linux-kernel - Re: [PATCH v3 3/3] rust: time: Add ktime

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Message-ID: <874iwo3tze.fsf@kernel.org>
Date: Tue, 10 Jun 2025 10:01:57 +0200
From: Andreas Hindborg <a.hindborg@...nel.org>
To: "FUJITA Tomonori" <fujita.tomonori@...il.com>
Cc: <alex.gaynor@...il.com>,  <ojeda@...nel.org>,  <aliceryhl@...gle.com>,
  <anna-maria@...utronix.de>,  <bjorn3_gh@...tonmail.com>,
  <boqun.feng@...il.com>,  <dakr@...nel.org>,  <frederic@...nel.org>,
  <gary@...yguo.net>,  <jstultz@...gle.com>,
  <linux-kernel@...r.kernel.org>,  <lossin@...nel.org>,
  <lyude@...hat.com>,  <rust-for-linux@...r.kernel.org>,
  <sboyd@...nel.org>,  <tglx@...utronix.de>,  <tmgross@...ch.edu>
Subject: Re: [PATCH v3 3/3] rust: time: Add ktime_get() to ClockSource trait

"FUJITA Tomonori" <fujita.tomonori@...il.com> writes:

> Introduce the ktime_get() associated function to the ClockSource
> trait, allowing each clock source to specify how it retrieves the
> current time. This enables Instant::now() to be implemented
> generically using the type-level ClockSource abstraction.
>
> This change enhances the type safety and extensibility of timekeeping
> by statically associating time retrieval mechanisms with their
> respective clock types. It also reduces the reliance on hardcoded
> clock logic within Instant.
>
> Reviewed-by: Andreas Hindborg <a.hindborg@...nel.org>
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>
> ---
>  rust/helpers/helpers.c |  1 +
>  rust/helpers/time.c    | 18 ++++++++++++++++++
>  rust/kernel/time.rs    | 32 ++++++++++++++++++++++++++++----
>  3 files changed, 47 insertions(+), 4 deletions(-)
>  create mode 100644 rust/helpers/time.c
>
> diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
> index 0f1b5d115985..0613a849e05c 100644
> --- a/rust/helpers/helpers.c
> +++ b/rust/helpers/helpers.c
> @@ -39,6 +39,7 @@
>  #include "spinlock.c"
>  #include "sync.c"
>  #include "task.c"
> +#include "time.c"
>  #include "uaccess.c"
>  #include "vmalloc.c"
>  #include "wait.c"
> diff --git a/rust/helpers/time.c b/rust/helpers/time.c
> new file mode 100644
> index 000000000000..9c296e93a560
> --- /dev/null
> +++ b/rust/helpers/time.c
> @@ -0,0 +1,18 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/timekeeping.h>
> +
> +ktime_t rust_helper_ktime_get_real(void)
> +{
> +	return ktime_get_with_offset(TK_OFFS_REAL);
> +}
> +
> +ktime_t rust_helper_ktime_get_boottime(void)
> +{
> +	return ktime_get_with_offset(TK_OFFS_BOOT);
> +}
> +
> +ktime_t rust_helper_ktime_get_clocktai(void)
> +{
> +	return ktime_get_with_offset(TK_OFFS_TAI);
> +}

This just caught my eye. I think policy is to make helpers as much 1:1 as
possible. We should not inject arguments here. Instead, we should have
just one function that passes the argument along.


Best regards,
Andreas Hindborg