Hi, > Am 06.03.2020 um 05:28 schrieb Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>: > > Hi all, > > After merging the nvmem tree, today's linux-next build (x86_64 > allmodconfig) produced this warning: > > In file included from include/linux/clk.h:13, > from drivers/nvmem/jz4780-efuse.c:25: > drivers/nvmem/jz4780-efuse.c: In function 'jz4780_efuse_read': > include/linux/kernel.h:842:29: warning: comparison of distinct pointer types lacks a cast > 842 | (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1))) > | ^~ > include/linux/kernel.h:856:4: note: in expansion of macro '__typecheck' > 856 | (__typecheck(x, y) && __no_side_effects(x, y)) > | ^~~~~~~~~~~ > include/linux/kernel.h:866:24: note: in expansion of macro '__safe_cmp' > 866 | __builtin_choose_expr(__safe_cmp(x, y), \ > | ^~~~~~~~~~ > include/linux/kernel.h:875:19: note: in expansion of macro '__careful_cmp' > 875 | #define min(x, y) __careful_cmp(x, y, <) > | ^~~~~~~~~~~~~ > drivers/nvmem/jz4780-efuse.c:76:24: note: in expansion of macro 'min' > 76 | unsigned int chunk = min(bytes, (start + JZ_EFU_READ_SIZE) > | ^~~ > > Introduced by commit > > 50a09dfd394a ("nvmem: add driver for JZ4780 efuse") The new kbuild robot message is more precise. drivers/nvmem/jz4780-efuse.c:76:38: sparse: sparse: incompatible types in comparison expression (different type sizes): drivers/nvmem/jz4780-efuse.c:76:38: sparse: unsigned long * drivers/nvmem/jz4780-efuse.c:76:38: sparse: unsigned int * A look into the code: /* main entry point */ static int jz4780_efuse_read(void *context, unsigned int offset, void *val, size_t bytes) { struct jz4780_efuse *efuse = context; while (bytes > 0) { unsigned int start = offset & ~(JZ_EFU_READ_SIZE - 1); unsigned int chunk = min(bytes, (start + JZ_EFU_READ_SIZE) - offset); The problem seems to be that size_t is not always compatible to unsigned int on all machines and compilers. My cross-gcc for MIPS did not complain. kbuild robot tried for ARCH=x86_64 and in the first warning for GCC_VERSION=7.5.0 make.cross ARCH=riscv So I think we have to use size_t start = offset & ~(JZ_EFU_READ_SIZE - 1); size_t chunk = min(bytes, (start + JZ_EFU_READ_SIZE) - offset); I'l send a patch (after trying on MIPS). BR and thanks, Nikolaus