lkml.org 
[lkml]   [2020]   [Mar]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: linux-next: build warning after merge of the nvmem tree
From
Date
Hi,

> Am 06.03.2020 um 05:28 schrieb Stephen Rothwell <sfr@canb.auug.org.au>:
>
> 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

\
 
 \ /
  Last update: 2020-03-06 11:03    [W:0.037 / U:0.204 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site