel.org Cc: Andrew Lunn , Alice Ryhl , Gary Guo , Fiona Behrens , rust-for-linux@vger.kernel.org, netdev@vger.kernel.org, hkallweit1@gmail.com, tmgross@umich.edu, ojeda@kernel.org, alex.gaynor@gmail.com, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@samsung.com, anna-maria@linutronix.de, frederic@kernel.org, tglx@linutronix.de, arnd@arndb.de, jstultz@google.com, sboyd@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, tgunders@redhat.com Subject: [PATCH v10 3/8] rust: time: Introduce Delta type Date: Fri, 7 Feb 2025 22:26:18 +0900 Message-ID: <20250207132623.168854-4-fujita.tomonori@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250207132623.168854-1-fujita.tomonori@gmail.com> References: <20250207132623.168854-1-fujita.tomonori@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 is different from Delta. as_millis() method isn't used in this patchset. It's planned to be used in Binder driver. Reviewed-by: Andrew Lunn Reviewed-by: Alice Ryhl Reviewed-by: Gary Guo Reviewed-by: Fiona Behrens Signed-off-by: FUJITA Tomonori --- rust/kernel/time.rs | 88 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 88 insertions(+) diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs index 48b71e6641ce..622cd01e24d7 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 = crate::ffi::c_ulong; @@ -81,3 +87,85 @@ fn sub(self, other: Ktime) -> Ktime { } } } + +/// A span of time. +/// +/// This struct represents a span of time, with its value stored as nanoseconds. +/// The value can represent any valid i64 value, including negative, zero, and +/// positive numbers. +#[derive(Copy, Clone, PartialEq, PartialOrd, Eq, Ord, Debug)] +pub struct Delta { + nanos: i64, +} + +impl Delta { + /// A span of time equal to zero. + pub const ZERO: Self = Self { nanos: 0 }; + + /// Create a new [`Delta`] from a number of microseconds. + /// + /// The `micros` can range from -9_223_372_036_854_775 to 9_223_372_036_854_775. + /// If `micros` is outside this range, `i64::MIN` is used for negative values, + /// and `i64::MAX` is used for positive values due to saturation. + #[inline] + pub const fn from_micros(micros: i64) -> Self { + Self { + nanos: micros.saturating_mul(NSEC_PER_USEC), + } + } + + /// Create a new [`Delta`] from a number of milliseconds. + /// + /// The `millis` can range from -9_223_372_036_854 to 9_223_372_036_854. + /// If `millis` is outside this range, `i64::MIN` is used for negative values, + /// and `i64::MAX` is used for positive values due to saturation. + #[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. + /// + /// The `secs` can range from -9_223_372_036 to 9_223_372_036. + /// If `secs` is outside this range, `i64::MIN` is used for negative values, + /// and `i64::MAX` is used for positive values due to saturation. + #[inline] + pub const fn from_secs(secs: i64) -> Self { + Self { + nanos: secs.saturating_mul(NSEC_PER_SEC), + } + } + + /// Return `true` if the [`Delta`] spans no time. + #[inline] + pub fn is_zero(self) -> bool { + self.as_nanos() == 0 + } + + /// Return `true` if the [`Delta`] spans a negative amount of time. + #[inline] + pub fn is_negative(self) -> bool { + self.as_nanos() < 0 + } + + /// Return the number of nanoseconds in the [`Delta`]. + #[inline] + pub const 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 const fn as_micros_ceil(self) -> i64 { + self.as_nanos().saturating_add(NSEC_PER_USEC - 1) / NSEC_PER_USEC + } + + /// Return the number of milliseconds in the [`Delta`]. + #[inline] + pub const fn as_millis(self) -> i64 { + self.as_nanos() / NSEC_PER_MSEC + } +}