There's this persistent build warning about missing prototypes with ARCH=um: [12:21:20] Configuring KUnit Kernel ... [12:21:20] Building KUnit Kernel ... Populating config with: $ make ARCH=um O=build.kunit olddefconfig Building with: $ make all compile_commands.json ARCH=um O=build.kunit --jobs=8 ../lib/iomap.c:156:5: warning: no previous prototype for ‘ioread64_lo_hi’ [-Wmissing-prototypes] 156 | u64 ioread64_lo_hi(const void __iomem *addr) | ^~~~~~~~~~~~~~ ../lib/iomap.c:163:5: warning: no previous prototype for ‘ioread64_hi_lo’ [-Wmissing-prototypes] 163 | u64 ioread64_hi_lo(const void __iomem *addr) | ^~~~~~~~~~~~~~ ../lib/iomap.c:170:5: warning: no previous prototype for ‘ioread64be_lo_hi’ [-Wmissing-prototypes] 170 | u64 ioread64be_lo_hi(const void __iomem *addr) | ^~~~~~~~~~~~~~~~ ../lib/iomap.c:178:5: warning: no previous prototype for ‘ioread64be_hi_lo’ [-Wmissing-prototypes] 178 | u64 ioread64be_hi_lo(const void __iomem *addr) | ^~~~~~~~~~~~~~~~ ../lib/iomap.c:264:6: warning: no previous prototype for ‘iowrite64_lo_hi’ [-Wmissing-prototypes] 264 | void iowrite64_lo_hi(u64 val, void __iomem *addr) | ^~~~~~~~~~~~~~~ ../lib/iomap.c:272:6: warning: no previous prototype for ‘iowrite64_hi_lo’ [-Wmissing-prototypes] 272 | void iowrite64_hi_lo(u64 val, void __iomem *addr) | ^~~~~~~~~~~~~~~ ../lib/iomap.c:280:6: warning: no previous prototype for ‘iowrite64be_lo_hi’ [-Wmissing-prototypes] 280 | void iowrite64be_lo_hi(u64 val, void __iomem *addr) | ^~~~~~~~~~~~~~~~~ ../lib/iomap.c:288:6: warning: no previous prototype for ‘iowrite64be_hi_lo’ [-Wmissing-prototypes] 288 | void iowrite64be_hi_lo(u64 val, void __iomem *addr) | ^~~~~~~~~~~~~~~~~ [12:21:24] Elapsed time: 3.945s I fail at figuring out where to stick an #include or #define readq or something to get the prototypes. Cc: Arnd who seems to have fixed similar issues before on other archs, do you have any ideas? Kconfig attached. Thanks, Jani. -- Jani Nikula, Intel