linux-kernel - Re: [PATCH] staging: pi433: Use div64_u64 instead of do

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Message-ID: <CA+uqrQDM6sQkVz8jQyv0VEoQK3Ucmx5i4CX5PxMEiA5Lsu28Vw@mail.gmail.com>
Date:   Wed, 19 Oct 2022 23:20:30 +0900
From:   Kang Minchul <tegongkang@...il.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@...il.com>,
        Dan Carpenter <error27@...il.com>,
        Sidong Yang <realwakka@...il.com>,
        "linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] staging: pi433: Use div64_u64 instead of do_div

2022년 10월 19일 (수) 오후 7:31, David Laight <David.Laight@...lab.com>님이 작성:
>
> From: Kang Minchul
> > Sent: 19 October 2022 10:40
> >
> > This commit removes warning generated by cocci as follows:
> >
> > do_div() does a 64-by-32 division, please consider using div64_u64 instead.
> >
> > Using div64_u64 instead of do_div can avoid potential truncation.
>
> Cocci is lying to you.
>
> do_div() exists because a 64 by 32 bit divide is significantly
> faster than a 64 by 64 divide.
> This is particularly true on 32bit cpu, but is also true on
> Intel x86_64 bit cpu.
I guess I have missed that point,
Thanks for your feedback!

Kang Minchul