On Wed, Jan 08, 2025 at 03:10:03PM +0100, Arnd Bergmann wrote: > On Tue, Jan 7, 2025, at 16:57, Niklas Cassel wrote: > > 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 think using div_u64_rem() instead of do_div() would make this > more readable as this is always an inline function, so the type can > remain resource_size_t, and the division gets optimized well when > that is a 32-bit type. After patch 1/2, we no longer care about the remainder, so I guess div64_u64() is the correct function to use then? Kind regards, Niklas
