linux-kernel - Re: [v8] misc: pci_endpoint_test: Fix overflow of bar

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Message-ID: <58a23cfb-190f-44aa-a06a-d496cc252fb0@163.com>
Date: Wed, 8 Jan 2025 00:12:32 +0800
From: Hans Zhang <18255117159@....com>
To: Niklas Cassel <cassel@...nel.org>
Cc: manivannan.sadhasivam@...aro.org, kw@...ux.com, kishon@...nel.org,
 arnd@...db.de, gregkh@...uxfoundation.org, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org, rockswang7@...il.com
Subject: Re: [v8] misc: pci_endpoint_test: Fix overflow of bar_size



On 2025/1/7 23:57, Niklas Cassel wrote:>>> The error:
>>> drivers/misc/pci_endpoint_test.c:315: undefined reference to `__udivmoddi4'
>>> sounds like the compiler is using a specialized instruction to do both div
>>> and mod in one. By removing the mod in patch 1/2, I expect that patch 2/2
>>> will no longer get this error.
>>
>> The __udivmoddi4 may be the way div and mod are combined.
>>
>> Delete remain's patch 1/2 according to your suggestion. I compiled it as a
>> KO module for an experiment.
>>
>> There are still __udivdi3 errors, so the do_div API must be used.
> 
> Ok. Looking at do_div(), it seems to be the correct API to use
> for this problem. Just change bar_size type to u64 (instead of casting)
> and use do_div() ? That is how it is seems to be used in other drivers.
> 
> I still think that a patch that removes the "remainder" code is a good
> cleanup, so please send it as patch 1/2, you can be the author, just add:
> Suggested-by: Niklas Cassel <cassel@...nel.org>
> 

Thank you very much for Niklas' discussion on this patch. I will 
resubmit two patches in the future.

Best regards
Hans