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

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Message-ID: <87h60o2b5j.fsf@kernel.org>
Date: Tue, 10 Jun 2025 11:34:00 +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:

> On Tue, 10 Jun 2025 10:01:57 +0200
> Andreas Hindborg <a.hindborg@...nel.org> wrote:
>
>> "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.
>
> Indeed, you're right. It should have been as follows:
>
> +++ 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_real();
> +}
> +
> +ktime_t rust_helper_ktime_get_boottime(void)
> +{
> +	return ktime_get_boottime();
> +}
> +
> +ktime_t rust_helper_ktime_get_clocktai(void)
> +{
> +	return ktime_get_clocktai();
> +}

Yes, even better 👍


Best regards,
Andreas Hindborg