From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 12FD22AD20; Sat, 22 Mar 2025 10:27:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742639276; cv=none; b=CHGjch9HbZGZ33c7zu9rzSVCnA78ohs/SnGlASFBhUJxWmoJL9kwxyvP1YzO9NqhhbO7Qq0gV3KleGXszRZRyXMeiqd1KLy0879AnyEIXm7ax81cZ+5rfk+vJth/s7oJOq56kh1doGH4w/77sW9aStQW/w6gPJHqxx9boerJLdo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742639276; c=relaxed/simple; bh=vLWfAQEsX8V/JhXcponrpJXR7sIl61gCbFDK1wZH7ZU=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=ikjh1Siyvt50XA9kXhdqYSLuD9Ui05JLDVsNn0pxOboitC+he0tZ83O5Sn0yWz6Zn35w8bUQmLLIsJpG/0nopfix6hI3ROKxB/PtmDZ/Qybn2TozQRpeNNOkbrpcjQhKMT58JZsV/HK1EpwkBrwr/I710EKkq8fONsULqH8wDuU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XAixLSS3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XAixLSS3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 01179C4CEED; Sat, 22 Mar 2025 10:27:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742639275; bh=vLWfAQEsX8V/JhXcponrpJXR7sIl61gCbFDK1wZH7ZU=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=XAixLSS3Kmb4bav7wKHDl16DBJM+KOO8A1Bj/akdC/Rzi1ifuKnKjFghzXtjyc31j 1QGOm5p8+750FEnvGEKGFSZSs+sb3r+qilu9Q5r42c077uabw2PyWotudk8ghDD9mt 3TKwbIgxeq7yLYHIMhMN/uvUMXa5SBu4X2ty7dcChKjB6xpj5gxTG1j4w2Ha9JlFLr yrMGjbzDGkjLCF1fUqIwNi9nc4Hqno9eQmhzxphwAUQRBH4Agy1YMLt8IRNjvL22xL 3+C1YHVx9vZT4v0zMKCTiim1St6IHeVZwHHrfQ0aPUH8kszrF3fA0VYIcVkXMbQbPm UEK1sYxZzMFyA== From: Andreas Hindborg To: FUJITA Tomonori Cc: linux-kernel@vger.kernel.org, Daniel Almeida , 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, david.laight.linux@gmail.com Subject: Re: [PATCH v11 3/8] rust: time: Introduce Delta type In-Reply-To: <20250220070611.214262-4-fujita.tomonori@gmail.com> (FUJITA Tomonori's message of "Thu, 20 Feb 2025 16:06:05 +0900") References: <20250220070611.214262-1-fujita.tomonori@gmail.com> <20250220070611.214262-4-fujita.tomonori@gmail.com> User-Agent: mu4e 1.12.7; emacs 29.4 Date: Sat, 22 Mar 2025 09:50:48 +0100 Message-ID: <8734f5cutz.fsf@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain FUJITA Tomonori writes: > 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. > > Tested-by: Daniel Almeida > Reviewed-by: Andrew Lunn > Reviewed-by: Alice Ryhl > Reviewed-by: Gary Guo > Reviewed-by: Fiona Behrens > Signed-off-by: FUJITA Tomonori Reviewed-by: Andreas Hindborg Two suggestions below, take or leave. > --- > 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. To make these numbers truly useful, it would be nice to have them as constants, for example `Delta::MAX_MICROS`, `Delta::MIN_MICROS`. > + /// 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`]. We might consider adding "rounded towards zero" to this doc string. Best regards, Andreas Hindborg