linux-kernel - Re: [PATCH net-next v3 2/8] rust: time: Introduce Delta type

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Message-Id: <20241017.201557.144371392063010807.fujita.tomonori@gmail.com>
Date: Thu, 17 Oct 2024 20:15:57 +0900 (JST)
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: aliceryhl@...gle.com
Cc: fujita.tomonori@...il.com, netdev@...r.kernel.org,
 rust-for-linux@...r.kernel.org, andrew@...n.ch, hkallweit1@...il.com,
 tmgross@...ch.edu, ojeda@...nel.org, alex.gaynor@...il.com,
 gary@...yguo.net, bjorn3_gh@...tonmail.com, benno.lossin@...ton.me,
 a.hindborg@...sung.com, anna-maria@...utronix.de, frederic@...nel.org,
 tglx@...utronix.de, arnd@...db.de, jstultz@...gle.com, sboyd@...nel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 2/8] rust: time: Introduce Delta type

On Wed, 16 Oct 2024 10:23:49 +0200
Alice Ryhl <aliceryhl@...gle.com> wrote:

> On Wed, Oct 16, 2024 at 5:53 AM FUJITA Tomonori
> <fujita.tomonori@...il.com> wrote:
>>
>> 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.
> 
> Is there a reason that Delta wraps i64 directly instead of wrapping
> the Ktime type? I'd like to see the reason in the commit message.

You meant that bindings::ktime_t is used instead of i64 like:

pub struct Delta {
    nanos: bindings::ktime_t,
}

? I've not considered but might make sense.