linux-kernel - Re: [PATCH] mtd: ubi: avoid expensive do

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Message-Id: <1ee86ea9-fa91-4795-b5f8-2e57609ae65e@app.fastmail.com>
Date: Wed, 13 Mar 2024 14:51:14 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Zhihao Cheng" <chengzhihao1@...wei.com>,
 "Arnd Bergmann" <arnd@...nel.org>, "Richard Weinberger" <richard@....at>,
 "Miquel Raynal" <miquel.raynal@...tlin.com>,
 "Vignesh Raghavendra" <vigneshr@...com>,
 "Daniel Golle" <daniel@...rotopia.org>
Cc: linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: ubi: avoid expensive do_div() on 32-bit machines

On Wed, Mar 13, 2024, at 14:43, Zhihao Cheng wrote:
> 在 2024/3/13 21:39, Arnd Bergmann 写道:
>
>>> Thanks for explaination, which means that do_div is used for 64-bit
>>> division to solve the link failure caused by missed libgcc. Since
>>> parameter 'from' is u32, there is no need to invoke do_div on a 32-bit
>>> platform, you just want to stop the wasting behavior on a 32-bit
>>> platform. Do I understand right?
>> 
> How do you find it? I mean there are so many types and many do_div 
> callers, do you have a static check tool?

I had a local fix with the same effect that I applied when
the code originally broke, but had not gotten around to
sending my fix.

After b8a77b9a5f9c ("mtd: ubi: fix NVMEM over UBI volumes on
32-bit systems") introduced a different workaround, I got the
link error because I had removed the do_div().

     Arnd