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Message-Id: <20241109.133839.322803434056714560.fujita.tomonori@gmail.com>
Date: Sat, 09 Nov 2024 13:38:39 +0900 (JST)
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: boqun.feng@...il.com
Cc: fujita.tomonori@...il.com, anna-maria@...utronix.de,
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Subject: Re: [PATCH v5 4/7] rust: time: Add wrapper for fsleep function
On Wed, 6 Nov 2024 10:13:57 -0800
Boqun Feng <boqun.feng@...il.com> wrote:
>> diff --git a/rust/kernel/time/delay.rs b/rust/kernel/time/delay.rs
>> new file mode 100644
>> index 000000000000..c3c908b72a56
>> --- /dev/null
>> +++ b/rust/kernel/time/delay.rs
>> @@ -0,0 +1,43 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +
>> +//! Delay and sleep primitives.
>> +//!
>> +//! This module contains the kernel APIs related to delay and sleep that
>> +//! have been ported or wrapped for usage by Rust code in the kernel.
>> +//!
>> +//! C header: [`include/linux/delay.h`](srctree/include/linux/delay.h).
>> +
>> +use crate::time::Delta;
>
> Nit: I think it's better to use:
>
> use super::Delta;
>
> here to refer a definition in the super mod.
Fixed.
>> +use core::ffi::c_ulong;
>> +
>> +/// Sleeps for a given duration at least.
>> +///
>> +/// Equivalent to the kernel's [`fsleep`], flexible sleep function,
>> +/// which automatically chooses the best sleep method based on a duration.
>> +///
>> +/// `delta` must be 0 or greater and no more than u32::MAX / 2 microseconds.
>
> Adding backquotes on "u32::MAX / 2" would make it easier to read and
> generates better documentation. For example.
>
> /// `delta` must be 0 or greater and no more than `u32::MAX / 2` microseconds.
>
>
>> +/// If a value outside the range is given, the function will sleep
>> +/// for u32::MAX / 2 microseconds at least.
>
> Same here.
Updated both.
> I would also add the converted result in seconds of `u32::MAX / 2`
> microseconds to give doc readers some intuitions, like:
>
> the function will sleep for `u32::MAX / 2` (= ~2147 seconds or ~36
> minutes) at least.
Yeah, looks good. Added.
>> +///
>> +/// This function can only be used in a nonatomic context.
>> +pub fn fsleep(delta: Delta) {
>> + // The argument of fsleep is an unsigned long, 32-bit on 32-bit architectures.
>> + // Considering that fsleep rounds up the duration to the nearest millisecond,
>> + // set the maximum value to u32::MAX / 2 microseconds.
>> + const MAX_DURATION: Delta = Delta::from_micros(u32::MAX as i64 >> 1);
>> +
>> + let duration = if delta > MAX_DURATION || delta.as_nanos() < 0 {
>
> I think it would be helpful if `Delta` has a `is_negative()` function.
Added.
Thanks a lot!
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