Re: [v8] misc: pci_endpoint_test: Fix overflow of bar_size

Niklas Cassel
2025-01-07T15:57:40Z

On Tue, Jan 07, 2025 at 11:44:21PM +0800, Hans Zhang wrote:
>
>
> On 2025/1/7 19:47, Niklas Cassel wrote:
>
> Hi Niklas,
>
> > 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@kernel.org>

Kind regards,
Niklas