linux-kernel - Re: [PATCH net-next v3 3/8] rust: time: Change output of Ktime's sub operation to Delta

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Message-Id: <20241017.181711.1319333992452672716.fujita.tomonori@gmail.com>
Date: Thu, 17 Oct 2024 18:17:11 +0900 (JST)
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: boqun.feng@...il.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, aliceryhl@...gle.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 3/8] rust: time: Change output of Ktime's
 sub operation to Delta

On Wed, 16 Oct 2024 13:03:48 -0700
Boqun Feng <boqun.feng@...il.com> wrote:

>>  impl core::ops::Sub for Ktime {
>> -    type Output = Ktime;
>> +    type Output = Delta;
>>  
>>      #[inline]
>> -    fn sub(self, other: Ktime) -> Ktime {
>> -        Self {
>> -            inner: self.inner - other.inner,
>> +    fn sub(self, other: Ktime) -> Delta {
>> +        Delta {
>> +            nanos: self.inner - other.inner,
> 
> My understanding is that ktime_t, when used as a timestamp, can only
> have a value in range [0, i64::MAX], so this substraction here never
> overflows, maybe we want add a comment here?

Sure, I'll add.